Plant loop exceeding upper temperature limit....

asked 2016-10-14 03:36:08 -0500

kifg
41 ●2

updated 2016-10-14 11:55:40 -0500

I'm having a problem with the Hot Water Loop in my model and I don't know what to do. I have this error: * Fatal * CheckForRunawayPlantTemps: Simulation terminated because of run away plant temperatures, too hot ...Summary of Errors that led to program termination: ..... Reference severe error count=1 ..... Last severe error=Plant temperatures are getting far too hot, check controls and relative loads and capacities

I'm using a Boiler, Chiller and a Heat Exchanger... My pump control type is Intermittent (I've seen that this sometimes solves the problem).

Thanks for the help....

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answered 2016-10-26 21:18:06 -0500

Carlos Vazquez

812 ●2 ●12

updated 2016-10-29 14:55:02 -0500

I have been doing troubleshooting for a model I´m working and has the same issue. I started building a chilled water loop within the openstudio GUI. So far, within the openstudio GUI, I have not found a solution. My situation analysis is that pump operation (whether if it´s on or off) is dependent of loop demand, and loop demand is not necessarily related to the operation of other cooling or heating equipment within the loop. Even though I have selected intermittent pump operation, undesirable heat is still being built-up within the loop.

Out of openstudio GUI within energyplus are more options to do something about it, and I added an availability manager to stop the loop when it reaches to an undesirable temperature. The object is AvailabilityManager:HighTemperatureTurnOff.

Another option is to use a measure "Enable Detailed Output for Each Node in a Loop" within OpenStudio in the Reporting/Troubleshooting tab. You can run the simulation in a shorter time period before it fails with this measure. Then you can verify the temperature patterns and tendencies for every loop that you want. That way maybe you can figure out better what is the cause of making the simulation fail.

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I did notice that the OpenStudio SDK has a stub for the availability manager you bring up here:

https://openstudio-sdk-documentation....

To the OS people..is it possible to use this in a measure to and simply add this to all plant loops. Or is this a stub class that is not fully implemented yet?

Phylroy Lopez ( 2017-02-05 12:03:38 -0500 )edit

After digging a bit found this issue that Andrew Parker submitted here https://github.com/NREL/OpenStudio/is...

Phylroy Lopez ( 2017-02-05 12:24:53 -0500 )edit

I was having the same problem with intermittent pumps. Your recommendation of using "AvailabilityManager:HighTemperatureTurnOff" worked for me. Thanks for the tip!

Jono ( 2021-09-08 12:07:43 -0500 )edit

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answered 2016-10-14 09:52:44 -0500

Adam Hilton

3455 ●1 ●14

It probably because you have constant speed pumps and the operation scheme is "Uncontrolled On" for the loop with the heat exchanger. Add a setpoint manager to the heat exchanger that's on the supply side or manually change the operation scheme to cooling load or heating load.

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