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), and the OA damper will be adjusted as needed to maintain the CO2 setpoint.
The UVC will remain in this state until one of the transition out conditions become true,
or until one of the super state transition out conditions becomes true.
Note:
The OAD is considered to be in “alarm” when the OAD is forced below the active
minimum position in the Low Limit state. This is not an actual unit “alarm” or “fault”
condition, but only a condition used for the purpose of transition arguments.
Figure 12: Heat state operation (occupied mode and auto fan)
Low Limit State (State 14)
The Low Limit state is a “non-normal” state the UVC can go into while Heat mode is active
when the unit reaches 100% heating and still cannot meet the current DATS (see "Dis-
charge Air Temperature Control" on page
29
) required to maintain the effective heating
set point (see "Space Temperature Set Points" on page
26
). This is likely to occur only if
the OA temperature is very cold, the OA damper minimum position is set too high, the unit
ventilator is oversized for the application, or if the heating has failed, or is set incorrectly.
When the Low Limit state becomes active, the heating output is set to 100% capacity
and the Low Limit logic can override the OA damper position (see "Outdoor Air Damper
Operation" on page
32
) and adjust the OA damper toward closed as necessary to
maintain the current DATS (see "Discharge Air Temperature Control" on page
29
).
Cant Heat State (State 11)
The Cant Heat state is a “non-normal” state the UVC can go to when Heat mode is active. An
IAT or DAT sensor fault during the Heat mode causes the UVC to make this state active.
When the Cant Heat state becomes active, no heating or ventilation takes place. The
OA damper goes to the minimum position unless it is forced closed by other functions
such as freezestat (T6) or morning warm-up.
Cool Mode (Super State)
When in Cool mode the UVC uses primary cooling (economizer) as needed to maintain
the effective cooling set point (see "Space Temperature Set Points" on page
26
). The
keypad/display or network connection can be used to force the unit into the Cool mode.
When the UVC is in Auto mode, it is “normal” for the UVC to “idle” in Cool mode when
there is no need to switch to another mode. The Cool mode super state consists of the
following UVC states: Econ [3], DA Heat [4], Low Limit [15], Cant Cool [12].
When the Cool mode super state becomes active, the UVC will automatically deter-
mine which UVC state to make active based upon the transitions for each state.
If the space temperature drops below EHS, and the Emergency Heat function is en-
abled, the UVC will be forced into the Emergency Heat mode (see "Emergency Heat
Mode (Super State)" on page
17
).
Summary of Contents for MicroTech II
Page 2: ......
