Greenheck ERCH - Energy Recovery Unit with Packaged DX (468151) - Manual (Page 41)

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Energy Recovery Unit with Packaged DX
SEQUENCE OF OPERATION
Other Accessories:
Rotation Sensor See Optional Accessories section
Dirty Filter Sensor See Optional Accessories section
CO2 Sensor See Optional Accessories section
Night Setback On a call for night setback (unoccupied mode), the outdoor air damper will
close and the energy wheel and exhaust fan will be de-energized . The night
setback dampers will open and the supply fan will remain on, providing 100%
recirculation . Units supplied with heating and cooling coils will temper air as
required by the controls to maintain desired conditions in the space .
DX Safety and General Control Sequence
To prevent damage to the system, there is a safety loop incorporated into the
controls . This loop includes a check to make sure the supply fan starter is pulled
in, ambient temperature is above 55ºF, and the low- and high-pressure switches
are not tripped out . After this loop is verified, a relay then pulls in to start the
anti-cycle timer . (Typical setting is 3 minutes) . Once the timer has counted down,
only then can the compressor contact pull in . Once the compressor contact pulls
in, the first stage of condensing fans turns on . If pressure in the condensing coil
increases to a point at which more heat needs to be removed from the system,
the fan cycle switch will close and the second stage of condensing fans turns on .