How does one set minimum water flow rates through WAHPs?
I have been recieving warnings on my plant loop temperatures getting far too hot and too cold. I have spent some time diagnosing my runaway plant temperatures. I have set my pumps controls in my EnergyPlus model to intermittent and I have tracked all of my node and temperature flows based on the questions here and here. I also see that someone has a similar question here.
I have found that the reason I am getting these temperature errors in my model is because there are a few periods when my WAHPs have very tiny flows through them, and so they raise the water temperature at those nodes tremendously. However, since the flow fraction through these branches is so small, my overall loop temperature stays within my dual setpoint schedule. I have three WAHPs and five WWHPs all sharing the same central plant loop with an autosized boiler and autosized cooling tower (EvaporativeFluidCooler:TwoSpeed). I want to find a way to stop this overheating and overcooling during times of very small flow through these individual water to air heat pumps. Does anyone know of a way to do this?
I tried setting minimum flows in my central loop, but this does not help, because there are bypass branches on both the supply and demand side of my loop. I have been trying to find a way to set minimum flows through only my WAHP branches, but haven't figured out how to do this yet. I have no issues with the operation for my water-to-water heat pumps, only my water to air heat pumps. Any advice is appreciated.
Which WAHP model are you using? Have you tried using heat transfer pipes, e.g. Pipe:Indoor?
I am using AirLoopHVAC:UnitaryHeatPump:WaterToAir objects with equation fit coils: Coil:Heating:WaterToAirHeatPump:EquationFit and Coil:Cooling:WaterToAirHeatPump:EquationFit. I have been using only pipe:Adiabatic types. I will try running with Pipe:Indoor objects now and see if that has any effect. Thank you for the reply!
Unfortunately @Archmage that did not seem to have an effect. I replaced all 30 pipes with the Pipe:Indoor object in my model, but I still have very extreme temperatures at my WAHP coils at times of very low flow. Do you have any other suggestions of things to try?
This was corrected in V8.6 for WAHP using cycling water flow. See 5691
@rraustad I am using V8.6 I have my max cycling rate set at 2.5 cycles/hour. I am using the default numbers for my coefficients for Coil:Heating/Cooling:WaterToAirHeatPump:EquationFitfrom the InputOutput reference. Is there one of these values that I should change?