HVAC System Name

Applicability

All system types

Definition

A unique descriptor for each HVAC system

Units

Text, unique

Input Restrictions

When applicable, input should match the tags that are used on the plans

Standard Design

None

Standard Design:

Existing Buildings

None

System Type

Applicability

All system types

Definition

A unique descriptor which identifies the HVAC system type.  The System Type indicates the cooling and heat source, and whether the system serves a single zone or multiple zones.

Units

List from the choices below

Input Restrictions

PTAC – Packaged Terminal Air Conditioner

SZAC – Single-zone Air Conditioner

PTHP – Packaged Terminal Heat Pump

PSZ-AC – Packaged Single Zone Air Conditioner

PSZ-HP – Packaged Single Zone Heat Pump Air Conditioner

PVAV* – Packaged Variable Air Volume (VAV) with Reheat

VAV* – Built-up VAV with Reheat

SZVAV-AC – Single Zone VAV Air Conditioner

SZVAV-HP – Single Zone VAV Heat Pump

HV – Heating and Ventilation Only

CRAC – Computer Room Air Conditioner

CRAH – Computer Room Air Handler

FPFC – Four-pipe Fan Coil

WSHP – Water-source Heat Pump

SPVAC – Single package vertical air conditioner

SPVHP – Single package vertical heat pump

* Choice includes series and parallel fan-powered boxes as zone terminal units

Standard Design

Based on the prescribed system type in the HVAC system map (see Section 5.1.2).

Standard Design:

Existing Buildings

Control System Type

Applicability

All HVAC systems that serve more than one control zone, as well as the hydronic systems that serve building HVAC systems

Definition

The type of control system for multi-zone HVAC systems and their related equipment.

This input affects the proposed design system specification for zone level controls, supply air temperature reset controls, ventilation controls and fan and pump static pressure part-load curves. See the following building descriptors:

•      Ventilation control method

•      Terminal heating control type

•      Pump part-load curve

•      Fan part-load curve

•      Optimal start

Units

None

Input Restrictions

List one of the following inputs:

Direct digital control (DDC) control to the zone level – DDC systems with control to the zone level

Other – other control systems, including pneumatic and DDC systems without control to the zone level

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

DDC control to the zone level

Standard Design:

Existing Buildings

Air Handler Schedule

Applicability

All systems that do not cycle with loads

Definition

A schedule that indicates when the air handler operates continuously

Units

Data structure: schedule, on/off

Input Restrictions

For healthcare facilities, same as the Proposed Design. For all others,

Schedule group is prescribed in Appendix 5.4A and schedule values are prescribed in Appendix 5.4B. See Section 2.3.3 on how software shall assign schedules when the spaces served by the system are assigned to different schedule groups in Appendix 5.4A.

The fan schedules and HVAC operations are defined so that the air handlers provide the necessary outside air 1 hour prior to scheduled occupancy.

When a fan system serves several occupancies, the fan schedule remains ON to serve the operating hours of each occupancy.

Standard Design

Same as the proposed design

Standard Design:

Existing Buildings

Air Handler Fan Cycling

Applicability

All fan systems

Definition

This building descriptor indicates whether the system supply fan operates continuously or cycles with building loads when the HVAC schedule indicates the building is occupied. (See night cycle control input for fan operation during unoccupied hours.) The fan systems in most commercial buildings operate continuously.

Units

List continuous or cycles with loads

Input Restrictions

As designed if the HVAC system serves zones with a dedicated outside air source for ventilation; otherwise, continuous.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Cycles with loads for FPFC systems; continuous for all other standard design system types

Standard Design:

Existing Buildings

Optimal Start Control

Applicability

Systems with the control capability for flexible scheduling of system start time based on building loads

Definition

Optimal start control adjusts the start time of the HVAC unit such that the space is brought to setpoint just prior to occupancy. This control strategy modifies the heating, cooling, and fan schedules.

Units

Boolean (Yes/No)

Input Restrictions

Fixed at yes if control system type is DDC to the zone level; otherwise, as designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Fixed at yes, if control system type is DDC to the zone level

Standard Design:

Existing Buildings

Night-Cycle HVAC Fan Control

Applicability

All air systems – not applicable for zone systems

Definition

The control of an HVAC system that is triggered by the heating or cooling temperature setpoint for thermal zones during periods when the heating, cooling and fan systems are scheduled to be off. For this control, the space is controlled to the setback or setup temperature only; this control is not equivalent to a night purge control. The choices are:

•      Cycle on call from any zone

•      Cycle on call from the primary control zone

•      Stay off

•      Cycle zone fans only (for systems with fan-powered boxes) Restart fans below given ambient temperature.

Units

None

Input Restrictions

Cycle on call from any zone, except for systems with fan-powered boxes, where either cycle on call from any zone or cycle zone fans only is allowed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Cycle on call from any zone

Standard Design:

Existing Buildings

Cooling Supply Air Temperature

Applicability

Applicable to all systems

Definition

The supply air temperature setpoint at design cooling conditions

Units

Degrees Fahrenheit (°F)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

15°F below the space temperature setpoint for interior zones that are served by multiple zone systems; for all other zones, 20°F below the space temperature setpoint

Standard Design:

Existing Buildings

Heating Supply Air Temperature

Applicability

All systems

Definition

The supply air temperature leaving the air handler when the system is in a heating mode (not the air temperature leaving the reheat coils in VAV boxes)

Units

Degrees Fahrenheit (°F)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

95°F for system types 1-4; 60°F for multiple zone systems; no heating for data centers and computer rooms

Standard Design:

Existing Buildings

Supply Air Temperature Control

Applicability

Any cooling system

Definition

The method of controlling the supply air temperature. Choices are:

•      No control – for this scheme the coils are energized whenever there is a call for heating or cooling at the zone.

•      Fixed (constant)

•      Reset by warmest zone, airflow first

•      Reset by warmest zone, temperature first

•      Reset by outside air dry-bulb temperature

•      Scheduled setpoint

Units

List (see above)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

For standard design systems 1 through 4, the SAT control is No Control. For systems 5 through 8, 10, and 11, the SAT control shall be reset by warmest zone, airflow first. For system 9 (heating and ventilation), this input is not applicable.

Standard Design:

Existing Buildings

Reset Schedule by OSA

Applicability

When the proposed design resets SAT by outside air dry-bulb temperature

Definition

A linear reset schedule that represents the SAT setpoint as a function of outdoor air dry-bulb temperature

This schedule is defined by the following data points (see Figure 9):

•      The coldest supply air temperature

•      The corresponding (hot) outdoor air dry-bulb setpoint

•      The warmest supply air temperature

•      The corresponding (cool) outdoor air dry-bulb setpoint

Figure 11: SAT Cooling Setpoint Reset Based On Outdoor Air Temperature (OAT)

Source: NORESCO for California Energy Commission

Units

Data structure (two matched pairs of SAT and OAT, see above)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Supply Fan Modeling Method

Applicability

All fan systems

Definition

Fans can be modeled in one of three ways. The simple method is for the user to enter the electric power per unit of flow (W/cfm). This method is commonly used for zonal equipment and other small fan systems. A more detailed method is to model the fan as a system whereby the static pressure, fan efficiency, part-load curve, and motor efficiency are specified at design conditions. A third method is to specify brake horsepower at design conditions instead of fan efficiency and static pressure. This is a variation of the second method whereby brake horsepower is specified in lieu of static pressure and fan efficiency. The latter two methods are commonly used for VAV and fan systems with significant static pressure.

Units

List power-per-unit-flow, static pressure, or brake horsepower

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

The standard design shall use the brake horsepower method for all HVAC systems except the SZAC unit used in residential spaces, the heating and ventilation only system, and the four-pipe fan coil system, which shall use the power-per-unit-flow method.

Standard Design:

Existing Buildings

Supply Fan Power Ratio

Applicability

All fan systems

Definition

The standard design fan power requirements apply to all fans that operate at design conditions. To apportion the fan power to the supply fan and exhaust fans, a ratio is defined that is the ratio of supply fan power to total system fan power. 

Units

Unitless ratio

Input Restrictions

As designed, not a user input.

This is the ratio of the supply fan power to total system fan power, which includes supply fans, exhaust fans, any return fans, and any series-powered fans.

