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Using PlantEquipmentOperation:OutDoorDryBulb to control Condenser Equipment

asked 2015-07-23 08:35:07 -0600

kbk78 gravatar image

updated 2017-05-17 12:34:19 -0600

I have a cooling tower and a fluid cooler in a EnergyPlus model. We are trying to control the operation based on outside temperature. If the Temperature is less than 40F the fluid cooler operates. If the temperature is greater than 40F the cooling tower operates. The following are the objects setup in the model:

    FluidCooler Equipment List,

    CoolingTower Equipment List,

    Condenser_Loop Scheme 1,
    -32,4.5,FluidCooler Equipment List,
     4.5,50,CoolingTower Equipment List;

    Condenser_Loop Operation,
    Condenser_Loop Scheme 1,

The condenser Loop operation is further referenced by the CondenserLoop Object.

However, Hourly outputs indicate both units operating at all times during the year. Is this setup not adequate for this type of control?


Scheduled Condenser operation File:C:\fakepath\CondDB_Sch.idf.gif

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Should be sufficient, some additional info could help resolve the problem.

What's your pumping scheme? What is the pump size compared to the design flows of the two units? Do you have a supply side bypass on the condenser loop?

Edwin gravatar image Edwin  ( 2015-07-23 10:01:26 -0600 )edit

Thanks for your Response, There is a variable speed Pump on the Supply Side That is autosized. Also there is a Bypass on the supply side. What is Even more surprising is that I set the CondenserEquipmentOperationScheme Schedule to Off and the Condenser equipment still runs. These controls seem to have no impact on the condenser Loop operation.

kbk78 gravatar image kbk78  ( 2015-07-23 10:44:45 -0600 )edit

Which version of E+ are you using?

Edwin gravatar image Edwin  ( 2015-07-23 11:02:54 -0600 )edit

Was using 8.1. Just updated this to version 8.3 and having the same problems. I have attached the file above if you could look at it (Rename .gif to .idf) . It uses LoadProfile to simulate the plant load.

kbk78 gravatar image kbk78  ( 2015-07-23 11:36:45 -0600 )edit

1 Answer

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answered 2015-07-23 18:15:19 -0600

updated 2015-07-25 00:38:37 -0600


So, I did some digging today with your example file. Unfortunately it has revealed some issues with that operation scheme that are going to require a workaround if you need to use this before the next release of E+.

I have opened an issue on our GitHub site here that details what I have seen so far today. If you have a GitHub account, please feel free to engage in the conversation on that issue. This is a high priority to me, so I anticipate having the issues fixed up soon, but the fix won't be available in a major release until our September 30 release.

In the meantime, if you need an immediate workaround, you could simply pull the outdoor dry bulb from the weather file for every hour, and then create an hourly 0/1 schedule for when the temperature is above or equal to the switch temperature, then one for when it is below. These schedules could be used in the CondenserEquipmentOperationSchemes object to schedule two separate PlantEquipmentOperation: instances. Of which neither should be the OutdoorDryBulb. I would imagine something like:

    Condenser_Loop Operation,            !- Name
    PlantEquipmentOperation:CoolingLoad, !- Control Scheme 1 Object Type
    AboveScheme,                         !- Control Scheme 1 Name
    AboveSchedule,                       !- Control Scheme 1 Schedule Name
    PlantEquipmentOperation:CoolingLoad, !- Control Scheme 2 Object Type
    BelowScheme,                         !- Control Scheme 2 Name
    BelowSchedule;                       !- Control Scheme 2 Schedule Name

where the AboveSchedule/BelowSchedule are the values you created above outside of E+. (You could use Schedule:File for convenience there). Then the operation schemes would look like:

    AboveScheme,                 !- Name
    0,                           !- Load Range 1 Lower Limit {W}
    100000000,                   !- Load Range 1 Upper Limit {W}
    CoolingTower Equipment List; !- Range 1 Equipment List Name

    BelowScheme,                 !- Name
    0,                           !- Load Range 1 Lower Limit {W}
    100000000,                   !- Load Range 1 Upper Limit {W}
    FluidCooler Equipment List;  !- Range 1 Equipment List Name

Thanks for helping identifying this.

So, after the comment by @kbk78, it is clear that there is a set of issues that need to be addressed, and this isn't the location for the conversation to figure it all out (and it will be a lengthy process to work through them all). I would recommend that we close this conversation and continue to work out all the issues together on the GitHub issue page if you already have or are willing to register on GitHub. If you are satisfied with that, please take this as the final answer for the UnmetHours conversation, and we'll work to address this over on the other side.

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There appears to be a problem with the CondesnserEquipmentOperationSchemes schedule too. I setup a schedule to turn the cooling tower off during the winter and the fluid cooler off during the summer. This does not work as anticipated. The cooling tower keeps running all year. I have attached this file too to the original message.

kbk78 gravatar image kbk78  ( 2015-07-23 21:49:33 -0600 )edit

@kbk78 I think we should leave UnmetHours at this point and move to work together directly on the GitHub issue tracker. I added this info to the above answer so that if you agree, it can be accepted, and this can be closed and we'll work it out over there. If not, let me know.

Edwin gravatar image Edwin  ( 2015-07-25 00:40:07 -0600 )edit

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Asked: 2015-07-23 08:35:07 -0600

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Last updated: Jul 25 '15