Re: [EnergyPlus_Support] Re: Modeling an air handler with a relief fan

[Fred Buhl <wfbuhl@xxxxxxx>]

Tj is basically right. The outside air system doesn't have any branches 
- you need to
do some thing like this:

  OUTSIDE AIR SYSTEM,
    OA Sys 1,                !- Name
    OA Sys 1 Controllers,    !- Name: Controller List
    OA Sys 1 Equipment,      !- Name of an Air Loop Equipment List
    VAV Sys 1 Avail List;    !- Name of a System Availability Manager List

  CONTROLLER LIST,
    OA Sys 1 Controllers,    !- Name
    CONTROLLER:OUTSIDE AIR,  !- Controller Type 1
    OA Controller 1;         !- Controller Name 1

  AIR LOOP EQUIPMENT LIST,
    OA Sys 1 Equipment,      !- Name
    FAN:SIMPLE:VariableVolume,!- KEY--System Component 1
    Relief Fan 1,             !- Component Name 1
    OUTSIDE AIR MIXER,       !- KEY--System Component 2
    OA Mixing Box 1;         !- Component Name 2

  OUTSIDE AIR MIXER,
    OA Mixing Box 1,         !- Name
    Mixed Air Node 1,        !- Mixed_Air_Node
    OA Mixing Box 1 Inlet Node,  !- Outside_Air_Stream_Node
    OA Mixer Relief Air Outlet Node 1,!- Relief_Air_Stream_Node
    VAV Sys 1 Inlet Node;    !- Return_Air_Stream_Node

  FAN:SIMPLE:VariableVolume,
    Relief Fan 1,            !- Fan Name
    FanAvailSched,           !- Available Schedule
    0.7,                     !- Fan Total Efficiency
    600.0,                   !- Delta Pressure {Pa}
    autosize,                !- Max Flow Rate {m3/s}
    autosize,                !- Min Flow Rate {m3/s}
    0.9,                     !- Motor Efficiency
    1.0,                     !- Motor In Airstream Fraction
    0.35071223,              !- FanCoefficient 1
    0.30850535,              !- FanCoefficient 2
    -0.54137364,             !- FanCoefficient 3
    0.87198823,              !- FanCoefficient 4
    0.000,                   !- FanCoefficient 5
    OA Mixer Relief Air Outlet Node 1,  !- Fan_Inlet_Node
    Relief Air Outlet Node 1;   !- Fan_Outlet_Node
Fred

tjutw wrote:
> You can include a relief fan in the outside air system equipment. The
>  relief fan inlet node is the relief air stream node in the "outside
> air mixer" Object.  
>   
> Given the airflow rate of this relief fan is much less than a return
> fan, you can just decrease the fan pressure from the energy use
> prospective.   
>
> Hope it helps,
>
> Tj Ywh
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "JV Dirkes II" <jvd2pe@...>
> wrote:
>   
>> Can anyone answer this question?
>>
>> Thanks!
>>
>> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "JV Dirkes II" <jvd2pe@>
>> wrote:
>>     
>>> Dear EPlus Forum,
>>>
>>> I want to model a relief fan working in concert with an air handler. 
>>> This is commonly operated like a variable speed exhaust fan which is
>>> placed in the relief airstream of an outdoor air mixer and removes
>>> excess economizer air. 
>>> As a result the fan heat does not go to the return air stream, and the
>>> airflow rate is often much less than a return fan, since some of the
>>> air exits the building through cracks.
>>> I could not find an example or previous forum discussion which shows
>>> this.  Can anyone give some guidance about how do model this?
>>>
>>> Thanks!
>>>
>>>       
>
>
>
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