Standard Design

Same as proposed

Standard Design:

Existing Buildings

Same as proposed

Supply Fan Design Airflow

Applicability

All fan systems

Definition

The air flow rate of the supply fan(s) at design conditions.

This building descriptor sets the 100 percent point for the fan part-load curve.

Units

CFM (ft³/min)

Input Restrictions

As designed*

*The airflow is typically between 250 cfm/ton and 500 cfm/ton; values well outside of this range may cause simulation engine runtime efforts that must be addressed by the user (currently there are no input restrictions on this).

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

The program shall automatically size the air flow at each thermal zone to meet the loads. The design air flow rate calculation shall be based on a 20°F temperature differential between supply air and the room air 20°F temperature differential between the supply air and the return air for exterior zones and a 15°F temperature differential for interior zones served by multiple zone systems. The design supply air flow rate is the larger of the flow rate required to meet space conditioning requirements and the required ventilation flow rate.

For equipment with DX cooling coils, the program applies the results of a sizing run, and oversizes both the cooling coil capacity and airflows by 15% to obtain the appropriate airflow.

For multizone systems, the supply fan design air flow rate shall be the system airflow rate that satisfies that coincident peak of all thermal zones at the design supply air temperature.

Standard Design:

Existing Buildings

Fan Control Method

Applicability

All fan systems

Definition

A description of how the supply (and return/relief) fan(s) are controlled

The options include:

•      Constant volume

•      Variable-flow, inlet, or discharge dampers

•      Variable-flow, inlet guide vanes

•      Variable-flow, variable speed drive (VSD)

•      Variable-flow, variable pitch blades

•      Two-speed

For variable-speed fans, the fan control method determines which part-load performance curve to use.

Units

List (see above)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. Based on the prescribed system type. Refer to the HVAC System Map in 5.1.2.

Standard Design:

Existing Buildings

Supply Fan Brake Horsepower

Applicability

All fan systems, except those specified using the power-per-unit-flow method

Definition

The design shaft brake horsepower of each supply fan.

This input does not need to be supplied if the supply fan kW is supplied.

Units

Horsepower (hp)

Input Restrictions

As designed

If this building descriptor is specified for the proposed design, then the static pressure and fan efficiency are not.

The compliance software shall apply the following rule to specify the proposed design bhp, based on user input:

A standard motor size table (hp) is defined as: 1/12, 1/8, ¼, ½, ¾, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, and 200.

The user entered brake horsepower for the proposed design is compared against the next smaller motor size from the user entered supply fan motor horsepower. The proposed design supply fan brake horsepower (bhp) is set to the maximum of the user entered bhp and 95 percent of the next smaller motor horsepower:

Proposed bhp = max(user bhp, 95 percent ×MHP_i-1)

Where User bhp is the user entered supply fan brake horsepower:

MHPi is the proposed (nameplate) motor horsepower

MHPi-1 is the next smaller motor horsepower from the Standard Motor Size table above. For example, if the proposed motor horsepower is 25, the next smaller motor horsepower from the table above is 20, and 95 percent of the next smaller motor horsepower is 19.

Standard Design

For healthcare facilities, same as the Proposed Design.

For FPFC and heating and ventilation systems, not applicable.

For laboratory systems where the building lab design exhaust flow is greater than 10,000 cfm, a separate exhaust fan power allowance is given, and the entire fan power budget can be allocated to the supply fan:

VAV Supply Fan BHP = (0.0013 x cfmmax + A)

CAV Supply Fan BHP = (0.00094 x cfmmax + A)

For PVAV and built-up VAV systems:

Supply Fan BHP = (0.0013 x cfmmax + A) x Supply Fan Ratio,

For other systems,

Supply Fan BHP = (0.00094 x cfm + A) x SupplyFanRatio, where

 cfm  = the design supply air flow, and

 A = the fan power adjustment (see separate building descriptor)

SupplyFanRatio is the ratio of supply fan brake horse power at design conditions to total system brake horsepower at design conditions

Standard Design:

Existing Buildings

Same as proposed if existing and unaltered; otherwise, same as new construction

Supply Fan Motor Horsepower

Applicability

All fan systems, except those specified using the power-per-unit-flow method

Definition

The motor nameplate horsepower of the supply fan

Units

List: choose from standard motor sizes: 1/12, 1/8, ¼, ½, ¾, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 200

Input Restrictions

As designed.

This building descriptor is required for the static pressure or the brake horsepower methods.

Standard Design

Set to the standard motor efficiency for the next larger nominal HP size, from NEMA standards

Standard Design:

Existing Buildings

Set to the standard motor efficiency for the next larger nominal HP size, from NEMA standards

Supply Fan Static Pressure

Applicability

All fan systems using the static pressure method

Definition

The design static pressure for the supply fan.

This is important for both fan electric energy usage and duct heat gain calculations.

Units

Inches of water column (in. H₂0)

Input Restrictions

As designed

The design static pressure for the supply fan does not need to be specified if the supply fan brake horsepower (bhp) is specified.

Standard Design

Not applicable. Defined in the software as a function of brake horsepower or power-per-unit flow.

Standard Design:

Existing Buildings

Not applicable

Supply Fan Efficiency

Applicability

All fan systems using the static pressure method

Definition

The efficiency of the fan at design conditions; this is the static efficiency and does not include motor losses

Units

Unitless

Input Restrictions

As designed

The supply fan efficiency does not need to be specified if the supply fan brake horsepower (bhp) is specified.

Standard Design

65%

Not applicable for the four-pipe fan coil system.

Standard Design:

Existing Buildings

Not applicable

Supply Motor Efficiency

Applicability

All supply fans, except those specified using the power-per-unit-flow method

Definition

The full-load efficiency of the motor serving the supply fan

Units

Unitless

Input Restrictions

As designed

Not applicable when the power-per-unit-flow method is used.

Standard Design

The motor efficiency is determined from Table 11 for the next motor size greater than the bhp.

Standard Design:

Existing Buildings

Same as proposed

Fan Power Adjustment

Applicability

Any system with special requirements for filtration or other process requirements

Definition

Additional system brake horsepower related to application-specific filtration requirements or other process requirements

An exceptional condition shall be included on compliance documentation when the user selects one of these adjustment conditions.

Units

List

Input Restrictions

The user chooses one or more fan power adjustment credits from the list below. If the adjustment credit is specified in terms of static pressure, the static pressure adjustment is fixed. For the credits that depend on the design, the user enters the pressure drop for each device.

The proposed design fan power adjustment (bhp) is given by the equation:

FPA = Σ SP_i x CFM_i / 4131

Where SPi = the static pressure through the device, inches w.c.

CFMi = the design airflow through the device

Standard Design

Same as proposed

Standard Design:

Existing Buildings

Same as proposed for new HVAC equipment; not applicable for existing, unaltered systems.

Fan Position

Applicability

All supply fans

Definition

The position of the supply fan relative to the cooling coil.

The configuration is either draw through (fan is downstream of the coil) or blow through (fan is upstream of the coil).

Units

List (see above)

Input Restrictions

As designed

Standard Design

Draw through

Standard Design:

Existing Buildings

Motor Position

Applicability

All supply fans

Definition

The position of the supply fan motor relative to the cooling air stream.

The choices are in the air stream or out of the air stream.

Units

List (see above)

Input Restrictions

As designed

Standard Design

In the air stream

Standard Design:

Existing Buildings

Fan Part-Flow Power Curve

Applicability

All variable flow fan systems

Definition

A part-load power curve that represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow.

The curve is typically represented as a quadratic equation with an absolute minimum power draw specified.

Units

Unitless ratio

Input Restrictions

As designed

The user shall not be able to select VSD with static pressure reset if the building does not have DDC controls to the zone level. The default fan curve shall be selected from Appendix 5.7 for the type of fan specified in the proposed design.

Where:

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable for standard design constant volume systems. The curve VSD with static pressure reset fans shall be used for variable volume systems.

Standard Design:

Existing Buildings

Supply Fan Power Index

Applicability

Fan systems that use the power-per-unit-flow method

Definition

The supply fan power (at the motor) per unit of flow

Units

W/cfm

Input Restrictions

As designed or specified in the manufacturers’ literature

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

For FPFC systems, 0.35 W/cfm for heating and ventilation only systems, 0.53 W/cfm ;

For CRAC and CRAH systems,  0.81 W/cfm (approximate value for 27 W/kBtu-h of sensible cooling capacity assuming 400 cfm/ton).

