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Anyone can explain how the common pipe and why is used in the plant loop?

asked 2023-05-19 11:40:34 -0500

Qamar's avatar

updated 2023-05-20 10:16:02 -0500

Is there an example of the examples of energyplus files with a common pipe so I can see an example of implement it in the plant loops.

Many thanks in advance, Kamar

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answered 2023-05-19 12:13:48 -0500

In the ExampleFiles folder is a file called ExampleFiles-ObjectLinks.html. This file shows all the EnergyPlus objects and which files those objects are used in. Since the common pipe is not an object it was just luck that showed the example file CommonPipe_Pri-Sec.idf. The common pipe is modeled in the PlantLoop object using the common pipe input field.

From CommonPipe_Pri-Sec.idf example file:

    Chilled Water Loop,      !- Name
    Water,                   !- Fluid Type
    ,                        !- User Defined Fluid Type
    CW Loop Operation,       !- Plant Equipment Operation Scheme Name
    CW Supply Outlet Node,   !- Loop Temperature Setpoint Node Name
    98,                      !- Maximum Loop Temperature {C}
    1,                       !- Minimum Loop Temperature {C}
    autosize,                !- Maximum Loop Flow Rate {m3/s}
    0.0,                     !- Minimum Loop Flow Rate {m3/s}
    autocalculate,           !- Plant Loop Volume {m3}
    CW Supply Inlet Node,    !- Plant Side Inlet Node Name
    CW Supply Outlet Node,   !- Plant Side Outlet Node Name
    Cooling Supply Side Branches,  !- Plant Side Branch List Name
    Cooling Supply Side Connectors,  !- Plant Side Connector List Name
    CW Demand Inlet Node,    !- Demand Side Inlet Node Name
    CW Demand Outlet Node,   !- Demand Side Outlet Node Name
    Cooling Demand Side Branches,  !- Demand Side Branch List Name
    Cooling Demand Side Connectors,  !- Demand Side Connector List Name
    SequentialLoad,          !- Load Distribution Scheme
    ,                        !- Availability Manager List Name
    ,                        !- Plant Loop Demand Calculation Scheme
    CommonPipe;              !- Common Pipe Simulation

From Energy+.idd:


  A17,  \field Common Pipe Simulation
    \note Specifies a primary-secondary loop configuration. The plant side is the
    \note primary loop, and the demand side is the secondary loop.
    \note A secondary supply pump is required on the demand side.
    \note None = Primary-only, no secondary simulation
    \note CommonPipe = Primary-secondary with no temperature control at primary-secondary interface
    \note TwoWayCommonPipe = Primary-secondary with control of secondary supply temperature or
    \note primary return temperature (requires a setpoint be placed on the
    \note plant side or demand side inlet node).
    \type choice
    \key CommonPipe
    \key TwoWayCommonPipe
    \key None
    \default None
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Thank you very much for your answer.

In fact, I do not know what the common pipe does but after adding it I have warnings about the plant loop temperatures that i did not have before. Could you please explain what is the function of the common pipe?

Best regards,


Qamar's avatar Qamar  ( 2023-05-22 04:31:41 -0500 )edit

The warnings are the following:

GetSpecificHeatGlycol: Temperature is out of range (too low) for fluid [WATER-GLYCOL MIX 1] specific heat supplied values * * ~~~ * ..Called From:UpdateGroundHeatExchanger,Temperature=[-4.99], supplied data range=[0.00,125.00] * ~~~ ** Environment=ANNUAL, at Simulation time=05/05 07:10 - 07:20 . . .

GetSpecificHeatGlycol: Temperature is out of range (too high) for fluid [WATER-GLYCOL MIX 1] specific heat * * ~~~ * ..Called From:UpdateGroundHeatExchanger,Temperature=[174.34], supplied data range=[0.00,125.00] * ~~~ ** Envir

Qamar's avatar Qamar  ( 2023-05-22 05:22:50 -0500 )edit

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Asked: 2023-05-19 11:40:34 -0500

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Last updated: May 22