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22 McQuay OM 751
Description of Operation
In each of these special purpose UVC modes, if the space temperature drops below EHS and
the Emergency Heat function is enabled, the UVC is forced into the Emergency Heat mode
(see “Emergency Heat Mode (Super State)” on page 16) and then return once the Emergency
Heat function is satisfied.
Table 9: Actions during special purpose unit modes
Pressurize Mode
When in Pressurize mode, the UVC uses the IAF, OAD, and exhaust output as needed to
pressurize the space. The UVC stops all normal heating and cooling but does allow emergency
heat if required. The pressurize mode can only be accessed via a network connection.
Depressurize Mode
When in Depressurize mode the UVC will use the IAF, OAD, and exhaust output as needed to
depressurize the space. The UVC stops all normal heating and cooling but does allow
emergency heat if required. The de-pressurize mode can only be accessed via a network
connection or with ServiceTools for MicroTech II Applied Terminal Unit Controllers (ATS).
Purge Mode
When in Purge mode, the UVC uses the IAF, OAD, and exhaust output as needed to purge the
space. The UVC stops all normal heating and cooling but does allow emergency heat if
required. The purge mode can only be accessed via a network connection or with ServiceTools
for MicroTech II Applied Terminal Unit Controllers (ATS).
Shutdown Mode
Shutdown mode is the equivalent of the Off mode, but is an Off mode forced by a network
connection. When in Shutdown mode, the UVC stops all normal heating, cooling, ventilation
(OA damper is closed), and fan operation. By default emergency heat is not be used during the
shutdown mode, however, the UVC can be configured (Emergency Heat Shutdown
Configuration) to allow emergency heat operation during shutdown mode. The shutdown
mode can be accessed via a network connection, a binary input to the UVC, or with
ServiceTools for MicroTech II Applied Terminal Unit Controllers (ATS).
Energy Hold Off Mode
The UVC supports an energy hold off state, which when active forces the UVC to stop all
normal heating, cooling and ventilation. Typically used by a network connection to force the
UVC to cease heating, cooling and ventilation when conditions exist where heating, cooling
and ventilation are not required or desired. Energy hold off mode is very similar to shutdown
mode except that energy hold off always allows emergency heat if required. The energy hold
off mode can only be accessed via a network connection or with ServiceTools for
MicroTech II Applied Terminal Unit Controllers (ATS).
Action
Indoor air fan
(IAF)
Outdoor air
damper (OAD)
Exhaust fan
output
Pressurize High 100% Open Off
Depressurize Off Closed On
Purge High 100% Open On
Shutdown Off Closed Off
Energy hold off Off Closed Off
WARNING
Shutdown mode and energy hold off mode are a “stop” state for
the unit ventilator. It is not a “power off” state.