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change from Fan:ConstantVolume to Fan:OnOff

asked 2014-12-10 17:17:42 -0600

Alex Vlachokostas gravatar image

updated 2015-01-09 12:36:32 -0600

Hi everyone, I currently have a Fan:ConstantVolume in a single thermal zone model: I want to change the Fan:ConstantVolume which does not cycle to a Fan:OnOff which cycles with heating/cooling. Therefore, after reading the InputOutput Reference document, I just substituted the Fan:ConstantVolume with the Fan:OnOff object.

However, I get the following severe error: * Severe * GetAirPathData: AirLoopHVAC = "SYS-1". * ~~~ * ..Invalid Air Loop Component Type = "FAN:ONOFF". * ~~~ * ..Air Loop Component Name = "SYS-1 SUPPLY FAN". * ~~~ * ..reference Branch = "SYS-1 MAIN BRANCH". * ~~~ * ...This component may only be referenced by a parent component such as AirLoopHVAC:Unitary:Furnace:HeatCool or similar. * Fatal * GetAirPathData: Errors found retrieving input for AirLoopHVAC.

Apparently there are more objects that I have to define. Any thoughts?

Thank you very much. I appreciate your help.


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answered 2014-12-10 17:44:26 -0600

updated 2014-12-10 17:45:28 -0600

You cannot just replace Fan:ConstantVolume with Fan:OnOff on an AirLoopHVAC, otherwise you get the error message you see.

Fan:OnOff must be used as part of a compound object, meaning it needs to be used in a AirLoopHVAC:Unitary:Furnace:HeatCool, ZoneHVAC:PackagedTerminalAirConditioner, etc.

That said, if you are using EnergyPlus 8.1 or higher you can use AirLoopHVAC:UnitarySystem. This will allow you to embed a Fan:OnOff on an AirLoopHVAC.

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And with any of these unitary or packaged equipment types, you use the Supply Fan Operating Mode Schedule to indicate when the fan should run in cycling mode (0) or continuously (1).

MJWitte gravatar image MJWitte  ( 2014-12-10 20:52:05 -0600 )edit

Thank you both for your prompt and very helpful postings.

Alex Vlachokostas gravatar image Alex Vlachokostas  ( 2014-12-12 15:24:36 -0600 )edit

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Asked: 2014-12-10 17:17:42 -0600

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Last updated: Dec 10 '14