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What is the correct order of Controllers in AirLoopHVAC:ControllerList?

asked 2023-09-28 08:33:06 -0500

Keigo's avatar

updated 2023-10-03 03:48:36 -0500

I want to model VAV system with preheating coil.

I/O Reference says "The order of the controllers in the list is significant: controllers are simulated sequentially in the order given in the Controller List. Typically the Controller List would contain a Controller:OutdoorAir. If there are chilled water or hot water coils in the outdoor air system, each such coil will need a Controller:WaterCoil."

I referred to ExampleFiles and found that 5ZoneAirCooled.idf and many idf files based on it have preheating coil and precooling coil before OutdoorAir:Mixer. However, the order of Controllers in AirLoopHVAC:ControllerList is Controller:OutdoorAir -> Controller:WaterCoil for precooling coil -> Controller:WaterCoil for preheating coil. It seems to me that the order of Controllers in AirLoopHVAC:ControllerList is inconsistent with the order of Equipment in AirLoopHVAC:OutdoorAirSystem:EquipmentList.

    OA Sys 1,                !- Name
    OA Sys 1 Controllers,    !- Controller List Name
    OA Sys 1 Equipment;      !- Outdoor Air Equipment List Name

    OA Sys 1 Controllers,    !- Name
    Controller:OutdoorAir,   !- Controller 1 Object Type
    OA Controller 1,         !- Controller 1 Name
    Controller:WaterCoil,    !- Controller 2 Object Type
    OA CC Controller 1,      !- Controller 2 Name
    Controller:WaterCoil,    !- Controller 3 Object Type
    OA HC Controller 1;      !- Controller 3 Name

    OA Sys 1 Equipment,      !- Name
    Coil:Heating:Water,      !- Component 1 Object Type
    OA Heating Coil 1,       !- Component 1 Name
    Coil:Cooling:Water,      !- Component 2 Object Type
    OA Cooling Coil 1,       !- Component 2 Name
    OutdoorAir:Mixer,        !- Component 3 Object Type
    OA Mixing Box 1;         !- Component 3 Name

image description

What is the correct order of Controllers in AirLoopHVAC:ControllerList in this case? At first, I thought that Controller:OutdoorAir should be listed after Controller:WaterCoil because OutdoorAir:Mixer is located after Coil:Heating:Water and Coil:Cooling:Water, but the ExampleFile shows the different order. I'm not sure if the ExampleFile is correct or not. Or is the order of the controllers not significant actually?

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I've said that before, but I really like your diagrams!

Julien Marrec's avatar Julien Marrec  ( 2023-09-29 06:23:51 -0500 )edit

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answered 2023-09-29 06:22:17 -0500

Having the Controller:OutdoorAir first makes sense though: the quantity of fresh air to bring in is the most important, and determines the amount of heating/cooling that is needed.

The fact that the Controller:WaterCoil for cooling coil is before the heating coil one... not sure that it has any impact. Have you tried switching the order and seeing the results?

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I changed the order of the controllers in response to your advice. The result (the End use, the conponent sizing, etc.) did not change. The result remained the same even if I listed the controllers of the preheating coil and the precooling coil to AirLoopHVAC instead of AirLoopHVAC:OutdoorAir System. It seems that the order and the location of controllers do not matter.

Keigo's avatar Keigo  ( 2023-10-03 04:00:25 -0500 )edit

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Asked: 2023-09-28 08:33:06 -0500

Seen: 84 times

Last updated: Oct 03 '23