Reheat State; Reheat/Low Limit State; Can't Cool State; Air Tempering Mode - Daikin MicroTech Operation And Maintenance

Reheat State

The Reheat state is a "normal" state during Cool mode. The
Reheat state typically is active when reheat is required to
maintain DATS during the Economizer mode, while maintaining
the required minimum OA damper position. The Reheat state
can also be made active if the optional CO
provided and CO levels are high, requiring the OA damper to
2
open beyond what is required for economizer cooling.
When Reheat state is active, the UVC uses the unit's heating
capability as needed to maintain Reheat DATS. The CO
function (optional) is active and the OA damper is adjusted
as needed to maintain the CO
Controlled Ventilation (optional)" on page 37).

Reheat/Low Limit State

The Reheat Low Limit state is a "non-normal" state during Cool
mode. The Reheat Low Limit state typically follows the Reheat
state when heat is unavailable or when the UVC reaches 100%
heat and still cannot maintain VCLL.
When the Low Limit state becomes active, the heating output
is set to 100% capacity and the Low Limit logic overrides the
OAD minimum position and adjusts the OAD toward closed
as necessary to maintain the DAT setpoint (see "Outdoor Air
Damper Operation" on page 35) and "Night Purge State
Diagram" on page 11.

Can't Cool State

The Can't Cool state is a "non-normal" state during Cool mode.
The Can't Cool state typically becomes active when primary
(economizer) and secondary (mechanical, hydronic) cooling is
not available (or disabled) or when an IAT, DAT or OAT sensor
failure occurs.
When the Can't Cool state becomes active, no cooling is available.
www.DaikinApplied.com
DCV feature is
2
DCV
2
setpoint. See "CO2 Demand
2

Air Tempering Mode

The Air Tempering mode is a "normal" state that the UVC
can go into when the Fan Only mode is active (the control
temperature is between the heating and cooling setpoints and
all heating/cooling is off), some form of heating is available,
and Air Tempering has been enabled using the LUI keypad or
ServiceTools software. The UVC will monitor the DAT during
Fan Only mode and if the DAT drops below the effective heating
setpoint minus the Air Tempering Mode Differential (default
5.0°F/2.78°C) the unit will use whatever heating is available to
reheat the DAT to the effective occupied heating setpoint.

Dehumidification Mode

The following unit configurations are capable of
dehumidification as noted:
1. Air Source Heat Pump with Electric Heat.
2. Water Source Heat Pump with Electric Heat.
3. Water Source Heat Pump without Electric Heat.
4. DX Cooling with Electric Heat.
5. DX Cooling with Hydronic Heat (Valve Control).
6. 2-Pipe Chilled Water Cooling and Hot Water Heating
(Face and Bypass).
7. 4-Pipe Chilled Water Cooling and Hot Water or Steam
Heating (Valve Control).
8. 4-Pipe Chilled Water Cooling and Hot Water or Steam
Heating (Face and Bypass).
9. 2-Pipe Chilled Water Cooling and Electric Heating
(Valve Control). 1
10. 2-Pipe Chilled Water Cooling and Electric Heating (Face
and Bypass). 1
11. 2-Pipe Chilled Water Cooling (Face and Bypass).
Note References:
1. Active dehumidification is available ONLY on these
configurations. The unit may only enter dehumidification
when the unit is in the Cooling super state, and the unit
will enter the dehumidification state when the space RH
is above the space RH setpoint or the Dehumidification
binary input is closed.
2. Passive Dehumidification ONLY.
23 OM 1280-2 • MICROTECH UNIT CONTROLLER
Description of Operation
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