SECTION 140.4 – PRESCRIPTIVE REQUIREMENTS FOR SPACE CONDITIONING SYSTEMS

A building complies with this section by being designed with and having constructed and installed a space-conditioning system that meets the applicable requirements of Subsections (a) through (m).

(a)  Sizing and Equipment Selection.  

Mechanical heating and mechanical cooling equipment shall be the smallest size, within the available options of the desired equipment line, necessary to meet the design heating and cooling loads of the building, as calculated according to Subsection (b).

EXCEPTION 1 to Section 140.4(a): Where it can be demonstrated to the satisfaction of the enforcing agency that oversizing will not increase building TDV energy use.

EXCEPTION 2 to Section 140.4(a): Standby equipment with controls that allow the standby equipment to operate only when the primary equipment is not operating.

EXCEPTION 3 to Section 140.4(a): Multiple units of the same equipment type, such as multiple chillers and boilers, having combined capacities exceeding the design load, if they have controls that sequence or otherwise optimally control the operation of each unit based on load.

(b) Calculations.

In making equipment sizing calculations under Subsection (a), all of the following rules shall apply:

1.   Methodology. The methodologies, computer programs, inputs, and assumptions approved by the Commission shall be used.

2.   Heating and cooling loads. Heating and cooling system design loads shall be determined in accordance with the procedures described in the ASHRAE Handbook, Fundamentals Volume, or as specified in a method approved by the Commission.

3.   Indoor design conditions. Indoor design temperature and humidity conditions for general comfort applications shall be determined in accordance with ASHRAE Standard 55 or the ASHRAE Handbook, Fundamentals Volume, Chapter 8, except that winter humidification and summer dehumidification shall not be required.

4.   Outdoor design conditions. Outdoor design conditions shall be selected from Reference Joint Appendix JA2, which is based on data from the ASHRAE Climatic Data for Region X. Heating design temperatures shall be no lower than the Heating Winter Median of Extremes values. Cooling design temperatures shall be no greater than the 0.5 percent Cooling Dry Bulb and Mean Coincident Wet Bulb values.

EXCEPTION to Section 140.4(b)4: Cooling design temperatures for cooling towers shall be no greater than the 0.5 percent Cooling Design Wet bulb values.

5.   Ventilation. Outdoor air ventilation loads shall be calculated using the ventilation rates required in Section 120.1.

6.   Envelope’. Envelope heating and cooling loads shall be calculated using envelope characteristics, including square footage, thermal conductance, solar heat gain coefficient or shading coefficient, and air leakage, consistent with the proposed design.

7.   Lighting. Lighting loads shall be based on actual design lighting levels or power densities as specified in Section 140.6.

8.   People. Occupant density shall be based on the expected occupancy of the building and shall be the same as determined under Section 120.1(b)2B, if used. Sensible and latent heat gains shall be as listed’ in the 2005 ASHRAE Handbook- Fundamentals, Chapter 30, Table 1.

9.   Process’ loads. Loads caused by a process shall be based upon actual information on the intended use of the building.

10.  Miscellaneous equipment. Equipment loads other than process loads shall be calculated using design data compiled from one or more of the following sources:

A.   Actual information based on the intended use of the building; or

B.   Published data from manufacturer's technical publications or from technical societies, such as the ASHRAE Handbook, Applications Volume; or

C.   Other data based on the designer's experience of expected loads and occupancy patterns.

11.  Internal heat gains. Internal heat gains may be ignored for heating load calculations.

12.  Safety factor. Design loads may be increased by up to 10 percent to account for unexpected loads or changes in space usage.

13.  Other loads. Loads such as warm-up or cool-down shall be calculated from principles based on the heat capacity of the building and its contents, the degree of setback, and desired recovery time; or may be assumed to be no more than 30 percent for heating and 10 percent for cooling of the steady-state design loads. 'In addition’, the steady-state load may include a safety factor in accordance with Section 140.4(b)12.

(c)  Power Consumption of Fans.

