[Equest-users] DHW loads difference

[Nathan Miller]

My guess is that it is the standby losses making the difference. You presumably have the tanks assigned to a zone. If there is a difference in envelope, lighting loads, plug loads, etc in that zone between the two runs, then it might affect the standby losses (because the delta-T in the space could be different). If you want to test that theory, assign the DHW heater to be "Outdoor" in both runs, that way standby losses should be identical. If the energy use aligns, you will know it was standby loss making the difference. If they are still different, it is something else (schedule, peak gpm, DHWH efficiency, etc).
[cid:image001.png at 01D02E45.74CB3540]


Nathan Miller, PE, LEED AP BD+C - Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100
www.rushingco.com<http://www.rushingco.com/>

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pramod .D
Sent: Monday, January 12, 2015 8:42 AM
To: Byron Burns; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] DHW loads difference

Byron,

Thanks for your immediate reply. I have compared all the schedules, volume, capacity, tanks loss, etc. Everything is same but I am getting difference in results. Please help me out on this and thanks for the manual.

Thanks,

Pramod D |  Junior Energy Analyst
d.pramod at setty.com<mailto:d.pramod at setty.com>

From: Byron Burns [mailto:B.Burns at ha-inc.com]
Sent: Monday, January 12, 2015 7:04 PM
To: Pramod .D; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: RE: DHW loads difference

Hello Pramod,

You should be able to get the results to line up, if you are interested in the algorithm used, here<http://doe2.com/download/DOE-21E/DOE-2EngineersManualVersion2.1A.pdf> is a link to the engineering manual.  Generally, the DHW energy is modeled just like a process load with a few more knobs (hourly demand * fractional schedule)/DHW efficiency + standby loss.  There is a portion of the calculation that accounts for the tank loss, which is a factor of the size of the tank, the amount of insulation on the tank and the ambient conditions, so make sure both the baseline and proposed models have the same volume, amount of insulation and are located in the same zone.

To ensure it is not something simple, I would recommend re-inputting the data and running it again.  You will notice that eQ rounds many of the inputs in the GUI, however it will input the actual values into the .inp file and .bld file when you run it, so make sure all inputs are the same regardless of how they are displayed.  Also the schedules are a common cause of these issues.  I recommend using something to compare the inputs of both your baseline and proposed .inp files to ensure they are the same.  Personally, I like Notepad++,<http://notepad-plus-plus.org/> it has a compare plug in that makes it a snap.

Hope that helps,

Byron D. Burns, EIT, BEMP
Energy Engineer, Building Sciences Studio

H&A | Hankins & Anderson | www.ha-inc.com<http://www.ha-inc.com>
d: (804) 420-1622 p: (804) 285-4171 f: (804) 217-8520
From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pramod .D
Sent: Monday, January 12, 2015 7:51 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] DHW loads difference

Hi,

I have modelled an apartment using eQuest. I have given the same inputs (capacities, schedules,etc) in both the models for DHW but I am getting difference in the results. Can anyone please tell how eQuest calculates DHW loads. Why I am getting difference in DHW loads. The images are attached.

Thanks,
Pramod

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