Boiler Name
Applicability: All boilers.
Definition: A unique descriptor for each boiler, heat pump, central heating heat-exchanger, or heat recovery device.
Units: None.
Input Restrictions: User entry.
Where applicable, this should match the tags that are used on the plans for the proposed design.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, Boilers are only designated in the standard design if the baseline system type uses hot water for space heating.
Boiler Fuel Source
Applicability: All boilers.
Definition: The fuel source for the central heating equipment.
The choices are:
•Gas
•Oil
•Electricity
Units: List (see above).
Input Restrictions: As designed.
This input is restricted, based on the choice of boiler type, according to the following rules:
•Steam Boiler
o Electricity - n/a
o Gas - n/a
o Steam - Allowed
•Hot Water Boiler
o Electricity - n/a
o Gas - Allowed
o Steam - n/a
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, Gas.
Standard Design: Existing Buildings: Same as proposed for existing, unaltered; same as newly constructed buildings if altered.
Boiler Type
Applicability: All boilers.
Definition: Type of fluid used for heat transfer.
The choices are:
•HotWater
•Steam
Units: List (see above).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as Proposed Design. For all others, HotWater boiler. HotWater boiler.
Standard Design: Existing Buildings: Same as proposed for existing, unaltered; same as newly constructed buildings if altered.
Boiler Draft Type
Applicability: All boilers.
Definition: How combustion airflow is drawn through the boiler.
The choices are Natural, Mechanical Noncondensing, or Condensing.
Natural draft boilers use natural convection to draw air for combustion through the boiler. Natural draft boilers are subject to outside air conditions and the temperature of the flue gases.
Condensing boilers reclaim heat of condensation from water in the flue gas to achieve efficiencies of 90 percent. However, if the water entering the boiler (return water temperature) is too hot, then condensing does not occur, and the boiler operates at efficiencies below 82 percent. Condensing boilers require a draft fan to ensure airflow through the complex flue gas passages.
Units: List (see above).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as Proposed Design. For all others, HotWater boiler.
For gas-fired boilers in climate zones 1 through 6, 9 through 14 and 16 with rated capacity above 1 MMBtu/h and less than 10 MMBtu/h, condensing boilers.
For all others, non-condensing.
Number of Identical Boiler Units
Applicability: All boilers.
Definition: The number of identical units for staging.
Units: Numeric: integer.
Input Restrictions: As designed; default is 1.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others the Standard Design shall have one boiler when the standard design plant serves a conditioned floor area of 15,000 ft2 or less and have two equally size boilers for plants serving more than 15,000 ft2.
Boiler Design Capacity
Applicability: All boilers.
Definition: The heating capacity at design conditions.
Units: Btu/h.
Input Restrictions: As designed.
If unmet load hours exceed 150, the user may need to manually adjust boiler design capacity.
Standard Design: For buildings with both healthcare and other occupancies, the proposed boiler capacity is scaled based on the ratio of the capacity of heating coils serving healthcare areas. For all others, the Standard Design boiler is sized to be 25 percent larger than the peak loads of the standard design. Standard design boilers shall be sized using weather files containing 99.6 percent heating design temperatures and 0.5 percent dry-bulb and 1 percent wet-bulb cooling design temperatures.
Boiler Efficiency Type
Applicability: All boilers.
Definition: The full load efficiency of a boiler is expressed as one of the following:
• Annual fuel utilization efficiency (AFUE) is a measure of the boiler’s efficiency over a predefined heating season.
• Thermal efficiency (Et) is the ratio of the heat transferred to the water divided by the heat input of the fuel.
• Combustion efficiency (Ec) is the measure of how much energy is extracted from the fuel and is the ratio of heat transferred to the combustion air divided by the heat input of the fuel.
Units: List (see above).
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design.
For all others, AFUE for all gas fired hot water boilers with less than 300,000 Btu/h capacity.
Thermal efficiency (Et) for all gas fired boilers with capacities between 225,000 and 2,500,000 Btu/h and all gas-fired steam water boilers with capacities above 225,000 Btu/h.
Combustion efficiency (Ec), for all gas fired hot water boilers with capacities above 2,500,000 Btu/h.
Boiler Efficiency
Applicability: All boilers.
Definition: The full load efficiency of a boiler at rated conditions (see efficiency type above) expressed as a dimensionless ratio of output over input. The compliance software must accommodate input in either thermal efficiency (Et), combustion efficiency (Ec), or AFUE. The compliance software shall make appropriate conversions to thermal efficiency if either AFUE or combustion efficiency is entered as the rated efficiency.
Where AFUE is provided, Et shall be calculated as follows:
•
•
If combustion efficiency is entered, the compliance software shall convert the efficiency to thermal efficiency by the relation:
All electric boilers will have an efficiency of 98 percent.
Units: Ratio.
Input Restrictions: The boiler efficiency should meet the minimum efficiency requirements per Table 110.2-J.
Standard Design: Boilers with rated capacity 1 MMBtu and below for the standard design have the minimum efficiency listed in Table E-4 of the California Appliance Efficiency Regulations.
Gas-fired boilers in climate zones 1 through 6, 9 through 14 and 16 with rated capacity above 1 MMBtu/h and less than 10 MMBtu/h have a standard design efficiency of 90 percent
Boiler Part-Load Performance Curve
Applicability: All boilers.
Definition: An adjustment factor that represents the percentage 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:
•FHeatPLC - The fuel heating part-load efficiency curve
•Fuelpartload - The fuel consumption at part-load conditions (Btu/h)
•Fueldesign - The fuel consumption at design conditions (Btu/h)
•Qpartload - The boiler capacity at part-load conditions (Btu/h)
•Qrated - The boiler capacity at design conditions (Btu/h)
•a- Constant
•b - Constant
•c - Constant
Units: Ratio.
Input Restrictions: Prescribed to the part-load performance curve in the ACM Appendix 5.7, based on the boiler draft type.
Standard Design: The standard design uses the mechanical draft fan curve in Appendix 5.7.
Boiler Forced Draft Fan Power
Applicability: All mechanical draft boilers.
Definition: The fan power of the mechanical draft fan at design conditions.
Units: Nameplate horsepower.
Input Restrictions: As designed.
The compliance software shall convert the user entry of motor horsepower to fan power in watts by the following equation:
Fan Power=Motor HP(7.46)(0.5)
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, Sized for an energy input ratio of 0.001018 (0.2984 W per kBtu/h heat input).
Boiler Minimum Unloading Ratio
Applicability: All boilers.