Each fan system used for space conditioning shall meet the requirements of Items 1, 2, 3 and 4 below.  Total fan system power demand equals the sum of the power demand of all fans in the system that are required to operate at design conditions in order to supply air from the heating or cooling source to the conditioned space, and to return it back to the source or to exhaust it to the outdoors; however, total fan system power demand need not include (i) the additional power demand caused solely by air treatment or filtering systems with final pressure drops more than 245 pascals or one-inch water column (only the energy accounted for by the amount of pressure drop that is over 1 inch may be excluded), or (ii) fan system power caused solely by exempt process loads.

1.   Constant volume fan systems. The total fan power index at design conditions of each fan system with total horsepower over 25 hp shall not exceed 0.8 watts per cfm of supply air.

2.   Variable air volume (VAV) systems.

A.   The total fan power index at design conditions of each fan system with total horsepower over 25 hp shall not exceed 1.25 watts per cfm of supply air; and

B.   Static Pressure Sensor Location. Static pressure sensors used to control variable air volume fans shall be placed in a position such that the controller set point is no greater than one-third the total design fan static pressure, except for systems with zone reset control complying with Section140.4(c)2C. If this results in the sensor being located downstream of any major duct split, multiple sensors shall be installed in each major branch with fan capacity controlled to satisfy the sensor furthest below its setpoint; and

C.   Setpoint Reset. For systems with direct digital control of individual zone boxes reporting to the central control panel, static pressure setpoints shall be reset based on the zone requiring the most pressure; i.e., the set point is reset lower until one zone damper is nearly wide open.

3.   Air-treatment or filtering systems. For systems with air-treatment or filtering systems, calculate the total adjusted fan power index using Equation 140.4-A:

Equation 140.4-A Adjusted TOTAL Fan Power Index

 Adjusted total fan power index = Fan power index  x  Fan Adjustment

Fan Adjustment =

WHERE:

4.   Fractional HVAC Motors for Fans. HVAC motors for fans that are less than1 hp and 1/12 hp or greater shall be electronically-commutated motors or shall have a minimum motor efficiency of 70 percent when rated in accordance with NEMA Standard MG 1-2006 at full load rating conditions. These motors shall also have the means to adjust motor speed for either balancing or remote control.  Belt-driven fans may use sheave adjustments for airflow balancing in lieu of a varying motor speed.

EXCEPTION 1 to Section 140.4(c)4: Motors in fan-coils and terminal units that operate only when providing heating to the space served.

EXCEPTION 2 to Section 140.4(c)4: Motors in space conditioning equipment certified under Section 110.1 or 110.2.

(d) Space-conditioning Zone Controls.   

Each space-conditioning zone shall have controls that prevent:

1.   Reheating; and

2.   Recooling; and

3.   Simultaneous provisions of heating and cooling to the same zone, such as mixing or simultaneous supply of air that has been previously mechanically heated and air that has been previously cooled either by cooling equipment or by economizer systems.

EXCEPTION 1 to Section 140.4(d): Zones served by variable air-volume systems that are designed and controlled to reduce, to a minimum, the volume of reheated, recooled, or mixed air are allowed only if the controls meet all of the following requirements:

A.   For each zone with direct digital controls (DDC):

i.    The volume of primary air that is reheated, recooled or mixed air supply shall not exceed the larger of:

a.   50 percent of the peak primary airflow; or

b.   The design zone outdoor airflow rate per Section 120.1.

ii.    The volume of primary air in the deadband shall not exceed the larger of:

a.   20 percent of the peak primary airflow; or

b.   The design zone outdoor airflow rate per Section 120.1.

iii.   The first stage of heating consists of modulating the zone supply air temperature setpoint up to a maximum setpoint no higher than 95ºF while the airflow is maintained at the dead band flow rate.

iv.   The second stage of heating consists of modulating the airflow rate from the dead band flow rate up to the heating maximum flow rate.

B.   For each zone without DDC, the volume of primary air that is reheated, re-cooled, or mixed air supply shall not exceed the larger of the following:

i.    30 percent of the peak primary airflow; or

ii.    The design zone outdoor airflow rate per Section 120.1.

EXCEPTION 2 to Section 140.4(d): Zones with special pressurization relationships or cross-contamination control needs.

EXCEPTION 3 to Section 140.4(d): Zones served by space-conditioning systems in which at least 75 percent of the energy for reheating, or providing warm air in mixing systems, is provided from a site-recovered or site-solar energy source.

