Heating Control - Daikin MicroTech III Operation Manuals

Heating Control

Entering Heating Operating State
The unit enters the Heating operating state from the Fan Only
operating state when the control temperature falls below the
Occupied or Unoccupied Heating Set Point by more than
half the Occupied or Unoccupied Heating Dead Band . The
unit transitions from the Heating to Fan Only operating state
when the control temperature rises above the Occupied or
Unoccupied Heating Set Point by more than half the Occupied
or Unoccupied Heating Dead Band . The unit will also transition
from the Heating to Fan Only operating state if heating
operation is disabled due to OA ambient lockout .
Morning Warmup Control
The unit does not enter a specific morning warmup operating
state to accomplish the morning warmup function . Instead
the unit enters the Heating operation state when morning
warmup operation is required . The dampers are held at zero
percent open for Zero OA Timer after the SAF starts . The Zero
OA Timer should be set long enough to accomplish morning
warmup with the dampers closed to minimize energy usage
during the warmup period .
Zone Control Units
When a Zone Control Unit (Ctrl Typ=Zone) first starts in the
morning it enters the Heating operating state if the Control
Temperature is below the Occupied Heating Setpoint by more
that ½ the heating dead band . In this case The Occupied
Heating Setpoint is the "morning warmup setpoint" .
DAT Control Units
For Discharge Temperature Control units (Ctrl Type=DAC)
there are two additional morning warmup related adjustable
parameters; MWU Heating Setpoint and MWU Sensor . When
a Discharge Temperature Control unit first starts in the morning
it enters the Heating operating state if the sensor selected by
the MWU Sensor parameter (RAT or Space) is below the MWU
Heating Setpoint by more that ½ the Heating dead band . The
MWU Sensor can also be set to None . If the MWU Sensor is
set to None the MWU Heating Setpoint has no effect and the
unit only enters heating based on the Occupied Setpoint in the
normal manner .
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Heating: Staged Zone Control
When the unit first enters the Heating operating state the unit
goes directly to Stage # 1 .
The number of heating stages increases when the time since
the last stage change exceeds the stage time, the Projected
Control Temperature and the actual Control Temperature are
less then the Occ Htg Spt (minus ½ the deadband), and the
DAT is less than the Max DAT Htg Spt .
The number of heating stages decreases when the time
since the last stage change exceeds the stage time, and the
Projected Control Temperature and actual Contro Temperature
are greater then the Occ Htg Spt (plus ½ the deadband) .
The number of heating stages also decreases when the time
since the last stage change exceeds the stage time, and the
DAT is greater than the MaxDATHtgSpt .
Heating DAT Staging or MinDAT Staging
When the unit enters the Heating or Minimum DAT states and
all heating is off, the unit goes directly to Heating Stage # 1 so
that the first stage of heat is turned on immediately.
The number of heating stages increases when the time since
the last stage change exceeds the stage time, and DAT is less
than the effective DAT setpoint (DAT staging) or the Min DAT
limit (MinDAT staging) by ½ the deadband . One exception
to this is that if the current heating stage is zero, the heating
stage can increase without regard to the stage timer .
The number of heating stages decreases when the time since
the last stage change exceeds the stage time, and the DAT is
greater than the effective DAT setpoint (DAT staging) or the
MIN DAT limit (MinDAT staging) by ½ the deadband .
The unit enters the Min DAT operating state during occupied
operation when neither cooling nor heating is required based
on the unit heat/cool changeover function but the discharge air
temperature falls below a minimum discharge temperature limit
by more than ½ the deadband . The Min DAT operating state
prevents cold discharge air temperatures during what would
normally be the Fan Only operating state .
131 OM 920-6 • MICROTECH UNIT CONTROLLER
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