For other systems, not applicable.

Standard Design:

Existing Buildings

Plenum Zone

Applicability

Any system with return ducts or return air plenum

Definition

A reference to the thermal zone that serves as return plenum or where the return ducts are located

Units

Text, unique

Input Restrictions

As designed

Standard Design

Not applicable

Standard Design:

Existing Buildings

Return Air Path

Applicability

Any system with return ducts or return air plenum

Definition

Describes the return path for air.

Can be ducted return, plenum return, or direct-to-unit.

Units

List (see above)

Input Restrictions

As designed

Standard Design

Applicable when the standard design has a relief fan. For standard design systems 1 and 2, the return air path shall be direct-to-unit. For standard design systems 3 through 11, the standard design shall be ducted return.

Standard Design:

Existing Buildings

Return/Relief Fan Modeling Method

Applicability

All fan systems

Definition

The specification method for return fan power. The simple method is for the user to enter the electric power-per-unit of flow (W/cfm). A more detailed method is to model the fan as a system whereby the static pressure, fan efficiency, part-load curve, and motor efficiency are specified at design conditions. A third method is to specify brake horsepower at design conditions instead of fan efficiency and static pressure. This is a variation of the second method whereby brake horsepower is specified in lieu of static pressure and fan efficiency. The latter two methods are commonly used for VAV and fan systems with significant static pressure.

Units

List power-per-unit-flow, static pressure, or brake horsepower

Input Restrictions

As designed

Standard Design

Not applicable (the standard design does not include return fans, and relief fans are not explicitly modeled)

Standard Design:

Existing Buildings

Not applicable

Return/Relief Fan Design Airflow

Applicability

All systems with a return or relief fan

Definition

The design air flow fan capacity of the return or relief fan(s).

This sets the 100 percent fan flow point for the part-load curve (see below).

Units

Cfm

Input Restrictions

For return fans, as designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, not modeled.

Standard Design:

Existing Buildings

Return/Relief Fan Brake Horsepower

Applicability

Any system with return fans that uses the brake horsepower method

Definition

The design shaft brake horsepower of the return/relief fan(s)

Units

Brake horsepower (bhp)

Input Restrictions

As designed

The compliance software shall apply the following pre-processing rule to specify the proposed design return/relief fan brake horsepower, based on user input:

A standard motor size table (hp) is defined as: 1/12, 1/8, ¼, ½, ¾, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, and 200.

The return/relief fan brake horsepower is determined from user inputs of brake horsepower and motor horsepower for the proposed design, in the same manner as the supply fan brake horsepower.

Proposed bhp = min (user bhp, 95 percent x MHP_i-1)

Where:

Proposed bhp is the return/relief fan brake horsepower used in the simulation;

User bhp is the actual fan bhp as entered by the user; and

MHP_i-1 is the motor horsepower of the next smaller motor size from the standard motor size table above; MHP_i is the motor size that the user enters for the return/relief fan.

See the supply fan brake horsepower descriptor for further details.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, not modeled.

Standard Design:

Existing Buildings

Return/Relief Fan Motor Horsepower

Applicability

All fan systems, except those specified using the power-per-unit-flow method

Definition

The motor nameplate horsepower of the supply fan

Units

List choose from standard motor sizes: 1/12, 1/8, ¼, ½, ¾, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 200

Input Restrictions

As designed

This building descriptor is required for the static pressure or the brake horsepower methods.

Standard Design

Not modeled

Standard Design:

Existing Buildings

Return/Relief Design Static Pressure

Applicability

Any system with return or relief fans that uses the static pressure method

Definition

The design static pressure for return fan system.

This is important for both fan electric energy usage and duct heat gain calculations.

Units

Inches of water column (in. H20 gauge)

Input Restrictions

As designed. The design static pressure for the return fan does not need to be specified if the return fan brake horsepower (bhp) is specified.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, not applicable (there are no return fans, and the relief fan is not modeled.

Standard Design:

Existing Buildings

Return/Relief Fan Efficiency

Applicability

Any system with return or relief fans that uses the static pressure method

Definition

The efficiency of the fan at design conditions. This is the static efficiency and does not include the efficiency loss of the motor.

Units

Unitless

Input Restrictions

As designed. The return/relief fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, not applicable.

Standard Design:

Existing Buildings

Return/Relief Motor Efficiency

Applicability

All return fans, except those specified using the power-per-unit-flow method

Definition

The full-load efficiency of the motor serving the supply fan

Units

Unitless

Input Restrictions

As designed. Not applicable when the power-per-unit-flow method is used.

Standard Design

Not applicable

Standard Design:

Existing Buildings

Motor Position

Applicability

All return fans

Definition

The position of the supply fan motor relative to the cooling air stream. The choices are in the air stream or out of the air stream.

Units

List (see above)

Input Restrictions

As designed.

Standard Design

In the air stream

Standard Design:

Existing Buildings

Fan Part-Flow Power Curve

Applicability

All return fans for variable flow fan systems.

Definition

A part-load power curve which represents the percentage full-load power draw of the supply fan as a function of the percentage full-load air flow.

Units

Unitless ratio

Input Restrictions

As designed. The default fan curve shall be selected from Appendix 5.7 for the type of fan specified in the proposed design.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Exhaust Fan Name

Applicability

All exhaust systems serving multiple thermal zones

Definition

A unique descriptor for each exhaust fan. This should be keyed to the construction documents, if possible, to facilitate plan checking. Exhaust rates and schedules at the thermal zone level refer to this name.

Units

Text, unique

Input Restrictions

Where applicable, this should match the tags that are used on the plans.

Standard Design

The standard design shall have an exhaust system that corresponds to the proposed design. However, if the user has specified an exhaust system as the ventilation system an equivalent standard design system will not be modeled since the standard design has its own definition for ventilation systems. The name can be identical to that used for the proposed design or some other appropriate name may be used.

Standard Design:

Existing Buildings

Exhaust Fan System Modeling Method

Applicability

All exhaust fan systems

Definition

Compliance software can model fans in three ways. See definition for supply system modeling method.

Units

List: power-per-unit-flow, static pressure or brake horsepower

Input Restrictions

As designed

Standard Design

The standard design shall use the static pressure method.

Standard Design:

Existing Buildings

Exhaust Fan Power Ratio

Applicability

All fan systems

Definition

The standard design fan power requirements apply to all fans that operate at design conditions. To apportion the fan power to the supply fan and exhaust fans, a ratio is defined that is the ratio of non-exempt exhaust fan power to total system fan power.

Units

List power-per-unit-flow, static pressure, or brake horsepower

Input Restrictions

As designed, not a user input.

This is the ratio of the exhaust fan power to total system fan power, which includes: supply fans, exhaust fans, return fans, and any series-powered fans. 

Standard Design

Same as proposed

Standard Design:

Existing Buildings

Same as proposed

Exhaust Fan Design Airflow

Applicability

All exhaust fan systems

Definition

The rated design air flow rate of the exhaust fan system. This building descriptor defines the 100 percent flow point of the part-flow curve. Actual air flow is the sum of the flow specified for each thermal zone, as modified by the schedule for each thermal zone.

Units

Cfm

Input Restrictions

As designed. The total design exhaust flow capacity for building (conditioned space) shall not exceed the sum of building story minimum ventilation (outdoor) air flow. Exhaust makeup can be transferred from other zones in the building provided that the total building exhaust rate does not exceed the total minimum outside air flow rate.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Same as proposed design, but with the same limitations described under input restrictions. The design supply air ventilation rate for zone(s) may need to be adjusted by the software, so that the total design outside air ventilation rate supplied to all zones on a floor equals the total exhaust fan design airflow for all zones on the floor.

Standard Design:

Existing Buildings

Exhaust Fan Control Method

Applicability

All exhaust fan systems

Definition

A description of how the exhaust fan(s) are controlled. The options include:

•      Constant volume

•      Variable-flow, variable speed drive (VSD)

Units

List (see above)

Input Restrictions

As designed, when exhaust fan flow at the thermal zone level is varied through a schedule, one of the variable-flow options shall be specified.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

The standard design exhaust fan control shall be the same as the proposed design, but subject to the conditions described above.

