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

[Kushagra Juneja]

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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