EXCEPTION 4 to Section 140.4(d): Zones in which specific humidity levels are required to satisfy exempt process loads. Computer Rooms or other spaces where the only process load is from IT equipment may not use this exception.

EXCEPTION 5 to Section 140.4(d): Zones with a peak supply-air quantity of 300 cfm or less.

(e)  Economizers.  

1.   Each cooling fan system that has a design total mechanical cooling capacity over 54,000 Btu/hr shall include either:

A.   An air economizer capable of modulating outside-air and return-air dampers to supply 100 percent of the design supply air quantity as outside-air; or

B.   A water economizer capable of providing 100 percent of the expected system cooling load as calculated in accordance with a method approved by the Commission, at outside air temperatures of 50°F dry-bulb and 45°F wet-bulb and below.

EXCEPTION 1 to Section 140.4(e)1: Where special outside air filtration and treatment, for the reduction and treatment of unusual outdoor contaminants, makes compliance infeasible.

EXCEPTION 2 to Section 140.4(e)1: Where the use of outdoor air for cooling will affect other systems, such as humidification, dehumidification, or supermarket refrigeration systems, so as to increase overall building TDV energy use.

EXCEPTION 3 to Section 140.4(e)1: Systems serving high-rise residential living quarters and hotel/motel guest rooms.

EXCEPTION 4 to Section 140.4(e)1: Where comfort cooling systems have the cooling efficiency that meets or exceeds the cooling efficiency improvement requirements in TABLE 140.4-A.

EXCEPTION 5 to Section 140.4(e)1: Fan systems primarily serving computer room(s). See Section 140.9(a) for computer room economizer requirements.

TABLE 140.4-A   ECONOMIZER TRADE-OFF TABLE FOR COOLING SYSTEMS

2.   If an economizer is required by Section 140.4(e)1 it shall be:

A.   Designed and equipped with controls so that economizer operation does not increase the building heating energy use during normal operation; and

EXCEPTION to Section 140.4(e)2A: Systems that provide 75 percent of the annual energy used for mechanical heating from site-recovered energy or a site-solar energy source.

B.   Capable of providing partial cooling even when additional mechanical cooling is required to meet the remainder of the cooling load.

3.   If an economizer is required by Section 140.4(e),and an air economizer is used to meet the requirement, then it  shall be a type 'listed in, and shall have high limit shutoff controls complying with TABLE 140.4-B,

TABLE 140.4-B  AIR ECONOMIZER HIGH LIMIT SHUT OFF CONTROL REQUIREMENTS

4.   If an economizer is required by Section 140.4(e)1, and an air economizer is used to meet the requirement, then the air economizer, and all return air dampers on any individual cooling fan system that has a total mechanical cooling capacity over 54,000 Btu/hr shall have the following features:

A.   Warranty. 5-year Manufacturer warranty of economizer assembly.

B.   Damper reliability testing. Suppliers of economizers shall certify that the economizer assembly, including but not limited to outdoor air damper, return air damper, drive linkage, and actuator, have been tested and are able to open and close against the rated airflow and pressure of the system after 60,000 damper opening and closing cycles.

C.   Damper leakage. Economizer and return dampers shall be certified to have a maximum leakage rate of 10 cfm/sf at 1.0 in. w.g. when tested in accordance with AMCA Standard 500.

D.   Adjustable setpoint. If the high-limit control is fixed dry-bulb or fixed enthalpy + fixed dry-bulb then the control shall have an adjustable setpoint.

E.   Sensor accuracy. Outdoor air, return air, mixed air, and supply air sensors shall be calibrated within the following accuracies. 

i.    Drybulb and wetbulb temperatures accurate to ±2°F over the range of 40°F to 80°F.

ii.    Enthalpy accurate to ±3 Btu/lb over the range of 20 Btu/lb to 36 Btu/lb.

iii.   Relative humidity (RH) accurate to ±5 percent over the range of 20percent to 80 percent RH.

F.   Sensor calibration data. Data used for control of the economizer shall be plotted on a sensor performance curve.

G.   Sensor high limit control. Sensors used for the high limit control shall be located to prevent false readings, including but not limited to being properly shielded from direct sunlight.