For exhaust fans serving kitchen spaces, the fan control method is constant volume for fans with flow rate 5,000 cfm and below, and variable flow, variable speed drive for fans with flow rate greater than 5,000 cfm.

For exhaust fans serving laboratory spaces, the fan control method is variable-flow, variable speed drive when the minimum exhaust flow is 10 ACH or less. If the lab exhaust flow minimum is greater than 10 ACH, the control method is the same as proposed.

Standard Design:

Existing Buildings

Exhaust Fan Brake Horsepower

Applicability

All exhaust fan systems

Definition

The design shaft brake horsepower of the exhaust fan(s).

Units

Brake horsepower (bhp)

Input Restrictions

As designed

The compliance software implements a pre-processing rule to specify the proposed design exhaust fan brake horsepower (bhp), based on user input:

A standard motor size table (hp) is defined as: 1/12, 1/8, ¼, ½, ¾, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 200

The exhaust fan brake horsepower is determined from user inputs of brake horsepower and motor horsepower for the proposed design, in the same manner as the supply fan brake horsepower.

Proposed bhp = max (user bhp, 95 percent x MHP_i-1)

Where:

Proposed bhp is the return/relief fan brake horsepower used in the simulation,

User bhp is the actual fan bhp as entered by the user

MHP_i-1 is the motor horsepower of the next smaller motor size from the standard motor size table above; MHP_i is the motor size that the user enters for the exhaust fan

See the supply fan brake horsepower descriptor for further details.

Standard Design

For healthcare facilities, same as the Proposed Design.

For laboratory exhaust, where the building lab design exhaust flow exceeds 10,000 cfm, 0.65 W/cfm. If the user designates that the system includes scrubbers or other air treatment devices, the standard design exhaust fan power shall be 0.85 W/cfm.

For all others, the standard design exhaust fan brake horsepower is equal to the fan system power allowance times the exhaust fan power ratio:

For constant volume systems, (0.00094 x cfm_max + A) x ExhaustFanPowerRatio

For variable volume systems, 0.0013 x cfm_max + A) x ExhaustFanPowerRatio

Exhaust Fan Motor Horsepower

Applicability

All fan systems, except those specified using the power-per-unit-flow method

Definition

The motor nameplate horsepower of the supply fan

Units

List - choose from standard motor sizes: 1/12, 1/8, ¼, ½, ¾, 1, 1.5, 2, 3, 5, 7.5, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 125, 150, 200

Input Restrictions

As designed

This building descriptor is required for the static pressure or the brake horsepower methods.

Standard Design

Not applicable

Standard Design:

Existing Buildings

Exhaust Fan Design Static Pressure

Applicability

Any system with exhaust fans that uses the static pressure method

Definition

The design static pressure for exhaust fan system.

Units

Inches of water column (in. of water)

Input Restrictions

As designed. The design static pressure for the exhaust fan does not need to be specified if the exhaust fan brake horsepower (bhp) or power-per-unit flow is specified.

Standard Design

For healthcare facilities, same as the Proposed Design.

For kitchen exhaust fans, the static pressure is fixed at 2.5 in. of water. For lab exhaust fans, fan power is specified as W/cfm, so this input is not applicable.

For all other exhaust fans, the standard design fan static pressure shall be the same as the proposed design.

Standard Design:

Existing Buildings

Exhaust Fan Efficiency

Applicability

Any exhaust fan system that uses the static pressure method

Definition

The efficiency of the exhaust fan at rated capacity.

This is the static efficiency and does not include losses through the motor.

Units

Unitless

Input Restrictions

For kitchen exhaust fans, the fan efficiency is prescribed at 50 percent.

For all other exhaust fans, as designed. The exhaust fan efficiency does not need to be specified if the return fan brake horsepower (bhp) is specified.

Standard Design

For healthcare facilities, same as the Proposed Design.

For kitchen exhaust fans, the fan efficiency is 50 percent, while for lab exhaust it is 62 percent.

For all other exhaust fans, the standard design efficiency (and resulting W/cfm) is 65%

Standard Design:

Existing Buildings

Exhaust Fan Motor Efficiency

Applicability

All exhaust fan systems

Definition

The full-load efficiency of the motor serving the exhaust fan

Units

Unitless

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design.

For exempt process fans other than lab, kitchen, and garage exhaust fans, same as proposed. For all other fans, the value is taken from Table 11.

Standard Design:

Existing Buildings

Fan Part-Flow Power Curve

Applicability

All variable flow exhaust fan systems

Definition

A part-load power curve that represents the ratio full-load power draw of the exhaust fan as a function of the ratio full-load air flow.

Units

Unitless ratio

Input Restrictions

As designed

The default fan curve shall be selected from Appendix 5.7 for the type of fan specified in the proposed design.

Standard Design

For healthcare facilities, same as the proposed design. For all others, the standard design fan curve shall be selected from Appendix 5.7 for the type of fan specified in the proposed design.

Standard Design:

Existing Buildings

Exhaust Fan Power Index

Applicability

Exhaust systems serving high-rise residential units and hotel/motel guestrooms

Definition

The fan power of the exhaust fan per unit of flow.

This building descriptor is applicable only with the power-per-unit-flow method.

Units

W/cfm

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design.

For high-rise residential units and hotel/motel guestrooms, 0.58 W/cfm

Standard Design:

Existing Buildings

Garage Exhaust Fan Name

Applicability

All garage exhaust systems

Definition

A unique descriptor for each garage exhaust fan or fan system

Fans with equivalent efficiency and motor efficiencies may be combined and modeled as one fan.

Units

Text, unique

Input Restrictions

Where applicable, this should match the tags that are used on the plans.

Standard Design

The standard design shall have an exhaust system that corresponds to the proposed design. The name can be identical to that used for the proposed design or some other appropriate name may be used.

Standard Design:

Existing Buildings

Garage Exhaust Fan System Modeling Method

Applicability

All exhaust fan systems

Definition

Software commonly models fans in three ways, see definition for supply system modeling method.

Units

List power-per-unit-flow, static pressure, or brake horsepower

Input Restrictions

Brake horsepower method (fixed value)

Standard Design

The standard design building shall use the power-per-unit-flow method.

Standard Design:

Existing Buildings

Garage Exhaust Fan Rated Capacity

Applicability

All exhaust systems

Definition

The rated design air flow rate of the garage exhaust fan system

Units

Cfm

Input Restrictions

As designed

Standard Design

Same as proposed design

Standard Design:

Existing Buildings

Garage Exhaust Fan Control Method

Applicability

All exhaust fan systems

Definition

The control method for the garage exhaust fan.

This input determines the fan power for the exhaust fan. No other fan inputs are required.

Units

List constant volume or CO control

Input Restrictions

None.

If constant volume is selected, proposed fan power is as designed.

If CO control is selected, proposed fan power is 12.5 percent of the design fan power.

Standard Design

Same as proposed

Standard Design:

Existing Buildings

Duct Leakage Rate

Applicability

Any single-zone systems with ducts in unconditioned space serving zones of 5,000 ft² or less

Definition

The leakage rate from the duct system into unconditioned space.

All leakage is assumed to occur to unconditioned space (not to outdoors).

Units

Percentage of design airflow (%)

Input Restrictions

For new systems: If duct leakage testing is performed as per instructions in the Reference Appendices and certified by a Home Energy Rating System (HERS) rater or Acceptance Test Technician (ATT), as designed. If not tested, 15 percent.

For existing, altered systems: 15 percent if tested and verified by the HERS procedures in Reference Appendix NA2. If untested or if failed test, 20 percent.

Standard Design

Not applicable

Standard Design:

Existing Buildings

Duct Leakage HERS Fan Power Adjustment

Applicability

Single zone, constant volume systems with ducts in unconditioned space, serving 5000 ft²

Definition

A fan power penalty or credit based on the testing performed when ducts are in unconditioned spaces

Units

List:  Penalty, No Change Credit

Input Restrictions

Not a user input

Penalty:  if the HERS duct leakage testing isn’t done when required, or if the testing fails the duct leakage rate criteria

No Change:  testing not required

Credit:  testing not required, but HERS testing performed and leakage rates are verified

Standard Design

All in conditioned space

Standard Design:

Existing Buildings

Maximum Outside Air Ratio

Applicability

All systems with modulating outside air dampers

Definition

The descriptor is used to limit the maximum amount of outside air that a system can provide as a percentage of the design supply air. It is used where the installation has a restricted intake capacity.

