[Equest-users] DHW Savings LEED NC 2.2

[Carol Gardner]

Thanks, Aaron, for providing much more detail than me. You have covered it
very well. For inlet cold water temperatures I have always seen 50-55 F
provided as the average temp: it may be hotter in the summer and colder in
the winter but overall I think those work.

Carol

On Thu, Jun 2, 2011 at 11:17 AM, Dahlstrom, Aaron
<ADahlstrom at in-posse.com>wrote:

> Tai:
>
>
>
> In general, I tend to follow the procedure laid out in WEc3 for the hot
> water savings from low-flow fixtures. I’ve found their calculation procedure
> for total flow (gallons / year) to be accepted by LEED reviewers.
>
>
>
> This does not address water flow from fixtures outside the WEc3 scope, like
> service sinks, so the ASHRAE handbook or a reasonably documented
> project-specific assumption sounds like the way to go to get total water use
> per year for these fixtures.
>
>
>
> Like you mentioned, this also does not specify the water temperatures,
> which are needed for the calc.
>
>
>
> Different hot water uses in a building often have different temperature
> needs (ie handwashing, dishwashing, showers, etc), so even if we know the
> total water use for each of these fixtures, we’d need to get the expected
> discharge temperature of each use in order to figure out how much hot water
> is required.
>
>
>
> Most of the time I get the temperatures I need from the project plumbing
> engineer, who has a better familiarity with these targets than I do.
>
>
>
> If you don’t have access to a plumbing engineer –
>
> -          For the inlet cold water temp, per the eQUEST dictionary, if
> you don’t specify the temp eQUEST uses the monthly average ground temp. I
> hope this would be available via an hourly report, although I haven’t
> checked.
>
> -          For the discharge hot water temp, various plumbing codes (IPC,
> NPC) specify limits on the hot water temp to prevent scalding, and I’ve seen
> engineers take a factor off of that to estimate the average hot water use
> temp. I’ve heard 110 deg F for showers and 105 deg F for lavs in our office.
> Service sinks might have something higher (say 120?).
>
> -          For the water storage temp, this is also something that should
> be obtainable from the plumbing engineer. As a starting point I’ve heard 120
> – 140 deg F in our office as well. I believe the IPC limits the maximum
> storage water temp to 140.
>
>
>
> This should enable you to calculate the quantity (gal / year) of hot water
> leaving the water heater to serve the annual total flow needed.
>
>
>
> Finally, you need to turn the gallons HW / year into a GPM PROCESS-FLOW, if
> you’re inputting into eQUEST. One way to do this is to take whatever
> use-schedule you had been using (ie eQUEST’s default, ASHRAE 90.1-2007 User
> Manual’s, or project-specific) and integrate it, to determine the annual
> total equivalent full load hours. Dividing total annual gallons by annual
> full-load hours (and converting units), you should be able to arrive at a
> GPM to enter as a process flow.
>
>
>
> Yours,
>
>
>
> *Aaron Dahlstrom , PE, LEED® AP*
>
> *In P**o**sse* – A subsidiary of *AKF*| 1500 Walnut Street, Suite 1414,
> Philadelphia, PA 19102
>
> d: 215-282-6753| m: 267-507-5470| In Posse: 215-282-6800| AKF:
> 215-735-7290
>
> e: ADahlstrom at in-posse.com | in posse web: www.in-posse.com | akf web:
> www.akfgroup.com
>
>
>
>
>
>
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Tai Lieu
> *Sent:* Wednesday, June 01, 2011 11:20 AM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] DHW Savings LEED NC 2.2
>
>
>
> Hello  All
>
> We're being audited on the energy model for the dhw saving.  I'm just
> wondering if this make sense and from your experience if it would be
> acceptable to the LEED reviewer.
>
> What I've done is taken numbers from ASHRAE Handbook HVAC Applications DHW
> consumption per fixture for office use.
> 7.6 L / hr for lavatory fixtures
>
> Showers, kitchen sinks, and Lavatory sinks.
> Service sinks I'm not quite sure whether i should include all 5 service
> sinks (one on each level) or just one sinks since there won't be any mopping
> done since most of the building Under floor air distribution and i'll do a
> write up of course to explain my reasoning.
>
> I took the consumptions per fixture numbers multiplied by the amount of
> fixture then by the demand factor given.
>
> 7.6 L/h x 55 # of fixtures x 0.3 demand factor
>
> for each type i took the savings percentage based on each fixture. So
> baseline is 2.5 and proposed case is .5 for lavatory fixtures
>
> .5 proposed case  / 2.5 base case
>
> So the proposed domestic hot water demand is 25.08 L / hr or 0.11 gpm.
>
> The reviewer had asked for percentage of hot water vs cold water, and
> temperature at the fixtures, i found that harder to substantiate.  So I
> thought this process would be a lot better.
>
> Tai Lieu
>
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-- 
Carol Gardner PE
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