H.   Relief air system. Relief air systems shall be capable of providing 100 percent outside air without over-pressurizing the building.

5.   Systems that include an air economizer to meet Section 140.4(e)1 shall include the following:

A.   Unit controls shall have mechanical capacity controls interlocked with economizer controls such that the economizer is at 100 percent open position when mechanical cooling is on and does not begin to close until the leaving air temperature is less than 45^oF.

B.   Direct Expansion (DX) units that control the capacity of the mechanical cooling directly based on occupied space temperature shall have a minimum of 2 stages of mechanical cooling capacity, per the following effective dates:

i.    ≥ 75,000 Btu/hr – Effective 1/1/2014

ii.    ≥ 65,000 Btu/hr – Effective 1/1/2016

C.   Effective 1/1/2014, DX units not within the scope of Section 140.4(e)5,B, such as those that control space temperature by modulating the airflow to the space, shall (i) comply with the requirements in Table 140.4 C, and (ii) shall have controls that do not false load the mechanical cooling system by limiting or disabling the economizer or by any other means, such as hot gas bypass, except at the lowest stage of mechanical cooling capacity.

TABLE 140.4-C  DIRECT EXPANSION (DX) UNIT REQUIREMENTS FOR COOLING STAGES
AND COMPRESSOR DISPLACEMENT

(f)  Supply Air Temperature Reset Controls.  

Space-conditioning systems supplying heated or cooled air to multiple zones shall include controls that automatically reset supply-air temperatures.  Air distribution systems serving zones that are likely to have constant loads, such as interior zones, shall be designed for the air flows resulting from the fully reset supply air temperature.  Supply air temperature reset controls shall be:

1.   In response to representative building loads or to outdoor air temperature; and

2.   At least 25 percent of the difference between the design supply-air temperature and the design room air temperature.

EXCEPTION 1 to Section 140.4(f): Systems that meet the requirements of Section 140.4(d), without using Exception 1 or 2 to that section.

EXCEPTION 2 to Section 140.4(f): Where supply-air temperature reset would increase overall building energy use.

EXCEPTION 3 to Section 140.4(f): Systems supplying zones in which specific humidity levels are required to satisfy exempt process loads. Computer Rooms or other spaces with only IT equipment may not use this exception.

(g) Electric Resistance Heating.  

Electric resistance heating systems shall not be used for space heating.

EXCEPTION 1 to Section 140.4(g): Where an electric-resistance heating system supplements a heating system in which at least 60 percent of the annual energy requirement is supplied by site-solar or recovered energy.

EXCEPTION 2 to Section 140.4(g): Where an electric-resistance heating system supplements a heat pump heating system, and the heating capacity of the heat pump is more than 75 percent of the design heating load calculated in accordance with Section 140.4(a)at the design outdoor temperature specified in Section 140.4(b)4.

EXCEPTION 3 to Section 140.4(g): Where the total capacity of all electric-resistance heating systems serving the entire building is less than 10 percent of the total design output capacity of all heating equipment serving the entire building.

EXCEPTION 4 to Section 140.4(g): Where the total capacity of all electric-resistance heating systems serving the entire building, excluding those allowed under Exception 2, is no more than 3 kW.

EXCEPTION 5 to Section 140.4(g): Where an electric resistance heating system serves an entire building that is not a high-rise residential or hotel/motel building; and has a conditioned floor area no greater than 5,000 square feet; and has no mechanical cooling; and is in an area where natural gas is not currently available and an extension of a natural gas system is impractical, as determined by the natural gas utility.

(h) Heat Rejection Systems.  

1.   Scope. Subsection 140.4(h) applies to heat rejection equipment used in comfort cooling systems such as air-cooled condensers, open cooling towers, closed-circuit cooling towers, and evaporative condensers.

2.   Fan Speed Control. Each fan powered by a motor of 7.5 hp (5.6 kW) or larger shall have the capability to operate that fan at 2/3 of full speed or less, and shall have controls that automatically change the fan speed to control the leaving fluid temperature or condensing temperature or pressure of the heat rejection device.

EXCEPTION 1 to Section 140.4(h)2: Heat rejection devices included as an integral part of the equipment 'listed’ in TABLE 110.2-A through TABLE 110.2-I.