Units

Ratio

Input Restrictions

1.0 for all systems above 54,000 Btu/h cooling capacity; 0.9 for other systems.

Standard Design

1.0 for all systems above 54,000 Btu/h cooling capacity; 0.9 for other systems

Standard Design:

Existing Buildings

Design Outside Air Flow

Applicability

All systems with outside air dampers

Definition

The rate of outside air that needs to be delivered by the system at design conditions. This input may be derived from the sum of the design outside air flow for each of the zones served by the system.

Units

Cfm

Input Restrictions

As designed but no lower than the ventilation rate of the standard design

Standard Design

For healthcare facilities, same as the Proposed Design.

For systems serving laboratory spaces, the system shall be 100 percent outside air.

Standard Design:

Existing Buildings

Outdoor Air Control Method

Applicability

All HVAC systems that deliver outside air to zones

Definition

The method of determining the amount of outside air that needs to be delivered by the system

Each of the zones served by the system report their outside air requirements on an hourly basis. The options for determining the outside air at the zone level are discussed above. This control method addresses how the system responds to this information on an hourly basis. Options include:

•      Average Flow - The outside air delivered by the system is the sum of the outside air requirement for each zone, without taking into account the position of the VAV damper in each zone. The assumption is that there is mixing between zones through the return air path.

Units

List (see above)

Input Restrictions

As designed

Standard Design

Average flow

Standard Design:

Existing Buildings

Economizer Control Type

Applicability

All systems with an air-side economizer

Definition

An air-side economizer increases outside air ventilation during periods when system cooling loads can be reduced from increased outside air flow. The control types include:

•      No economizer.

•      Fixed dry-bulb. The economizer is enabled when the temperature of the outside air is equal to or lower than temperature fixed setpoint (e.g., 75°F).

•      Differential dry-bulb. The economizer is enabled when the temperature of the outside air is lower than the return air temperature.

•      Differential enthalpy. The economizer is enabled when the enthalpy of the outside air is lower than the return air enthalpy.

•      Differential dry-bulb and enthalpy. The system shifts to 100 percent outside air or the maximum outside air position needed to maintain the cooling SAT setpoint, when the outside air dry-bulb is less than the return air dry-bulb AND the outside air enthalpy is less than the return air enthalpy. This control option requires additional sensors.

Units

List (see above)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

The control should be no economizer when the standard design total cooling capacity < 54,000 Btu/h and when the standard design cooling system is not a computer room air handling unit (CRAH). Otherwise, the standard design shall assume an integrated differential dry-bulb economizer.

An exception is that economizers shall not be modeled for systems serving high-rise residential or hotel/motel guestroom occupancies.

Standard Design:

Existing Buildings

Economizer Integration Level

Applicability

Airside economizers

Definition

This input specifies whether or not the economizer is integrated with mechanical cooling. It is up to the modeling software to translate this into software-specific inputs to model this feature. The input could take the following values:

•      Non-integrated - The system runs the economizer as the first stage of cooling. When the economizer is unable to meet the load, the economizer returns the outside air damper to the minimum position and the compressor turns on as the second stage of cooling.

•      Integrated - The system can operate with the economizer fully open to outside air and mechanical cooling active (compressor running) simultaneously, even on the lowest cooling stage.

Units

List (see above)

Input Restrictions

List non-integrated or integrated

Standard Design

I For healthcare facilities, same as the Proposed Design. For all others,

integrated for systems above capacity 54,000 Btu/h at Air-Conditioning, Heating, and Refrigeration Institute (AHRI) conditions

Standard Design:

Existing Buildings

Economizer High Temperature Lockout

Applicability

Systems with fixed dry-bulb economizer

Definition

The outside air setpoint temperature above which the economizer will return to minimum position

Units

Degrees Fahrenheit (°F)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Economizer Low Temperature Lockout

Applicability

Systems with air-side economizers

Definition

A feature that permits the lockout of economizer operation (return to minimum outside air position) when the outside air temperature is below the lockout setpoint.

Units

Degrees Fahrenheit (F°)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Economizer High Enthalpy Lockout

Applicability

Systems with differential enthalpy economizers

Definition

The outside air enthalpy above which the economizer will return to minimum position

Units

Btu/lb

Input Restrictions

As designed

The default is 28 Btu/lb (high altitude locations may require different setpoints.)  The compliance software shall apply a fixed offset and add 2 Btu/lb to the user-entered value.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

not applicable

Standard Design:

Existing Buildings

Cooling Source

Applicability

All systems

Definition

The source of cooling for the system; either chilled water, direct expansion (DX), or other

Units

List (see above)

Input Restrictions

As designed (determined automatically from system type)

Standard Design

The standard design cooling source is:

For built-up VAV (system 6) and CRAH (system 10): chilled water,

For heating and ventilation (system 9), none, and

For all other systems, direct expansion (DX)

shown in Table 33

Standard Design:

Existing Buildings

Same as proposed for unaltered

Gross Total Cooling Capacity

Applicability

All cooling systems

Definition

The total gross cooling capacity (both sensible and latent) of a cooling coil or packaged DX system at AHRI conditions. The building descriptors defined in this chapter assume that the fan is modeled separately, including any heat it adds to the air stream. The cooling capacity specified by this building descriptor should not consider the heat of the fan.

Units

Input Restrictions

NOT A USER INPUT

For packaged equipment that has the fan motor in the air stream such that it adds heat to the cooled air, the software shall calculate the net total cooling capacity as follows:

Q_{(t,net,rated)}=Q_{(t,gross,rated)}-Q_(fan,rated)

Where:

If the gross and net total cooling capacities at AHRI conditions are known, the fan heat at rated conditions is the difference between the two values. If the either the gross or net total cooling capacity is unknown, the fan heat at rated conditions shall be accounted for by using Equation 4:

Q_{(fan,rated) =} Q_{(t,gross,rated)} X 0.0415

Equation 4 is based on an AHRI rated fan power of 0.365 W/cfm, and a cooling airflow of 400 cfm/ton.

If the number of UMLH in the proposed design exceeds 150, the software shall warn the user to resize the equipment.

Standard Design

The gross total cooling capacity of the systems in the standard design is determined from the standard design net cooling capacity, and from applying the fan power rules above for adjusting for fan heat.

Standard Design:

Existing Buildings

Gross Sensible Cooling Capacity

Applicability

All cooling systems

Definition

The gross sensible cooling capacity of the coil or packaged equipment at AHRI conditions. The building descriptors defined in this chapter assume that the fan is modeled separately, including any heat it adds to the air stream. The cooling capacity specified by this building descriptor should be adjusted to calculate the net sensible cooling capacity, which includes the effect of fan motor heat.

The sensible heat ratio (SHR) used by some energy simulation tools can be calculated from the sensible cooling capacity and total cooling capacity:

SHR = sensible cooling capacity/total cooling capacity

Units

Btu/h

Input Restrictions

As designed.

For packaged equipment, the compliance software adjusts the user input of gross sensible cooling capacity to account for the effect of fan motor heat as follows:

Q_{(s,net,rated)} = Q_{(s,gross,rated)-}Q_(fan,rated)

Where:

If the number of UMLH in the proposed design exceeds 150, the software shall warn the user to resize the equipment.

Standard Design

The gross total cooling capacity of the systems serving the standard design is autosized by the compliance software, and then oversized by 15 percent. Sizing calculations shall be based on 0.5 percent design dry-bulb and mean coincident wet-bulb.

Standard Design:

Existing Buildings

Gross Total Cooling Capacity Curve

Applicability

All cooling systems

Definition

A curve that represents the available total cooling capacity as a function of cooling coil and/or condenser conditions. The common form of these curves is given as follows:

For air-cooled direct expansion:

For water-cooled direct expansion:

For chilled water coils:

Where:

Note: If an air-cooled unit employs an evaporative condenser, t_odb is the effective dry-bulb temperature of the air leaving the evaporative cooling unit.

