Chilled water supply temperature

I have a chilled ceiling system. and I put the chilled water loop exit temperature as 13C and the design temperature difference as 5C. also in setpoint manager, the loop is controlled to supply 13C all the time. but when I ran the chilled ceiling system, the result shows the supply temperature increased to 20C and the return is much higher than design temperature too. the chiller CHW outlet and inlet node temperatures are pretty similar, the supply water is not 13C. What's the reason of the unexpected and fluctuated supply and return temperature? image description

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CY_BH

asked 2015-10-02 19:15:11 -0500

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A simple reason for your unexplained temperature fluctuations may be that Chiller outlet node temperature will typically deviate from setpoint temperatures during times when Chiller is not operating, i.e. whenever Chiller outlet node mass flow rate is zero. You can check this immediately by looking at temperatures and mass flow rates simultaneously in ResultsViewer.

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OS-user-AT

answered 2015-10-05 08:24:25 -0500

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I think the reason for your chiller water exit temperature varying is because you have a setpoint on the outlet node of the chilled water loop. If you also put one on the chiller outlet node it should stay constant. This might also help keeping the temperature down when it enters your chilled ceiling. My initial thought would be to try a scheduled setpoint on your chiller and see if that helps. Just as an aside, I find when I model chilled ceilings, it helps to put hard values in wherever possible this seems to control them better.