Definition: The minimum unloading capacity of a boiler expressed as a percentage of the rated capacity. Below this level, the boiler must cycle to meet the load.
Units: Percent (%).
Input Restrictions: As designed.
If the user does not use the default value, the compliance software must indicate that supporting documentation is required on the output forms. Fixed at 1 percent (this accounts for jacket losses and start/stop losses).
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, 1 percent.
Boiler Minimum Flow Rate
Applicability: All boilers.
Definition: The minimum flow rate recommended by the boiler manufacturer for stable and reliable operation of the boiler.
Units: Gpm.
Input Restrictions: As designed.
If the boiler(s) is piped in a primary only configuration in a variable flow system then the compliance software shall assume there is a minimum flow bypass valve that allows the hot water pump to bypass water from the boiler outlet back to the boiler inlet to maintain the minimum flow rate when boiler is enabled.
Note: The boiler entering water temperature must accurately reflect the mixed temperature (colder water returning from the coil(s) and hotter bypass water) to accurately model boiler efficiency as a function of boiler entering water temperature.
Standard Design: For buildings with both healthcare and other occupancies, the proposed boiler minimum low rate is scaled based on the ratio to the capacity of heating coils serving healthcare areas. For all others, 0 gpm.
Hot Water Supply Temperature
Applicability: All boilers.
Definition: The temperature of the water produced by the boiler and supplied to the hot water loop.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, Use 160°F for standard design boiler.
Hot Water Temperature Difference
Applicability: All boilers.
Definition: The difference between the temperature of the water returning to the boiler from the hot water loop and the temperature of the water supplied to the loop.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, Use 40°F for standard design boiler.
Hot Water Supply Temperature Reset
Applicability: All boilers.
Definition: Variation of the hot water supply temperature with outdoor air temperature.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed (not allowed for non-condensing boilers).
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, the hot water supply temperature is fixed at 160 °F.
Chiller Name
Applicability: All chillers.
Definition: A unique descriptor for each chiller.
Units: Text, unique.
Input Restrictions: User entry: where applicable, this should match the tags that are used on the plans.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, Chillers are only designated when the standard design system uses chilled water.
Chiller Type
Applicability: All chillers.
Definition: The type of chiller, either a vapor-compression chiller or an absorption chiller.
Vapor compression chillers operate on the reverse Rankine cycle, using mechanical energy to compress the refrigerant, and include:
•Reciprocating*
•Scroll*
•Screw*
•Centrifugal – uses rotating impeller blades to compress the air and impart velocity
•Direct-Fired Single Effect Absorption – uses a single generator and condenser
•Direct-Fired Double Effect Absorption – uses two generators/ concentrators and condensers, one at a lower temperature and the other at a higher temperature. It is more efficient than the single effect, but it must use a higher temperature heat source.
•Indirect-Fired Double Effect Absorption
•Gas Engine-Driven
*Positive displacement – includes reciprocating (piston-style), scroll and screw compressors.
Units: List (see above). The compliance software shall support all chiller types listed above.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, the standard design chiller is based on the design capacity of the standard design as follows:
Table 15: Type and Number of Chillers
|
Building Peak Cooling Load |
Number and type of chiller(s) |
|
≤ 300 tons |
One water-cooled screw chiller |
|
300 < Load < 600 |
Two water-cooled screw chillers, sized equally |
|
≥ 600 tons |
A minimum of two water-cooled centrifugal chillers, sized to keep the unit size below 800 tons |
Source: California Energy Commission
NUMBER OF IDENTICAL CHILLER UNITS
Applicability: All chillers.
Definition: The number of identical units for staging.
Units: None.
Input Restrictions: As designed; default is 1.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, From the number indicated in Chiller Type.
Chiller Fuel Source
Applicability: All chillers.
Definition: The fuel source for the chiller.
The choices are:
•Electricity (for all vapor-compression chillers)
•Gas (absorption units only, designated as direct-fired units)
•Hot water (absorption units only, designated as indirect-fired units)
•Steam (absorption units only, designated as indirect-fired units)
Units: List (see above).
Input Restrictions: As designed.
This input is restricted, based on the choice of chiller type, according to the following rules:
•Reciprocating
o Electricity - Allowed
o Gas - n/a
o Hot Water - n/a
o Steam - n/a
•Scroll
o Electricity - Allowed
o Gas - n/a
o Hot Water - n/a
o Steam - n/a
•Screw
o Electricity - Allowed
o Gas - n/a
o Hot Water - n/a
o Steam - n/a
•Centrifugal
o Electricity - Allowed
o Gas - n/a
o Hot Water - n/a
o Steam - n/a
•Single Effect Absorption
o Electricity - n/a
o Gas - Allowed
o Hot Water - Allowed
o Steam - Allowed
•Direct-Fired Double Effect Absorption
o Electricity - n/a
o Gas - Allowed
o Hot Water - Allowed
o Steam - Allowed
•Indirect-Fired Absorption
o Electricity - n/a
o Gas - Allowed
o Hot Water - Allowed
o Steam - Allowed
Standard Design: For healthcare facilities, same as the proposed design. For all others, Electricity.
Chiller Rated Capacity
Applicability: All chillers.
Definition: The cooling capacity of a piece of heating equipment at rated conditions.
Units: Btu/h or tons.
Input Restrictions: As designed.
The user may need to manually adjust the capacity if the number of unmet load hours exceeds 150.
Standard Design: For buildings with both healthcare and other occupancies, the proposed chiller capacity is scaled based on the ratio to the capacity of cooling coils serving healthcare areas. For all others, the Standard Design chiller is sized to be 15 percent larger than the peak loads of the Standard Design.
Chiller Rated Efficiency
Applicability: All chillers.
Definition: The efficiency of the chiller (EER for air-cooled chillers, kW/ton for water-cooled electric chillers, and COP for fuel-fired and heat-driven chillers) at AHRI 550/590 rated full-load conditions.
Units: Ratio (kW/ton, COP, EER, depending on chiller type and condenser type).
Water-cooled electric chiller - kW/ton.
Air-cooled or evaporatively-cooled electric chiller - EER
All non-electric chillers – COP
Input Restrictions: As designed.
Must meet the minimum requirements of Table 110.2-D.
Standard Design: Use the minimum efficiency requirements from Tables 110.2-D Path B.
If chiller type is reciprocating, scroll, or screw, use the efficiency for positive displacement chillers from Table 110.2-D.
Standard Design: Existing Buildings: Same as proposed if unaltered; same as newly constructed buildings rules if altered or replacement.
Integrated Part-Load Value
Applicability: All chillers.