Software may represent the relationship between cooling capacity and temperature in ways other than the equations given above.

Units

Data structure

Input Restrictions

As designed

The equations and coefficients given above are the default.

Standard Design

Use the default curves or equivalent data for other models

Standard Design:

Existing Buildings

Coil Latent Modeling Method

Applicability

All DX cooling systems

Definition

The method of modeling coil latent performance at part-load conditions

Units

List

Input Restrictions

One of the following values:

Bypass factor – used by DOE-2 based programs

NTU-effectiveness – used by EnergyPlus

Standard Design

Same as proposed

Standard Design:

Existing Buildings

Coil Bypass Factor

Applicability

All DX cooling systems using the bypass factor coil latent modeling method

Definition

The ratio of air that bypasses the cooling coil at design conditions to the total system airflow

Units

Ratio

Input Restrictions

Prescribed values defined in Appendix 5.7

Standard Design

Defaults

Standard Design:

Existing Buildings

Coil Bypass Factor Adjustment Curve

Applicability

All DX cooling systems using the bypass factor coil latent modeling method

Definition

Adjustments for the amount of coil bypass due to the following factors:

•      Coil airflow rate as a percentage of rated system airflow

•      Entering air wet-bulb temperature

•      Entering air dry-bulb temperature

•      Part load ratio

Units

Data structure

Input Restrictions

Where applicable, prescribed (fixed) simulation engine defaults based on HVAC system type. The following default values shall be used for the adjustment curves:

Where:

Standard Design

Defaults

Standard Design:

Existing Buildings

Cooling Capacity Airflow Adjustment Curve

Applicability

All DX cooling systems using the NTU effectiveness coil latent modeling method

Definition

Normalized curve that varies cooling capacity as a function of airflow, which affects system latent capacity

Units

Data structure

Input Restrictions

Where applicable, prescribed (fixed) simulation engine defaults based on HVAC system type. The following default values shall be used for the adjustment curves:

Where:

The curve takes the form:

With the coefficients defined in Appendix 5.7.

Standard Design

Use defaults as described above

Standard Design:

Existing Buildings

Direct Expansion Cooling Efficiency

Applicability

Packaged DX equipment

Definition

The cooling efficiency of a direct expansion (DX) cooling system at AHRI rated conditions as a ratio of output over input in Btu/h per W, excluding fan energy.

The abbreviation used for this full-load efficiency is Energy Efficiency Ratio (EER).

For all unitary and applied equipment where the fan energy is part of the equipment efficiency rating, the EER shall be adjusted as follows:

Where:

Units

Btu/h-W

Input Restrictions

As designed, except that the user-entered value must meet mandatory minimum requirements of Table 110.2-A, Table 110.2-B, Table 110.2-C, or Table 110.2-E for the applicable equipment type. When possible, specify the SEER and EER for packaged equipment with cooling capacity less than 65,000 Btu/h from manufacturer’s literature. For equipment with capacity above 65,000 Btu/h, specify EER.

Equipment subject to minimum efficiency requirements under the Appliance Efficiency Regulations (small packaged air conditioners and heat pumps with SEER ratings) must meet the applicable mandatory minimum efficiency requirements.

When EER is not available for packaged equipment with SEER ratings (AHRI cooling capacity of 65,000 Btu/h or smaller), it shall be calculated as follows:

The default EER shall be calculated by the equation above, but constrained to be no greater than 13.

Evaporative cooling systems that pass the requirements of the Western Cooling Challenge may be modeled with an EER as if the equipment were packaged unitary equipment. See Section 5.7.5.4.

Standard Design

Use the minimum cooling efficiency (EER) from tables in Tables 110.2-A, 110.2-B, and 110.2-E in Section 110.2 of the standards.

Standard Design:

Existing Buildings

Seasonal Energy Efficiency Ratio

Applicability

Packaged DX equipment with AHRI cooling capacity of 65,000 Btu/h or smaller

Definition

The seasonal cooling efficiency of a direct expansion (DX) cooling system at AHRI rated conditions as a ratio of output over input in Btu/h per W, excluding fan energy. The software must accommodate user input in terms of either the EER or the SEER. For equipment with SEER ratings, EER shall be taken from manufacturers’ data when it is available.

Units

Btu/h-W

Input Restrictions

As designed

This input is required for small DX systems. The Direct Expansion Cooling Efficiency input is optional for these systems.

Standard Design

Use the minimum SEER from the 2015 Appliance Efficiency Standards.

Standard Design:

Existing Buildings

Integrated Energy Efficiency Ratio

Applicability

Packaged DX equipment with AHRI cooling capacity of 65,000 Btu/h or greater

Definition

Integrated Energy Efficiency Ratio

This is a SEER that is a composite rating for a range of part-load conditions and different ambient conditions. The rating is determined according to AHRI procedures. Equipment with this rating is subject to mandatory minimum requirements.

This input is currently only used for mandatory minimum efficiency checks.

Units

Btu/h-W

Input Restrictions

As designed

If the IEER rating is below mandatory minimum required levels specified in Section 110.2 of the standards, the compliance run shall fail.

Standard Design

Not applicable

Standard Design:

Existing Buildings

Direct Expansion Cooling Efficiency Temperature Adjustment Curve

Applicability

Packaged DX equipment

Definition

A curve that varies the cooling efficiency of a direct expansion (DX) coil as a function of evaporator conditions, condenser conditions, and for small packaged equipment, part-load ratio.

For air-cooled DX systems:

For air-cooled DX systems:

For water-cooled DX systems:

Where:

Units

Data structure

Input Restrictions

User may input curves or use default curves. If defaults are overridden, the software must indicate that supporting documentation is required on the output forms.

For DX equipment with a capacity greater than 65,000 Btu/h, the user may not enter data on the temperature dependent equipment performance. However, the ACM compliance software vendor may work with manufacturers to collect such data and build this data into the ACM compliance software. The user may either select equipment for which the ACM compliance software vendor has collected or use the defaults.

Standard Design

For all systems except packaged DX units with cooling capacity <= 65,000 Btu/h, use default curves from Appendix 5.7. For packaged DX units with cooling capacity less than or equal to 65,000 Btu/h that have SEER ratings, the user inputs EER and SEER. The software generates the equipment performance curve based on the pre-defined performance curves specified in Appendix 5.7.

Standard Design:

Existing Buildings

Direct Expansion Part-Load Efficiency Adjustment Curve

Applicability

Packaged systems with DX cooling

Definition

A normalized performance adjustment curve to the rated efficiency (energy input ratio) that describes how the efficiency varies at part-load conditions. At a value of 1 (full load), the normalized efficiency is 1 (same as part-load conditions).

The default curves are given as follows as adjustments to the energy input ratio (EIR) :

This curve may take the form of a part-load factor (PLF) or EIR-FLPR, which is the fraction of time that the unit must run to meet the part-load for that hour. For example, at 40 percent of full load, the equipment might need to run 50 percent of the hour for cycling losses.

Note: For small packaged equipment with SEER ratings <65,000 Btu/h, the part-load efficiency curve is set to no degradation, since the part-load degradation is built into the direct expansion cooling efficiency temperature adjustment curve.

Default curves are provided for the different major classes of equipment. Where:

Units

Coefficients (three for a quadratic, or up to four for a cubic)

Input Restrictions

The coefficients should sum to 1 (within a small tolerance). This corresponds to a curve output of 1 for an input of 1.

Standard Design

The standard design part-load efficiency adjustment curves are shown in the tables below.

Standard Design:

Existing Buildings

Number of Cooling Stages

Applicability

Single zone VAV systems and DX systems with multiple stages

Definition

This applies to single zone VAV and any HVAC systems with multiple compressors or multiple discrete stages of cooling. This system is a packaged unit with multiple compressors and a two-speed or variable-speed fan. Systems with unequally sized compressors may have additional cooling stages.

Units

None (Integer)

Input Restrictions

As designed

Standard Design

The standard design shall be two for the single zone VAV baseline and packaged VAV baseline.

Standard Design:

Existing Buildings

Total Cooling Capacity Ratio by Stage

Applicability

Single zone VAV systems and DX systems with multiple stages

Definition

This provides the total cooling capacity of each cooling stage, at AHRI rated conditions. The capacity is expressed as an array, with each entry a fraction of the total rated cooling capacity for the unit. For example, if the stage cooling capacity is 4 tons (48,000 Btu/h) and the total cooling capacity is 8 tons (96,000 Btu/h), the capacity is expressed as “0.50” for that stage.

