CFR > Title 10 - Energy > CHAPTER II—DEPARTMENT OF ENERGY > SUBCHAPTER D—ENERGY CONSERVATION (parts 400 to 491) > PART 434—ENERGY CODE FOR NEW FEDERAL COMMERCIAL AND MULTI-FAMILY HIGH RISE RESIDENTIAL BUILDINGS > SUBPART D—Building Design Requirements—Electric Systems and Equipment (§434.401 to §434.404) > 434.403—Building mechanical systems and equipment.

434.403—Building mechanical systems and equipment.

Mechanical systems and equipment used to provide heating, ventilating, and air conditioning functions as well as additional functions not related to space conditioning, such as, but not limited to, freeze protection in fire projection systems and water heating, shall meet the requirements of this section.
403.1Mechanical Equipment Efficiency. When equipment shown in Tables 403.1a through 403.1f is used, it shall have a minimum performance at the specified rating conditions when tested in accordance with the specified reference standard. The reference standards listed in Tables 403.1a through 403.1f are incorporated by reference, see § 434.701. Omission of minimum performance requirements for equipment not listed in Tables 403.1a through 403.1f does not preclude use of such equipment.
Table 403.1a—Unitary Air Conditioners and Condensing Units, Electrically Operated, Minimum Efficiency Requirements
Equipment type Size category Subcategory or rating condition Minimum Efficiency 2 Test procedure 1
Air Conditioners, Air Cooled < 65,000 Btu/h Split systemSingle Package 10.0 SEER9.7 SEER ARI 210/240(RS-15)*
≥ 65,000 Btu/h and < 135,00 Btu/h Split System and Single Package 8.9 EER 3 8.3 IPLV 3 ARI 210/240(RS-15)*
Code of Federal Regulations 575
≥ 135,000 Btu/h and < 240,000 Btu/h Split System and Single Package 8.5 EER3 7.5 IPLV3
≥ 240,000 Btu/h and < 760,000 Btu/h Split System and Single Package 8.5 EER3 7.5 IPLV3 ARI-340/360(RS-16)*
≥ 760,000 Btu/h Split System and Package 8.3 EER3 7.5 IPLV3 ARI-340/360(RS-16)*
Air Conditioners, Water and Evaporatively Cooled < 65,000 Btu/h Split System and Single Package 9.3 EER3 8.4 IPLV3 ARI 210/240(RS-15)*
≥ 65,000 Btu/h and < 135,000 Btu/h Split System and Single Package 10.5 EERc 9.7 IPLVc ARI 210/240(RS-15)*
≥ 135,000 Btu/h and < 240,000 Btu/h Split System and Single Package 9.6 EERc 9.0 IPLVc ARI-340/360(RS-16)*
≥ 240,000 Btu/h Split System and Single Package 9.6 EERc 9.0 IPLVc ARI-340/360(RS-16)*
Condensing Units, Air Cooled 135,000 Btu/h 9.9 EER11.0 IPLV ARI 365(RS-29)*
Condensing Units, Water or Evaporatively Cooled 135,000 Btu/h 12.9 EER12.9 IPLV ARI 365(RS-29)*
