[Equest-users] Hot Water Usage Percent

Sefa Şahin ssahin at mimtarch.com
Fri Dec 4 02:04:36 PST 2015

Hi Nick,

First of all, thank you for your kindly helping. Your advices are make 
easier to my workflow. I have also two question. Do we have to use same 
service hot water temperatures for baseline and proposed design case? 
How can you adjust baseline service hot water temperature ?
Additionally, my project includes residential lavatory faucets and 
common lavatory faucets and these faucets fixture temperatures are 
same.  Residential lavatory faucets %hot water and common lavatory 
faucets % hot water are must be different because of  the following 
sentence that exist on Table 1.4.5.  "e.g. residential lavatories would 
be expected to have cold water usage associated with brushing teeth". 
How can we calculate this difference?

Thank you

04.12.2015 01:02 tarihinde Nicholas Caton yazdı:
> Regarding the mixed hot water % example:
> Yes, the % hot water for mixed water is proportional to the relative
> deltas... this can be figured/proven from basic energy balance equations but
> I'm too rusty/forgetful to derive it from memory.  Here's how it looks in
> *my* brain if I type it out:
> % hot water = ( Tmixed - Tcold ) / ( Thot - Tcold)
> Regarding baseline/proposed concerns... this is simpler than it may seem.
> Here's my typical workflow outlined:
> 1. Figure out your proposed case hot water supply temperature to the service
> hot water loop.  This is technically the temperature leaving the heat
> exchanger for your case, but you might interpret this to be the temperature
> leaving the hot water boilers (to exclude piping/exchanger losses from the
> simulation).
> 2. Calculate the loop demand flow rate (gpm) based on the fractional
> schedule used and the outputs the Table 1.4 spreadsheet provides you to
> effect matching annual hot water consumption  (gph/60 = gpm).
> 3. Baseline case supply/storage temperatures MATCH the supply/storage for
> hot water in the proposed case.  Fractional consumption schedules match
> also.  Baseline case however will provide the higher annual consumption you
> calculated by way of entering a higher demand gpm for the loop.
> 4. Concerning storage, the only other typical difference in inputs between
> baseline/proposed would be to account for differing rates for standby
> losses.  There are other threads in the archives that go into detail on that
> topic, but a "one stop shop" for most conversion effort cases is the
> 'Domestic Hot Water' tab in RMI's EMIT spreadsheet:
> http://www.rmi.org/ModelingTools
> Hope that gets you moving!
> Owner
> Caton Energy Consulting
>    306 N Ferrel
>    Olathe, KS  66061
>    office:  785.410.3317
> www.catonenergy.com
> -----Original Message-----
> From: Sefa Şahin [mailto:ssahin at mimtarch.com]
> Sent: Thursday, December 03, 2015 8:42 AM
> To: Nicholas Caton; equest-users at lists.onebuilding.org
> Subject: Re: [Equest-users] Hot Water Usage Percent
> Hi Nick,
> For example: the annual ground water temperature is 60 F , delivery
> temperatures of SHW equipment is 120 F and the mixed fixture outlet
> temperature is 104 F. In this case, hot water percent is 73.3, cold water
> percent is 26.7. Is it true?
> Our proposed design uses the heating hot water boilers to provide service
> hot water through a heat exchanger. Baseline case uses gas-fired water
> heater with storage tank. How can we calculate percent of hot water or cold
> water When delivery temperatures of proposed and baseline case are
> different? Additionally, How can we adjust Baseline service water storage
> temperature ?
> Thank you for helping,
> 02.12.2015 21:18 tarihinde Nicholas Caton yazdı:
>> I advise grabbing a copy of your project's reprequisite preliminary
>> documentation (as occurring) to avoid conflicts in your calculations,
>> then to leverage the 'Service Water Heating' tables in the Seciton 1.4
>> tables spreadsheet to work out the % of hot water consumption per
>> fixture.  This will account for cold water usage.
>> I typically leverage the annual ground water temperature
>> (representative of cold water at delivery), the delivery temperature
>> from the SHW equipment, and the mixed fixture outlet temperatures
>> weight the % of hot water delivered for each fixture type consuming hot
>> water.
>> The spreadsheet will then calculate the "peak" gal/hr (provided the
>> "annual equivalent hours" determined from your fractional schedule)
>> w0hich you can easily convert to gal/min for equest input.
>> It's a relatively easy number crunching exercise.  Hope that helps!
>> Owner
>> Caton Energy Consulting
>>     306 N Ferrel
>>     Olathe, KS  66061
>>     office:  785.410.3317
>> www.catonenergy.com
>> -----Original Message-----
>> From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org]
>> On Behalf Of Sefa Sahin
>> Sent: Wednesday, December 02, 2015 10:03 AM
>> To: equest-users at lists.onebuilding.org
>> Subject: [Equest-users] Hot Water Usage Percent
>> Dear All,
>> We have received the following  from GBCI regarding the energy
>> modeling
>> review:
>> "The percent hot water listed in Table 1.4.5 does not appear to be
>> calculated based on the storage and fixture supply temperature and
>> adjusted to account for expected cold water only use"
>> How can we adjust hot water usage percent?
>> Thanks for all replies,
>> Sefa Sahin
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>> Equest-users mailing list
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> Sefa Sahin

Sefa Sahin

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