Re: [EnergyPlus_Support] Re: cooled beam with VAV

["Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

Francesco,

I think you are suggesting:

• Model a VAV DOAS
• Supplement that with 4 pipe fan coils in each zone
• I'm not sure what you mean by "calculate the fan power/flow ratio of the fan coils in order to consider that in the real design the recirculated air goes through the AHU"

Assuming that the fan coil fan energy is ~0 (because a chilled beam has no fan), and the pump energy for the fan coils is about the same as for chilled beams ... that sounds like a nice solution.

Part of your challenge will be to establish zones and zone scheduling in such a way as to represent the occupant diversity properly.  You want the VAV box to actually turn OFF (zero flow) when no one is in the room, so you can't just use a fractional diversity schedule (values 0 - 1.0).  I think it must be either 0 or 1, no in-between values.

I did something similar a while ago for a hotel which had room HVAC interlocked with whether the room was rented or not.  I made some assumptions about the occupancy rates and made sure some of the rooms were completely off / unoccupied, while others were on a regular schedule.

On Tue, Sep 8, 2015 at 9:32 AM, fpasserini.tn@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

Do you have any idea of a possible workaround, please?

I would model a VAV system without cooled beams and I would balance the cooling loads with fan coils (I would calculate the fan power/flow ratio of the fan coils in order to consider that in the real design the recirculated air goes through the AHU).

Do you think that the calculated energy consumption would be an acceptable approximation?

Best Regards

Francesco

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James V Dirkes II, PE, BEMP, LEED AP
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Posted by: Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>

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