[Equest-users] Chillers in Series inputs

[Pasha Korber-Gonzalez]

Thanks Rob & James for your prompt input to my dilemma....after I sent the
email to the list, I went back in my plants to try and make sense why the
secondary wasn't seeing a load--so for a random test I switched the
assignement of the two chillers (just reversed which loops they are on.) and
then ran the sim without errors.  That was the good news.   I don't have my
head around the logic of why that worked on the first try, but maybe I was
having some dislexia-input moments and spec'd my chiller conditions
backwards (i.e. high chiller & low chiller in the series).

Since it has ran I noticed an immediate reduction in chiller energy use, but
I haven't yet verified if the reduction is realistic and if there are any
other QC error type things to verify that this approach is indeed modeling
the chiller temps in series.   I don't think I will mess with custom chiller
curves at this point because this project model is only SD.  Therefore I
won't be held to any compliance reviews and strict performance results...at
least not at this point in time.

I'll try to send feedback when I can verify that this is a valid input
option for chillers in series, or if it holds no water at all...

Cheers,
Pasha

On Fri, Apr 22, 2011 at 12:18 PM, James Hansen <JHANSEN at ghtltd.com> wrote:

>  Most manufacturers will give you a “single chiller” performance curve for
> the two chillers in series.  I typically just make custom chiller curves to
> represent series chillers as a single chiller.  If a designer creates
> valving that allows water to NOT have to flow through both chillers during
> low load operation, this gets a little tricky, and I end up averaging the
> delta P across the chillers to represent partial operation thru both
> chillers and partial operation thru a single chiller.  No easy way to do
> this.
>
>
>
> *GHT Limited**
> **James Hansen**, PE, LEED AP*
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> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Rob Hudson
> *Sent:* Friday, April 22, 2011 2:15 PM
> *To:* Pasha Korber-Gonzalez
> *Cc:* eQUEST Users List; Arunabha Sau
> *Subject:* Re: [Equest-users] Chillers in Series inputs
>
>
>
> I won't claim that this is correct whatsoever, but briefly looking at your
> set up, it is clear that the water isn't pulling extra load from the second
> chiller.  I think you may want to set up a single chiller because I don't
> see a way to get the water to go through both chillers.  You could also
> create your own custom curves so that you match the combined performance of
> the modeled chiller.
>
>
>
> Just a thought.
>
>
>
> Rob
>
> On Fri, Apr 22, 2011 at 1:55 PM, Pasha Korber-Gonzalez <
> pasha.pkconsulting at gmail.com> wrote:
>
> Hi,
>
>
>
> I could use some guidance to make sure I'm assuming the correct inputs to
> set up chillers in series.  This is the first time I'm trying to model this
> and I have it set up with a primary & secondary loop for a total delta T of
> 16 across 2 chillers.    I'm getting a run error of the secondary loop
> having NO DESIGN FLOW/LOAD, but I'm not sure how to show that load on the
> secondary loop.....maybe I have the chillers listed backwards???
>
>
>
> Can anyone take a quick look at the setup in the Plant Module and let me
> know what I am missing on this?  I couldn't find any info on chillers in
> series in the DOE-2 docs to guide me on the correct inputs and setup.
>
>
>
> .pd2 & inp files attached.
>
>
>
> Thanks in advance for your keen eye and guidance on my model.
>
>
>
> Pasha
>
>
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>
>
> --
> Rob Hudson
>
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