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"Plant temperatures are getting far too hot"

asked 2017-11-06 11:27:35 -0500

map1995 gravatar image

updated 2017-11-06 14:30:31 -0500

Used DesignBuilder...

I am trying to run a full year simulation with all of the HVAC equipment turned off in order to make sure the building is responding to outdoor air temperature fluctuations properly. Around June 11, I start getting a fatal error, "Plant temperatures are getting far too hot, check controls and relative loads and capacities", and the simulation stops. In addition, when I plot the zone temperatures up until the point where the simulation stopped, they are getting to be up to 40 degC, which is much hotter than the outdoor temperature. I do not know how the zone temperatures are getting this high without any of the heating and cooling systems on. I also do not know how to resolve the Plant Temperature error I am getting.

Suggestions?

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Is your pump on that plant loop set to constant or intermittent flow? If there is no load, and the pump is continuous, it can build up heat in the loop.

mdahlhausen gravatar imagemdahlhausen ( 2017-11-06 12:52:33 -0500 )edit

Changing the pumps to intermittent allowed the simulation to complete for the entire year. However, the zone temperatures are still getting up to around 40 degC throughout the summer, which is much too high. I can't figure out what equipment in the building is still on that would make the temperature that high.

map1995 gravatar imagemap1995 ( 2017-11-06 20:25:36 -0500 )edit

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answered 2017-11-07 08:48:35 -0500

kwalkerman gravatar image

I see that you have resolved the plant Loop Temperatures by setting your pump flow to "intermittent".

In regards to the zone temperatures getting up to 40C:

A number non-HVAC factors can increase internal heat gains:

  1. Internal loads - lights, electric equipment and heat produced by occupants
  2. Solar gains
  3. conductive gains or losses - when the outdoor temperature is greater than the indoor temperature, there will be mild heat loads on the building from conductive heat gains. When the outdoor air temperature is less than the indoor temperature, there will be a loss of heat through conduction.
  4. infiltration of outdoor air into the space - like #3, infiltration can contribute to heat add, or heat removal. Leaving out

If your indoor air temperature is 40C, I suspect that you may have a lot of glass, and thus high solar gains, and that you are not adequately taking infiltration into account. Keep in mind that occupied buildings in moderate climates do not often reach 40C because the occupants will take action to cool the building through ventilation. If you have taken infiltration into account, you have a lot of glass, and you have a well insulated building, your model may be correct.

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Asked: 2017-11-06 11:27:35 -0500

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Last updated: Nov 07 '17