Definition: The part-load efficiency of a chiller developed from a weighted average of four rating conditions, according to AHRI Standard 550.
Units: Ratio (kW/ton, COP, EER, depending on chiller type and condenser type).
Water-cooled electric chiller - kW/ton
Air-cooled or evaporatively-cooled electric chiller - EER
All non-electric chillers – COP
Input Restrictions: As designed; must meet the minimum requirements of Table 110.2-D.
Standard Design: For healthcare facilities, use the minimum efficiency requirements from Tables 110.2-D Path B. For all others, not used.
When the standard design system has a chiller, the standard design will always use Path B performance curves.
Chiller Minimum Unloading Ratio
Applicability: All chillers.
Definition: The minimum unloading capacity of a chiller expressed as a fraction of the rated capacity.
Below this level the chiller must either cycle to meet the load or false-load the compressor (such as with hot gas bypass).
Table 16: Default Minimum Unloading Ratios
|
Chiller Type |
Default Unloading Ratio |
|
Reciprocating |
25% |
|
Screw |
15% |
|
Centrifugal |
10% |
|
Scroll |
25% |
|
Single Effect Absorption |
10% |
|
Double Effect Absorption |
10% |
Source: California Energy Commission
Units: Percent (%).
Input Restrictions: As designed but constrained to a minimum value of 10 percent. If the user does not employ the default values, supporting documentation is required.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, use defaults listed above.
Chiller Minimum Part Load Ratio
Applicability: All chillers.
Definition: The minimum unloading capacity of a chiller expressed as a fraction of the rated capacity.
Below this level the chiller must cycle to meet the load. If the chiller minimum part-load ratio (PLR) is less than the chiller minimum unloading ratio, then the compliance software shall assume hot gas bypass operation between the minimum PLR and the minimum unloading ratio.
Units: Percent (%).
Input Restrictions: As designed but constrained to a minimum value of 10 percent. If the user does not employ the default values, supporting documentation is required.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, When the standard design has a screw chiller, the minimum PLR is 15 percent. When the standard design has a centrifugal chiller, the minimum PLR is 10 percent.
Chiller Cooling Capacity Adjustment Curve
Applicability: All chillers.
Definition: A curve or group of curves or other functions that represent the available total cooling capacity as a function of evaporator and condenser conditions and perhaps other operating conditions. The default curves are given as:
For air-cooled chillers:
For water-cooled chillers:
Where:
•Qavailable - Available cooling capacity at present evaporator and condenser conditions (MBH)
•tchws - The chilled water supply temperature (°F)
•tcws - The condenser water supply temperature (°F)
•todb - The outside air dry-bulb temperature (°F)
•Qrated - Rated capacity at AHRI conditions (MBH)
Note: If an air-cooled unit employs an evaporative condenser, todb is the effective dry-bulb temperature of the air leaving the evaporative cooling unit.
Separate curves are provided for Path A and Path B chillers in Appendix 5.7.
Units: Data structure.
Input Restrictions: Prescribed curves are provided in Appendix 5.7 for the proposed design chiller type and the compliance path (A or B). If the default curves are overridden, supporting documentation is required.
Standard Design: Use prescribed curve for Path B chiller as applicable to the standard design chiller type.
Electric Chiller Cooling Efficiency Adjustment Curves
Applicability: All chillers.
Definition: A curve or group of curves that varies the cooling efficiency of an electric chiller as a function of evaporator conditions, condenser conditions and part-load ratio.
Note: For variable-speed chillers, the part-load cooling efficiency curve is a function of both part-load ratio and leaving condenser water temperature. The default curves are given as:
Variable Speed:
Air-Cooled:
Water-Cooled:
Where:
•PLR - Part-load ratio based on available capacity (not rated capacity)
•Qoperating - Present load on chiller (Btu/h)
•Qavailable - Chiller available capacity at present evaporator and condenser conditions (Btu/h)
•tchws - The chilled water supply temperature (°F)
•tcws - The condenser water supply temperature (°F)
•todb - The outside air dry-bulb temperature (°F)
•Prated- Rated power draw at AHRI conditions (kW)
•Poperating - Power draw at specified operating conditions (kW)
Note: If an air-cooled chiller employs an evaporative condenser, todb is the effective dry-bulb temperature of the air leaving the evaporative cooling unit.
Units: Data structure.
Input Restrictions: Curves are prescribed in Appendix 5.7 given the chiller capacity and type. A separate set of curves are provided for Path A chillers and Path B chillers. The path is determined by comparing compliance software inputs of full-load efficiency and integrated part-load value with the requirements of Table 110.2-D of the Energy Code.
Standard Design: Use Path B curves specified in Appendix 5.7.
Fuel and Steam Chiller Cooling Efficiency Adjustment Curves
Applicability : All chillers.
Definition: A curve or group of curves that varies the cooling efficiency of a fuel-fired or steam chiller as a function of evaporator conditions, condenser conditions, and part-load ratio. The default curves are given as follows:
Default curves for steam-driven single and double effect absorption chillers:
Default curves for direct-fired double effect absorption chillers:
The default curves for engine driven chillers are the same format as those for the steam-driven single and double effect absorption chillers but there are three sets of curves for different ranges of operation based on the engine speed.
Where:
•PLR - Part-load ratio based on available capacity (not rated capacity)
•FIRFPLR - A multiplier on the fuel input ratio (FIR) to account for part-load conditions
•FIRFT - A multiplier on the fuel input ratio (FIR) to account for the chiller water supply temperature and the condenser water temperature
•FIRFT1 - A multiplier on the fuel input ratio (FIR) to account for chilled water supply temperature
•FIRFT2 - A multiplier on the fuel input ratio (FIR) to account for condenser water supply temperature
•CAPFT - A multiplier on the capacity of the chiller (Equation 45)
•Qoperating - Present load on chiller (in Btu/h)
•Qavailable - Chiller available capacity at present evaporator and condenser conditions (in Btu/h)
•tchws - The chilled water supply temperature (in °F)
•tcws - The condenser water supply temperature (in °F)
•todb - The outside air dry-bulb temperature (°F)
•Fuelrated - Rated fuel consumption at AHRI conditions (in Btu/h)
•Fuelpartload - Fuel consumption at specified operating conditions (in Btu/h)
Units: Data structure.
Input Restrictions: Restricted to curves specified in Appendix 5.7.
Standard Design: Use prescribed curves specified in Appendix 5.7.
Chilled Water Supply Temperature
Applicability: All chillers.
Definition: The chilled water supply temperature of the chiller at design conditions.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, the standard design chilled water supply temperature is set to 44°F.