Units

Array of fractions

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

The default shall be (0.50, 1) for the single zone VAV baseline.

Standard Design:

Existing Buildings

Condenser Type

Applicability

All direct expansion systems including heat pumps

Definition

The type of condenser for a DX cooling system

The choices are:

•      Air-cooled

•      Water-cooled

•     

Units

List (see above)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Based on the prescribed system type

Refer to the HVAC System Map in section 5.7.1. Air-cooled for systems 1 (SZAC), 3, (PSZ), 5 (PVAV) and 11 (CRAC). Not applicable for other standard design systems.

Standard Design:

Existing Buildings

Supplementary DX Cooling Unit

Applicability

Required when no cooling system is specified, or when a zone has excessive unmet load hours

Definition

The specification of a supplementary DX cooling system that must be used when the user-defined cooling system results in unmet load hours exceeding 150 for any zone.

Units

List

Input Restrictions

The compliance software shall define the following prescribed system characteristics:

Cooling Capacity (Btu/h) – Autosized by software

Efficiency - minimum efficiency from Table 110.2-A, based on cooling capacity and assuming 3-phase

System airflow – Autosized by software

Economizer - none

Design supply air temperature - 55°F

Supply air temperature control - None

Design heating supply air temperature - 95°F

Standard Design

Not applicable

Standard Design:

Existing Buildings

Evaporative Cooling Type

Applicability

Systems with evaporative cooling

Definition

The type of evaporative pre-cooler, including:

•      None

•      Non-integrated direct

•      Non-integrated indirect

•      Non-integrated direct/Indirect

•      Integrated direct

•      Integrated indirect

•      Integrated direct/indirect

An integrated cooler can operate together with compressor or CHW cooling. A non-integrated cooler will shut down the evaporative cooling whenever it is unable to provide 100 percent of the cooling required.

Direct evaporative cooling can only be applied to the outside air. Indirect evaporative cooling can be applied to outside air or return air.

Units

None

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Evaporative Cooling System Capacity

Applicability

Systems with evaporative cooling

Definition

The total sensible cooling capacity of the evaporative cooling system at design outdoor dry-bulb conditions. This value may be derived from other inputs of supply fan design air rated capacity (Section 5.7.3), direct stage effectiveness, indirect stage effectiveness, and design outdoor conditions.

Units

None

Input Restrictions

Not applicable

Derived input. If there are excessive unmet load hours in any zone served by the evaporative cooling system, a supplementary DX cooling unit must be defined by the user. See Section 5.7.5.2.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design: Existing Buildings

Direct Stage Effectiveness

Applicability

Systems with evaporative cooling

Definition

The effectiveness of the direct stage of an evaporative cooling system. Effectiveness is defined as:

Where:

Units

Numeric (0 ≤ EFF ≤1)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Indirect Stage Effectiveness

Applicability

Systems with evaporative cooling

Definition

The effectiveness of the indirect stage of an evaporative cooling system. Effectiveness is defined as:

Where:

Units

Numeric (0 ≤ EFF ≤1)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Evaporative Cooling Performance Curves

Applicability

Systems with evaporative cooling

Definition

A curve that varies the evaporative cooling effectiveness as a function of primary air stream airflow. The default curves are given as:

Where:

Units

Data structure

Input Restrictions

User may input \curves or use default curves. If defaults are overridden, the software must indicate that supporting documentation is required on the output forms.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Auxiliary Evaporative Cooling Power

Applicability

Systems with evaporative cooling

Definition

The auxiliary energy of the indirect evaporative cooler fan, and the pumps for both direct and indirect stages

Units

Watts

Input Restrictions

As designed

Standard Design

Not applicable

Standard Design:

Existing Buildings

Capacity Control Method

Applicability

Four-pipe fan coil systems

Definition

The control method for the fan coil unit at the zone.

The following choices are available:

•      Constant Fan Variable Flow

•      Cycling Fan

•      Variable Fan Constant Flow

•      Variable Fan Variable Flow

Units

List (with choices above)

Input Restrictions

Not a user input. It comes from building descriptors for fan control and chiller loop flow control

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Cycling Fan

Standard Design:

Existing Buildings

Rated Gross Capacity

Applicability

Four-pipe fan coil systems and chilled beams

Definition

The gross cooling capacity of the cooling coil

Units

Input Restrictions

None

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Cooling Coil Design Flow rate

Applicability

Four-pipe fan coil systems and chilled beams

Definition

The design flow rate of the cooling coil

Units

Gallons per minute (gpm)

Input Restrictions

None

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Chilled Beam Name

Applicability

Chilled beams

Definition

A unique name designating the chilled beam

Units

None

Input Restrictions

None

Standard Design

For healthcare facilities, same as the proposed design. For all others, not applicable

Standard Design:

Existing Buildings

Chilled Beam Type

Applicability

Chilled beams

Definition

Specification of the beam as active or passive

Units

List:

•      Active

•      Passive

Input Restrictions

None

Standard Design

For healthcare facilities, same as the proposed design. For all others, not applicable

Standard Design:

Existing Buildings

Design Cooling Capacity

Applicability

Chilled beams

Definition

The designed cooling capacity of the chilled beam

Units

Input Restrictions

None

Standard Design

For healthcare facilities, same as the Proposed Design. For all others,

Not applicable

Standard Design:

Existing Buildings

Design Chilled Water Temperature

Applicability

Chilled beams

Definition

The minimum supplied chilled water temperature to the beam.

This is typically at least 2°F higher than the space dewpoint temperature at design conditions, to prevent condensation.

Units

°F

Input Restrictions

None

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Maximum Chilled Water Temperature

Applicability

Chilled beams

Definition

The maximum supplied chilled water temperature to the beam. This allows for chilled water temperature reset at the source.

Units

°F

Input Restrictions

Should be equal to or greater than the design chilled water temperature

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Active Beam Maximum Primary Flow Rate

Applicability

Chilled beams

Definition

The design flow rate of the active fan

Units

Cfm

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Active Beam Induced Air Rate

Applicability

Active chilled beams

Definition

The rate at which induced air is drawn through the chilled beam.

The total airflow across the beam is the sum of the maximum primary flow rate and the active beam induced air flow rate.

Units

Cfm

Input Restrictions

None

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Active Fan Static Pressure

Applicability

Chilled beams

Definition

The design status of the active fan

Units

in. of water

Input Restrictions

None

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Active Fan Static Efficiency

Applicability

Chilled beams

Definition

The fan static efficiency

Units

in. of water

Input Restrictions

Between 0 and 1

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Active Fan Motor Efficiency

Applicability

Chilled beams

Definition

The motor efficiency of the fan

Units

in. of water

Input Restrictions

None

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Chilled Beam Heating Capacity

Applicability

Chilled beams

Definition

The heating capacity of the chilled beam

Units

Btu/h

Input Restrictions

None; defaults to 1 if no heating

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Chilled Beam Heating Source

Applicability

Chilled beams

Definition

Defaults to electric resistance, whether there is heating provided by the beam or not

Units

None

Input Restrictions

Electric resistance

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Heating Source

Applicability

All systems that provide heating

Definition

The source of heating for the heating and preheat coils

The choices are:

•      Hot water

•      Electric resistance

•      Electric heat pump

•      Gas furnace

•      Oil furnace

Units

List (see above)

Input Restrictions

As designed

Standard Design

Based on the prescribed system type. Refer to the HVAC system map in Section 5.1.2. The heat source is:

For system types 5 (packaged VAV), 6 (built-up VAV):  hot water;

For system types 1 (SZAC), 7 (SZVAV) and 9 (Heat Vent): Gas Furnace

For system type 3: (PSZ): gas or oil furnace

Standard Design:

Existing Buildings

Same as proposed if unaltered

Heating Coil Capacity

Applicability

All systems with a heating coil

Definition

The heating capacity of a heating coil at AHRI conditions

Units

Input Restrictions

As designed

The user may need to manually adjust the capacity if the number of unmet load hours exceeds 150.

