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

Andrew McNamara amcnamara at brightpower.biz
Tue Jan 8 09:13:28 PST 2008

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.


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