Sequence of Operation
Basic Unit
The ERV units are prewired such that when a call for outside air is made (via field supplied 24 VAC control signal wired to unit control center), the supply fan, exhaust fan and energy wheel are energized and optional motorized dampers open. The ERV is normally slaved (24 volt) to the roof top air handler. When the roof top air handler starts, the auxiliary contactor in the air handler closes to start the ERV.
Summer Operation
Outdoor air is preconditioned (temperature and moisture levels are decreased) by the transfer of energy from the cooler, drier, exhaust air via the energy recovery wheel. The preconditioned air is typically mixed with return air going back to the air handler for final conditioning.
Economizer Operation: Refer to Economizer Application/Operation section.
Winter Operation
Outdoor air is preconditioned (temperature and moisture levels are increased) by the transfer of energy from the warmer, more humid exhaust air via the energy recovery wheel. The preconditioned air is typically mixed with return air going back to the air handler for final conditioning.
Frost Control Operation: Refer to Frost Control Application/Operation section.
Other Accessories:
Rotation Sensor: Refer to Optional Accessories section
Dirty Filter Sensor: Refer to Optional Accessories section
CO2 Sensor: Refer to Optional Accessories section
Variable Frequency Drive (VFD) on Blowers: VFDs on blowers are often used as part of a demand control ventilation system. This type of system takes advantage of varying occupancy through the use of CO2 sensors to monitor space CO2 levels. If CO2 levels are low in the space, the VFD will operate the blowers at minimum airflow required by code. As the space occupancy increases and CO2 levels increase, the VFD will increase the amount of fresh outdoor air being brought in to offset the CO2 levels in the space (exhaust airflow is increased proportionally as outdoor airflow increases). As CO2 levels come back down, the airflow will decrease back to minimum requirements.
Model ERV Energy Recovery Unit 31
