VAV Supply air temperature reset.
VAV Supply air temperature reset.
(OP)
Can somebody please tell me the best way for the BMS to calculate what the supply air temperature should be set at in a VAV system that has heating and cooling coils in the air handling unit. The cooling coil was designed for an off coil temp of 12 Deg C and the heating coil was designed for an off coil temp of 28 Deg C. This is for max cooling and max heating. How do I reset the temp sensor in the suppl;y duct so as to control the operation of the Heating and cooling valves.
Thanks!
Thanks!





RE: VAV Supply air temperature reset.
0°C outside = 20°C discharge
20°C outside = 12°C discharge
Initially, then it can be tweaked if needed.
The other way I've seen it done (which almost always results in hot/cold complaints) is by using a thermostat voting scheme, where if a majority call for heat, the AHU will put out the design heating temperature (28°C). At this point, all the VAV boxes are switched to act in reverse, meaning they open during a call for heat and close during a call for cooling. When the majority vote calls for cooling, the boxes go back to controlling normally and the discharge setpoint resets to 12°C.
RE: VAV Supply air temperature reset.
RE: VAV Supply air temperature reset.
RE: VAV Supply air temperature reset.
Lilliput, right on, but DX makes life difficult. If not staged right, we can blow right past DAT setpoints (which is often the case) if there is not sufficient staging. The operative word in Mr. Billyg's post is "Heating and cooling valves," which leads me to believe this is a HW/CHW system.
RE: VAV Supply air temperature reset.