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Radiant Baseboard not meeting heating requirements

Hey all,

This is a question that stems off one of my previous questions. Basically the radiant baseboards I have modelled are not meeting the heating requirements. This is the type of error I am getting.

** Warning ** ControlCompOutput: Maximum iterations exceeded for ZoneHVAC:Baseboard:RadiantConvective:Water = CEILING 2SW
**   ~~~   ** ... Load met       = 4.42731 W.
**   ~~~   ** ... Load requested = 2.77647 W.
**   ~~~   ** ... Error          = 1.65083736 %.
**   ~~~   ** ... Tolerance      = 0.10000000 %.
**   ~~~   ** ... Error          = (Load met - Load requested) / MAXIMUM(Load requested, 100)
**   ~~~   ** ... Actuated Node Mass Flow Rate =1.752835318E-008 kg/s
**   ~~~   **  Environment=SHEARWATER ANN HTG WIND 99.6% CONDNS WS=>MCDB, at Simulation time=01/21 00:30 - 00:45

Sometimes these errors go up to 300% or more. My only thought is that something is set incorrectly that is associated with the mass flow rate of water through the panel.

I have these hot water radiant baseboards hooked up to my DHW plant. That plant has a temperature setpoint of 87.8C but that was the only thing I had set on the loop. The rest was supposed to be autosized and should supply the correct flow to all the radiant baseboards. Is there anything special that need to be done when applying these to a model?

Note: Working in OpenStudio

Dustin's avatar
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Dustin
asked 2015-12-16 08:23:38 -0500
__AmirRoth__'s avatar
4.4k
__AmirRoth__
updated 2017-05-09 10:08:41 -0500
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1 Answer

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This result does not look to be a major issue, certainly not one that would affect the simulation results. Since the load is 3 W, the model has difficulty converging on a solution. A real system would not even turn on to meet a load this small since the thermostat would not activate the baseboard. An additional complexity is that the water mass flow rate is very near a no flow condition and the model may choose to disable the baseboard one iteration and allow it to operate another, making convergence impossible.

rraustad's avatar
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rraustad
answered 2015-12-18 17:09:54 -0500, updated 2015-12-18 18:19:16 -0500
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Sometimes the errors go up to 300% or more. So what is the explanation for those cases?

Edit: This can be ignored. I guess my question would be is there any way to increased the tolerance to eliminate my file from have 200 000 warnings regarding this?

Dustin's avatar Dustin (2015-12-21 05:53:23 -0500) edit

The last input in this object is the tolerance. It may help somewhat to increase this value.

ZoneHVAC:Baseboard:Convective:Water
  N6 ; \field Convergence Tolerance
       \type real 
        \minimum> 0.0
       \default 0.001
rraustad's avatar rraustad (2015-12-21 09:32:29 -0500) edit
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