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Waterside economizer integrated with chiller: min temperature difference not zero?

asked 2016-02-02 11:30:57 -0500

After much puzzlement, I noticed that my HeatExchanger:FluidtoFluid, set to control type CoolingSetpointOnOffWithComponentOverride is preventing the integrated chiller to turn on (at all) if you use a Minimum Temperature Difference to Activate Heat Exchanger that is greater than zero (and it won't accept less than zero...)

Also the HX doesn't seem to do much in this case either (but that could just be for a reason...), so I'm not that concerned with it.

Why doesn't the HX let the chiller run when it clearly cannot meet the load itself?

You can take the E+ FreeCoolingChiller.idf example file and change the Min temp of the HX to something like 1C or 2C, and see for yourself.

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I just replicated this same issue in my own very simple model. I think this is an E+ issue, so I filed one here.

aparker gravatar imageaparker ( 2016-04-22 17:30:07 -0500 )edit

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answered 2016-09-01 09:28:00 -0500

Archmage gravatar image

The problem with minimum temperature difference is a bug that should be fixed in version 8.6. With the bug, conditions could get stuck in mode where neither the chiller nor HX would run. With the fix the chiller and HX use the minimum delta temperature tolerance in the same way to decide which should run.

Thanks to Chandan Sharma for pointing out the tricky one-line fix.

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Asked: 2016-02-02 11:30:57 -0500

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Last updated: Sep 01 '16