1 See Subpart E for detailed references
2 IPLVs are only applicable to equipment with capacity modulation.
3 Deduct 0.2 from the required EERs and IPLVs for units that have a heating section.
* Incorporation by reference, see § 434.701
Table 403.1b—Unitary and Applied Heat Pumps, Electrically Operated, Minimum Efficiency Requirements
Equipment type Size category Subcategory or rating condition Minimum efficiency 2 Test procedure 1
Air Cooled (Cooling Mode) <65,000 Btu/h Split SystemSingle Package 10.0 SEER9.7 SEER ARI 210/240(RS-15)*
≥65,000 Btu/h and <135,000 Btu/h Split System and Single Package 8.9 EER 3 8.3 IPLV 3 ARI 210/240(RS-15)*
≥135,000 Btu/h and <240,000 Btu/h Split System and Single Package 8.5 EER 3 7.5 IPLV 3 ARI-340/360(RS-16)*
≥240,000 Btu/h Split System and Single Package 8.5 EER 3 7.5 IPLV 3 ARI-340/360(RS-16)*
Water Source (Cooling Mode) <65,000 Btu/h 85 °F Entering Water75 °F Entering Water 9.3 EER10.2 EER ARI-320(RS-27)*
≥65,000 Btu/h and <135,000 Btu/h 85 °F Entering Water75 °F Entering Water 10.5 EER11.0 EER ARI-320(RS-27)*
Groundwater-Source (Cooling Mode) <135,000 Btu/h 70 F Entering Water50 F Entering Water 11.0 EER11.5 EER ARI 325(RS-28)*
Ground Source (Cooling Mode) <135,000 Btu/h 77 F Entering Water70 F Entering Water 10.0 EER10.4 EER ARI 325(RS-28)*
Air Cooled (Heating Mode) <65,000 Btu/h (Cooling Capacity) Split SystemSingle Package 6.8 HSPF6.6 HSPF ARI 210/240(RS-15)*
65,000 Btu/h and <135,000 Btu/h (Cooling Capacity) 47 F db/43 F wb Outdoor Air17 F db/15 F wb Outdoor Air 3.00 COP2.00 COP ARI 210/240(RS-15)*
135,000 Btu/h (Cooling Capacity) 47 F db/43 F wb Outdoor Air17 F db/15 F wb Outdoor 2.90 COP2.00 COP ARI-340/360(RS-1/)*
Water-Source (Heating Mode) <135,000 Btu/h (Cooling Capacity) 70 F Entering Water75 F Entering Water 3.80 COP3.90 COP ARI-320(RS-27)*
Groundwater-Source (Heating Mode) <135,000 Btu/h (Cooling Capacity) 70 F Entering Water50 F Entering Water 3.40 COP3.00 COP ARI 325(RS-28)*
Ground Source (Heating Mode) <135,000 Btu/h (Cooling Capacity) 32 F Entering Water41 F Entering Water 2.50 EER2.70 EER ARI-330(RS-45)*
1 See Subpart E for detailed references.
2 IPLVs are only applicable to equipment with capacity modulation.
3 Deduct 0.2 from the required EERs and IPLVs for units that have a heating section.
* Incorporation by reference, see § 434.701 .
Table 403.1c—Water Chilling Packages, Minimum Efficiency Requirements
Equipment type Size category Subcategory or rating condition Minimum efficiency 2 Test procedure 1
Air-Cooled, With Condenser, Electrically Operated <150 Tons ≥150 Tons 2.70 COP2.80 IPLV 2.50 COP 2.50 IPLV ARI 550 Centrifugal/Rotary Screw (RS-30)* or ARI 590 Reciprocating (RS-31)*
Air-Cooled, Without Condenser, Electrically Operated All Capacities 3.10 COP3.20 IPLV
Water Cooled, Electrically Operated, Positive Displacement (Reciprocating) All Capacities 3.80 COP3.90 IPLV
Water Cooled, Electrically Operated, Positive Displacement (Rotary Screw and Scroll) <150 Tons≥150 Tons and <300 Tons ≥300 Tons 3.80 COP3.90 IPLV 4.20 COP 4.50 IPLV 5.20 COP 5.30 IPLV
Water-Cooled, Electrically Operated, Centrifugal <150 Tons 150 Tons and <300 Tons 300 Tons 3.80 COP3.90 IPLV 4.20 COP 4.50 IPLV 5.20 COP 5.30 IPLV ARI 550(RS-30)*
Absorption Single Effect All Capacities 0.48 COP
Absorption Double Effect, Indirect-Fired All Capacities 0.95 COP1.00 IPLV ARI 560(RS-46)*
Absorption Double-Effect, Direct-Fired All Capacities 0.95 COP1.00 IPLV
1 See Subpart E for detailed references.
2 Equipment must comply with all efficiencies when multiple efficiencies are indicated.
*Incorporation by reference, see § 434.701 .