Chilled Water Return Temperature
Applicability: All chillers.
Definition: The chilled water return temperature setpoint at design conditions.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, the standard design chilled water return temperature is set to 64°F.
Chilled Water Supply Temperature Control Type
Applicability: All chillers.
Definition: The method by which the chilled water setpoint temperature is reset.
The chilled water setpoint may be reset based on demand or outdoor air temperature.
Units: List none, outside air-based reset, or demand-based reset.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, outside air-based reset.
Chilled Water Supply Temperature Reset
Applicability: All chillers.
Definition: The reset schedule for the chilled water supply temperature. The chilled water setpoint may be reset based on demand or outdoor air temperature.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, 10°F from design chilled water supply temperature.
The chilled water supply temperature reset follows an outside air reset scheme, where the setpoint is 44°F at outside air conditions of 80°F dry-bulb and above; the setpoint is 54°F at outside air conditions of 60°F dry-bulb and below; and ramps linearly from 44°F to 54°F as the outside air dry-bulb temperature varies between 80°F and 60°F.
Condenser Type
Applicability: All chillers.
Definition: The type of condenser for a chiller.
The choices are:
•Air-cooled
•Water-cooled
Air-cooled chillers use air to cool the condenser coils. Water-cooled chillers use cold water to cool the condenser and additionally need either a cooling tower or a local source of cold water. Evaporatively-cooled chillers are similar to air-cooled chillers, except a water mist is used to cool the condenser coil, making them more efficient.
Units: List (see above).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, the standard design chiller is always assumed to have a water-cooled condenser, although the chiller type will change depending on the design capacity.
Standard Design Summary. Standard design system 6 has one or more cooling towers. One tower is assumed to be matched to each standard design chiller. Each standard design chiller has its own condenser water pump that operates when the chiller is brought into service.
Cooling Tower Name
Applicability: All cooling towers.
Definition: A unique descriptor for each cooling tower.
Units: Text, unique.
Input Restrictions: User entry: where applicable, this should match the tags that are used on the plans.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others descriptive name that keys the standard design building plant.
Cooling Tower Type
Applicability: All cooling towers.
Definition: Type of cooling tower employed.
The choices are:
•Open tower, centrifugal fan
•Open tower, axial fan
•Closed tower, centrifugal fan
•Closed tower, axial fan
•Closed tower evaporative, centrifugal fan
•Closed tower evaporative, axial fan
Open cooling towers collect the cooled water from the tower and pump it directly back to the cooling system. Closed towers circulate the evaporated water over a heat exchanger to indirectly cool the system fluid.
Units: List (see above).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, if the open tower design condenser flow rate is greater than 900 gpm, the fan is axial, otherwise same as the proposed design. For all others, the standard design cooling tower is an open tower axial fan device.
Cooling Tower Capacity
Applicability: All cooling towers.
Definition: The tower thermal capacity per cell adjusted to Cooling Technology Institute (CTI) rated conditions of 95°F condenser water return, 85°F condenser water supply, and 78°F wet-bulb with a 3 gpm/nominal ton water flow. The default cooling tower curves below are at unity at these conditions.
Units: Btu/h.
Input Restrictions: As designed.
Standard Design: For buildings with both healthcare and other occupancies, the proposed cooling tower capacity is scaled based on the ratio to the capacity of chillers serving healthcare areas. For all others, the Standard Design tower is sized to supply 85°F condenser water at design conditions for the oversized chiller.
Cooling Tower Number of Cells
Applicability: All cooling towers.
Definition: The number of cells in the cooling tower.
Each cell will be modeled as equal size. Cells are subdivisions in cooling towers into individual cells, each with their own fan and water flow, that allow the cooling system to respond more efficiently to lower load conditions.
Units Numeric: integer.
Input Restrictions: As designed.
Standard Design: One cell per tower and one tower per chiller.
Cooling Tower Total Fan Horsepower
Applicability: All cooling towers.
Definition: The sum of the nameplate rated horsepower (hp) of all fan motors on the cooling tower. Pony motors should not be included.
Units: Gpm/hp or unitless if energy input ratio (EIR) is specified (if the nominal tons but not the condenser water flow is specified, the condenser design water flow shall be 3.0 gpm per nominal cooling ton).
Input Restrictions: As designed, but the cooling towers shall meet minimum performance requirements in Table 110.2-F of the Energy Code.
Standard Design: The cooling tower fan horsepower is 60 gpm/hp in climate zones 2 to 15, when design condenser flow rate is greater than 900 gpm. Otherwise, cooling towers shall set the standard design to the mandatory requirements in Table 110.2-F.
Standard Design: Existing Buildings: 42.1 gpm/hp.
Cooling Tower Design Wet-Bulb
Applicability: All cooling towers.
Definition: The design wet-bulb temperature that was used for selection and sizing of the cooling tower.
Units: Degrees Fahrenheit (°F).
Input Restrictions: Specified from design wet-bulb conditions from Reference Appendix JA2 for the city where the building is located, or the city closest to where the building is located.
Standard Design: Specified from design wet-bulb conditions from Reference Appendix JA2 for the city where the building is located, or from the city closest to where the building is located.
Cooling Tower Design Entering Water Temperature
Applicability: All cooling towers.
Definition: The design condenser water supply temperature (leaving tower) that was used for selection and sizing of the cooling tower.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed; default to 85°F.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, 85°F or 10°F above the design wet-bulb temperature, whichever is lower.
Cooling Tower Design Return Water Temperature
Applicability: All cooling towers.
Definition: The design condenser water return temperature (entering tower) that was used for selection and sizing of the cooling tower.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed; default to 95°F.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, set to a range of 10°F (10°F above the cooling tower design entering water temperature).
Cooling Tower Capacity Adjustment Curve
Applicability: All cooling towers.
Definition: A curve or group of curves that represent the available total cooling capacity as a function of outdoor air wet-bulb, condenser water supply, and condenser water return temperatures.