Standard Design

Autosize with a heating oversizing factor of 25 percent. If the number of unmet load hours for the standard design exceeds 150, increase the heating coil capacity as indicated in Section 2.6.2.

Standard Design:

Existing Buildings

Furnace Capacity

Applicability

Systems with a furnace

Definition

The full load heating capacity of the unit

Units

Input Restrictions

As designed

The user may need to manually adjust the capacity if the number of unmet load hours exceeds 150.

Standard Design

Autosize with an oversizing factor of 25 percent (let the software determine heating capacity based on the building loads). If the number of unmet load hours for the standard design exceeds 150, increase the furnace capacity as indicated in Section 2.4 and 2.6.2

Standard Design:

Existing Buildings

Furnace Fuel Heating Efficiency

Applicability

Systems with a furnace

Definition

The full load thermal efficiency of either a gas or oil furnace at design conditions. The software must accommodate input in either thermal efficiency (Et) or annual fuel utilization efficiency (AFUE). Where AFUE is provided, Et shall be calculated as:

Where:

Units

Fraction

Input Restrictions

As designed

Standard Design

Look up the requirement from the equipment efficiency tables in Table 6.8.1E of the Appliance Efficiency Standards. The standard design efficiency requirement is located in Table E-3 or Table E-4 of the Appliance Efficiency Standards. Use the heating input of the standard design system to determine the size category.

Standard Design:

Existing Buildings

Furnace Fuel Heating Part Load Efficiency Curve

Applicability

Systems with a furnace

Definition

An adjustment factor that represents the percentage of full load fuel consumption as a function of the percentage full load capacity. This curve shall take the form of a quadratic equation as follows:

Where:

Units

Data structure

Input Restrictions

Standard Design

Fixed

Standard Design:

Existing Buildings

Furnace Fuel Heating Pilot

Applicability

Systems that use a furnace for heating

Definition

The fuel input for a pilot light on a furnace

Units

Btu/h

Input Restrictions

As designed

Standard Design

Zero (pilotless ignition)

Standard Design:

Existing Buildings

Furnace Fuel Heating Fan/Auxiliary

Applicability

Systems that use a furnace for heating

Definition

The fan energy in forced draft furnaces and the auxiliary (pumps and outdoor fan) energy in fuel-fired heat pumps

Units

Kilowatts (kW)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Electric Heat Pump Heating Capacity

Applicability

All heat pumps

Definition

The full load heating capacity of the unit, excluding supplemental heating capacity at AHRI rated conditions

Units

Input Restrictions

As designed

Standard Design

Autosize and use an oversizing factor of 25 percent. The software determines heating capacity based on the building loads.

Standard Design:

Existing Buildings

Electric Heat Pump Supplemental Heating Source

Applicability

All heat pumps

Definition

The auxiliary heating source for a heat pump heating system

The common control sequence is to lock out the heat pump compressor when the supplemental heat is activated. Other building descriptors may be needed if this is not the case. Choices for supplemental heat include:

•      Electric resistance

•      Gas furnace

•      Oil furnace

•      Hot water

•      Other

Units

List (see above)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Electric resistance

Standard Design:

Existing Buildings

Electric Heat Pump Heating Efficiency

Applicability

All heat pumps

Definition

The heating efficiency of a heat pump at AHRI rated conditions as a dimensionless ratio of output over input. The software must accommodate user input of either the coefficient of performance (COP) or the heating season performance factor (HSPF). Where HSPF is provided, COP shall be calculated as:

For all unitary and applied equipment where the fan energy is part of the equipment efficiency rating, the COP shall be adjusted as follows to remove the fan energy:

Where:

Units

Unitless

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Electric Heat Pump Heating Capacity Adjustment Curve(s)

Applicability

All heat pumps

Definition

A curve or group of curves that represent the available heat-pump heating capacity as a function of evaporator and condenser conditions. The default curves are given as:

For air-cooled heat pumps:

For water-cooled heat pumps:

Where:

Units

Data structure

Input Restrictions

Fixed. Use curves in Appendix 5.7 for water-source or air-source heat pumps as appropriate.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Electric Heat Pump Heating Efficiency Adjustment Curve(s)

Applicability

All heat pumps

Definition

A curve or group of curves that varies the heat pump heating efficiency as a function of evaporator conditions, condenser conditions and part-load ratio. The default curves are given as:

Air-Source Heat Pumps:

Water-Source Heat Pumps:

Where:

Units

None

Input Restrictions

Fixed from appropriate curve from Appendix 5.7

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Electric Heat Pump Supplemental Heating Capacity

Applicability

All heat pumps

Definition

The design heating capacity of a heat pump supplemental heating coil at AHRI conditions

Units

Btu/h

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Electric Supplemental Heating Control Temp

Applicability

All heat pumps

Definition

The outside dry-bulb temperature below which the heat pump supplemental heating is allowed to operate

Units

Degrees Fahrenheit (°F)

Input Restrictions

As designed; default to 40°F

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Heat Pump Compressor Minimum Operating Temp

Applicability

All heat pumps

Definition

The outside dry-bulb temperature below which the heat pump compressor is disabled

Units

Degrees Fahrenheit (°F)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Coil Defrost

Applicability

Air-cooled electric heat pump

Definition

The defrost control mechanism for an air-cooled heat pump

The choices are:

•      Hot-gas defrost, on-demand

•      Hot-gas defrost, timed 3.5 minute cycle

•      Electric resistance defrost, on-demand

•      Electric resistance defrost, timed 3.5 minute cycle

Defrost shall be enabled whenever the outside air dry-bulb temperature drops below 40°F.

Units

List (see above)

Input Restrictions

Default to use hot-gas defrost, timed 3.5 minute cycle. User may select any of the above.

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Coil Defrost kW

Applicability

Heat pumps with electric resistance defrost

Definition

The capacity of the electric resistance defrost heater

Units

Kilowatts (kW)

Input Restrictions

As designed; defaults to 0 if nothing is entered

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Crank Case Heater kW

Applicability

All heat pumps

Definition

The capacity of the electric resistance heater in the crank case of a direct expansion (DX) compressor. The crank case heater operates only when the compressor is off.

Units

Kilowatts (kW)

Input Restrictions

As designed; defaults to 0.1 if nothing is entered

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Crank Case Heater Shutoff Temperature

Applicability

All heat pumps

Definition

The outdoor air dry-bulb temperature above which the crank case heater is not permitted to operate

Units

Degrees Fahrenheit (°F)

Input Restrictions

As designed; defaults to 50°F

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Recovery Type

Applicability

All systems with airside heat recovery

Definition

The type of heat recovery system

Units

List: sensible, latent, or total (sensible and latent)

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Exhaust Air Sensible Heat Recovery Effectiveness

Applicability

Any system with outside air heat recovery

Definition

The effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams. Effectiveness is defined as:

Where:

Units

Two unitless numbers (ratio between 0 and 1), separate for cooling and heating

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Exhaust Air Sensible Part-Load Effectiveness

Applicability

Any system with outside air heat recovery

Definition

The effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams at 75 percent of design airflow. Effectiveness is defined as:

Where:

Units

Two unitless numbers (ratio between 0 and 1), separate for cooling and heating

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Exhaust Air Latent Heat Recovery Effectiveness

Applicability

Any system with outside air enthalpy heat recovery

Definition

The latent heat recovery effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams. Effectiveness is defined as:

Where:

Note: For sensible heat exchangers, this term is not applicable.

Units

Two unitless numbers (ratio between 0 and 1), separate for cooling and heating

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Exhaust Air Latent Part-Load Effectiveness

Applicability

Any system with outside air enthalpy heat recovery

Definition

The latent heat recovery effectiveness of an air-to-air heat exchanger between the building exhaust and entering outside air streams at 75 percent of design airflow. Effectiveness is defined as:

Where:

Note: For sensible heat exchangers, this term is not applicable.

Units

Two unitless numbers (ratio between 0 and 1), separate for cooling and heating

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings

Economizer Enabled during Heat Recovery

Applicability

All systems with airside heat recovery

Definition

A flag to indicate whether or not the economizer is enabled when heat recovery is active

Units

Boolean

Input Restrictions

As designed

Standard Design

For healthcare facilities, same as the Proposed Design. For all others, Not applicable

Standard Design:

Existing Buildings