This section applies to buildings served by unitary or packaged HVAC equipment listed in Tables C403.2.3(1) through C403.2.3(8), each serving one zone and controlled by a single thermostat in the zone served. It also applies to two-pipe heating systems serving one or more zones, where no cooling system is installed.
Each cooling system that has a fan shall include an air economizer meeting the requirements of Sections C403.3.1.1 through C403.3.1.1.4.
Exception: Economizers are not required for the systems listed below.
1. Individual fan-cooling units with a supply capacity less than 54,000 Btu/h for comfort cooling applications.
2. Individual fan-cooling units with a supply capacity less than 135,000 Btu/h for computer room applications in Climate Zones 5A and 6A.
3. Individual fan-cooling units, without regard to supply capacity, for computer room applications in Climate Zone 4A.
4. In Group I-2 occupancies, hospitals, Group B occupancies, and ambulatory care facilities, where more than 75 percent of the air designed to be supplied by the system is to spaces that are required to be humidified above a 35°F (1.7 °C) dew-point temperature to comply with applicable codes or accreditation standards. In other occupancies, where more than 25 percent of the air designed to be supplied by the system is to spaces that are designed to be humidified above 35°F (1.7 °C) dew-point temperature to satisfy process needs.
5. Systems that serve residential spaces where the total building residential cooling capacity is less than 270,000 Btu/h.
6. Systems expected to operate less than 20 hours per week.
7. Where the use of outdoor air for cooling will affect supermarket open refrigerated casework systems.
8. Where the cooling efficiency meets or exceeds the efficiency requirements in Table C403.3.1.
9. Systems that include a condenser heat recovery system that is designed to utilize 60 percent of the peak heat rejection load at design conditions and there is a documented need for that rejected heat for either service hot water or space heating during peak heat rejection design conditions.
10. Systems that serve spaces estimated as having a sensible cooling load at design conditions, excluding transmission and infiltration loads, of less than or equal to transmission and infiltration losses at an outdoor temperature of 60°F.
TABLE C403.3.1 EQUIPMENT EFFICIENCY PERFORMANCE EXCEPTION FOR ECONOMIZERS
Exception: Economizers are not required for the systems listed below.
1. Individual fan-cooling units with a supply capacity less than 54,000 Btu/h for comfort cooling applications.
2. Individual fan-cooling units with a supply capacity less than 135,000 Btu/h for computer room applications in Climate Zones 5A and 6A.
3. Individual fan-cooling units, without regard to supply capacity, for computer room applications in Climate Zone 4A.
4. In Group I-2 occupancies, hospitals, Group B occupancies, and ambulatory care facilities, where more than 75 percent of the air designed to be supplied by the system is to spaces that are required to be humidified above a 35°F (1.7 °C) dew-point temperature to comply with applicable codes or accreditation standards. In other occupancies, where more than 25 percent of the air designed to be supplied by the system is to spaces that are designed to be humidified above 35°F (1.7 °C) dew-point temperature to satisfy process needs.
5. Systems that serve residential spaces where the total building residential cooling capacity is less than 270,000 Btu/h.
6. Systems expected to operate less than 20 hours per week.
7. Where the use of outdoor air for cooling will affect supermarket open refrigerated casework systems.
8. Where the cooling efficiency meets or exceeds the efficiency requirements in Table C403.3.1.
9. Systems that include a condenser heat recovery system that is designed to utilize 60 percent of the peak heat rejection load at design conditions and there is a documented need for that rejected heat for either service hot water or space heating during peak heat rejection design conditions.
10. Systems that serve spaces estimated as having a sensible cooling load at design conditions, excluding transmission and infiltration loads, of less than or equal to transmission and infiltration losses at an outdoor temperature of 60°F.
TABLE C403.3.1 EQUIPMENT EFFICIENCY PERFORMANCE EXCEPTION FOR ECONOMIZERS
| CLIMATE ZONE | COOLING EQUIPMENT EFFICIENCY IMPROVEMENT (%)a |
| 4A | 42 |
| 5A | 49 |
| 6A | 56 |
| a. A system qualifies for Exception 8 to the requirements of Section C403.3.1 if: |
| (1) the energy efficiency of the HVAC unit is rated with a "part load" metric (such as IPLV, IEER or SEER); Tables C403.2.3 (1) through C403.2 (8) specify a required minimum cooling efficiency for such HVAC unit using the same "part load" metric; and the rated efficiency of the HVAC unit exceeds the required minimum efficiency (expressed in the same "part load" metric) by at least the percentage shown in this Table; or |
| (2) the energy efficiency of the HVAC unit is not rated with any "part load" metric but is rated with a "full load" metric (such as EER or COP); Tables C403.2.3 (1) through C403.2 (8) specify a required minimum cooling efficiency for such HVAC unit using the same "full load" metric; and the rated efficiency of the HVAC unit exceeds the required minimum efficiency (expressed in the same "full load" metric) by at least the percentage shown in this table. |
Air economizer systems shall be capable of modulating outdoor air and return air dampers to provide up to 100 percent of the design supply air quantity as outdoor air for cooling.
Economizer dampers shall be capable of being sequenced with the mechanical cooling equipment and shall not be controlled by only mixed air temperature.
Exception: The use of mixed air temperature limit control shall be permitted for systems controlled from space temperature (such as single-zone systems).
Exception: The use of mixed air temperature limit control shall be permitted for systems controlled from space temperature (such as single-zone systems).
Air economizers shall be capable of automatically reducing outdoor air intake to the design minimum outdoor air quantity when outdoor air intake will no longer reduce cooling energy usage. High-limit shutoff control types for specific climates shall be chosen from Table C403.3.1.1.3(1). High-limit shutoff control settings for these control types shall be those specified in Table C403.3.1.1.3(2).
