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DN-Series Integrated Programmable Controls
DOAS
SYSTEM MONITORING
13.9.5 Tempering Control
The DN DOAS unit may provide heating and cooling/dehumidification if ordered as such. For
heating and/or cooling, there will be a conditioned air temperature sensor which measured the
air coming out of the unit as Input Register 32 “CA_Temp.Val.” For dehumidification with either
hot gas reheat or reheat by a heat source, there will also be a coil leaving temperature sensor
as Input Register 28 “Cooling_LAT.Val.”
SA
T
T
Cooling
Heat Source
Coil Leaving
Temperature
CA
Temperature
13.9.5.1 Determining Tempering Mode
To determine the mode in which the unit is operating, the following values are considered:
u
Holding Register 62 “Dehumid_Chageover_SetP.Val”
u
Holding Register 26 “HeatLockoutTemp”
u
Holding Register 24 “CoolLockoutTemp”
In addition, the BMS has the potential to use one more setting to determine whether the unit
will lock out heating or cooling functions. This is required for the dual temp systems and may
be useful for other situations. The Coil 4 “BMS_SetHeatCool” must be true and then the mode
is set through Coil 5 “BMS_HeatCoolMode” where 0 =Heat and 1 = Cool. The BMS mode is
shown for troubleshooting.
Dehumidification
and
Cooling Mode
Heating Mode
Vent Mode
Sensible
Cooling Mode
Design Dew Point
1. Dehumidification: Is the unit configured
for dehumidification? If so, is the unit in
dehumidification mode?
2. Heating: Is the unit configured for heating?
Is the outdoor air temperature lower than
the heating lockout temperature?
3. Cooling: Is the unit configured for cooling?
Is the outdoor air temperature higher than
the cooling lockout temperature?
4. If it in no other mode and the unit is on, it
will be in Ventilation Mode.
See the following sections for more information on these modes. The mode is determined in
this order:
The current Tempering Mode is viewed at Discrete Input 16 “Tempering_Mode.Val.” It is also
an output used for VRF applications. The tempering mode will show heating when in heating or
ventilation only mode, and cooling for cooling or dehumidification mode.
