Greenheck ERCH - Energy Recovery Unit with Packaged DX (468151) - Manual (Page 40)

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Energy Recovery Unit with Packaged DX
Basic Unit
The ERCH units are 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 ERCH units can be supplied with or without heating coils . Controls can be
supplied by Greenheck 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 Greenheck for purposes of monitoring via the Building Management System (see Optional
Accessories section) .
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 .
Standard DX Sequence of Operation:
Unit without economizer
Ambient temperatures above 55ºF
• First call for cool, the unit will turn on the first compressor.
• On the second call for cool, the unit will turn on the second compressor if available.
(10 or larger tonnage system) .
Unit without economizer
Ambient temperatures below 55ºF
• DX system locked out and will not operate.
Unit with economizer
With economizer conditions available and ambient temperature above 55ºF
• First call for cool - the unit will check if it can use economizer air. If it can, the wheel will shut off or
modulate and the cooling coil will be de-energized .
• Second call for cool - the unit will turn on a compressor to provide the space with further cooling.
With economizer conditions available and ambient temperature below 55ºF
• First call for cool - the unit will engage economizer allowing free cooling down to minimum set point,
factory set at 50ºF .
• Second call for cool - the DX system is locked out, not allowing compressors to run below 55ºF. First
stage of cooling will still operate unless ambient temperature drops below economizer set point .
Without economizer conditions available and ambient temperature above 55ºF
• First call for cool - the unit will turn on compressor one.
• Second call for cool - the unit will turn on the second compressor if available.
(10 or larger tonnage system) .
Economizer Operation: See 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 . Units supplied with heating coils can further
heat the air coming off the wheel to levels at or above room design .
Frost Control Operation: See Frost Control Application/Operation section .
SEQUENCE OF OPERATION