EXCEPTION 2 to Section 140.4(h)2: Condenser fans serving multiple refrigerant circuits.

EXCEPTION 3 to Section 140.4(h)2: Condenser fans serving flooded condensers.

EXCEPTION 4 to Section 140.4(h)2: Up to one third of the fans on a condenser or tower with multiple fans where the lead fans comply with the speed control requirement.

3.   Tower Flow Turndown. Open cooling towers configured with multiple condenser water pumps shall be designed so that all cells can be run in parallel with the larger of:

A.   The flow that is produced by the smallest pump; or

B.   50 percent of the design flow for the cell.

4.   Limitation on Centrifugal Fan Cooling Towers. Open cooling towers with a combined rated capacity of 900 gpm and greater at 95°F condenser water return, 85°F condenser water supply, and 75°F outdoor wet-bulb temperature, shall use propeller fans and shall not use centrifugal fans.

EXCEPTION 1 to Section 140.4(h)4: Cooling towers that are ducted (inlet or discharge) or have an external sound trap that requires external static pressure capability.

EXCEPTION 2 to Section 140.4(h)4: Cooling towers that meet the energy efficiency requirement for propeller fan towers in Section 110.2, TABLE 110.2-G.

5.   Multiple Cell Heat Rejection Equipment. Multiple cell heat rejection equipment with variable speed fan drives shall:

A.   Operate the maximum number of fans allowed that comply with the manufacturer’s requirements for all system components, and

B.   Control all operating fans to the same speed. Minimum fan speed shall comply with the minimum allowable speed of the fan drive per the manufactures recommendation.  Staging of fans is allowed once the fans are at their minimum operating speed.

(i)   Minimum Chiller Efficiency.  

Chillers shall meet or exceed Path B from TABLE 110.2-D

EXCEPTION 1 to Section 140.4(i): Chillers with electrical service > 600V.

EXCEPTION 2 to Section 140.4(i): Chillers attached to a heat recovery system with a design heat recovery capacity > 40 percent of the design chiller cooling capacity.

EXCEPTION 3 to Section 140.4(i): Chillers used to charge thermal energy storage systems where the charging temperature is < 40 °F.

EXCEPTION 4 to Section 140.4(i): In buildings with more than 3 chillers, only 3 chillers are required to meet the Path B efficiencies.

(j)   Limitation of Air-Cooled Chillers.  

Chilled water plants shall not have more than 300 tons provided by air-cooled chillers.

EXCEPTION 1 to Section 140.4(j): Where the water quality at the building site fails to meet manufacturer’s specifications for the use of water-cooled chillers.

EXCEPTION 2 to Section 140.4(j): Chillers that are used to charge a thermal energy storage system with a design temperature of less than 40 degrees F (4 degrees C).

EXCEPTION 3 to Section 140.4(j): Air cooled chillers with minimum efficiencies approved by the Commission pursuant to Section 10-109(d).

(k)  Hydronic System Measures.  

1.   Hydronic Variable Flow Systems. HVAC chilled and hot water pumping shall be designed for variable fluid flow and shall be capable of reducing pump flow rates to no more than the larger of: a) 50 percent or less of the design flow rate; or b) the minimum flow required by the equipment manufacturer for the proper operation of equipment served by the system.

EXCEPTION 1 to Section 140.4(k)1: Systems that include no more than three control valves.

EXCEPTION 2 to Section 140.4(k)1: Systems having a total pump system power less than or equal to 1.5 hp.

2.   Chiller Isolation. When a chilled water system includes more than one chiller, provisions shall be made so that flow through any chiller is automatically shut off when that chiller is shut off while still maintaining flow through other operating chiller(s). Chillers that are piped in series for the purpose of increased temperature differential shall be considered as one chiller.

3.   Boiler Isolation. When a hot water plant includes more than one boiler, provisions shall be made so that flow through any boiler is automatically shut off when that boiler is shut off while still maintaining flow through other operating boiler(s).

4.   Chilled and Hot Water Temperature Reset Controls. Systems with a design capacity exceeding 500,000 Btu/hr supplying chilled or heated water shall include controls that automatically reset supply water temperatures as a function of representative building loads or outside air temperature.

