Section 120.2 Required Controls for Space-Conditioning Systems
Nonresidential, high-rise residential, and hotel/motel buildings shall comply with the applicable requirements of Sections 120.2(a) through 120.2(k).
(a) Thermostatic controls for each zone. The supply of heating and cooling energy to each space-conditioning zone or dwelling unit shall be controlled by an individual thermostatic control that responds to temperature within the zone and that meets the applicable requirements of Section 120.2(b). An energy management control system (EMCS) may be installed to comply with the requirements of one or more thermostatic controls if it complies with all applicable requirements for each thermostatic control.
Exception to Section 120.2(a): An independent perimeter heating or cooling system may serve more than one zone without individual thermostatic controls if:
- All zones are also served by an interior cooling system; and
- The perimeter system is designed solely to offset envelope heat losses or gains; and
- The perimeter system has at least one thermostatic control for each building orientation of 50 feet or more; and
- The perimeter system is controlled by at least one thermostat located in one of the zones served by the system.
(b) Criteria for zonal thermostatic controls. The individual thermostatic controls required by Section 120.2(a) shall meet the following requirements as applicable:
- Where used to control comfort heating, the thermostatic controls shall be capable of being set, locally or remotely, down to 55°F or lower.
- Where used to control comfort cooling, the thermostatic controls shall be capable of being set, locally or remotely, up to 85°F or higher.
(c) Hotel/motel guest room and high-rise residential dwelling unit thermostats.
- Have numeric temperature setpoints in °F and °C; and
- Have setpoint stops, which are accessible only to authorized personnel, such that guest room occupants cannot adjust the setpoint more than ±5°F (±3°C); and
- High-rise residential dwelling unit thermostats shall meet the requirements of Section 110.2(c).
(e) Shut-off and reset controls for space-conditioning systems. Each space-conditioning system shall be installed with controls that comply with the following:
- An automatic time switch control device complying with Section 110.9(c), with an accessible manual override that allows operation of the system for up to 4 hours; or
- An occupancy sensor; or
- Automatically set up the operating cooling temperature set point by 2°F or more and set back the operating heating temperature set point by 2°F or more; or
- For multiple zone systems with Direct Digital Controls (DDC) to the zone level, setup the operating cooling temperature setpoint by 0.5°F or more and setback the operating heating temperature setpoint by 0.5°F or more.
(f) Dampers for air supply and exhaust equipment. Outdoor air supply and exhaust equipment shall be installed with dampers that automatically close upon fan shutdown.
Exception 1 to Section 120.2(f): Equipment that serves an area that must operate continuously.
Exception 2 to Section 120.2(f): Gravity and other non-electrical equipment that has readily accessible manual damper controls.
Exception 3 to Section 120.2(f): At combustion air intakes and shaft vents.
Exception 4 to Section 120.2(f): Where prohibited by other provisions of law.
(g) Isolation area devices. Each space-conditioning system serving multiple zones with a combined conditioned floor area of more than 25,000 square feet shall be designed, installed and controlled to serve isolation areas.
- Each zone, or any combination of zones not exceeding 25,000 square feet, shall be a separate isolation area.
- Each isolation area shall be provided with isolation devices, such as valves or dampers, that allow the supply of heating or cooling to be reduced or shut off independently of other isolation areas.
(h) Automatic demand shed controls. See Section 110.12 for requirements for automatic demand shed controls.
(i) Economizer fault detection and diagnostics (FDD). All newly installed air handlers with a mechanical cooling capacity greater than 54,000 Btu/hr and an installed air economizer shall include a stand-alone or integrated Fault Detection and Diagnostics (FDD) system in accordance with Subsections 120.2(i)1 through 120.2(i)8.
- The following temperature sensors shall be permanently installed to monitor system operation: outside air, supply air, and when required for differential economizer operation a return air sensor, and
- Temperature sensors shall have an accuracy of ±2°F over the range of 40°F to 80°F; and
- The controller shall have the capability of displaying the value of each sensor; and
- Free cooling available;
- Economizer enabled;
- Compressor enabled;
- Heating enabled, if the system is capable of heating; and
- Mixed-air low limit cycle active.
- The unit controller shall allow manual initiation of each operating mode so that the operation of cooling systems, economizers, fans and heating system can be independently tested and verified; and
- Reported to an Energy Management Control System regularly monitored by facility personnel.
- On the thermostat, device, or an adjacent written sign, display instructions to contact appropriate building personnel or an HVAC technician; and
- In buildings with multiple tenants, the annunciation shall either be within property management offices or in a common space accessible by the property or building manager.
- Reported to a fault management application which automatically provides notification of the fault to a remote HVAC service provider.
- Air temperature sensor failure/fault;
- Not economizing when it should;
- Economizing when it should not;
- Damper not modulating; and
- Excess outdoor air.
(j) Direct Digital Controls (DDC). Direct Digital Controls to the zone shall be provided as specified by Table 120.2-A.
The provided DDC system shall meet the control logic requirements of Sections 120.1(d) and 120.2(h), and be capable of the following:
- Monitoring zone and system demand for fan pressure, pump pressure, heating and cooling;
- Transferring zone and system demand information from zones to air distribution system controllers and from air distribution systems to heating and cooling plant controllers;
- Automatically detecting the zones and systems that may be excessively driving the reset logic and generate an alarm or other indication to the system operator;
- Readily allow operator removal of zones(s) from the reset algorithm;
- For new buildings, trending and graphically displaying input and output points; and
- Resetting heating and cooling setpoints in all noncritical zones upon receipt of a signal from a centralized contact or software point as described in Section 120.2(h).
(k) Optimum start/stop controls. Space conditioning systems with DDC to the zone level shall have optimum start/stop controls. The control algorithm shall, as a minimum, be a function of the difference between space temperature and occupied setpoint, the outdoor air temperature, and the amount of time prior to scheduled occupancy. Mass radiant floor slab systems shall incorporate floor temperature onto the optimum start algorithm.
Exception to Section 120.2(k): Systems that must operate continuously.
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.
DDC APPLICATIONS AND QUALIFICATIONS
|Newly Constructed Buildings||Air handling system and all zones served by the system||Individual systems supplying more than three zones and with design heating or cooling capacity of 300 kBtu/h and larger|
|Chilled water plant and all coils and terminal units served by the system||Individual plants supplying more than three zones and with design cooling capacity of 300 kBtu/h (87.9 kW) and larger|
|Hot water plant and all coils and terminal units served by the system||Individual plants supplying more than three zones and with design heating capacity of 300 kBtu/h (87.9 kW) and larger|
|Additions or Alterations||Zone terminal unit such as VAV box||Where existing zones served by the same air handling, chilled water, or hot water systems that have DDC|
|Air handling system or fan coil||Where existing air handling system(s) and fan coil(s) served by the same chilled or hot water plant have DDC|
|New air handling system and all new zones served by the system||Individual systems with design heating or cooling capacity of 300 kBtu/h and larger and supplying more than three zones and more than 75 percent of zones are new|
|New or upgraded chilled water plant||Where all chillers are new and plant design cooling capacity is 300 kBtu/h (87.9 kW) and larger|
|New or upgraded hot water plant||Where all boilers are new and plant design heating capacity is 300 kBtu/h (87.9 kW) and larger|