View all text of Subpart E [§ 434.501 - § 434.521]
§ 434.517 - HVAC systems and equipment.
517.1 The specifications and requirements for the HVAC systems of the Prototype and Reference Buildings shall be those in Table 517.1.1, HVAC Systems for Prototype and Reference Buildings. For the calculation of the Design Energy Consumption, the HVAC systems and equipment of the Proposed Design shall be used.
517.2 The systems and types of energy presented in Table 517.1.1 are assumptions for calculating the Energy Cost Budget. They are not requirements for either systems or the type of energy to be used in the Proposed Building or for the calculation of the Design Energy Cost.
Table 517.1.1—HVAC Systems of Prototype and Reference Buildings 1 2
| Building/space occupancy | System No.
(Table 517.4.1) | Remarks
(Table 517.4.1) | Assembly: | a. Churches (any size) | 1 | b. ≤50,000 ft 2 or ≤3 floors | 1 or 3 | Note 1. | c. >50,000 ft 2 or >3 floors | 3 | Office: | a. ≤20,000 ft 2 | 1 | b. ≤50,000 ft 2 and either ≤3 floors or ≤75,000 ft 2 | 4 | c. <75,000 ft 2 or >3 floors | 5 | Retail: | a. ≤50,000 ft 2 | 1 or 3 | Note 1. | b. >50,000 ft 2 | 4 or 5 | Note 1. | Warehouse | 1 | Note 1. | School: | a. ≤75,000 ft 2 or ≤3 floors | 1 | b. >75,000 ft 2 or >3 floors | 3 | Hotel/Motel: | a. ≤3 stories | 2 or 7 | Note 5, 7. | b. >3 stories | 6 | Note 6. | Restaurant | 1 or 3 | Note 1. | Health: | a. Nursing Home (any size) | 2 or 7 | Note 7. | b. ≤15,000 ft 2 | 1 | c. <15,000 ft 2 or ≤50,000 ft 2 | 4 | Note 2. | d. >50,000 ft 2 | 5 | Note 2, 3. | Multi-family High Rise Residential >3 stories | 7 |
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1 Space and Service Water Heating budget calculations shall be made using both electricity and natural gas. The Energy Cost Budget shall be the lower of these two calculations. If natural gas is not available at the rate, electricity and #2 fuel oil shall be used for the budget calculations.
2 The system and energy types presented in this Table are not intended as requirements or recommendations for the proposed design. Floor areas below are the total conditioned floor areas for the listed occupancy type in the building. The number of floors indicated below is the total number of occupied floors for the listed occupancy type.
517.3 HVAC Zones. HVAC zones for calculating the Energy Cost Budget of the Prototype or Reference Building shall consist of at least four perimeter and one interior zones per floor. Prototype Buildings shall have one perimeter zone facing each cardinal direction. The perimeter zones of Prototype and Reference Buildings shall be 15 ft in width, or one-third the narrow dimension of the building, when this dimension is between 30 ft and 45 ft inclusive, or one-half the narrow dimension of the building when this dimension is less than 30 ft. Zoning requirements shall be a default assumption for calculating the Energy Cost Budget. For multi-family high-rise residential buildings, the prototype building shall have one zone per dwelling unit. The proposed design shall have one zone per unit unless zonal thermostatic controls are provided within units; in this case, two zones per unit shall be modeled. Building types such as assembly or warehouse may be modeled as a single zone if there is only one space.
517.4 For calculating the Design Energy Consumption, no fewer zones shall be used than were in the Prototype and Reference Buildings. The zones in the simulation shall correspond to the zones provided by the controls in the Proposed Design. Thermally similar zones, such as those facing one orientation on different floors, may be grouped together for the purposes of either the Design Energy Consumption or Energy Cost Budget simulation.