Table 403.1d—Packaged Terminal Air Conditioners, Packaged Terminal Heat Pumps, Room Air Conditioners, and Room Air-Conditioner Heat Pumps Electrically Operated, Minimum Efficiency Requirements
Equipment type Size category Subcategory or rating condition Minimum efficiency 2 Test procedure 1
PTAC (Cooling Mode) All Capacities 95°F db Outdoor Air82°F db Outdoor Air 10.0- (0.16 × Cap/1,000) 3EER12.2-(0.20 × Cap/1,000) 3EER ARI 310/380(RS-17)* ARI 310/380 (RS-17)*
PTHP (Cooling Mode) All Capacities 95°F db Outdoor Air82°F db Outdoor Air 10.0-(0.16 × Cap/1,000) 3 EER12.2-(0.20 × Cap/1,000) EER
PTHP (Heating Mode) All Capacities 2.90-(0.026 × CAP/1,000) 3 COP
Room Air Conditioners, With Louvered Sides <6,000 Btu/h≥6,000 Btu/h and <8,000 Btu/h ≥8,000 Btu/h and <14,000 Btu/h ≥14,000 Btu/h and <20,000 Btu/h ≥20,000 Btu/h 8.0 EER8.5 EER 9.0 EER 8.8 EER 8.2 EER ANSI/AHAM RAC-1(RS-40)*
Room Air Conditioner, Without Louvered Sides <6,000 Btu/h≥6,000 Btu/h and <20,000 Btu/h ≥20,000 Btu/h 8.0 EER8.5 EER 8.2 EER ANSI/AHAM RAC-1(RS-40)*
Room Air-Conditioner Heat Pumps With Louvered Sides All Capacities 8.5 EER ANSI/AHAM RAC-1(RS-40)*
Room Air-Conditioner Heat Pumps Without Louvered Sides All Capacities 8.0 EER ANSI/AHAM RAC-1(RS-40*
1 See Subpart E for detailed references.
2 Equipment must comply with all efficiencies when multiple efficiencies are indicated. (Note products covered by the 1992 Energy Policy Act have no efficiency requirement for operation at other than standard rating conditions for products manufactured after 1/1/94).
Code of Federal Regulations 577
3 Cap means the rated capacity of the product in Btu/h. If the unit's capacity is less than 7,000 Btu/h, use 7,000 Btu/h in the calculation. If the unit's capacity is greater than 15,000 Btu/h, use 15,000 Btu/h in the calculation.
* Incorporation by reference, see § 434.701 .
Table 403.1e—Warm Air Furnaces and Combination Warm Air Furnaces/Air Conditioning Units, Warm Air Duct Furnaces and Unit Heaters, Minimum Efficiency Requirements
Equipment type Size category Subcategory or rating condition Minimum efficiencyb,e Test procedure a
Warm Air-Furnace, Gas-Fired < 225,000 Btu/h 78% AFUE or 80% Et DOE 10 CFR 430 Appendix N
≥ 225,000 Btu/h Maximum Capacity c Minimum Capacityc 80% Et 78% Et ANSI Z21.47(RS-21)*
Warm Air-Furnace, Oil-Fired < 225,000 Btu/h 78% AFUE or 80% Et d DOE 10 CFR 430 Appendix N
≥ 225,000 But/h Maximum Capacity c Minimum Capacity 81% Et 81% Et U.L. 727(RS-22)*
Warm Air Duct Furnaces, Gas-Fired All Capacities Maximum Capacity c Minimum Capacity 78% Et 75% Et ANSI Z83.9(RS-23)
Warm Air Unit Heaters, Gas Fired All Capacities Maximum Capacity c Minimum Capacity 78% Et 74% Et ANSI Z83.8(RS-24)*
Oil-Fired All Capacities Maximum Capacity c Minimum Capacity 81% Et 81% Et U.L. 731(RS-25)*
a See Subpart E for detailed references.
b Minimum and maximum ratings as provided for and allowed by the unit's controls.
c Combination units not covered by NAECA (Three-phase power or cooling capacity ≥ 65,000 Btu/h) may comply with either rating.
d Et = thermal efficiency. See referenced document for detailed discussion.
e Ec = combustion efficiency. Units must also include an IID and either power venting or a flue damper. For those furnaces where combustion air is drawn from the conditioned space, a vent damper may be substituted for a flue damper.
* Incorporation by reference, see § 434.701
Table 403.1f—Boilers, Gas- and Oil-Fired, Minimum Efficiency Requirements
Equipment type Size category Subcategory or rating condition Minimum efficiency b Test procedure a
Boilers, Gas-Fired <300,000 Btu/h Hot Water 80% AGUE DOE 10 CFR 430 Appendix N
Steam 75% AGUE DOE 10 CFR 430 Appendix N
<300,000 Btu/h Maximum Capacity c Minimum Capacity 80% Ec 80% Ec ANSI Z21.13(RS-32)*
Boilers, Oil-Fired <300,000 Btu/h 80% AGUE DOE 10 CFR 430 (RS-20)*
<300,000 Btu/h Maximum Capacity c Minimum Capacity 83% Ec 83% Ec U.L. 726(RS-33)*
Oil-Fired (Residual) <3000,000 Btu/h Maximum Capacity c Minimum Capacity 83% Ec 83% Ec
a See Subpart E for detailed references.
b Minimum and maximum ratings as provided for and allowed by the unit's controls.
c Ec = combustion efficiency (100% less flue losses). See reference document for detailed information.