EXCEPTION to Section 140.4(k)4: Hydronic systems that use variable flow to reduce pumping energy in accordance with Section 140.4(k)1.

5.   Water-Cooled Air Conditioner and Hydronic Heat Pump Systems. Water circulation systems serving water-cooled air conditioners, hydronic heat pumps, or both, that have total pump system power exceeding 5 hp shall have flow controls that meet the requirements of  Section 140.4(k)6. Each such air conditioner or heat pump shall have a two-position automatic valve interlocked to shut off water flow when the compressor is off.

6.   Variable Flow Controls.

A.   Variable Speed Drives. Individual pumps serving variable flow systems and having a motor horsepower exceeding 5 hp shall have controls or devices (such as variable speed control) that will result in pump motor demand of no more than 30 percent of design wattage at 50 percent of design water flow. The pumps shall be controlled as a function of required differential pressure.

B.   Pressure Sensor Location and Setpoint.

i.    For systems without direct digital control of individual coils reporting to the central control panel, differential pressure shall be measured at the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure.

ii.    For systems with direct digital control of individual coils with a central control panel, the static pressure set point shall be reset based on the valve requiring the most pressure, and the setpoint shall be no less than 80 percent open. Pressure sensors may be mounted anywhere.

EXCEPTION 1 to Section 140.4(k)6: Heating hot water systems.

EXCEPTION 2 to Section 140.4(k)6: Condenser water systems serving only water-cooled chillers.

7.   Hydronic Heat Pump (WLHP) Controls. Hydronic heat pumps connected to a common heat pump water loop with central devices for heat rejection and heat addition’ shall have controls that are capable of providing a heat pump water supply temperature deadband of at least 20°F between initiation of heat rejection and heat addition by the central devices.

EXCEPTION to Section 140.4(k)7: Where a system loop temperature optimization controller is used to determine the most efficient operating temperature based on real-time conditions of demand and capacity, dead bands of less than 20°F shall be allowed.

(l)   Air Distribution System Duct Leakage Sealing.  

Duct systems shall be sealed to a leakage rate not to exceed 6 percent of the nominal air handler airflow rate as confirmed through field verification and diagnostic testing, in accordance with the applicable procedures in Reference Nonresidential Appendices NA1 and NA2 if the criteria in Subsections 1, 2 and 3 below are met:

1.   The duct system provides conditioned air to an occupiable space for a constant volume, single zone, space-conditioning system; and

2.   The space conditioning system serves less than 5,000 square feet of conditioned floor area; and

3.   The combined surface area of the ducts located in the following spaces is more than 25 percent of the total surface area of the entire duct system:

A.   Outdoors; or

B.   In a space directly under a roof that

i.    Has a U-factor greater than the U-factor of the ceiling, or if the roof does not meet the requirements of Section 140.3(a)1B, or

ii.    Has fixed vents or openings to the outside or unconditioned spaces; or

C.   In an unconditioned crawlspace; or

D.   In other unconditioned spaces.

(m)      Fan Control.  

As of the applicable date 'listed’ in TABLE 140.4-D, each cooling system 'listed’ in TABLE 140.4-D shall be designed to vary the indoor fan airflow as a function of load and shall comply with the following requirements:

1.   DX and chilled water cooling systems that control the capacity of the mechanical cooling directly based on occupied space temperature shall (i) have a minimum of 2 stages of fan control with no more than 66 percent speed when operating on stage 1; and (ii) draw no more than 40 percent of the fan power at full fan speed, when operating at 66 percent speed.

2.   All other systems, including but not limited to DX cooling systems and chilled water systems  that control the space temperature by modulating the airflow to the space, shall have proportional fan control such that at 50 percent air flow the power draw is no more than 30 percent of the fan power at full fan speed.

3.   Systems that include an air side economizer to meet 140.4(e)1 shall have a minimum of two speeds of fan control during economizer operation.

EXCEPTION to Section 140.4(m): Modulating fan control is not required for chilled water systems with all fan motors <1 HP, or for evaporative systems with all fan motors < 1 HP, if the systems are not used to provide ventilation air and all indoor fans cycle with the load.

TABLE 140.4-D  EFFECTIVE DATES FOR FAN CONTROL SYSTEMS