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

Andrew McNamara amcnamara at brightpower.biz
Tue Jan 8 13:23:46 PST 2008

Thank you for your reply.  Your response leads me to two more questions:

1) In the case of an 180 kBTU/h instantaneous heater is it standard practice
to use EF equal to 0.80 (or some other number based on a "bottom of the
heap" instantaneous heater) as you suggested rather than the 0.62 listed in
the standard?

2) How does one translate EF (this or any other) to HIR (Heat-input-ratio)
for use in eQUEST?  Or might it be acceptable to simply look up the "bottom
of the heap" HIR values for instantaneous heaters and use one of them as a

I would appreciate responses from any and all - thanks in advance for your


Andrew McNamara, LEED AP
tel: 212.803.5868
fax: 866.379.8026
cell: 917.974.4499

On 1/8/08, Alex Lekov <ABLekov at lbl.gov> wrote:
>  Andrew,
> 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
> ------------------------------
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