Table 517.4.1—HVAC System Description for Prototype and Reference Buildings 1 2
| HVAC component | System #1 | System #2 | System #3 | System #4 | System Description | Packaged rooftop single room, one unit per zone | Packaged terminal air conditioner with space heater or heat pump, one heating/cooling unit per zone | Air handler per zone with central plant | Packaged rooftop VAV w/perimeter reheat. | Fan system—Design supply circulation rate | Note 9 | Note 10 | Note 9 | Note 9. | Supply fan total static pressure | 1.3 in. W.C | N/A | 2.0 in. W.C | 3.0 in. W.C. | Combined supply fan, motor, and drive efficiency | 40% | N/A | 50% | 45%. | Supply fan control | Constant volume | Fan Cycles with call for heating or cooling | Constant volume | VAV w/forward curved contrifugal fan and variable inlet vanes. | Return fan total static pressure | N/A | N/A | 0.6 in. W.C. | 0.6 in. W.C. | Combined return fan, motor, and drive efficiency | N/A | N/A | 25% | 25%. | Return fan control | N/A | N/A | Constant volume | VAV w/forward curved centrifugal fan and discharge dampers. | Cooling System | Direct expansion air cooled | Direct expansion air cooled | Chilled water (Note 1) | Direct expansion air cooled. | Heating System | Furnace, heat pump, or electric resistance (Note 8) | Heat pump w/electric resistance auxiliary or air conditioner w/space heater (Note 8) | Hot water (Note 8, 12) | Hot water (Note 12) or electric resistance (Note B). | Remarks | Dry bulb economizer per Section 7.4.3 (barometric relief) | No economizer | Dry bulb economizer per Section 434.514 | Dry bulb economizer per Section 434.514. Minimum VAV setting per 434.514 exception 1. Supply air reset by zone of greatest cooling demand. |
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1 The systems and energy types presented in this Table are not intended as requirements or recommendations for the proposed design.
2 For numbered notes see end of Table 517.4.1.
Table 517.4.1—HVAC System Description for Prototype and Reference Buildings 1
| HVAC component | Systems #5 | System #6 | System #7 | System Description | Built-up central VAV with perimeter reheat | Fourpipe fan coil per zone with central plant | Water source heat pump | Fan system—Design supply circulation rate | Note 9 | Note 9 | Note 10. | Supply fan total static pressure | 4.0 in W.C | 0.5 in W.C | 0.5 in. W.C. | Combined supply fan, motor, and drive efficiency | 55% | 25A | 25%. | Supply fan control | VAV w/air-foil centrifugal fan and AC frequency variable speed drive | Fan Cycles with call for heating or cooling | Fan cycles w/call for heating or cooling. | Return fan total static pressure | 1.0 in W.C | N/A | N/A. | Combined return fan, motor, and drive efficiency | 30% | N/A | N/A. | Return fan control | VAV with air-foil centrifugal fan and AC frequency variable speed drive | N/A | N/A. | Cooling System | Chilled water (Note 11) | Chilled water (Note 11) | Closed circuit, centrifugal blower type cooling tower sized per Note 11. Circulating pump sized for 2.7 GPM per ton. | Heating System | Hot water (Note 12) or electric resistance (Note 8) | Hot water (Note 12) or electric resistance (Note 8) | Electric or natural draft fossil fuel boiler (Note 8). | Remarks | Dry bulb economizer per Section 7.4.3. Minimum VAV setting per Section 7.4.4.3. Supply air reset by zone of greatest cooling demand | No economizer | Tower fans and boiler cycled to maintain circulating water temperature between 60 and design tower leaving water temperature. |
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Notes:
1. For occupancies such as restaurants, assembly and retail which are part of a mixed use building which, according to Table 517.4.1, includes a central chilled water plant (systems 3, 5, or 6), chilled water system type 3 or 5, as indicated in the Table, shall be used.
2. Constant volume may be used in zones where pressurization relationships must be maintained by code. VAV shall be used in all other areas, in accordance with § 517.4
3. Provide run-around heat recovery systems for all fan systems with minimum outside air intake greater than 75%. Recovery effectiveness shall be 0.60.
4. If a warehouse is not intended to be mechanically cooled, both the Energy Cost Budgets and Design Energy Costs, may be calculated assuming no mechanical cooling.
