[Equest-users] Chiller curves for ASHRAE 90.1 2010

Mon May 8 12:53:13 PDT 2017

Nick;

I believe the curves in the PNNL guide are a copy/match to those in COMnet. I’ve found & avoid these for a couple reasons:

·         The source of COMnet data is not explicitly clear. They’re any (great) citations in the document. And the ‘Acknowledgements’ section at the front leaves much to be desired if this is to serve as the references /citations/bibliography section.

·         The curves are 2 bi-quadratics and a single quadratic. In eQuest the default for a water cooled centrifugal chiller is 3 bi-quadratics. From real chiller selections and curve data from equipment manufacturers 3 bi-quadratics  is what is needed. Describing the relationship of EIR-F(PLR) is complex…

·         I don’t love the eQuest defaults either. It would appear as though they unload unrealistically well compared to ‘real’ chillers.

·         Semi-related is that EnergyPlus comes with a bunch of Chiller Data performance curves in its DataSet File. Come of the chillers use the 2 bi-quadratic + 1 quadratic; others use 3 bi-quadratics, with the 3rd bi-quadrates referring to a ‘ReformEIRChiller’ as the curve…would be interested to know what this exactly means…

Any resources anyone has & can share are appreciated (ex: HVAC Simulation Guidebook) , but chillers are tricky…I mean ‘fun’…

Thanks,
DARIC R. ADAIR  PE, C.E.M.
Henderson Engineers, Inc. | Mechanical Engineer, Energy Analyst
dir 913 742 5530  tel 913 742 5000  fax 913 742 5001  tx id #F-001236  email daric.adair at hei-eng.com  www.hei-eng.com<http://www.hei-eng.com/>
Licensed in KS. 

From: Nicholas Caton via Equest-users [mailto:equest-users at lists.onebuilding.org]
Sent: Friday, May 5, 2017 5:30 PM
To: Harshul Singhal <hsinghal at psdconsulting.com>; Rathna Shree <rathnashreep at yahoo.in>
Cc: equest-users at onebuilding.org
Subject: Re: [Equest-users] Chiller curves for ASHRAE 90.1 2010

IPLV is a functional metric for a consistent, “binary” pass/fail requirement for something resembling part-load performance between manufacturers.  IPLV cannot be translated into a part load performance curve for an energy simulation, however.

Here’s a technical recap for those curious/interested:

IPLV (or NPLV) = 0.01A+0.42B+0.45C+0.12D
Where:
A = COP or EER @ 100% Load
B = COP or EER @ 75% Load
C = COP or EER @ 50% Load
D = COP or EER @ 25% Load

A, B, C, and D are determined at various operating conditions stipulated by AHRI 550/590<https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwj1oNi-3tjTAhVIxCYKHWlbBjwQFggrMAE&url=http%3A%2F%2Fwww.ahrinet.org%2FApp_Content%2Fahri%2Ffiles%2Fstandards%2520pdfs%2FANSI%2520standards%2520pdfs%2FANSI.AHRI%2520Standard%2520550-590%2520(I-P)%2520with%2520Addendum%25203.pdf&usg=AFQjCNEwFDy4kJpL3HbxK4uiL8otyG9RoQ&sig2=yg-KUv7ja0SuR1v_kn_21g>, Section 5.4, Table 3 (page 41 of the linked PDF):
[cid:image001.png at 01D2C805.23240300]

You can’t take a prescribed IPLV of, say, 13.0 and turn that into knowledge of what efficiency your chiller should reflect at 100% or 75% loading conditions.  Even if an ASHRAE standard or a manufacturer publishes those part load factors, you still are going to have conditions in reality (and your simulations) where it isn’t always 65 degrees outside while you’re 50% loaded (for example)… the major message/takeaway here is that IPLV was made to marry manufacturers and laboratory conditions, to the general benefit of specifiers and prescriptive standards, not for us in the simulation world.

That’s not to say IPLV can’t be made useful...  Someone could (if so inclined) built a “AHRI chiller test bed” model to try and replicate AHRI lab conditions for your simulated chiller.  Custom hourly reports alongside a weather file coving the full range of AHRI conditions to “backtrack” the effective IPLV of a simulated chiller to see how closely the selected library or your own custom curves come to replicating the IPLV prescribed/tested.  If I had such a “test bed” model on-hand I’d share it with the community here, but I haven’t invested time to pursue that concept to completion yet.

After some spot checking I observe the baseline curves in the cited PNNL reference link below do NOT match up with at least one set of library curves in eQUEST (the one that came with v3.65 b7163 anyway)… they might match exactly elsewhere… has anyone done the legwork to assess what equipment/research was used to develop those curves in relation to the eQUEST curve library?  They might be generally preferable as a default if they’re built from trustable and better/more current sources, and if so I’d be inclined to transpose into a custom library file (and possibly share with the community thereafter)…

~Nick
[cid:image002.png at 01D2C805.23240300]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Regional Energy Engineering Manager
  Energy and Sustainability Services
  Schneider Electric

D  913.564.6361
M  785.410.3317
F  913.564.6380
E  nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

[cid:image003.png at 01D2C805.23240300]

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Harshul Singhal via Equest-users
Sent: Friday, May 05, 2017 8:17 AM
To: Rathna Shree <rathnashreep at yahoo.in<mailto:rathnashreep at yahoo.in>>; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Chiller curves for ASHRAE 90.1 2010

I would suggest to use the values from the given reference manual: http://www.pnnl.gov/main/publications/external/technical_reports/PNNL-25130.pdf

I don’t use eQuest these days but a cross-check will be helpful to generate the correct energy consumption figures.

Harshul Singhal LEED AP BD+C, CMVP
Building Energy Modeling Analyst
psdconsulting.com<http://psdconsulting.com/>

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rathna Shree via Equest-users
Sent: Friday, May 05, 2017 6:28 AM
To: Equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: [Equest-users] Chiller curves for ASHRAE 90.1 2010

Dear All,

Can we use the default chiller curves available in Equest while constructing the baseline case using ASHRAE 90.1 2010?

Since the IPLV changes from previous ASHRAE standard, is it required to change the part load curve?

Regards,
Rathnashree

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