J01-B Economizer and Control Requirements.pdf

Economizer and Control Requirements – Sequence and Priority Operations

Required inputs and logging ~ 5 Minute Intervals

Outdoor-air-temperature (OAT)

Mixed-air temperature (MAT)

Return-air temperature (RAT)

Discharge-air temperature and set point (DAT and DATSP)

Outdoor-air damper position signal (OAD)

Cooling and heating signal

Pressure transducer signal

Sequence of Operation in Priority Order

1. The economizer must maintain a minimum or greater than 20% damper position at all times to provide code-compliant ventilation.

2. The economizer must provide freeze protection when outside air temperatures drop below freezing. In extreme cold situations, the damper may be closed to prevent damage. A warning indicator inside the building must illuminate to notify staff that fresh air ventilation has been reduced below minimum or is at zero.

3. The economizer must modulate to maintain an indoor building differential pressure of 0.02 in.wg. This is due to multiple building exhaust fans that require makeup air. These fans are manually operated and do not have predictable operation. Damper position for maximum makeup air is approximated at 50%.

4. In cooling mode, when the RAT > OAT, then the economizer shall modulate to increase the amount of outside air to the system to reduce the MAT.

5. In heating mode, when the RAT < OAT, then the economizer shall modulate to increase the amount of outside air to the system to increase the MAT.