TABLE C403.3.1.1.3(1) HIGH-LIMIT SHUTOFF CONTROL OPTIONS FOR AIR ECONOMIZERS
TABLE C403.3.1.1.3(2) HIGH-LIMIT SHUTOFF CONTROL SETTING FOR AIR ECONOMIZERS
TABLE C403.3.1.1.3(1) HIGH-LIMIT SHUTOFF CONTROL OPTIONS FOR AIR ECONOMIZERS
| CLIMATE ZONES | ALLOWED CONTROL TYPES | PROHIBITED CONTROL TYPES |
| 1B, 2B, 3B, 3C, 4B, 4C, 5B, 5C, 6B, 7, 8 | Fixed dry bulb Differential dry bulb Electronic enthalpya Differential enthalpy Dew-point and dry-bulb temperatures | Fixed enthalpy |
| 1A, 2A, 3A, 4A | Fixed dry bulb Fixed enthalpy Electronic enthalpya Differential enthalpy Dew-point and dry-bulb temperatures | Differential dry bulb |
| All other climates | Fixed dry bulb Differential dry bulb Fixed enthalpy Electronic enthalpya Differential enthalpy Dew-point and dry-bulb temperatures | ‒ |
a. Electronic enthalpy controllers are devices that use a combination of humidity and dry-bulb temperature in their switching algorithm.
TABLE C403.3.1.1.3(2) HIGH-LIMIT SHUTOFF CONTROL SETTING FOR AIR ECONOMIZERS
| DEVICE TYPE | CLIMATE ZONE | REQUIRED HIGH LIMIT (ECONOMIZER OFF WHEN): | |
| Fixed dry bulb | 1B, 2B, 3B, 3C, 4B, 4C, 5B, 5C, 6B, 7, 8 | EQUATION | DESCRIPTION |
| TOA > 75°F | Outdoor air temperature exceeds 75°F | ||
| 5A, 6A, 7A | TOA > 70°F | Outdoor air temperature exceeds 70°F | |
| All other zones | TOA > 65°F | Outdoor air temperature exceeds 65°F | |
| Differential dry bulb | 1B, 2B, 3B, 3C, 4B, 4C, 5A, 5B, 5C, 6A, 6B, 7, 8 | TOA > TRA | Outdoor air temperature exceeds return air temperature |
| Fixed enthalpy | All | hOA > 28 Btu/lba | Outdoor air enthalpy exceeds 28 Btu/lb of dry aira |
| Electronic Enthalpy | All | (TOA,RHOA) > A | Outdoor air temperature/RH exceeds the "A" setpoint curveb |
| Differential enthalpy | All | hOA > hRA | Outdoor air enthalpy exceeds return air enthalpy |
| Dew-point and dry bulb temperatures | All | DPOA > 55°F or TOA > 75°F | Outdoor air dry bulb exceeds 75°F or outside dew point exceeds 55°F (65 gr/lb) |
| For SI: °C = (°F - 32) × 5/9, 1 Btu/lb = 2.33 kJ/kg. 5/9 |
| a. At altitudes substantially different than sea level, the Fixed Enthalpy limit shall be set to the enthalpy value at 75°F and 50-percent relative humidity. As an example, at approximately 6,000 feet elevation the fixed enthalpy limit is approximately 30.7 Btu/lb. |
| b. Setpoint "A" corresponds to a curve on the psychometric chart that goes through a point at approximately 75°F and 40-percent relative humidity and is nearly parallel to dry-bulb lines at low humidity levels and nearly parallel to enthalpy lines at high humidity levels. |
Systems shall be capable of relieving excess outdoor air during air economizer operation to prevent over-pressurizing the building. The relief air outlet shall be located to avoid recirculation into the building.
Exhaust/relief and outdoor air dampers shall meet the requirements of Section C403.2.4.4.2.
Hydronic systems of at least 300,000 Btu/h (87 930 W) design output capacity supplying heated and chilled water to comfort conditioning systems shall include controls that meet the requirements of Section C403.4.3.
All air-conditioning equipment and air-handling units with direct expansion cooling and a cooling capacity of at least 110,000 Btu/h that serve single zones shall have their supply fans controlled by multi-speed motors or variable-speed drives. The supply fan controls shall be configured to reduce the airflow to no more than the larger of the following at cooling demands no larger than 50 percent of the cooling capacity:
1. Two-thirds of the full fan speed, or
2. The volume of outdoor air required to meet the ventilation requirements of the 2010 Mechanical Code of New York State (or, in New York City, the corresponding portion of the Mechanical Code of New York City).
1. Two-thirds of the full fan speed, or
2. The volume of outdoor air required to meet the ventilation requirements of the 2010 Mechanical Code of New York State (or, in New York City, the corresponding portion of the Mechanical Code of New York City).
In Group R-1 occupancies, each sleeping room shall be provided with a dedicated system to control automatically the heating, ventilating, and air-conditioning (HVAC) systems to control the energy consumption during unoccupied periods. The controls shall be designed to (change) raise cooling and lower heating temperature set points by at least 4°F (2.22°C) during periods when the sleeping room is unoccupied.
Exception:
Automatic controls are not required in Group R-1 occupancies with fewer than 20 sleeping rooms.
Exception:
Automatic controls are not required in Group R-1 occupancies with fewer than 20 sleeping rooms.
The provisions of Section C403.2.6 shall apply to simple HVAC systems and equipment.
The provisions of Section C403.2.10 shall apply to simple HVAC systems and equipment.