[Equest-users] SIM report for annual water consumption?

Nicholas Caton Nicholas.Caton at se.com
Tue Jul 21 20:14:30 PDT 2020 

Hi Sharad – your contribution provoked me to consider this further (read: I have work I’m supposed to be doing and I like indulging in a distraction on occasion),

I’ve spent a little time trying to intuit your recommended shortcut. I think I understand it now, but want to explain the estimation method for others and to confirm understanding.  Perhaps I have missed a more elegant shortcut?

To preface: We should observe the formula Q = 500*GPM*dT can be tricky when applied against open loop fluid systems, if all inlet/outlet streams aren’t considered.  If you focus too narrowly on only supply and return (recirc), without accounting for the makeup fluid stream… One might say you could end up in hot water ;-).

We can use this equation to estimate consumption (kgal) of domestic hot water (DHW) per year, but it will require some assumptions and manipulations along the way:

  *   To first recap: Q = 500*GPM*dT is, without further modification, intended to calculate the rate at which heat is imparted/extracted (Btu/h) at a given flow rate (gallons per minute) and difference in temperatures (dT), for a fluid with thermal properties substantially aligning with plain water (the constant 500).
  *   Let’s also clarify what we’re trying to solve for:  Gallons of DHW consumed per year.  Provided no leaks in the system and ignoring drains for maintenance/repairs, this volume should match the makeup water introduced into the DHW system over the same time period.
  *   Assuming Makeup water = Groundwater Temps, then
     *   Ignoring tank/storage losses, and ignoring losses in distribution between makeup water entry and the points of delivery,
     *   and further asserting DHW consumption is equalized through the year (there is not a lot more DHW consumption in August vs. February),
     *   the annualized delta will be dT,ann = (Supply Water Temp – Mean Groundwater Temp)_
  *   eQuest with no special/extra effort generates Btu/year of metered fuel/electricity used for DHW heating, as part of the rainbow report outputs.
     *   This is not directly Q, which represents heat applied to the fluid
     *   We need to consider and condense into an annualized figure the “system heating efficiency”, considering
        *   Combustion efficiency
        *   Startup/cycling losses
        *   The presence/frequency/degree of condensing operations and heat recovery, if applicable
     *   This system efficiency may naturally involve many or few assumptions depending upon the DHW system type
     *   Then the annualized heat addition is Q,ann (Btu/h) = (Consumed Btu/year from Fuel Meter End-Use rainbow report) / (System Heating Efficiency) * (1 year / 8760 hours)
  *   Taking these together, we can solve for annualized flow rate, GPM,ann:
     *   GPM,ann = Q,ann / (500 * dT,ann) = (Consumed Btu/year from Fuel Meter End-Use rainbow report) / (System Heating Efficiency) * (1 year / 8760 hours) / 500 / (Supply Water Temp – Mean Groundwater Temp)_
  *   And from the annulalized flow rate, we can calculate kGal/year
     *   GPM,ann * (1 kGal / 1000gal) * (525,600 minutes / year) = kGal/year
  *   So altogether, we’ve had to make a few assumptions to leverage the following shorthand:
     *   kGal/year = (1 kGal / 1000gal) * (525,600 minutes / year) * (Consumed Btu/year from Fuel Meter End-Use rainbow report) / (System Heating Efficiency) * (1 year / 8760 hours) / 500 / (Supply Water Temp – Mean Groundwater Temp)
     *   Aside:  At this juncture you should recognize there’s a qualifier that’ll affect a lot of commercial DHW applications.  This is kGals/year of water at the given Supply Water Temp.  If the DHW requires a mixing valve at the point of delivery or upstream, to avoid scalding hazards, and you want to calculate the gallons leaving all of the faucets (at a safer, lower temperature), then you need to factor this result to reflect how many gallons of, say, 120F water will be consumed given fewer gallons of 140 or 180F generated.

TLDR: I’m not sure this approach, which requires a number of assumptions/rounded corners, is much faster than working out the annual delta between supply vs return flow on the DHW loop, as originally suggested by Phil.  That does seem to be the most direct route to understanding exactly what was simulated (with some of the same caveats from that final bullet around mixing valves).  3 Points for Phil’s favorite Hogwarts House!

~Nick

[cid:image002.jpg at 01D65FAC.49430170]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Energy and Sustainability Services
  Energy Performance Contracting
D
M
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913 . 564 . 6361
785 . 410 . 3317
nicholas.caton at se.com<mailto:nicholas.caton at se.com>
15200 Santa Fe Trail Drive
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From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Sharad Kumar via Equest-users
Sent: Sunday, July 19, 2020 2:12 AM
To: equest-users <equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] SIM report for annual water consumption?

________________________________



Hi Phil,
The way that I am thinking about is the option to get the result on the basis of eQuest software back calculations.
The calculation on which DHW outputs are based is the formulae  Q= 500X GPM X delta T.
Now to get the GPM or the actual flow one will have to deter the Q or the total heat across the DHW in Btuh. From the heat delta T across the DHW one will come to know the delta T across the DHW in degree Fahrenheit.
Now from the basic formula Q= 500 XGPM X delta T knowing the two factors GPM and delta T one can easily determine GPM across the DWH.
As per my experience the energy simulation software are based on these easy back calculations of which one is above here.
From this Gallon per minute (GPM) or the flow is got ahead.
Thanks and Regards,
Sharad.Kumar
Freelancer
India



---------- Forwarded message ----------
From: Phil Jordan <phil.jordan at clearesult.com<mailto:phil.jordan at clearesult.com>>
To: "equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>" <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Cc:
Bcc:
Date: Wed, 15 Jul 2020 20:43:51 +0000
Subject: [Equest-users] SIM report for annual water consumption?
Does eQUEST output annual water consumption in the SIM report (for DHW)? Or do you have to set up an hourly report to sum the DHW loop “Fluid flow, supply side” variable?

Thanks,

Phil Jordan




---------- Forwarded message ----------
From: Phil Jordan <phil.jordan at clearesult.com<mailto:phil.jordan at clearesult.com>>
To: "equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>" <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Cc:
Bcc:
Date: Thu, 16 Jul 2020 01:39:55 +0000
Subject: Re: [Equest-users] SIM report for annual water consumption?
I think the way to do this is to set up an hourly report for both the “Fluid flow, supply side” and “Fluid flow, return side” for the DHW loop – the difference between the two should be the flow that’s going down the drain at each hour; the sum of this would be the annual DHW water consumption.

But if anyone knows of an easier way to get this from the SIM report please share.

Thanks,

Phil Jordan

From: Equest-users <equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>> On Behalf Of Phil Jordan via Equest-users
Sent: Wednesday, July 15, 2020 1:44 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] SIM report for annual water consumption?

EXTERNAL email. Please exercise caution. This e-mail is from a sender outside of CLEAResult. Do not click any links or open any attachments from unknown senders or unexpected email. ***************************************************
Does eQUEST output annual water consumption in the SIM report (for DHW)? Or do you have to set up an hourly report to sum the DHW loop “Fluid flow, supply side” variable?

Thanks,

Phil Jordan

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