Outside air flow rate is not constant for WSHP OS
I am modeling a building served by water source heat pumps, the first option was to serve the outside air by DOAS, an alternative design is introducing the OA directly to the WSHP. When I used the DOAS the outside air was delivered at a constant rate and fluctuates between the minimum OA and 0 based on the operation schedule of the DOAS as shown in the first image. However when the outside air is delivered directly to the WSHP it seems to fluctuate randomly and never reaches the minimum OA rate as shown in the second image, I was expecting the OA in this case to be constant 24/7 since there is no schedule governs the operation of the WSHP. Any ideas what is causing this?
Thank you,
Air Outlet Node
OA inlet Node
Air Outlet Node and Air Outlet Node
OA can only flow through the WSHP when the WSHP fan is on. You need to check OA flow at the inlet to each WSHP to see more detail. Plot WSHP supply node and OA inlet node flow to the WSHP.
I plotted the supply node and OA inlet node flow and added them to the question. The OA is still looks fluctuating. Also I am not sure why the supply air flow is not constant since the fan is “Fan:OnOff”
It appears that the WSHP is cycling to meet the load which will vary the air flow rate during each time step. What is the object name? Is it
ZoneHVAC:WaterToAirHeatPump? Is itAirLoopHVAC:UnitaryHeatPump:WaterToAir? Answer this question and a more specific answer can be provided.it is
ZoneHVAC:WaterToAirHeatPump. If the fan is constant flow shouldn't the flow stay constant all the time? I am thinking of this unit like the AC in my apartment either it is off and the flow is zero or it is on and the flow is 500 cfm, not sure if this hold true in EnergyPlus simulationIn EnergyPlus a cycling fan cycles based on load each time step. This is analogous to the AC system in your home operating for only a portion of the hour. If the load is high, the AC would operate the entire hour, if load is low the system will cycle.