The default curves are given as follows:
Approach = Coeff(1) + Coeff(2)•Frair + Coeff(3)•(Frair)2 +Coeff(4)•(Frair)3 + Coeff(5)•Frwater + Coeff(6)•Frair•Frwater + Coeff(7)•(Frair)2•Frwater + Coeff(8)•(Frwater)2 + Coeff(9)•Frair•(Frwater)2 +
Coeff(10)•(Frwater)3 + Coeff(11)•Twb + Coeff(12)•Frair•Twb + Coeff(13)•(Frair)2•Twb + Coeff(14)•Frwater•Twb + Coeff(15)•Frair•Frwater•Twb + Coeff(16)•(Frwater)2•Twb +
Coeff(17)•(Twb)2 + Coeff(18)•Frair•(Twb)2 + Coeff(19)•Frwater•(Twb)2 + Coeff(20)•(Twb)3 + Coeff(21)•Tr + Coeff(22)•Frair•Tr + Coeff(23)•Frair•Frair•Tr + Coeff(24)•Frwater•Tr + Coeff(25)•Frair•Frwater•Tr +
Coeff(26)•(Frwater)2•Tr + Coeff(27)•Twb•Tr + Coeff(28)•Frair•Twb•Tr + Coeff(29)•Frwater•Twb•Tr +
Coeff(30)•(Twb)2•Tr + Coeff(31)•(Tr)2 + Coeff(32)•Frair•(Tr)2 + Coeff(33)•Frwater•(Tr)2 + Coeff(34)•Twb•(Tr)2 + Coeff(35)•(Tr)3
Where:
•Frair – ratio of airflow to airflow at design conditions
•Frwater – ratio of water flow to water flow at design conditions
•Tr – tower range (°F)
•Twb – wet-bulb temperature
Coefficients for this performance curve are provided in Appendix 5.7.
Units: Data structure.
Input Restrictions: User must use one of the prescribed curves defined in Appendix 5.7.
Standard Design: Use one of the prescribed curves defined in Appendix 5.7.
Cooling Tower Set Point Control
Applicability: All cooling towers.
Definition: The type of control for the condenser water supply.
The choices are fixed, or wet-bulb reset.
A fixed control will modulate the tower fans to provide the design condenser water supply temperature at all times when possible. A wet-bulb reset control will reset the condenser water setpoint to a fixed approach to outside air wet-bulb temperature. The approach defaults to 10°F. A lower approach may be used with appropriate documentation.
Units: List (see above).
Input Restrictions: As designed; default to 95°F
Standard Design: For healthcare facilities, same as the proposed design. For all others, fixed at the 0.4 percent design wet-bulb temperature, which is prescribed and specified for each of the 86 weather data files.
Cooling Tower Capacity Control
Applicability: All cooling towers.
Definition: Describes the modulation control employed in the cooling tower.
Choices include:
•Fluid Bypass provides a parallel path to divert some of the condenser water around the cooling tower at part-load conditions.
•Fan Cycling is a simple method of capacity control where the tower fan is cycled on and off. This is often used on multiple-cell installations.
•Two-Speed Fan/Pony Motor are the same from an energy perspective. A lower horsepower pony motor is an alternative to a two-speed motor. The pony motor runs at part-load conditions (instead of the full-sized motor) and saves fan energy when the tower load is reduced. Additional building descriptors are triggered when this method of capacity control is selected.
•Variable-Speed Fan is a variable frequency drive is installed for the tower fan so that the speed can be modulated.
Units: List (see above).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, if the fan motor hp is 7.5 or larger, variable-speed fan, otherwise, same as the proposed design. For all others, variable-speed fan.
Cooling Tower Low-Speed Airflow Ratio
Applicability: All cooling towers with two-speed or pony motors.
Definition: The percentage full-load airflow that the tower has at low speed or with the pony motor operating; equivalent to the percentage full-load capacity when operating at low speed.
Units: Ratio.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, Not applicable.
Cooling Tower Low-Speed kW Ratio
Applicability: All cooling towers with two-speed or pony motors.
Definition: The percentage full-load power that the tower fans draw at low speed or with the pony motor operating.
Units: Ratio.
Input Restrictions: Calculated, using the as-designed flow ratio and the cooling tower power adjustment curve below.
Standard Design: For healthcare facilities, same as the proposed design. For all others, Not applicable.
Cooling Tower Power Adjustment Curve
Applicability: All cooling towers with VSD control.
Definition: A curve that varies the cooling tower fan energy usage as a function of part-load ratio for cooling towers with variable speed fan control. The default curve is given as:
Where:
•PLR- Part-load ratio based on available capacity (not rated capacity)
•Qoperating - Present load on tower (in Btu/h)
•Qavailable - Tower available capacity at present range, approach, and outside wet-bulb conditions (in Btu/h)
•tOWB- The outside air wet-bulb temperature (°F)
•tR - The tower range (°F)
•tA - The tower approach (°F)
•Prated - Rated power draw at CTI conditions (kW)
•Poperating - Power draw at specified operating conditions (kW)
Refer to Appendix 5.7 for the fixed cooling tower curve coefficients.
Units: Data structure.
Input Restrictions: User shall use only default curves.
Standard Design: Use default curves given above.
Cooling Tower Minimum Speed
Applicability: All cooling towers with a VSD control.
Definition: The minimum fan speed setting of a VSD controlling a cooling tower fan expressed as a ratio of full load speed.
Units: Ratio.
Input Restrictions: As designed; default is 0.50.
Standard Design: For healthcare facilities, if the fan motor hp is 7.5 or larger, 0.5, otherwise, same as the proposed design. For all others, 0.5.
None of the standard design building systems use a water-side economizer.
Water-Side Economizer Name
Applicability: All water-side economizers.
Definition: The name of a water-side economizer for a cooling system.
Units: Text, unique.
Input Restrictions: Descriptive reference to the construction documents; default is no water-side economizer.
Standard Design: For healthcare facilities, same as the proposed design. For all others, no water economizer.
Water Economizer Type
Applicability: All water-side economizers.
Definition: The type of water-side economizer. Choices include:
•None
•Heat exchanger in parallel with chillers. This would be used with an open cooling tower and is often referred to as a non-integrated economizer because the chillers are locked out when the plant is in economizer mode.
•Heat exchanger in series with chillers. This would be used with an open cooling tower and is often referred to as integrated because the chillers can operate simultaneously with water economizer operation.
•Direct water economizer. This would be used with a closed cooling tower. In this case, a heat exchanger is not needed. This type works only as a non-integrated economizer (also known as strainer-cycle).
Units: List (see above).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, no water economizer.
Water-Side Economizer HX Effectiveness
Applicability: Water-side economizers with an open cooling tower.
Definition: The effectiveness of a water-side heat exchanger at design conditions.
This is defined as:
Where:
•Qecon - The maximum load that the economizer can handle
•mCHW - The chilled water flow rate
•CpCHW - The chilled water specific heat
•TCHW,R - The chilled water return temperature
•TCW,S - The condenser water supply temperature
•WSEeff - The effectiveness of the water-side economizer coil
•tea - The entering coil air dry-bulb temperature (°F)
•tla - The leaving coil air dry-bulb temperature (°F)
Units: Ratio
Input Restrictions: As designed; default is 60 percent
Standard Design: For healthcare facilities, same as the proposed design. For all others, no water economizer
Water-Side Economizer Heat Exchanger Heat Transfer Coefficient
Applicability: Water-side economizers with an open cooling tower.
