# [Equest-users] 90.1-2007 Table 7.8 Water Heater Efficiencies

Nick Caton ncaton at smithboucher.com
Wed Oct 5 06:40:19 PDT 2011

```I expect the natural followup is "how do I put this (SL) into eQuest?"

includes an example with the electric heater equation.

~Nick

NICK CATON, P.E.

SENIOR ENGINEER

Smith & Boucher Engineers

25501 west valley parkway, suite 200

olathe, ks 66061

direct 913.344.0036

fax 913.345.0617

www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
Kushagra Juneja
Sent: Wednesday, October 05, 2011 12:13 AM
To: 'Paul Diglio'; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] 90.1-2007 Table 7.8 Water Heater
Efficiencies

Hi Paul,

There are two things being talked about, one is thermal efficiency and
the other is standby loss. Standby loss represented as (Q/800+110 SqRt
V) and thermal efficiency represented as 80%. I had the same doubt a
while back. If you look at other Formulae they are represented in the
same way. Like for instantaneous water heaters Energy Factor is given by
0.62-0.0019V. Btu/h is the unit for Standby Loss. Not a multiplication
factor. Hope this helps.

Cheers

Kushagra

________________________________

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul
Diglio
Sent: Tuesday, October 04, 2011 5:07 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] 90.1-2007 Table 7.8 Water Heater Efficiencies

Could anyone help me understand the calculation for the minimum
efficiency of gas storage water heaters per the table above?

The calculation is 80%Et (Q/800+110 SqRt V) SL, Btuh.

I understand that Q is the nameplate input rate in Btuh and V is the
volume.

Do I use the volume of the whole system, the storage tank only or the
recovery rate volume?

I understand SL is the standby loss.  Does SL, Btuh mean multiply the
equation in parenthesis by the standby loss in btu's per hour?

Thanks for the help,

Paul Diglio

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