[Bldg-sim] eQUEST Hot Water Heater Appendix G Baseline

Alex Lekov ABLekov at lbl.gov
Tue Jan 8 10:11:59 PST 2008


It is probably incorrect to baseline the instantaneous water heater 
using the current minimum efficiency standard for the residential size 
gas instantaneous water heaters (EF=0.62). According to GAMA's 
Consumer's Directory of Certified Efficiency Ratings for Heating and 
Water Heating Equipment's directory, very few gas instantaneous water 
heater models have EF below 0.80.

Alex Lekov, Ph.D., P.E.
office 925-486-6849

Andrew McNamara wrote:

> Hello all,
> I am modeling a building with eQUEST that has a tankless, a.k.a. 
> instantaneous, gas-fired hot water heater.  I am uncertain of how to 
> baseline the system according to ASHRAE 90.1-2004 Appendix G. The 
> standard states that for a 180,000 BTU/h system the EF (Energy Factor) 
> = 0.62-0.0019V.  So, I set V equal to zero for the 
> tankless/instantaneous gas water heater and get an EF =0.62. 
> The question I have for everyone is: How do I translate this baseline 
> EF to HIR (Heat-input-ratio) for eQUEST?  Is there an accepted method 
> for doing so?  I saw in a previous post from David Eldridge on 3/21/07 
> that calculating HIR = 1/EF leads to unreasonably high values for HIR 
> (In my example, 1/0.62 = 1.61), but I'm having trouble seeing how else 
> to come up with a baseline.
> Thanks in advance for your help.
> Best,
> Andy
> -- 
> Andrew McNamara, LEED AP
> tel: 212.803.5868
> fax: 866.379.8026
> cell: 917.974.4499
>Bldg-sim mailing list
>Bldg-sim at lists.onebuilding.org
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