Section 140.4 Prescriptive Requirements for Space-Conditioning Systems
A building complies with this section by being designed with and having constructed and installed a space-conditioning system that meets the applicable requirements of Subsections (a) through (o).
- For systems serving high-rise residential buildings, hotel/motel buildings, and nonresidential buildings other than healthcare facilities, the method in the 2017 ASHRAE Handbook, Fundamentals shall be used or as specified in a method approved by the Commission.
- For system serving healthcare facilities the method in the California Mechanical Code shall be used.
- For systems serving high-rise residential buildings, hotel/motel buildings, and nonresidential buildings other than healthcare facilities, ASHRAE Standard 55 or the 2017 ASHRAE Handbook, Fundamentals Volume, except that winter humidification and summer dehumidification shall not be required.
- For systems serving high-rise residential buildings, hotel/motel buildings, and nonresidential buildings other than healthcare facilities the design conditions from Reference Joint Appendix JA2 shall be used, which is based on data from the ASHRAE Climatic Data for Region X. Heating design temperatures shall be no lower than the Heating Winter Median of Extremes values. Cooling design temperatures shall be no greater than the 0.5 percent Cooling Dry Bulb and Mean Coincident Wet Bulb values.
- Ventilation. Outdoor air ventilation loads shall be calculated using the ventilation rates required in Section 120.1(c)3.
- Envelope. Envelope heating and cooling loads shall be calculated using envelope characteristics, including square footage, thermal conductance, Solar Heat Gain Coefficient or shading coefficient, and air leakage, consistent with the proposed design.
- Lighting. Lighting heating and cooling loads shall be based on actual design lighting levels or power densities as specified in Section 140.6.
- People. Occupant density shall be based on the expected occupancy of the building and shall be the same as determined under Section 120.1(c)3A, if used. Sensible and latent heat gains shall be as listed in the 2005 ASHRAE Handbook- Fundamentals, Chapter 30, Table 1.
- Process loads. Loads caused by a process shall be based upon actual information on the intended use of the building.
- Actual information based on the intended use of the building; or
- Published data from manufacturer's technical publications or from technical societies, such as the ASHRAE Handbook, Applications Volume; or
- Other data based on the designer's experience of expected loads and occupancy patterns.
- Internal heat gains. Internal heat gains may be ignored for heating load calculations.
- Safety factor. Calculated design loads based on 140.4(b)1 through 10 may be increased by up to 10 percent to account for unexpected loads or changes in space usage.
- Other loads. Loads such as warm-up or cool-down shall be calculated from principles based on the thermal capacity of the building and its contents, the degree of setback, and desired recovery time; or may be assumed to be no more than 30 percent for heating and 10 percent for cooling of the steady-state design loads. In addition, the steady-state load may include a safety factor in accordance with Section 140.4(b)11.
- Fan power limitation. At design conditions each fan system shall not exceed the allowable fan system power of option 1 or 2 as specified in Table 140.4-A.
- Static pressure sensor location. Static pressure sensors used to control variable air volume fans shall be placed in a position such that the controller set point is no greater than one-third the total design fan static pressure, except for systems with zone reset control complying with Section 140.4(c)2B. If this results in the sensor being located downstream of any major duct split, multiple sensors shall be installed in each major branch with fan capacity controlled to satisfy the sensor furthest below its setpoint; and,
- Reheating; and
- Recooling; and
- Simultaneous provisions of heating and cooling to the same zone, such as mixing or simultaneous supply of air that has been previously mechanically heated and air that has been previously cooled, either by cooling equipment or by economizer systems; or
- The first stage of heating consists of modulating the zone supply air temperature setpoint up to a maximum setpoint no higher than 95°F while the airflow is maintained at the dead band flow rate.
- The second stage of heating consists of modulating the airflow rate from the dead band flow rate up to the heating maximum flow rate.
- An air economizer capable of modulating outside- air and return-air dampers to supply 100 percent of the design supply air quantity as outside air; or
- A water economizer capable of providing 100 percent of the expected system cooling load at outside air temperatures of 50°F dry-bulb and 45°F wet-bulb and below.
