[Equest-users] CHW loop process load

[James Hess]

I definitely agree with that suggestion, versus reinventing the wheel. Our experience with the RMI tool is that it works.  There seems to be a quirk regarding a little shifting due to DST, but that's a very small thing in the grand scheme of things.  I want to say we tested it and the annual average value coming out of eQuest was ~ 99.3% of the average input value.  Close enough!  :)

Also, I don't know if you are modeling the other buildings because a GBCI reviewer said you had to do that (assuming this is a LEED project) in order to ensure that correct part load ratios on the chillers operating profile are appropriately accounted for.  I got that sort of comment on a recent project and my response was something to the effect of ... I could do that, but since we aren't getting paid by the owner to model buildings outside of the project scope just to make the chiller modeling more accurate, instead I will just use the default efficiency allowed by the DESv2.0 guidelines for water cooled chiller plants --> 4.4 COP + 5% losses = ~ 0.839 kW/ton on average.

That saved a lot of time with that change because if you do that, you don't have to model any other buildings served by the system.  If you are comparing against air cooled equipment for the Baseline, you still get a decent amount of savings.  I probably left some savings on the table because the plant had high efficiency VFD water cooled chillers, and VFDs on the pumps and cooling tower.  I'm positive that the annual efficiency was much better than 0.839 kW/ton, but (the way I look at this) we have to balance the level of effort on energy modeling versus the fees we are getting for the modeling.

Hope this helps!  :)

Regards,

JAH

James A. Hess, PE, CEM, BEMP
Energy Engineer
TME, Inc.
Little Rock, AR
Mobile: (501) 351-4667

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Javed Iqbal
Sent: Thursday, March 28, 2013 1:55 PM
To: Kimberly Wiebe
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] CHW loop process load

You should use RMI tool to generate schedule which will eventually gives you schedule in INP format.

Here is the link to download it..

http://www.rmi.org/Content/Files/EMIT1.4.zip
On Thu, Mar 28, 2013 at 1:41 PM, Kimberly Wiebe <Kimberly.Wiebe at burohappold.com<mailto:Kimberly.Wiebe at burohappold.com>> wrote:
Hello,

I am modelling a central cooling plant that serves many buildings on an college campus. For some buildings I am building the geometry and inputting internal gains. For other buildings I have annual 8760 cooling load profiles. If I want to add these annual cooling load profiles to the CHW loop as process loads, would I have to make 365 day schedules (and 52 weeks)? If so I will write some sort of text generator out of an excel file and paste in the .inp, but before I do want to see if there was any other way.

Thank you,
Kim

Kim Wiebe
Direct: +1 310 945 4813
kimberly.wiebe at burohappold.com<mailto:kimberly.wiebe at burohappold.com>


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--


Javed Iqbal, LEED AP, CEA
Energy Analyst





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