5. The system listed is for guest rooms only. Areas such as public areas and back-of-house areas shall be served by system 4. Other areas such as offices and retail shall be served by the systems listed in Table 517.4.1 for those occupancy types.
6. The system listed is for guest rooms only. Areas such as public areas and back-of-house areas shall be served by System 5. Other areas such as offices and retail shall be served by the systems listed in Table 517.4.1.1 for those occupancy types.
7. System 2 shall be used for Energy Cost Budget calculation except in areas with design heating outside air temperatures less than 10 °F.
8. Prototype energy budget cost calculations shall be made using both electricity and natural gas. If natural gas is not available at the site, electricity and #2 fuel oil shall be used. The Energy Cost Budget shall be the lower of these results. Alternatively, the Energy Cost Budget may be based on the fuel source that minimizes total operating, maintenance, equipment, and installation costs for the prototype over the building lifetime. Equipment and installation cost estimates shall be prepared using professionally recognized cost estimating tools, guides, and techniques. The methods of analysis shall conform to those of subpart A of 10 CFR part 436. Energy costs shall be based on actual costs to the building as defined in this Section.
9. Design supply air circulation rate shall be based on a supply air to room air temperature differences of 20 °F. A higher supply air temperature may be used if required to maintain a minimum circulation rate of 4.5 air changes per hour or 15 cfm per person at design conditions to each zone served by the system. If return fans are specified, they shall be sized from the supply fan capacity less the required minimum ventilation with outside air, or 75% or the supply air capacity, whichever is larger. Except where noted, supply and return fans shall be operated continually during occupied hours.
10. Fan System Energy when included in the efficiency rating of the unit as defined in § 403.2.4.3 need not be modeled explicitly for this system. The fan shall cycle with calls for heating or cooling.
11. Chilled water systems shall be modeled using a reciprocating chiller for systems with total cooling capacities less than 175 tons, and centrifugal chillers for systems with cooling capacities of 175 tons or greater. For systems with cooling or 600 ton or more, the Energy Cost Budget shall be calculated using two centrifugal chillers lead/lag controlled. Chilled water pumps shall be sized using a 12 °F temperature rise, from 44 °F to 56 °F operating at 65 feed of head and 65% combined impeller and motor efficiency. Condenser water pumps shall be sized using a 10 °F temperature rise, operating at 60 feet of head and 60% combined impeller and motor efficiency. The cooling tower shall be an open circuit, centrifugal blower type sized for the larger of 85 °F leaving water temperature or 10 °F approach to design wet bulb temperature. The tower shall be controlled to provide a 65 °F leaving water temperature whenever weather conditions permit, floating up to design leaving water temperature at design conditions. Chilled water supply temperature shall be reset in accordance with § 434.518.
12. Hot water system shall include a natural draft fossil fuel or electric boiler per Note 8. The hot water pump shall be sized based on a 30 °F temperature drop, for 18 °F to 150 °F, operating at 60 feet of head and a combined impeller and motor efficiency of 60%. Hot water supply temperature shall be reset in accordance with § 434.518.
517.5 Equipment Sizing and Redundant Equipment. For calculating the Energy Cost Budget of Prototype or Reference Buildings, HVAC equipment shall be sized to meet the requirements of subsection 403.2.2, without using any of the exceptions. The size of equipment shall be that required for the building without process loads considered. Redundant or emergency equipment need not be simulated if it is controlled so that it will not be operated during normal operations of the building. The designer shall document the installation of process equipment and the size of process loads.
517.6 For calculating the Design Energy Consumption, actual air flow rates and installed equipment size shall be used in the simulation, except that excess capacity provided to meet process loads need not be modeled unless the process load was not modeled in setting Energy Cost Budget. Equipment sizing in the simulation of the Proposed Design shall correspond to the equipment actually selected for the design and the designer shall not use equipment sized automatically by the simulation tool.
517.6.1 Redundant or emergency equipment need not be simulated if it is controlled to not be operated during normal operations of the building.