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CAV system water coil controller Energy plus

asked 2018-08-20 04:39:27 -0500

Siva's avatar

updated 2018-08-20 09:52:30 -0500

I am Modelling a CAV system in Energy plus. I am using Chiller. I am trying to put a set point near the Mixed air inlet or at the return air temperature. I want chilled water actuator to operate based on the thermostat temperature. software is not accepting chilled water actuator operation based on either return air temperature/Mixed air inlet. instead it is only accepting a cooling coil outlet based setpoint which is Fine for VAV systems but it cannot be the case for CAV systems. In CAV system the supply air temperature cannot remain constant. the supply air temperature keeps on changing depending upon the load that is prevailing inside the room (Return air temperature) other wise one will end up in overcooling if the setpoint is based on cooling coil outlet during part load conditions.

So Keeping the above thing in view, can any one suggest me how to place this controller ?

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How about you use a SetpointManager:Warmest on the supply outlet node of the PlantLoop, and ensure your fan is constant volume and your AirTerminals are of the "ConstantVolume" type?

Julien Marrec's avatar Julien Marrec  ( 2018-08-20 06:42:54 -0500 )edit

@ Julien Marrec. could you please give me another hint on how it would resolve my issue.....Like what is that you want to do regarding supply outlet node of the plant loop?

Siva's avatar Siva  ( 2018-08-20 07:06:19 -0500 )edit

You can control your plant loop as you wish (or per the control sequence of your project). eg: if set it to a constant supply temperature of 45°F, the AHU Coil will vary the ChW flow based on the water temperature and the load it's seeing (which will vary the flow on the plantLoop as a result too).

Julien Marrec's avatar Julien Marrec  ( 2018-08-22 02:25:37 -0500 )edit

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answered 2019-02-27 22:49:40 -0500

A water coil is controlled by specifying a set point at the coil air outlet node. There are many types of SetpointManagers that can be used to place the set point. For your application, the set point at the air outlet node of the water coil should be calculated based on the load, not the thermostat temperature or return air temperature.

See SetpointManager:SingleZone:Cooling, SetpointManager:Warmest, or SetpointManager:MultiZone:Cooling:Average for setting the chilled water coil outlet air node temperature set point.

There are also example files that show how these set point managers are used. See the ExampleFiles-ObjectsLink.html file in the ExampleFiles folder to see which example files use these set point managers.

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Asked: 2018-08-20 04:39:27 -0500

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Last updated: Feb 27 '19