Coil:Cooling:Water has cooling rate output when chilled water flow is 0

asked 2023-08-08 12:48:51 -0500

xchen's avatar

updated 2023-08-08 14:39:19 -0500

In my energyplus 9.5 model for a VAV reheat AHU, I noticed quite a few hours when the Coil:Cooling:Water in AirLoopHVAC:UnitarySystem cools the air down to about 8-9C (setpoint at 12.7C) at the outlet node. But for these hours, the chilled water flow at the inlet node of the coil is 0. The CHW plant flow is also 0 at these hours. The cooling coil has positive total cooling rate output, which means the coil is working. Not sure how this is possible.

This happens during winter seasons. And the AHU heating coil after the cooling coil has to heat up the supply air from 8-9C to the setpoint, which causes high heating energy.

The system configuration is supply fan -> cooling coil -> heating coil -> supply node, with an outdoor air controller before the supply fan.

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I think the fact that I have an availability manager that turns of chiller in winter season causes this abnormal behavior of the cooling coil. When I delete the availability manager, the cooling coil works fine.

xchen's avatar xchen  ( 2023-08-15 11:53:50 -0500 )edit