Definition: The heat transfer coefficient of the plate-and-frame heat exchanger with the waterside economizer.
Units: Btu/h-°F .
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, not applicable.
Water-Side Economizer Approach
Applicability: All water-side economizers.
Definition: The design temperature difference between the chilled water temperature leaving the heat exchanger and the condenser water inlet to the heat exchanger.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed; default is 4°F.
Standard Design: For healthcare facilities, same as the proposed design. For all others, no water economizer.
Water-Side Economizer Maximum CWS
Applicability: All water-side economizers.
Definition: The control temperature (condenser water supply temperature) above which the water-side economizer is disabled.
Units: Degrees Fahrenheit (°F).
Input Restrictions: As designed; default is 50°F.
Standard Design: For healthcare facilities, same as the proposed design. For all others, no water economizer.
Water-Side Economizer Availability Schedule
Applicability: All water-side economizers.
Definition: A schedule which represents the availability of the water-side economizer.
Units: Data structure: schedule, on/off.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, no water economizer.
Water-Side Economizer Auxiliary kW
Applicability: Water-side economizers with an open tower.
Definition: The electrical input (pumps and auxiliaries) for a dedicated pump for the chilled water side of the heat exchanger.
This power is in excess of the condenser water pumps and cooling tower fans for the system during water-side economizer operation.
Units: KW or kW/ton.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, no water economizer.
Standard Design Summary - Hot water pumping in the standard design shall be modeled as a variable flow, primary only system. Two-way valves are assumed at the heating coils.
Chilled water pumping in the standard design (system 6) is a primary system. Each chiller has its own primary and condenser water pumps that operate when the chiller is activated.
General Notes - The building descriptors in this chapter are repeated for each pumping system. See the pump service building descriptor for a list of common pump services.
Pump Name
Applicability: All pumps.
Definition: A unique descriptor for each pump.
Units: Text, unique.
Input Restrictions: User entry: where applicable, should match the tags that are used on the plans.
Standard Design: Same as proposed design.
If there is no equivalent in the proposed design, assign a sequential tag to each piece of equipment. The sequential tags should indicate the pump service as part of the descriptor (e.g., CW for condenser water, CHW for chilled water, or HHW for heating hot water).
Pump Service
Applicability: All pumps.
Definition: The service for each pump.
Choices include:
• Chilled water
• Chilled water (primary)
• Chilled water (secondary)
• Heating water
• Heating water (primary)
• Heating water (secondary)
• Service hot water
• Condenser water (for heat rejection or water-source heat pump loops)
• Loop water (for hydronic heat pumps)
Units: List (see above).
Input Restrictions: As designed.
Standard Design: As needed by the standard design system. See Chapter 5.1.2 HVAC System Map.
Number of Pumps
Applicability: All pumps.
Definition: The number of identical pumps in service in a particular loop, e.g., the heating hot water loop, chilled water loop, or condenser water loop.
Units: Numeric: integer.
Input Restrictions: As designed.
Standard Design: There will be one heating hot water pump for each boiler, one chilled water pump, and one condenser water pump for each chiller.
Water Loop Design
Applicability: All pumps.
Definition: The heating and cooling delivery systems can consist of a simple primary loop system, or more complicated primary/secondary loops or primary/secondary/tertiary loops.
Units: List (see above).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, assume primary loops only for heating hot water; for chilled water loops, a primary loop design is assumed.
Pump Motor Modeling Method
Applicability: All pumps.
Definition: Compliance software commonly models pumps in one of two ways. The simple method is for the user to enter the electric power per unit of flow (W/gpm). This method is commonly used for smaller systems. A more detailed method requires a specification of the pump head, design flow, impeller, and motor efficiency.
Units: List power-per-unit-flow or detailed.
Input Restrictions: Detailed.
Standard Design: Detailed for chilled water and condenser water pumps; power-per-unit-flow for heating hot water and service hot water pumps.
Pump Motor Power-Per-Unit-Flow
Applicability: All proposed design pumps that use the power-per-unit-flow method.
Definition: The electric power of the pump divided by the flow at design conditions.
Units: W/gpm.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, Not applicable for chilled water and condenser water pumps; 19 W/gpm for heating hot water and service hot water pumps.
Pump Motor Horsepower
Applicability: All pumps.
Definition: The nameplate motor horsepower.
Units: Horsepower (hp).
Input Restrictions: Constrained to be a value from the following 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
Alternatively, the nameplate horsepower can be entered as a numeric value.
Standard Design: For buildings with both healthcare and other occupancies, the proposed pump horsepower is scaled based on the ratio of plant equipment serving healthcare areas. Otherwise, set to the next larger nominal motor size, from Table 10: Minimum Nominal Efficiency for Electric Motors (Percent), for the calculated input brake horsepower.
Pump Design Head
Applicability: All standard and proposed design pumps that use the detailed method.
Definition: The head of the pump at design flow conditions.
Units: ft of water.
Input Restrictions: As designed but subject to an input restriction. The user inputs of pump design head, impeller efficiency, and pump design flow shall be used to calculate the proposed brake horsepower. This shall be compared to the pump motor.
Horsepower for the next smaller motor size (MHPi-1) than the one specified by the user (MHPi).
The proposed pump design head shall be constrained so that the resulting brake horsepower is no smaller than 95 percent of the next smaller motor size:
Where:
•design bhpprop - The brake horsepower used in the simulation
•design bhpprop-user-head - The brake horsepower resulting from the user input of design head
•MHPi - The pump motor horsepower specified by the user
•i- The index into the standard motor size table for the user motor horsepower
•MHPi-1 - The motor horsepower for the next smaller motor size. For example, if the user-specified pump motor horsepower is 25, the next smaller motor size in the table above is 20
Since all other user inputs that affect the proposed design brake horsepower are not modified, the proposed design pump design head is adjusted in the same proportion as the pump brake horsepower in the equation above. If the user-entered pump design head results in a brake horsepower that is at least 95 percent of the horsepower of the next smaller motor size, no modification of the user input is required.
Standard Design: For healthcare facilities, same as the proposed design. For all others, for chilled water pumps:
(40 ft) + (0.03 ft/ton) x [chiller plant nominal capacity (tons)]
(not to exceed 100 ft)
For condenser water pumps: 45 ft
Impeller Efficiency
Applicability: All pumps in proposed design that use the detailed modeling method.
