I received a suggestion to use a Type 1669 controller for a radiant slab, and it seems to work well (thanks Ben Heymer). However, right now I am using it to modulate temperature, but what I would really like to do is modulate the flow rate through the slab because I have a variable (uncontrolled) input temperature. The problem is that TRNSYS will not allow me to decrease the flow rate much below 2,000 kg/hr based on the size of my radiant floor.
(Error Message: "Specific fluid mass flow of active layer in surface 9 below minimum value of 6.74 kg/m2h Please, increase the minimum mass flow rate or use the autosegmentation feature of TRNBuild for subdividing the surface").
The proportional controller will inevitably fall below this rate because it will ramp down to zero when no heating (or cooling) is needed. Is there a workaround for this? I looked into the autosegmentation feature and it doesn't seem to subdivide the surface at all, and I'm not sure how this would help. Thanks again.
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Brad Painting
Master of Science Candidate, Renewable Energy Engineering
Department of Technology & Environmental Design
Appalachian State University
Boone, NC 28608