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

Zoeteman, Mark R. mrzoeteman at FTCH.com
Tue Oct 4 04:44:11 PDT 2011

I interpret as the allowable Standby Loss is:
80%Et (Q/800+110 SqRt V)

Footnote a indicates SL is maximum BTU/h based on 70 degree temp difference between stored water and ambient requirements.

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 7:37 AM
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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