[Equest-users] DHW standby loss

Bishop, Bill wbishop at pathfinder-ea.com
Mon Sep 27 08:22:48 PDT 2010


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> 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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