OM 1280-2 • MICROTECH UNIT CONTROLLER 14 www.DaikinApplied.com
Description of Operation
Heat Mode (Super State)
When in Heat mode, the UVC will use primary heat and
secondary electric heat (if available) as needed to maintain
the effective heating setpoint (see “Effective Setpoint
Calculations” on page 31). The keypad/ display or a
network connection can be used to force the unit into the
Heat mode. Additionally, the UVC when set to Auto mode can
automatically force the unit into the Heat mode as needed.
The Heat mode super state consists of UVC states: Heat,
Low Limit, Defrost, and Can’t Heat.
When the Heat mode super state becomes active, the UVC
automatically determines which of the Heat Mode states to
make active based upon the transitions for each state.
Heat State (Mechanical Heating)
The Heat state is the “normal” state during Heat mode. When
the Heat state becomes active, the UVC will use primary heat
(compressor or hot water/steam) and secondary heat (electric
heat) as needed to maintain the current DATS. If no other
form of heat is available, the UVC will use electric heat as the
primary source of heat. The DATS will not be allowed to go
above DAHL. The CO
2
demand controlled ventilation function
will be active, if the unit is equipped for CO
2
control (see ”CO2
Demand Controlled Ventilation (optional)” on page 37), and
the OA damper will be adjusted as needed to maintain the
CO
2
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.
Electric Heat Control
When using electric heat to maintain the current DATS there is
a 30 second interstage timer (default, adjustable that limits how
frequently the controller will switch between stages of heat.
Additionally the UVC will keep the fan running for at least 30
seconds after the electric heat has shut off to cool down the
coils. Following Table 7 the UVC will bring on stages of electric
heat based on calculated percent capacity required.
Table 7:
Electric Heat Stage Transitions
Heat PI Output
Electric Heat Response
1%
Stage 1 Off
5%
Stage 1 On
35%
Stage 2 Off
45%
Stage 2 On
65%
Stage 3 Off
75%
Stage 3 On
Figure 6: Heat State Operation - Electric Heat
-Electric Heat Stage 1, 2 and 3 On
Staging
Down
Staging
Up
100%
75%
65%
45%
35%
5%
1%
-Electric Heat Stage 1 and 2 On
-Electric Heat Stage 1 On
Degrees Below
Setpoint and Time
Satisfied
Discharge Air
-OA Damper at 30% Open
-IA Fan Low Speed
Primary
Heating
Capacity
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