- Capable of providing partial cooling even when additional mechanical cooling is required to meet the remainder of the cooling load.
- Warranty. 5-year manufacturer warranty of economizer assembly.
- Damper reliability testing. Suppliers of economizers shall certify that the economizer assembly, including but not limited to outdoor air damper, return air damper, drive linkage and actuator, have been tested and are able to open and close against the rated airflow and pressure of the system for 60,000 damper opening and closing cycles.
- Damper leakage. Economizer outdoor air and return air dampers shall have a maximum leakage rate of 10 cfm/sf at 250 Pascals (1.0 in. of water) when tested in accordance with AMCA Standard 500-D. The economizer outside air and return air damper leakage rates shall be certified to the Energy Commission in accordance with Section 110.0.
- Adjustable setpoint. If the high-limit control is fixed dry bulb or fixed enthalpy ± fixed dry bulb, then the control shall have an adjustable setpoint.
- Drybulb and wetbulb temperatures accurate to ±2°F over the range of 40°F to 80°F;
- Enthalpy accurate to ±3 Btu/lb over the range of 20 Btu/lb to 36 Btu/lb;
- Relative humidity (RH) accurate to ±5 percent over the range of 20 percent to 80 percent RH;
- Sensor calibration data. Data used for control of the economizer shall be plotted on a sensor performance curve.
- Sensor high limit control. Sensors used for the high limit control shall be located to prevent false readings, including but not limited to being properly shielded from direct sunlight.
- Relief air system. Relief air systems shall be capable of providing 100 percent outside air without over-pressurizing the building.
- The space conditioning system shall include the following:
- Unit controls shall have mechanical capacity controls interlocked with economizer controls such that the economizer is at 100 percent open position when mechanical cooling is on and does not begin to close until the leaving air temperature is less than 45°F.
- Direct Expansion (DX) units greater than 65,000 Btu/hr that control the capacity of the mechanical cooling directly based on occupied space temperature shall have a minimum of two stages of mechanical cooling capacity.
- DX units not within the scope of Section 140.4(e)2E.B shall (i) comply with the requirements in Table 140.4-F, and (ii) shall have controls that do not false load the mechanical cooling system by limiting or disabling the economizer or by any other means except at the lowest stage of mechanical cooling capacity.
- Maximum pressure drop. Precooling coils and water-to-water heat exchangers used as part of a water economizer shall either have a waterside pressure drop of less than 15 feet of water, or a secondary loop shall be installed so that the coil or heat exchanger pressure drop is not contributing to pressure drop when the system is in the normal cooling (non-economizer) mode.
- Economizer systems shall be integrated with the mechanical cooling system so that they are capable of providing partial cooling even when additional mechanical cooling is required to meet the remainder of the cooling load. Controls shall not false load the mechanical cooling system by limiting or disabling the economizer or by any other means, such as hot gas bypass, except at the lowest stage of mechanical cooling.
- In response to representative building loads or to outdoor air temperature; and
- At least 25 percent of the difference between the design supply-air temperature and the design room air temperature.
- The flow that is produced by the smallest pump, or
- 50 percent of the design flow for the cell.
- Operate the maximum number of fans allowed that comply with the manufacturer's requirements for all system components, and
- Control all operating fans to the same speed. Minimum fan speed shall comply with the minimum allowable speed of the fan drive as specified by the manufacturer's recommendation. Staging of fans is allowed once the fans are at their minimum operating speed.
- Chiller isolation. When a chilled water system includes more than one chiller, provisions shall be made so that flow through any chiller is automatically shut off when that chiller is shut off while still maintaining flow through other operating chiller(s). Chillers that are piped in series for the purpose of increased temperature differential shall be considered as one chiller.
- Boiler isolation. When a hot water plant includes more than one boiler, provisions shall be made so that flow through any boiler is automatically shut off when that boiler is shut off while still maintaining flow through other operating boiler(s).
