[Bldg-sim] Appendix G Fan Power Calculation Clarification

[Carol Gardner]

Hi Karen,

How are you?? Well, I trust. I will look at your calcs as soon as I can but
I must go watch the PORTLAND TRAILBLAZERS (go BLAZERS!!) win! I hope!! The
game is starting right now.

Sorry in advance to any/all Suns fans (just kidding). You know the
Trailblazers are all we have here in Portland and we are FANS!

Carol!!



On Mon, Apr 26, 2010 at 2:07 PM, Karen Walkerman <kwalkerman at gmail.com>wrote:

> Hello,
>
> I have seen some discussion on how to separate fan power from EER on the
> various list-serves, but never seen an explicit description of exactly how
> to go about it.  Below are my calculation methodologies and I'm hoping to
> generate some thumbs up/thumbs down discussion and clarification:
>
> From ASHRAE 90.1 Users manual formula G-A:
>
> EER = (Net Cooling [BTU/h]) / (Total Input Power [W])
>
>      = ((Gross Cooling - Supply Fan Power) [Btu/h]) / (Total Input Power
> [W])
>
> Definitions
>
> Total Input Power:  Includes supply and condenser fan power, and condenser
> power
>
> Supply Fan Power [btu h ] : this is the heat rejected by the fan to the
> supply air stream.  If 100% of the fan power is eventually converted to
> heat, then this is 3,413 X Supply Fan KW.
>
>
> To Calculate the EER, minus the fan, do the following:
>
> Break Total Input Power into Supply Fan Power and condenser fan and
> compressor power
>
> I'll use the following abbreviations for subsequent formulas to minimize
> typing:
>
> GC : Gross Cooling [btu/h]
> SPb: Supply Fan Power [btu/h]
> SPw: Supply Fan Power [w]
> CP: Compressor Power [w]
>
> For an Appendix G baseline model, we have GC, SPb, SPw, and EER.  So, from
> formula G-A, we solve for CP::
>
> CP + SPw = (GC - SPb) / EER
>
> CP = (GC - SPb) / EER - SPw
>
> Now, we can determine the EER, excluding the fan power so:
>
> Modified EER = GC / CP
>
> A few things to discuss:
>
> 1.  Is this really appropriate for systems where the fan power is
> calculated using the G.3.1.2.9 guidelines?
>
> 2.  What is done when the requirements for cooling system efficiency is
> listed as a SEER instead of an EER?  Is there an acceptable conversion
> factor for use in these calculations?
>
> 3.  I this methodology what is intended?  ASHRAE Appendix G, and even the
> User's Manual is extremely brief of this.
>
> Thanks,
>
> --
> Karen
>
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