* Incorporation by reference, see § 434.701 .
403.1.1Where multiple rating conditions and/or performance requirements are provided, the equipment shall satisfy all stated requirements.
403.1.2Equipment used to provide water heating functions as part of a combination integrated system shall satisfy all stated requirements for the appropriate space heating or cooling category.
403.1.3The equipment efficiency shall be supported by data furnished by the manufacturer or shall be certified under a nationally recognized certification program or rating procedure.
403.1.4Where components, such as indoor or outdoor coils, from different manufacturers are used, the system designer shall specify component efficiencies whose combined efficiency meets the standards herein.
403.2HVAC Systems.
403.2.1Load Calculations. Heating and cooling system design loads for the purpose of sizing systems and equipment shall be determined in accordance with the procedures described in RS-1 (incorporated by reference, see § 434.701) using the design parameters specified in subpart C of this part.
403.2.2Equipment and System Sizing. Heating and cooling equipment and systems shall be sized to provide no more than the loads calculated in accordance with sub section 403.2.1. A single piece of equipment providing both heating and cooling must satisfy this provision for one function with the other function sized as small as possible to meet the load, within available equipment options. Exceptions are as follows:
(a) When the equipment selected is the smallest size needed to meet the load within available options of the desired equipment line.
(b) Standby equipment provided with controls and devices that allow such equipment to operate automatically only when the primary equipment is not operating.
(c) Multiple units of the same equipment type with combined capacities exceeding the design load and provided with controls that sequence or otherwise optimally control the operation of each unit based on load.
403.2.3Separate Air Distribution System. Zones with special process temperature and/or humidity requirements shall be served by air distribution systems separate from those serving zones requiring only comfort conditions or shall include supplementary provisions so that the primary systems may be specifically controlled for comfort purposes only. Exceptions: Zones requiring only comfort heating or comfort cooling that are served by a system primarily used for process temperature and humidity control need not be served by a separate system if the total supply air to these comfort zones is no more than 25% of the total system supply air or the total conditioned floor area of the zones is less than 1000 ft2.
403.2.4Ventilation and Fan System Design. Ventilation systems shall be designed to be capable of reducing the supply of outdoor air to the minimum ventilation rates required by Section 6.1.3 of RS-41 (incorporated by reference, see § 434.701) through the use of return ducts, manually or automatically operated control dampers, fan volume controls, or other devices. Exceptions are as follows: Minimum outdoor air rates may be greater if:
(a) Required to make up air exhausted for source control of contaminants such as in a fume hood.
(b) Required by process systems.
(c) Required to maintain a slightly positive building pressure. For this purpose, minimum outside air intake may be increased up to no greater than 0.30 air changes per hour in excess of exhaust quantities.
403.2.4.1Ventilation controls for variable or high occupancy areas. Systems with design outside air capacities greater than 3,000 cfm serving areas having an average design occupancy density exceeding 100 people per 1,000 ft 2 shall include means to automatically reduce outside air intake to the minimum values required by RS-41 (incorporated by reference, see § 434.701) during unoccupied or low-occupancy periods. Outside air shall not be reduced below 0.14 cfm/ft 2. Outside air intake shall be controlled by one or more of the following:
(a) A clearly labeled, readily accessible bypass timer that may be used by occupants or operating personnel to temporarily increase minimum outside air flow up to design levels.
(b) A carbon dioxide (CO2) control system having sensors located in the spaces served, or in the return air from the spaces served, capable of maintaining space CO2 concentrations below levels recommended by the manufacturer, but no fewer than one sensor per 25,000 ft 2 of occupied space shall be provided.
(c) An automatic timeclock that can be programmed to maintain minimum outside air intake levels commensurate with scheduled occupancy levels.
(d) Spaces equipped with occupancy sensors.
403.2.4.2Ventilation Controls for enclosed parking garages. Garage ventilation fan systems with a total design capacity greater than 30,000 cfm shall have automatic controls that stage fans or modulate fan volume as required to maintain carbon monoxide (CO) below levels recommended in RS-41.
