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Emergency Heat Mode (Super State)
The Emergency Heat mode is provided for situations where the UVC is in a mode
that does not normally allow heating, such as OFF, Cool, Night Purge, or Fan Only.
If Emergency Heat mode is enabled, the UVC can automatically force itself into the
Emergency Heat mode from OFF, Cool, Night Purge, Fan Only, Purge, Pressurize, De-
pressurize, and Shutdown. Emergency Heat mode consists of UVC states: Full Heat [7]
and Cant Heat [13].
When the Emergency Heat mode becomes active, the UVC automatically determines
which state to make active, Full Heat [7], or Cant Heat [13], based on the transitions for
each of those states.
Figure 10: Emergency heat state diagram
EMERGENCY
HEAT
Mode
FULL HEAT
Mode
(State 7)
Is SpaceTemp
> (EHS+5.4F)
If entered
automatically
return to
previous state
Enter from:
Network Input
Automatically from OFF, Cool, Night
Purge, Fan Only, Purge, Pressurization,
De-pressurization or Shutdown
Yes
Are inputs
valid?
Return to
previous state
Continually
Check Inputs
IAT
DAT
Are inputs
valid?
CANT HEAT
Mode
(State 13)
No
Continue in
current mode
Yes
Yes
No
No
Full Heat State [State 7]
The Full Heat [7] state is the “normal” state that the UVC goes into when Emergency
Heat mode is active. It is activated when the space temperature is lower than the EHS.
When Emergency Heat mode becomes active, the UVC goes into 100% heating until
the space temperature raises to the EHS plus a fixed differential (5.4°F/3°C). In the
Emergency Heat mode, the space fan is set to high speed, and the OA damper oper-
ates normally.
If the UVC automatically forces itself into the Emergency Heat mode from another
mode (e.g., Cool, Fan Only, etc.), then the UVC returns to the appropriate unit mode
once the space temperature rises to the EHS plus a fixed differential (5.4°F/3°C).
The UVC monitors the DAT to ensure it does not exceed DAHL. If the DAT does ex-
ceed DAHL, then heating is set to 0% for a minimum of 2-minutes (fixed) and until the
DAT drops 36°F (20°C) fixed differential below DAHL.
Cant Heat State (State 13)
The Cant Heat [13] state is a “non-normal” state that the UVC can go into when Emer-
gency Heat mode is active. An IAT or DAT sensor fault during Emergency Heat mode
causes the UVC to make this state active.
When the Cant Heat state becomes active, the space fan remains at high speed as set
during the Full Heat state.
The UVC will remain in the Cant Heat state until heat becomes available.
Summary of Contents for MicroTech II
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