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38 McQuay OM 751
Description of Operation
Exhaust Interlock Input Signal
This input allows a single set of dry contacts to be used to signal the UVC that an exhaust fan
within the space is energized. The UVC repositions the OA damper to a user adjustable
minimum position (Exhaust Interlock OA Damper Min Position Setpoint). When the contacts
close (exhaust fan on signal), the UVC uses the value defined by the Exhaust Interlock OA
Damper Min Position Setpoint as the new minimum OA damper position regardless of IA fan
speed. When the contacts open, the UVC returns to normal OA damper operation.
External Binary Outputs
The UVC is provided with three binary outputs that provide the functions described below.
Figure 25: Binary outputs
These outputs are relay type outputs that are intended to be used with signal level voltages (24
VAC maximum) only. For wiring examples, see MicroTech II Unit Ventilator Controller IM
747.
Note – Not all of the functions listed can be used at the same time. The UVC is provided with
configuration parameters that can be adjusted to select which function will be used for
these outputs when multiple functions are indicated below.
External Binary Output 1
This output can only be used as a signal for space lights.
Lights On/Off Signal
This relay output provides one set of Normally Open dry contacts that can be used to signal
the operation of the space lights. When the UVC is in occupied, standby, or bypass occupancy
modes, the relay output signals the lights ON (contacts closed). When the UVC is in
unoccupied occupancy mode, the relay output signals the lights OFF (contacts open).
External Binary Output 2
This output can only be used as a fault signal.
Fault Signal
This relay output provides Normally Open, Normally Closed, and Common connections that
can be used to signal a fault condition. When a fault exists, the UVC energizes this relay
output. When the fault or faults are cleared, the UVC de-energizes this relay output.
External Binary Output 3
This output can only be used to signal exhaust fan operation (default) or operate an auxiliary
heat device.
Binary Outputs
3 relay type outputs w/signal voltage
Output 1: Relay output for light signal
Output 2: Fault signal
Output 3: Exhaust fan operation (default)
or
Auxiliary heat device