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Run away plant temps -far too hot

asked 2018-04-29 22:27:44 -0500

adireddi's avatar

updated 2018-04-30 08:48:45 -0500


I am trying to model CHW and HW load profiles on central plant. I am getting the following server error and simulation is terminating. I am looking for Suggestions/direction on how to address the issue of Run away plant temperatures.

image description

Description of the Central Plant: CHW- generated by two water cooled chillers with a heat recovery chiller ( currently not modeled ), connected to two cooling towers. HW- Generated by two condensing boilers. The demand side of each loop has load profile object, where I referenced 8760 hourly load data and flow fraction for various building on campus. The load profiles are generated using individual OSM files.

The following is the CHW plant configuration screen shot: image description

Thank you! for your time and input.

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answered 2018-04-30 08:53:02 -0500

We have limited data to work with, but given the eplusout.err snippet you shared, I think your LoadProfile:Plantobject is generating demand far in excess of what your PlantLoop supply side (chillers and pump) can actually provide.

The root cause can be one (or a combination) of several factors:

  • Equipment capacities too small compared to what the LoadProfile is asking for
  • If the equipment are autosized, it could be that the Design Day behavior for your loadProfile object is badly defined.

Anyways, I'd start investigating on that front, it shouldn't be too long until you find a severe mismatch (your plant temperatures are getting really hot and you have a TON of unmet demand on your plant loop).

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Thank you @Julien, I will look into to design day and capacities. Question- For a loadProfile:plant, do I need to specify hourly supply water temperatures on the supply side node just before the loadProfile object ? in addition to hourly loads and flow fraction.

adireddi's avatar adireddi  ( 2018-04-30 10:45:57 -0500 )edit

The SetpointManager on Plant Supply Outlet Node determines the temperature of the water coming into your LoadProfile:Plant object, which in turns uses the Flow Rate (m3/s) and load (W) to calculate the temperature of the water coming out. The Engineering reference explains that here

Julien Marrec's avatar Julien Marrec  ( 2018-05-02 06:34:50 -0500 )edit

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Asked: 2018-04-29 22:27:44 -0500

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Last updated: Apr 30 '18