120.2(i)Economizer Fault Detection and Diagnostics (FDD) - 2022

Synopsys

All newly installed air handlers with a mechanical cooling capacity over 33,000 Btu/hr and an installed air economizer shall include a stand-alone or integrated Fault Detection and Diagnostics (FDD) system. This article will discuss the requirements for that FDD system.

Requirements

1. 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
2. Temperature sensors shall have an accuracy of ±2°F over the range of 40°F to 80°F; and
3. The controller shall have the capability of displaying the value of each sensor; and
4. The controller shall provide system status by indicating the following conditions:
   • Free cooling available;
   • Economizer enabled;
   • Compressor enabled;
   • Heating enabled if the system is capable of heating; and
   • Mixed-air low-limit cycle active.
5. The unit controller shall allow manual initiation of each operating mode so that the operation of cooling systems, economizers, fans, and heating systems can be independently tested and verified; and
6. Faults shall be reported in one of the following ways:
   
   1. Reported to an Energy Management Control System regularly monitored by facility personnel.
   2. Annunciated locally on one or more zone thermostats or a device within five (5) feet of the zone
      thermostat(s), clearly visible, at eye level, and meeting the following requirements:
      
      1. On the thermostat, device, or an adjacent written sign, display instructions to contact appropriate building personnel or an HVAC technician; and
      2. In buildings with multiple tenants, the annunciation shall either be within the property
         management offices or in a common space accessible by the property or building manager.
      3. Reported to a fault management application which automatically provides notification of the
         fault to a remote HVAC service provider.
7. The FDD system shall detect the following faults:
   • Air temperature sensor failure/fault;
   • Not economizing when it should;
   • Economizing when it should not;
   • Damper not modulating; and
   • Excess outdoor air.
8. The FDD System shall be certified by the Energy Commission as meeting requirements of Subsections 120.2(i)1 through 120.2(i)7 in accordance with Section 110.0 and JA6.3.
   Exception to Section 120.2(i)8: FDD algorithms based in direct digital control systems are not required to be certified by the Energy Commission