403.2.4.3Ventilation and Fan Power. The fan system energy demand of each HVAC system at design conditions shall not exceed 0.8 W/cfm of supply air for constant air volume systems and 1.25 W/cfm of supply air for variable- air-volume (VAV) systems. Fan system energy demand shall not include the additional power required by air treatment or filtering systems with pressure drops over 1 in. w.c. Individual VAV fans with motors 75 hp and larger shall include controls and devices necessary for the fan motor to demand no more than 30 percent of design wattage at 50 percent of design air volume, based on manufacturer's test data. Exceptions are as follows:
(a) Systems with total fan system motor horsepower of 10 hp or less.
(b) Unitary equipment for which the energy used by the fan is considered in the efficiency ratings of sub section 403.1.
403.2.5Pumping System Design. HVAC pumping systems used for comfort heating and/or comfort air conditioning that serve control valves designed to modulate or step open and closed as a function of load shall be designed for variable fluid flow and capable of reducing system flow to 50 percent of design flow or less. Exceptions are as follows:
(a) Systems where a minimum flow greater than 50% of the design flow is required for the proper operation of equipment served by the system, such as chillers.
(b) Systems that serve no more than one control valve.
(c) Systems with a total pump system horse power ≤10 hp.
(d) Systems that comply with sub section 403.2.6.8 without exception.
403.2.6Temperature and Humidity Controls.
403.2.6.1System Controls. Each heating and cooling system shall include at least one temperature control device.
403.2.6.2Zone Controls. The supply of heating and cooling energy to each zone shall be controlled by individual thermostatic controls responding to temperature within the zone. For the purposes of this section, a dwelling unit is considered a zone. Exceptions are as follows: Independent perimeter systems that are designed to offset building envelope heat losses or gains or both may serve one or more zones also served by an interior system when the perimeter system includes at least one thermostatic control zone for each building exposure having exterior walls facing only one orientation for at least 50 contiguous ft and the perimeter system heating and cooling supply is controlled by thermostat(s) located within the zone(s) served by the system.
403.2.6.3Zone Thermostatic Control Capabilities. Where used to control comfort heating, zone thermostatic controls shall be capable of being set locally or remotely by adjustment or selection of sensors down to 55°F or lower. Where used to control comfort cooling, zone thermostatic controls shall be capable of being set locally or remotely by adjustment or selection of sensors up to 85°F or higher. Where used to control both comfort heating and cooling, zone thermostatic controls shall be capable of providing a temperature range or deadband of at least 5°F within which the supply of heating and cooling energy to the zone is shut off or reduced to a minimum. Exceptions are as follows:
(a) Special occupancy or special usage conditions approved by the building official or
(b) Thermostats that require manual changeover between heating and cooling modes.
403.2.6.4Heat Pump Auxiliary Heat. Heat pumps having supplementary electric resistance heaters shall have controls that prevent heater operation when the heating load can be met by the heat pump. Supplemental heater operation is permitted during outdoor coil defrost cycles not exceeding 15 minutes.
403.2.6.5Humidistats. Humidistats used for comfort purposes shall be capable of being set to prevent the use of fossil fuel or electricity to reduce relative humidity below 60% or increase relative humidity above 30%.
403.2.6.6Simultaneous Heating and Cooling. Zone thermostatic and humidistatic controls shall be capable of operating in sequence the supply of heating and cooling energy to the zone. Such controls shall prevent: Reheating; recooling; mixing or simultaneous supply of air that has been previously mechanically heated and air that has been previously cooled, either by mechanical refrigeration or by economizer systems; and other simultaneous operation of heating and cooling systems to the same zone. Exceptions are as follows:
(a) Variable-air-volume systems that, during periods of occupancy, are designed to reduce the air supply to each zone to a minimum before heating, recooling, or mixing takes place. This minimum volume shall be no greater than the larger of 30% of the peak supply volume, the minimum required to meet minimum ventilation requirements of the Federal agency. (0.4 cfm/ft 2 of zone conditioned floor area, and 300 cfm).
(b) Zones where special pressurization relationships or cross-contamination requirements are such that variable-air-volume systems are impractical, such as isolation rooms, operating areas of hospitals and clean rooms.
(c) At least 75% of the energy for reheating or for providing warm air in mixing systems is provided from a site-recovered or site-solar energy source.
(d) Zones where specified humidity levels are required to satisfy process needs, such as computer rooms and museums.
(e) Zones with a peak supply air quantity of 300 cfm or less.
