[Equest-users] DHW Savings LEED NC 2.2

[Carol Gardner]

Hi Tai,

I'm going to attempt to answer this question for you even though I don't
really know what it is exactly that the reviewer wants to see. I think, in
general, that reviewers are pretty flexible as to the calculation
methodology you use as long as you are using a methodology that is
technically sound.

The excerpt from the ASHRAE Handbook HVAC Applications that you are using is
correct for designing the the design demand flow of your system. The demand
factor you are given is, I think, an estimate of when all of these fixtures
might be in use at the same time. The result of this calculation would be
the demand on your DHW system. Think of this "demand" as being somewhat the
same as "kW" on the rest of your energy systems. With that in mind, you will
see that you need to then apply the Usage Schedule that you have created in
your model to get the associated reduction in DHW usage, similar to kWh
saved.

Since we are ultimately interested in the reduction of energy use here, the
last bit of information I would provide the reviewer is your estimate of how
much of this water will be heated by the DHW heater and to what temperature.
Your mop sinks will contribute a bit to this if the janitorial staff like to
mop with hot water, but the majority of the heated water will be at the
lavatory sinks. You may have to make some educated guesses here so back them
up.

Lastly, always, always provide your units. For us and for the reviewers.

Best,

Carol



On Wed, Jun 1, 2011 at 8:20 AM, Tai Lieu <tailieu at gmail.com> wrote:

> 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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