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EnergyPlus Fan:OnOff or Fan:SystemMode don't show on/off cycling pattern

Hi, all.

I am trying to build two systems: 1) a single-stage heat pump system with on/off cycling fan. 2) a single-stage heat pump system with descrete fan (2 speeds).

An UnitarySystem was used including DX cooling and heating coils. I hvae set the Supply Air Fan Operating Mode Schedule Name to Always 0 to combine the fan and coil's operation into cycling mode.

The problem is, when I look at the output(system node mass flow rate on zone inlet node), The airflow rate seems like variable air volume fan. It does not show on/off cycling pattern or 2 levels of flow rate.

Can anyone could give me an advise?

zeroJ's avatar
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zeroJ
asked 2024-10-21 12:55:02 -0500
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The air flow rate is showing an average across the time step. It's:

mass flow rate = design mass flow rate * part load ratio

If you divide the mass flow rate by part load ratio you will see the design mass flow rate.

rraustad's avatar
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rraustad
answered 2024-10-21 14:49:25 -0500
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This is amazing thank you so much!

Additionally, is there any way that I can model the cycling of indoor air temperature, not using the EMS? Since the supply airflow rate is calculated based on the cooling and heating load, the zone mean air temperature doesn't mimic the cylcing dynamics of real building indoor air temperature derived from the on/off control.

zeroJ's avatar zeroJ (2024-10-21 15:04:28 -0500) edit
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Look at SetpointManager:SingleZone:OneStageCooling and SetpointManager:SingleZone:OneStageHeating to see if that gives the response your looking for. You might try these with the UnitarySystem using Setpoint control.

rraustad's avatar rraustad (2024-10-22 08:15:37 -0500) edit
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Thank you for the response.

I just tried this method, and got an error:

* Severe * Input errors for AirLoopHVAC:UnitarySystem:1F HEATPUMP * ~~~ * Did not find Air Node (Zone with Thermostat or Thermal Comfort Thermostat). * ~~~ * specified Controlling Zone or Thermostat Location name = 1F_ENTRANCE

I have changed the Control Type of my AirLoopHVAC:UnitarySystem into SetPoint as well as the zone thermostat into ZoneControl:Thermostat:StagedDualSetpoint. It seems that the setpoint manager and zone termostat are not compatible with AirLoopHVAC:UnitarySystem.

zeroJ's avatar zeroJ (2024-10-22 09:29:14 -0500) edit
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@zeroJ this should work with setpoint control. send me the idf file, see my profile for my email address

rraustad's avatar rraustad (2024-10-22 12:46:59 -0500) edit
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Also, what version of E+ are you using?

rraustad's avatar rraustad (2024-10-22 12:48:01 -0500) edit
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