Greenheck ERV (476412) - Manual (Page 15)

15 Energy Recovery Ventilator
Optional Component Overview
Economizer
The energy wheel operation can be altered to take
advantage of economizer operation (free cooling).
Two modes are available:
1. Stopping the wheel
2. Modulating the wheel
Stopping the wheel: A field-supplied call for
cool (Y1) is required. De-energizing the wheel is
accomplished one of three ways:
1. The outdoor air temperature is less than the
outdoor drybulb set point (DRYBLB SET)
2. The outdoor air temperature is less than the
return air temperature
3. The outdoor air enthalpy is within the preset
enthalpy curve
A low temperature lock out (LOW T LOCK) is also set
to deactivate mechanical cooling when it exceeds
the outdoor air temperature (factory default 32ºF).
Effectively, the two sensors create a deadband where
the energy recovery wheel will not operate and free
cooling from outside can be brought into the building
unconditioned.
Modulating the wheel (factory): A variable
frequency drive is fully programmed at the factory.
A “call for cool” must be field wired to the unit
(terminals provided in unit-refer to wiring diagram
in unit control center) to allow for initiation of
economizer mode. The unit recognizes economizer
conditions based one of the previously mention
sensors and set points. The unit will then modulate
the wheel speed to maintain the mixed air
temperature set point (MAT SET).
Modulating the wheel (by others): A variable
frequency drive is fully programmed at the factory.
A field-supplied 0-10 VDC signal will be required
for operation of the energy wheel. The field will be
required to have full control of the energy wheel
speed at all times. If no 0-10 VDC signal is provided,
the energy wheel will run at the factory default of 3 Hz
and no energy transfer will be captured.
Unit Overview
Basic Unit
The unit is pre-wired 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 unit can be supplied with or without heating
and cooling coils. For units with coils, controls can
be supplied by manufacturer or by the controls
contractor. If supplied by the controls contractor,
they would provide, mount, and wire any temperature
controllers and temperature or relative humidity
sensors required for the unit to discharge air at the
desired conditions. However, temperature, pressure,
and current sensors can be provided by manufacturer
for purposes of monitoring via the BMS.
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.
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.
Exhaust Air
Outdoor Air
95° F
117 grains/lb.
Supply Air
79° F
75 grains/lb.
Room Air
75° F
50% RH
Exhaust Air
Outdoor Air
10° F
5 grains/lb.
Supply Air
60° F
39 grains/lb.
Room Air
72° F
40% RH