[Equest-users] DHW standby loss

[Paul Riemer]

I imagine they are asking you because you did not report it and/or the reviewer perceives you are claiming savings, perhaps due to instantaneous water heaters.

ASHRAE 90.1 regulates standby losses in water heating equipment (Table 7.8 in 90.1-2007).  In some fossil fuel equipment it is a separate number, in electric equipment and other fossil fuel equipment it is captured within EF.  The new EAp2 section 1.4 workbook asks for efficiencies referenced to ASHRAE 90.1 tables.  I suggest you do that regardless of your project's LEED version.  Bill's suggestion below may lead you to document a standby loss that is different than the regulated value and significant review headaches.

If your equipment meets the required performance and you are not claiming standby loss savings, I really doubt they will highly scrutinize how you manage the translation between SL & EF ratings into DOE-2 inputs.  If you are claiming standby loss savings, I would expect more scrutiny and sharpen your pencil accordingly.

Good luck,

Paul Riemer, PE, LEED AP
Associate / Mechanical
Direct: 612-465-7696

DUNHAM
Celebrating 50 Years of Service




From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Monday, September 27, 2010 10:23 AM
To: jacob goodman
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DHW standby loss

Jacob,

If you look at your water heater properties in DD Edit mode you will see the overall heat loss coefficient (UA). If you multiple this by the temperature difference between the water and space temperature, you get Btu/h. Adjust the UA, if necessary, to get the needed baseline standby loss (SL) as calculated in Table 7.8, using 70°F temperature difference. I would keep this identical in the proposed model unless you know what the actual heater standby losses are. The modeled SL will vary hourly based on the space temperature of the DHW zone (which you select in the DHW Basic Specifications tab).

Regards,
Bill

William Bishop, PE, BEMP, LEED® AP | Pathfinder Engineers & Architects LLP
Mechanical Engineer

134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Sustainability - less is more.
________________________________
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Carol Gardner
Sent: Monday, September 27, 2010 10:08 AM
To: jacob goodman
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DHW standby loss

Seriously? They asked you about standby loss? Where is your gas storage water heater located? If it's inside a conditioned space tell them you didn't worry about it. Also, if it's wrapped with insulation, or even just has insulation in the jacket, tell them it was negligible and you didn't worry about it. They mustn't have much to do at GBIC!

Carol
On Mon, Sep 27, 2010 at 6:42 AM, jacob goodman <jacobg at lseng.com<mailto:jacobg at lseng.com>> wrote:
I'm working on a review response for LEED and a question came up about how I calculated Standby Loss for the Gas storage water heater in my baseline building. For the model I left the default %/hr in the wizard screen. My question is what is this a % of and is there some way I could convert this into Btu/h to compare to the number calculated from ASHRAE 90.1 2004 Table 7.8 for the ANSI Z21.10.3 test procedure.

Thank you all,

Jacob

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--
Carol Gardner PE
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