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Fan:Systemmodel and ZoneHVAC:FourPipeFanCoil control methods

asked 2021-05-20 13:32:58 -0500

Abarker's avatar

updated 2021-05-20 14:00:55 -0500

I am trying to model a 4 pipe fancoil with 4 discrete speeds which remains ON at the lowest speed when there is no load, never turning off. I've created the 4 discrete speeds in the Fan:SystemModel object and set the ZoneHVAC:FourPipeFanCoil Capacity Control to MultiSpeedFan or Cycling, which both give very similar results. However, both of these still cycle the fan off when there is no load. Any of the other Capacity Control Methods that might work aren't valid with a Discrete control strategy.

Is there a combination of inputs that can do what I'm looking for between these two objects? I fear I am under reporting my fan energy by allowing the fan to cycle off.

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answered 2021-05-21 12:52:41 -0500

Abarker's avatar

The answer to this turned out to be a simple one. I didn't realize that when choosing the MutliSpeedFan control option in the Four Pipe Fan Coil object, that the 'Supply Air Fan Operating Mode Schedule Name' input become relevant and defaults to always 0 (cycling). Choosing a schedule that is Always 1 in this field produced the exact result I was looking for, and the fan no longer cycles off.

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answered 2021-05-21 09:00:20 -0500

Someone else may know the direct answer to your question, but an alternative option could be to set up an EMS script that turns on an (electric)Exterior:FuelEquipment object, with a capacity of your fan at its lowest speed, anytime the FPFC fan turns off. Or if the fan was a considerable size and you wanted that heat to go into a certain zone you could instead use an OtherEquipment object.

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Asked: 2021-05-20 13:32:58 -0500

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Last updated: May 21 '21