403.2.6.7Temperature Reset for Air Systems. Air systems supplying heated or cooled air to multiple zones shall include controls that automatically reset supply air temperatures by representative building loads or by outside air temperature. Temperature shall be reset by at least 25% of the design supply air to room air temperature difference. Zones that are expected to experience relatively constant loads, such as interior zones, shall be designed for the fully reset supply temperature. Exception are as follows: Systems that comply with sub section 403.2.6.6 without using exceptions (a) or (b).
403.2.6.8Temperature Reset for Hydronic Systems. Hydronic systems of at least 600,000 Btu/hr design capacity supplying heated and/or chilled water to comfort conditioning systems shall include controls that automatically reset supply water temperatures by representative building loads (including return water temperature) or by outside air temperature. Temperature shall be reset by at least 25% of the design supply-to-return water temperature difference. Exceptions are as follows:
(a) Systems that comply with sub section 403.2.5 without exception or
(b) Where the design engineer certifies to the building official that supply temperature reset controls cannot be implemented without causing improper operation of heating, cooling, humidification, or dehumidification systems.
403.2.7Off Hour Controls.
403.2.7.1Automatic Setback or Shutdown Controls. HVAC systems shall be equipped with automatic controls capable of accomplishing a reduction of energy use through control setback or equipment shutdown. Exceptions are as follows:
(a) Systems serving areas expected to operate continuously or
(b) Equipment with full load demands not exceeding 2 kW controlled by readily accessible, manual off-hour controls.
403.2.7.2Shutoff Dampers. Outdoor air supply and exhaust systems shall be provided with motorized or gravity dampers or other means of automatic volume shutoff or reduction. Exceptions are as follows:
(a) Systems serving areas expected to operate continuously.
(b) Individual systems which have a design airflow rate or 3000 cfm or less.
(c) Gravity and other non-electrical ventilation systems controlled by readily accessible, manual damper controls.
(d) Where restricted by health and life safety codes.
403.2.7.3Zone Isolation systems that serve zones that can be expected to operate nonsimultaneously for more than 750 hours per year shall include isolation devices and controls to shut off or set back the supply of heating and cooling to each zone independently. Isolation is not required for zones expected to operate continuously or expected to be inoperative only when all other zones are inoperative. For buildings where occupancy patterns are not known at the time of system design, such as speculative buildings, the designer may predesignate isolation areas. The grouping of zones on one floor into a single isolation area shall be permitted when the total conditioned floor area does not exceed 25,000 ft 2 per group.
403.2.8Economizer Controls.
403.2.8.1Each fan system shall be designed and capable of being controlled to take advantage of favorable weather conditions to reduce mechanical cooling requirements. The system shall include either: A temperature or enthalpy air economizer system that is capable of automatically modulating outside air and return air dampers to provide up to 85% of the design supply air quantity as outside air, or a water economizer system that is capable of cooling supply air by direct and/or indirect evaporation and is capable of providing 100% of the expected system cooling load at outside air temperatures of 50°F dry-bulb/45°F wet-bulb and below. Exceptions are as follows:
(a) Individual fan-cooling units with a supply capacity of less than 3000 cfm or a total cooling capacity less than 90,000 Btu/h.
(b) Systems with air-cooled or evaporatively cooled condensers that include extensive filtering equipment provided in order to meet the requirements of RS-41 (incorporated by reference, see § 434.701 ).
(c) Systems with air-cooled or evaporatively cooled condensers where the design engineer certifies to the building official that use of outdoor air cooling affects the operation of other systems, such as humidification, dehumidification, and supermarket refrigeration systems, so as to increase overall energy usage.
(d) Systems that serve envelope-dominated spaces whose sensible cooling load at design conditions, excluding transmission and infiltration loads, is less than or equal to transmission and infiltration losses at an outdoor temperature of 60°F.
(e) Systems serving residential spaces and hotel or motel rooms.
(f) Systems for which at least 75% of the annual energy used for mechanical cooling is provided from a site-recovered or site-solar energy source.
(g) The zone(s) served by the system each have operable openings (windows, doors, etc.) with an openable area greater than 5% of the conditioned floor area. This applies only to spaces open to and within 20 ft of the operable openings. Automatic controls shall be provided that lock out system mechanical cooling to these zones when outdoor air temperatures are less than 60°F.
403.2.8.2Economizer systems shall be capable of providing partial cooling even when additional mechanical cooling is required to meet the remainder of the cooling load. Exceptions are as follows:
(a) Direct-expansion systems may include controls to reduce the quantity of outdoor air as required to prevent coil frosting at the lowest step of compressor unloading. Individual direct-expansion units that have a coo