Definition: The full load efficiency of the impeller.
Units: Ratio.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, 70%.
Motor Efficiency
Applicability: All pumps in proposed design that use the detailed modeling method.
Definition: The full load efficiency of the pump motor.
Units: Ratio.
Input Restrictions: For healthcare facilities, same as the proposed design. For all others, as designed.
Standard Design: For healthcare facilities, same as the proposed design. The motor efficiency is taken from Table 10: Minimum Nominal Efficiency for Electric Motors (Percent), using the calculated nameplate motor size.
Pump Minimum Speed
Applicability: All two-speed or variable-speed pumps.
Definition: The minimum pump speed for a two-speed for variable-speed pump.
For two-speed pumps this is typically 0.67 or 0.5.
Note: The pump minimum speed is not necessarily the same as the minimum flow ratio since the system head may change.
Units: Ratio.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the proposed design. For all others, 0.10.
Pump Design Flow
Applicability: All pumps.
Definition: The flow rate of the pump at design conditions; derived from the load, and the design supply and return temperatures.
Units: gpm or gpm/ton for condenser and primary chilled water pumps.
Input Restrictions: Not a user input.
Standard Design: For buildings with both healthcare and other occupancies, the proposed pump flow is scaled based on the ratio to the capacity of plant equipment serving healthcare areas. For all others, the temperature change on the evaporator side of the chillers is 20°F (64°F less 44°F) and this equates to a flow of 1.2 gpm/ton. The temperature change on the condenser side of the chillers is 12°F, which equates to a flow of 2.0 gpm/cooling ton. For hot water pumps servicing boilers, the flow rate in gpm shall correspond to a loop temperature drop of 40°F.
Pump Control Type
Applicability: All pumps.
Definition: The type of control for the pump.
Choices are:
• Constant speed, fixed flow
• Constant speed, variable flow (the default, with flow control via a valve)
• Two-speed
• Variable speed, variable flow
Units: List, see above.
Input Restrictions: As designed; default is “constant speed, variable flow”, which models the action of a constant speed pump riding the curve against two-way control valves.
Standard Design: For healthcare facilities, same as the proposed design. For all others, the chilled water and hot water pumps shall be modeled as variable-speed, variable flow, and the condenser water pumps shall be modeled as fixed speed.
Pump Operation
Applicability: All pumps.
Definition: The type of pump operation can be either on-demand, standby, or scheduled. On-demand operation means the pumps are only pumping when their associated equipment is cycling. Chiller and condenser pumps are on when the chiller is on and the heating hot water pump operates when its associated boiler is cycling. Standby operation allows hot or chilled water to circulate through the primary loop of a primary/secondary loop system or through a reduced portion of a primary-only system, assuming the system has appropriate three-way valves. Scheduled operation means that the pumps and their associated equipment are turned completely off according to occupancy schedules, time of year, or outside conditions. Under scheduled operation, when the systems are on, they are assumed to be in on-demand mode.
Units: List (see above).
Input Restrictions: As designed.
Standard Design: The standard design system pumps are assumed to operate in on-demand mode. The chilled water and condenser pumps are tied to the chiller operation, cycling on and off with the chiller, and the heating hot water pumps are tied to the boiler operation.
Pump Part-Load Curve
Applicability: All pumps.
Definition: A part-load power curve for the pump:
Where:
•PLR - Part-load ratio (the ratio of operating flow rate in gpm to design flow rate in gpm)
•Ppump - Pump power draw at part-load conditions (W)
•Pdesign - Pump power draw at design conditions (W)
Refer to Appendix 5.7 for a specification of the default pump part-load curve, and the pump part-load curve if there is differential pressure reset (if DDC controls are present).
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, DP Reset curve for chilled water pumps; heating hot water pump power is assumed to be constant even though the pump is riding the curve.
Variable refrigerant flow systems consist of an outdoor unit and one or more zonal systems as indoor units. The required system level inputs are shown below. Refer to the HVAC zone level systems chapter for zonal (indoor) units connected to a VRF system. Equipment performance curves are prescribed and defined in Appendix 5.4B for VRF systems.
VRF System Name
Applicability: VRF.
Definition: A unique name designating the VRF System.
Units: None.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable..
Heat Recovery
Applicability: VRF.
Definition: Identification if heat recovery (refrigerant loop) is present.
Units: Boolean.
Input Restrictions: None (default : No).
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not ot applicable.
Control Priority
Applicability: VRF.
Definition: A control parameter used to determine when outdoor unit is in heating or cooling.
Units: List: Master Thermostat Priority or Load Priority.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable..
Control Zone
Applicability: Master Thermostat Control Zone.
Definition: The name of the control zone that controls the outdoor unit, when the Control Priority is Master Thermostat Priority.
Units: None.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Minimum Part-Load Ratio
Applicability: VRF.
Definition: The minimum part-load ratio for the heat pump. Below this ratio the unit will cycle to meet the load.
Units: Unitless.
Input Restrictions: 0.25 to 1.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Rated EER
Applicability: VRF.
Definition: Full load cooling efficiency (Btu/h of net cooling output divided by the electrical energy consumption in Watts) per AHRI rating conditions.
Units: Btu/h-W.
Input Restrictions: As designed, the user-entered value must meet mandatory minimum requirements of the Appliance Standards for the applicable equipment type.
Standard Design: For healthcare facilities, the minimum heating efficiency from the Energy Code for the applicable equipment type. For all others, not applicable.
Rated COP
Applicability: VRF.
Definition: Full load heating efficiency (net heating output divided by the electrical energy consumption, both in the same units) per AHRI rating conditions.
Units: None.
Input Restrictions: As designed, the user-entered value must meet mandatory minimum requirements of the Appliance Standards for the applicable equipment type.
Standard Design: For healthcare facilities, the minimum heating efficiency from the Energy Code for the applicable equipment type. For all others, not applicable.
Rated Indoor Type
Applicability: VRF.
Definition: A flag to determine when the VRF system was rated with ducted or unducted indoor units.
Units: List: ducted, unducted.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Equivalent Pipe Length
Applicability: VRF.
Definition: The equivalent pipe length between the farthest terminal unit and the condensing unit, including liquid refrigerant line length, fitting losses, and other losses.
Units: ft.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Max Vertical Height
Applicability: VRF.
Definition: The vertical height difference between the highest or lowest terminal unit and outdoor unit.
Units: ft.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Defrost Heat Source
Applicability: VRF.
