Greenheck ERCH (476054) - Manual (Page 23)

General Description - NOT model specific Model ERCH Energy Recovery Ventilator
®
23
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.
Units supplied with cooling coils can further cool the
air coming off the wheel and strip out moisture to levels
at or below room design. A heating coil downstream of
the cooling coil can reheat the air to a more comfortable
discharge temperature to the space.
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. Units supplied with heating coils can further heat
the air coming off the wheel to levels at or above room
design.
Exhaust Air
Outdoor Air
95°F
117 grains/lb.
Supply Air
79°F
75 grains/lb.
Return Air
75°F
50% RH
Exhaust Air
Outdoor Air
10°F
5 grains/lb.
Supply Air
60°F
39 grains/lb.
Return Air
72°F
40% RH
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 in
one of three ways:
1.
The outdoor air temperature is less than the
outdoor dry bulb 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 32°F).
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.