Re: [EnergyPlus_Support] Merging zones having FCUs (Merging FCUs)

[Richard Raustad <RRaustad@xxxxxxxxxxxx>]

Obviously there is a flaw in the DB approach. Try averaging the fan 
pressure rise instead.

Fan:ConstantVolume,
75.0,   !- Pressure Rise {Pa}


On 9/18/2013 6:38 AM, hisham.rashrash wrote:
> Hi,
> For one case, I tried to merge actual zones into larger thermal zones. Now, I have to model FCUs, using TemplateHVAC:Zone:FanCoil objects, in such a way that I put one FCU in each zone that must represent 4, 5 or even 11 real FCUs for example. I used the following approach:
> 1. I used the formula from DesignBuilder website (http://www.designbuilder.co.uk/programhelp/fans.htm) to find Fan Delta Pressure:
> Delta P = 1000 * SFP * Fan total efficiency (SFP: Specific Fan Power [W/(L/s)]
> I calculated each real FCU's Fan Delta P and added them up to find the equivalent FCU's fan Delta P.
> For example:
> I have 4 FCU's one for each of 4 guest rooms that I merged into one large room for simplification, the actual HVAC schedules give the following:
>
> FCU No.      Power [kW]             Air Flow [L/s]
> ==================================================
> 1              0.3                       160
> 2              0.3                       145
> 3              0.3                       145
> 4              0.3                       145
>
>
> Eqv. Delta P= 1000*(300[W]/160[L/s]+3*300[W]/145[L/s])*0.7=5657.33[Pa]
>
>
> 2. I found the equivalent FCU's airflow rate by adding the real FCUs' flow rates:
> Eqv. Flow Rate=160+3*145=595[L/s]
>
>
> I used the above values in the HVACTemplate:Zone:FanCoil object for the corresponding zone. The results were that the equivalent FCU's power calculated is 5 times larger (about 6[kW]) than actual component-FCUs' power when added up:
> >From table above: 0.3[kW/FCU]*4[FCUs]=1.2[kW]<6[kW]
>
>
> Please advise.
>
>
> Thank you very much.
>
>
> Regards,
> Hisham
>
>
>
>
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-- 
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
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