McQuay OM 751
25
Description of Operation
Bypass Mode
The bypass mode (also called Tenant Override) is the equivalent of a temporary occupied
mode. Once the bypass mode is initiated, it remains in effect for a set period of time (120
minutes, default). During the bypass mode, the UVC uses the occupied heating and cooling set
points, the OAD operates normally, and by default the IAF remains on.
Additional Occupancy Features
Networked Occupancy Sensor Capability
A networked occupancy sensor can be interfaced with the Occupancy Sensor Input variable to
select occupancy modes. When the Occupancy Sensor Input variable is used, it automatically
overrides any hard-wired unoccupied binary input signal.
Unit-Mounted Time-Clock
An optional unit-mounted factory-installed electronic 24-hour/7-day time clock can be
provided on stand-alone unit ventilator configurations. It is factory wired to the UVC
unoccupied binary input and can be set to automatically place the unit into occupied and
unoccupied modes based upon its user configured schedule.
Unit-Mounted Tenant Override Switch
A tenant override switch is factory installed in all floor mounted units and is located near the
LUI on the unit. This switch provides a momentary contact closure that can be used by room
occupants to temporarily force the UVC into the bypass occupancy mode from unoccupied
mode.
Note –
The Occupancy Override Input can override the tenant override feature. For example, if
the network uses the Occupancy Override Input to force the unit into unoccupied mode,
then the unit-mounted tenant override switch does not operate as expected. Therefore,
McQuay strongly recommends using the Occupancy Sensor Input to control occupancy
modes over a network and only using the Occupancy Override Input if there is reason to
ensure tenant override does not occur.
Remote Wall-Mounted Sensor Tenant Override Switch
The optional remote wall-mounted sensors include a tenant override switch. This switch
provides a momentary contact closure that can be used by room occupants to temporarily force
the UVC into the bypass occupancy mode from unoccupied mode.
Note –
The Occupancy Override Input can override the tenant override feature. For example, if
the network uses the Occupancy Override Input to force the unit into unoccupied mode,
then the wall sensor tenant override switch does not operate as expected. Therefore,
McQuay strongly recommends using the Occupancy Sensor Input to control occupancy
modes over a network and only using the Occupancy Override Input if there is reason to
ensure tenant override does not occur.
Remote Wall-Mounted Sensor Status LED
The optional remote wall-mounted sensors each include a UVC status LED. This status LED
aids diagnostics by indicating the UVC occupancy mode and fault condition.
Table 13: Remote wall-mounted sensor status LED
Indication
LED operation
Occupied
On continually
Unoccupied
On 1 second/off 9 seconds
Bypass
On continually
Standby
On 9 seconds/off 1 second
Fault
On 5 seconds/off 5 seconds
