OM 750
Page 11 of 32
FAN ONLY MODE (STATE NUMBER A)
The Fan Only mode is provided so that the UVC can be forced into a
Fan Only operation. The LUI or a network connection can force the unit
into the Fan Only mode. Fan Only mode consists of a single UVC state:
Fan Only [A].
Transition
(UVC Mode = Fan Only)
into State
Operation
When Fan Only mode becomes active, the UVC stops
within State
all normal heating and cooling. If the space temperature
drops below the EHS, and the Emergency Heat function
is enabled, the UVC will be forced into the Emergency
Heat mode (see the Emergency Heat Mode).
The UVC will remain in this state until one of the
transition out conditions become true.
Transition
(UVC Mode
≠
Fan Only)
out of State
Figure 9. Fan Only State Diagram
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. Additionally, the LUI or a network connection can be
used to force the unit into the Emergency Heat mode. Emergency Heat
mode consists of two UVC states: Full Heat [7] and Cant Heat [D].
Transition
into
(UVC Mode = Emergency Heat)
Super State
Operation
When the Emergency Heat mode super state becomes
within
active, the UVC will automatically determine which
Super State
which UVC state to make active, Full Heat [7] or Cant
Heat [D], based upon the transitions for each of those
states.
The UVC will remain in this super state until one of the
transition out conditions become true.
Transition
out of
(UVC Mode
≠
Emergency Heat)
Super State
Figure 10. Emergency Heat State Diagram
Full Heat State (State Number 7)
The Full Heat state is the “normal” state that the UVC will go into when
Emergency Heat mode is active.
Transition
Heat = Available
into State
Operation
When Emergency Heat mode becomes active, the
within State
UVC will go into 100% heating until the space
temperature raises to the EHS plus a fixed differential
(9
O
F / 5
O
C). In the Emergency Heat mode the space fan
will be set to high speed, and the OA damper will
operate normally. If the UVC forces itself into the
Emergency Heat mode from another mode, then the
UVC will return to the appropriate unit mode once the
space temperature rises to the EHS plus the fixed
differential. The UVC will monitor the DAT to ensure
it does not exceed DAHL. If the DAT does exceed
DAHL (140
O
F / 60
O
C default), then heating will be set
to 0% for a minimum of 2-minutes (fixed) and until the
DAT drops 18
O
F (10
O
C) fixed differential below
DAHL.
The UVC will remain in this state until one of the
transition out conditions become true, or until one of
the superstate transition out conditions becomes true.
Transition
(Heat
≠
Available)
out of State
Notes:
(Heat
≠
Available) is true when an IAT or DAT sensor fault exists (see
Unit Faults).
purging process. In the Night Purge mode the space
fan will be set to high speed, the OA damper will be set
to 100% open, and the Exhaust Fan binary output (see
External Binary Outputs) will be set to On. If not set to
another mode within 1-hour, the UVC will force itself
into the Fan Only mode (see Fan Only Mode). If the
space temperature drops below the EHS, and the
Emergency Heat function is enabled, the UVC will be
forced into the Emergency Heat mode (see Emergency
Heat Mode).
The UVC will remain in this state until one of the
transition out conditions become true.
Transition
(UVC Mode
≠
Night Purge)
out of State
