[Equest-users] Centrifugal Chiller Curves

Wed Apr 8 15:31:12 PDT 2015

Michael,

Thanks for the spreadsheet. That is definitely more elaborate than the one
I put together.

I was able to successfully model air-cooled screws using the spreadsheet I
attached, but the issue I'm running into with the water-cooled centrifugals
is that the capacity provided by the rep does not change as a result of
entering condenser water temperature. KW changes, but tonnage does not.
This creates an unrealistic curve for CAPFT and EIRFT.

I'm at the mercy of the reps to provide this data and so far I have struck
out. I was just curious if there was something I'm missing. Does something
need to be held constant that will allow the capacity to change based on
entering condenser water temperature and leaving chilled water temperature?

On a similarly frustrating note... I'm trying to come up with a workaround
to model series chillers in eQuest with free cooling on the upstream
chiller. From reading the DOE manual it seems waterside economizer won't do
what I need it to since I can't be in WSE and supplementing with the
downstream chiller. I considered combining performance of the two chillers
into one machine, but I haven't totally figured out how that will work.

Any ideas are welcome.

Thanks,

Jordan Jackson.

On Tue, Apr 7, 2015 at 8:44 AM, Michael Busman <mbusman at opterraenergy.com>
wrote:

>  Jordan,
>
>
>
> Many, many years ago I used to do a lot of modeling in VisualDOE.  I don’t
> do much in eQUEST or other simulation program anymore.
>
>
>
> Anyway, I’ve attached a spreadsheet I put together way back when that is
> based on calculation methodology that was published by Pacific Gas &
> Electric.  If you look through the tabs you’ll see that I have some sample
> data that is used to calculate the curve coefficients.  Originally it was
> based on a constant speed chiller, however, a few years ago I added a tab
> for a variable speed chiller.
>
>
>
> Don’t expect the manufacturers’ reps to produce the curves for you but
> they should be able to generate the data you need.  Key to this for reasons
> I don’t recall is that the reps need to generate at least 10 data points of
> full load data at different chilled and condenser water temperatures in
> order to map the chiller.  You will also need several part load data points
> at different water temps also.  If you give the reps the blank data sheet
> they should be able to run their software to generate the data you need.
>
>
>
> Browse through the spreadsheet tabs and hopefully it will make sense to
> you.  Any questions, I’ll do my best to answer you, however, please
> remember that it’s been a long time since I’ve developed custom curves.
>
>
>
> My best,
>
>
>
> Mike
>
>
>
>
>
> *Mike Busman, C.E.M.*
>
> Lead Project Engineer
>
>
>
> 765 The City Dr South Suite 475
>
> Orange, CA 92868
>
> T.   657-216-3261
>
> M. 310.387.2083
>
> mbusman at opterraenergy.com
>
>
>
> [image: OpTerra] <http://opterraenergy.com/>
>
>
>
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>
>
> *From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
> Behalf Of *jordan jackson
> *Sent:* Monday, April 06, 2015 3:55 PM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* [Equest-users] Centrifugal Chiller Curves
>
>
>
> I have been using eQuest to evaluate chiller performance for retrofit
> projects. I have not had a problem modeling air-cooled, but I can't seem to
> get the data from the reps that I would like for water-cooled centrifugal
> projects. I have settled on using standard curves for CAPFT and EIRFT and
> using a cubic curve with coefficients created through a curve fit in excel
> for EIRFPLR.
>
>
>
> The manufacturers reps aren't able to produce a capacity or EIR curve as a
> function of temperature (entering condenser water temp). Has this been
> everyone's experience with this.
>
>
>
> I'm attaching the excel file I created to calculate all of this.
>
>
>
> Any feedback is appreciated. I'm just concerned about the data I'm
> reporting to the client without touching those curves.
>
>
>
> Thanks,
>
>
>
> Jordan Jackson.
>
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