[Equest-users] Ashrae 90.1 Table 7.8 Base Water Heater Sizing for Leed Model

[Nick Caton]

Hi Lee,

In the case you're describing, standby losses are defined discretely via UA.  The thermal efficiency of a submerged electric resistance coil is effectively 1, so the EIR = 1/1 = 1.

What skews this typical fundamental rule from thermodynamics is when we modelers are made to match 90.1's requirements with an energy factor (EF), which combines the gas/electric thermal efficiency with standby jacket losses into a single number.  In such cases, it's simpler to zero out jacket losses (UA=0), and enter EIR or HIR as the inverse of the prescribed EF.

~Nick
[cid:489575314 at 22072009-0ABB]

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 Lee Chorney
Sent: Thursday, June 21, 2012 11:23 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Ashrae 90.1 Table 7.8 Base Water Heater Sizing for Leed Model

Dear All.

I sized my base water heater as an electric water heater > 12KW and got the standby loss. I converted the standby loss to the UA value for equest. I am wondering what you put as your EIR value since the formula in Ashrae 90.1 only gives me the standby loss value.

Thank you in advance,

Lee
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