- Water-cooled air conditioner and hydronic heat pump systems. Water circulation systems serving water-cooled air conditioners, hydronic heat pumps, or both that have total pump system power exceeding 5 hp shall have flow controls that meet the requirements of Section 140.4(k)6. Each such air conditioner or heat pump shall have a two-position automatic valve interlocked to shut off water flow when the compressor is off.
- Variable speed drives. Individual pumps serving variable flow systems and having a motor horsepower exceeding 5 hp shall have controls or devices (such as variable speed control) that will result in pump motor demand of no more than 30 percent of design wattage at 50 percent of design water flow. The pumps shall be controlled as a function of required differential pressure.
- For systems without direct digital control of individual coils reporting to the central control panel, differential pressure shall be measured at the most remote heat exchanger or the heat exchanger requiring the greatest differential pressure.
- For systems with direct digital control of individual coils with a central control panel, the static pressure setpoint shall be reset based on the valve requiring the most pressure, and the setpoint shall be no less than 80 percent open. Pressure sensors may be mounted anywhere.
- The duct system provides conditioned air to an occupiable space for a constant volume, single zone, space-conditioning system; and
- The space conditioning system serves less than 5,000 square feet of conditioned floor area; and
- Outdoors, or
- Has a U-factor greater than the U-factor of the ceiling, or if the roof does not meet the requirements of Section 140.3(a)1B, or
- Has fixed vents or openings to the outside or unconditioned spaces, or
- In an unconditioned crawlspace, or
- In other unconditioned spaces.
- Duct systems serving healthcare facilities shall be sealed in accordance with the California Mechanical Code.
- DX and chilled water cooling systems that control the capacity of the mechanical cooling directly based on occupied space temperature shall (i) have a minimum of two stages of fan control with no more than 66 percent speed when operating on stage 1; and (ii) draw no more than 40 percent of the fan power at full fan speed, when operating at 66 percent speed.
- All other systems, including but not limited to DX cooling systems and chilled water systems that control the space temperature by modulating the airflow to the space, shall have proportional fan control such that at 50 percent air flow the power draw is no more than 30 percent of the fan power at full fan speed.
- Systems that include an air side economizer to meet 140.4(e)1 shall have a minimum of two speeds of fan control during economizer operation.
- The supply flow required to meet the space heating or cooling load; or
- The ventilation rate required by the authority having jurisdiction, the facility Environmental Health and Safety Department, or by Section 120.1(c)3; or
- The mechanical exhaust flow minus the available transfer air. Available transfer air shall be from another conditioned space or return air plenums on the same floor and same smoke or fire compartment, and that at their closest point are within 15 feet of each other.
Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code. Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.8, and 25943, Public Resources Code.
TABLE 140.4 -A
FAN POWER LIMITATION
|LIMIT||CONSTANT VOLUME||VARIABLE VOLUME|
|Option 1: Fan system motor nameplate hp||Allowable motor nameplate hp||hp ≤ cfms x 0.0011||hp ≤ cfms x 0.0015|
|Option 2: Fan system bhp||Allowable fan system bhp||bhp ≤ cfms x 0.00094 + A||bhp ≤ cfms x 0.0013 + A|
FAN POWER LIMITATION PRESSURE DROP ADJUSTMENT
