C403.2.4.7 Economizer Fault Detection and Diagnostics (FDD)
Air-cooled unitary direct-expansion units listed in Tables C403.2.3(1) through C403.2.3(3) and variable refrigerant flow (VRF) units that are equipped with an economizer in accordance with Section C403.3 shall include a fault detection and diagnostics (FDD) system complying with the following:
- 1.1. Outside air.
- 1.2. Supply air.
- 1.3. Return air.
- Temperature sensors shall have an accuracy of ±2°F (1.1°C) over the range of 40°F to 80°F (4°C to 26.7°C).
- Refrigerant pressure sensors, where used, shall have an accuracy of ±3 percent of full scale.
- 4.1. Free cooling available.
- 4.2. Economizer enabled.
- 4.3. Compressor enabled.
- 4.4. Heating enabled.
- 4.5. Mixed air low limit cycle active.
- 4.6. The current value of each sensor.
- The unit controller shall be capable of manually initiating each operating mode so that the operation of compressors, economizers, fans and the heating system can be independently tested and verified.
- The unit shall be capable of reporting faults to a fault management application accessible by dayto-day operating or service personnel, or annunciated locally on zone thermostats.
- 7.1. Air temperature sensor failure/fault.
- 7.2. Not economizing when the unit should be economizing.
- 7.3. Economizing when the unit should not be economizing.
- 7.4. Damper not modulating.
- 7.5. Excess outdoor air.