Definition: The defrost heat source type.
Units: List – electric or gas.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Defrost Control Strategy
Applicability: VRF.
Definition: The control method for enabling defrost.
Units: List – TimedCycle or OnDemand.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Max Defrost Temp
Applicability: VRF.
Definition: The maximum outdoor dry-bulb temperature at which defrost will occur.
Units: Deg F.
Input Restrictions: None.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Crankcase Heater Capacity
Applicability: VRF.
Definition: The capacity of the resistive heating element in or around the crank case of a compressor. The crank case heater operates only when the compressor is off.
Units: W.
Input Restrictions: The value is prescribed to be 10 W per ton (rated net cooling capacity).
Standard Design: Not applicable.
CRANKCASE HEATER SHUTOFF TEMPERATURE
Applicability: VRF.
Definition: The outdoor air dry-bulb temperature above which the crankcase heater is not permitted to operate.
Units: Deg F.
Input Restrictions: The value is prescribed to be 50°F.
Standard Design: Not applicable..
Plant management is a method of sequencing equipment. Separate plant management schemes may be entered for chilled water systems, hot water systems, etc. The following building descriptors are specified for each load range, e.g., when the cooling load is below 300 tons, between 300 tons and 800 tons, and greater than 800 tons.
Equipment Type Managed
Applicability: All plant systems.
Definition: The type of equipment under a plant management control scheme.
Choices include:
•Chilled water cooling
•Hot water space heating
•Condenser water heat rejection
•Electrical generation
Units: None.
Input Restrictions: As designed.
Standard Design: Same as the proposed design.
Equipment Schedule
Applicability: All plant equipment.
Definition: A schedule that identifies when the equipment is in service.
Units: Data structure.
Input Restrictions: As designed.
Standard Design: Operation staging when multiple equipment is used.
Equipment Operation
Applicability: All plant equipment.
Definition: Equipment operation can be either on-demand or always-on.
On-demand operation means the equipment cycles on when it is scheduled to be in service and when it is needed to meet building loads. Otherwise, it is off.
Always-on means that equipment runs continuously when it scheduled to be in service. For the purpose of the compliance model, always-on is used for equipment such as chillers that are base-loaded, and on-demand equipment is scheduled to be on only when the base-loaded equipment (one or more) cannot meet the load.
Units: None.
Input Restrictions: As designed; default is on-demand.
Standard Design: Assume on-demand operation.
Equipment Staging Sequence
Applicability: All plant equipment.
Definition: The staging sequence for plant equipment (chillers and boilers) indicates how multiple pieces of equipment will be staged on and off when a single piece of equipment is unable to meet the load. In both the proposed and standard design, the compliance software uses the optimal sequence to determine plant staging based on part-load performance. This descriptor is used to identify sequencing when the plant contains unequal equipment, where the order in which the plant equipment is enabled affects plant energy use.
Units: Structure – an array, where each element includes a) the load range, in minimum tons and maximum tons; and b) a list of equipment that is enabled to operate. The equipment will run in the priority matching the order of the equipment listed.
Input Restrictions: As designed; user may specify load ranges for staging each plant equipment.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
The standard design chiller and boiler plant each consist of one or more equal chillers or boilers, so the loading order is not applicable
The compliance model inputs below document the requirements to model a chilled water thermal energy storage system with compliance software. Some systems (ice storage, eutectic salts) cannot be modeled with compliance software.
Thermal Energy Storage Systems Name
Applicability: All thermal energy storage systems.
Definition: A unique descriptor for thermal energy storage systems.
Units: Text, unique.
Input Restrictions: Where applicable, this should match the tags that are used on the plans such that a plan reviewer can make a connection.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Thermal Energy Storage Systems Type
Applicability: All thermal energy storage systems.
Definition: The type of thermal energy storage system being used.
Chilled water storage system is the only currently supported option.
Units: List chilled water.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Discharge Priority
Applicability: All thermal energy storage systems.
Definition: A descriptor determines whether the storage system or a chiller will operate first to meet cooling loads during the discharge period. Storage priority will normally provide larger demand charge savings but requires a larger storage system. Chiller priority allows use of a significantly smaller storage system, but demand reduction will be smaller.
Units: List storage or chiller.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Operation Mode Schedule
Applicability: All thermal energy storage systems.
Definition: A schedule which controls operating mode of the thermal energy storage system.
A thermal energy storage system can be discharging (supplying chilled water to meet cooling loads), charging (receiving chilled water to be stored for later use), or off. The operation mode schedule specifies one of these modes for each of the 8,760 hours in a year.
Units: Data structure - thermal energy storage mode schedule, specifies charging, discharging, or off on an hourly basis.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Rated Capacity
Applicability: All thermal energy storage systems.
Definition: The design cooling capacity of the thermal energy storage system.
The rated cooling capacity of the thermal energy storage system is determined by design flow rate of the thermal energy storage system and the temperature difference between the fluid system supply and return water temperature during discharging.
Units: Btu/hr.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Tank Location
Applicability: All thermal energy storage systems.
Definition: The location of the heat pump water heater for determining losses and heat energy interaction with the surroundings.
Units: List zone, outdoors, or underground.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Tank Shape
Applicability: All thermal energy storage systems.
Definition: The shape of the energy storage system tank used to calculate surface area of the tank for heat gain/loss calculations.
Units: List: Vertical cylinder, Horizontal cylinder, or rectangular.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Tank Volume
Applicability: All thermal energy storage systems.
Definition: The volume of water held in the thermal energy storage system tank.
The tank volume and the rated capacity will determine how long the storage system can meet the load.
Units: Gallons.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Tank Height
Applicability: All thermal energy storage systems.
Definition: For vertical cylinder or rectangular tank, the height will be the maximum internal height of water held in the upright storage tank. For horizontal cylinder tank, the height of the storage tank will be the inner diameter of the storage tank.
Units: Feet.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.
Tank Length to Width Ratio
Applicability: All thermal energy storage systems.
Definition: The length to width ratio of a rectangular storage tank in plan view. It is required only if tank shape is rectangular.
If the tank is square, the length to width ratio is one. For a rectangular tank, the ratio will be greater than one since the length of the tank is always greater than the width of the tank. This is used to determine the surface area of the tank.
Units: Unitless ratio.
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable
Tank R-Value
Applicability: All thermal energy storage systems.
Definition: The insulation applied to the tank used in calculating the tank U-factor.
Units: R-value (h-ft²-F/Btu).
Input Restrictions: As designed.
Standard Design: For healthcare facilities, same as the Proposed Design. For all others, not applicable.