How to create a representative floor TABS model?

asked 2018-11-22 16:21:06 -0500

alex j gravatar image

updated 2018-11-26 16:35:40 -0500


I'm trying to model a representative floor, similar to what is being done here, in question 1305. However, in my model I'm attempting to model radiant floors, without thermal isolation between the slab (like TABS). Splitting the slab and setting to adiabatic isn't ideal, as then the ceiling would no longer be a radiant surface, but rather just passive thermal mass.

In order to capture the heat transfer from the radiant floor to the ceiling of the floor below, I tried to manually surface-match the floor to the ceiling in each room. IE, the boundary condition of the floor is set to the ceiling of the same room.

This seems to create issues. It seems as if the "floor" is then converted to an internal mass object, similar to what happens to walls between spaces in the same thermal zone. I've set the default constructions for interior, ground and exterior surfaces all to internal source constructions, however once converted this doesn't seem to allow it to function as an internal source surface.

When I try to run with all the floor in a zone "surfaced-matched" to the ceiling I get the critical error:

   ** Severe  ** ZoneHVAC:LowTemperatureRadiant:SurfaceGroup = LOW TEMP RADIANT ELEC SFLOORS does not have any surfaces listed.

As soon as one floor in the zone is set to a normal boundary condition (Outside) or Adiabatic conditions, the simulation runs.

Any ideas how to simulate a single floor of a TABS building? I'd upload photos but I don't have enough Karma yet.

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