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Surface NAME_OF_SURFACE is referenced by more than one radiant system--this is not allowed

asked 2018-10-05 18:09:16 -0500

mldichter's avatar

updated 2018-10-06 08:55:48 -0500

I was trying to model a ceiling/floor surface in energyplus with radiant cooling on the ceiling side and radiant heating on the floor side using ZoneHVAC:LowTemperatureRadiant:VariableFlow objects but was having trouble with this error.

* Severe * Surface NAME_OF_SURFACE is referenced by more than one radiant system--this is not allowed

I was able to get around it by changing the BuildingSurface:Detailed field of Outside Boundary Condition from Surface to Adiabatic for the floor ceiling I was adding radiant heating and cooling to. This decoupled the surfaces in the model and energyplus ran without a severe error.

This error is mentioned in another post with a proposed solution, but references a 'Radiant Surface Type' which doesn't seem to exist.

Is this behavior a feature of energyplus, a bug, or can my idf file (Google Drive link) be changed to have a surface with a radiant system on either side with Outside Boundary Condition of Surface?

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answered 2018-10-12 07:52:16 -0500

Construction:InternalSource can only handle a single source within a given surface. If I'm following correctly, you are trying to model a surface with two separate hydronic loops embedded within it. The best solution I can think of is to split the surface into two parts (so the two paired surfaces become four surfaces). Put the radiant cooling in one part, and the radiant heating in the other.

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@MJWitte Not quite. Two story building. First story floor touches ground. First story ceiling touches second story floor. Second story ceiling is roof. I wanted to have radiant cooling in the first story ceiling and radiant heating in the second story floor. Even though the radiant heating referenced the second story floor object and the radiant cooling referenced the first story ceiling object, energyplus outputted "* Severe * Surface NAME_OF_SURFACE is referenced by more than one radiant system--this is not allowed". Got around it by making the surfaces adiabatic, which works quite well.

mldichter's avatar mldichter  ( 2018-10-12 08:20:02 -0500 )edit

The drawback of making the surfaces adiabatic is that the second story floor is now thermally isolated from the first floor ceiling. I would expect that the actual building will see some of the heat from the second story floor warm the first story ceiling, and likewise some of the cooling from the first floor ceiling would conduct into the second story floor. That won't happen with adiabatic surfaces.

MJWitte's avatar MJWitte  ( 2018-10-15 15:57:57 -0500 )edit

@MJWitte Yeah, but hopefully the insulation makes heat transfer negligible between the floor and ceiling surfaces. Not perfect, but it works.

I would prefer the ceiling and floor to to have heat transfer between them though. Any ideas on how to pair the surfaces without an error? I fear the problem is in the C++ code for the object.

mldichter's avatar mldichter  ( 2018-10-15 16:15:30 -0500 )edit

That's my suggestion above - create a pair of surfaces that cover half the area which contain the radiant cooling, and another pair of surfaces to cover the other half which contain the radiant heating. Again, not perfect, but maybe better, maybe not. The "problem" is that the solution technique for the surface heat transfer with internal source is currently formulated for a single source, not two.

MJWitte's avatar MJWitte  ( 2018-10-15 17:31:39 -0500 )edit

@MJWitte So if I understand you correctly, exactly 1/2 of the floor area would contain radiant heating and 1/2 of the floor area would be a regular surface, exactly 1/2 of the ceiling area would contain radiant cooling and 1/2 of the ceiling area would be a regular surface? That way I could pair a 1/2 floor and 1/2 ceiling with only radiant heating and the other 1/2 floor and 1/2 ceiling with only radiant cooling?

mldichter's avatar mldichter  ( 2018-10-15 17:44:00 -0500 )edit

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Asked: 2018-10-05 18:09:16 -0500

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Last updated: Oct 12 '18