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McQuay OM 751 39
Description of Operation
Exhaust Fan ON/OFF Signal
This relay output provides one set of Normally Open dry contacts that can be used to signal
the operation of an exhaust fan. When the OA damper opens more than the Energize Exhaust
Fan OA Damper set point, then the relay output signals the exhaust fan ON (contacts closed).
When the OA damper closes below this set point, the relay output signals the exhaust fan OFF
(contacts open).
Auxiliary Heat Signal
This relay output provides one set of Normally Open dry contacts that can be used to operate
an auxiliary heat device. The UVC by default is configured to operate a Normally Open
auxiliary heat device (de-energize when heat is required), such as a wet heat valve actuator
with a spring setup to open upon power failure. However, the Auxiliary Heat Configuration
variable can be used to set the UVC to use a Normally Closed auxiliary heat device (energize
when heat is required), such as electric heat.
Table 20: Auxiliary heat start/stop calculation
Start/Stop Calculation
Auxiliary heat
starts when:
Primary Heat PI-Loop = saturated high (100%) for
more than two minutes
AND
EffectiveSpaceTemp
≤
EffectiveSetpoint –
AuxiliaryHeatStartDifferential
Auxiliary heat
stops when:
EffectiveSpaceTemp
≥
(EffectiveSetpoint –
AuxiliaryHeatStartDifferential) +
AuxiliaryHeatStopDifferential