|Return or exhaust systems required by code or accreditation standards to be fully ducted, or systems required to maintain air pressure differentials between adjacent rooms||0.5 in. of water|
|Return and/or exhaust airflow control devices||0.5 in. of water|
|Exhaust filters, scrubbers, or other exhaust treatment||The pressure drop of device calculated at fan system design condition|
|Particulate Filtration Credit: MERV 16 and greater and electronically enhanced filters||Pressure drop calculated at 2 x clean filter pressure drop at fan system design condition|
|Carbon and other gas-phase air cleaners||Clean filter pressure drop at fan system design condition|
|Biosafety cabinet||Pressure drop of device at fan system design condition|
|Energy recovery device, other than coil runaround loop||For each airstream [(2.2 x Energy Recovery Effectiveness) — 0.5] in. of water|
|Coil runaround loop||0.6 in. of water for each airstream|
|Exhaust systems serving fume hoods||0.35 in. of water|
CHILLED WATER SYSTEM COOLING CAPACITY
|TOTAL BUILDING CHILLED WATER |
SYSTEM CAPACITY, MINUS CAPACITY
OF THE COOLING UNITS WITH AIR ECONOMIZERS
|Building Water-Cooled |
Chilled Water System
|Air-Cooled Chilled Water |
Systems or District Chilled
|15||≥ 960,000 Btu/h (280 kW)||≥ 1,250,000 Btu/h (365 kW)|
|1-14||≥ 720,000 Btu/h (210 kW)||≥ 940,000 Btu/h (275 kW)|
|16||≥ 1,320,000 Btu/h (385 kW)||≥ 1,720,000 Bu/h (505 kW)|
ECONOMIZER TRADE-OFF TABLE FOR COOLING SYSTEMS
|CLIMATE ZONE||EFFICIENCY IMPROVEMENTa|
- If a unit is rated with an IPLV, IEER or SEER, then to eliminate the required air or water economizer, the applicable minimum cooling efficiency of the HVAC unit must be increased by the percentage shown. If the HVAC unit is only rated with a full load metric, such as EER or COP cooling, then that metric must be increased by the percentage shown.
AIR ECONOMIZER HIGH LIMIT SHUT OFF CONTROL REQUIREMENTS
|DEVICE TYPEa||CLIMATE |
|REQUIRED HIGH LIMIT (ECONOMIZER OFF WHEN):|
|Fixed dry bulb||1, 3, 5, 11—16||TOA > 75°F||Outdoor air temperature exceeds 75°F|
|2, 4, 10||TOA > 73°F||Outdoor air temperature exceeds 73°F|
|6, 8, 9||TOA > 71°F||Outdoor air temperature exceeds 71°F|
|7||TOA > 69°F||Outdoor air temperature exceeds 69°F|
|Differential dry bulb||1, 3, 5, 11—16||TOA > TRA°F||Outdoor air temperature exceeds return air temperature|
|2, 4, 10||TOA > TRA-2°F||Outdoor air temperature exceeds return air temperature minus 2°F|
|6, 8, 9||TOA > TRA-4°F||Outdoor air temperature exceeds return air temperature minus 4°F|
|7||TOA > TRA-6°F||Outdoor air temperature exceeds return air temperature minus 6°F|
|Fixed Enthalpyc + Fixed dry bulb||All||hOA > 28 Btu/lbc or TOA > 75°F||Outdoor air enthalpy exceeds 28 Btu/lb of dry airc or Outdoor air temperature exceeds 75°F|
- Only the high limit control devices listed are allowed to be used and at the setpoints listed. Others such as Dew Point, Fixed Enthalpy, Electronic Enthalpy, and Differential Enthalpy Controls may not be used in any climate zone for compliance with Section 140.4(e)1 unless approval for use is provided by the Energy Commission Executive Director.
- Devices with selectable (rather than adjustable) setpoints shall be capable of being set to within 2°F and 2 Btu/lb of the setpoint listed.
- At altitudes substantially different than sea level, the Fixed Enthalpy limit value shall be set to the enthalpy value at 75°F and 50% relative humidity. As an example, at approximately 6,000 foot elevation, the fixed enthalpy limit is approximately 30.7 Btu/lb.
DIRECT EXPANSION (DX) UNIT REQUIREMENTS FOR COOLING STAGES AND COMPRESSOR DISPLACEMENT
|COOLING CAPACITY||MINIMUM NUMBER |
|≥ 65,000 Btu/h and < 240,000 Btu/h||3 stages||≤ 35% full load|
|≥ 240,000 Btu/h||4 stages||≤ 25% full load|
FAN CONTROL SYSTEMS
|COOLING SYSTEM TYPE||FAN MOTOR |
|DX cooling||Any||≥ 65,000 Btu/hr|
|Chilled water and evaporative||≥ 1/4 HP||Any|