Commissioning Instructions

Supply Air Temperature Reset using Central Functions
Configuration
4
8 | 21
Restricted
A6V12006922
4.1 Configuration
Description
BACnet Name
(Abbreviated Name)
Type
Comment
Default Value
Maximum Supply Air
Temperature
TSuMax
(TSU MAX)
ACnfVal
Maximum allowable
supply air temperature.
During Heating, the SAT
will not be reset above
this temperature.
89.6 °F (32 °C)
Start Value for Cooling
SttValC
(START CLG)
ACnfVal
Value at which Cooling
mode would begin if the
temperature was above
this point. Used as Max
SAT if the changeover is
Neutral.
75.2 °F (24 °C)
Start Value for Heating
SttValH
(START HTG)
ACnfVal
Value at which Heating
mode would begin if the
temperature was below
this point. Used as Min
SAT if the changeover is
Neutral.
71.6 °F (22 °C)
Minimum Supply Air
Temperature
TSuMin
(TSU MIN)
ACnfVal
Minimum allowable
supply air temperature.
During Cooling, the SAT
will not be reset below
this temperature.
60.8 °F (16 °C)
4.2 Acceptable Reset Ranges
According to standards such as ASHRAE 90.1 and IECC 2017 (see Appendix [➙ 20] ), the reset must be at
25% of the difference between the design supply air temperature and the design room temperature.
For example, if the design supply air temperature is 55 °F (13 °C) and the design space temperature is
72 °F (22 °C), the reset must be not less than 4.25 °F (2.36 °C). The minimum cooling supply air
temperature should be set no lower than the design coil leaving air temperature 55 °F (13 °C) to prevent
excessive chilled water temperature reset requests which will reduce chiller plant efficiency.
The maximum cooling supply air temperature is typically 65 °F (18 °C) in mild and dry climates or 60 °F
(16 °C) or lower in humid climates. It should not typically be greater than 65 °F (18 °C) since this may
lead to excessive fan energy that can offset the mechanical cooling savings from economizer operation.