[Equest-users] Question: Modeling Specific Chillers

Hall, Brendan BHall at karpinskieng.com
Thu Sep 19 10:13:36 PDT 2013

In general, there is also a database of chiller curves that is provided for energyplus that I believe are also valie for eQuest if you convert them into Fahrenheit temperatures. If the one in questions happens to be on that list it could be helpful.


Brendan Hall

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Jeremy McClanathan
Sent: Thursday, September 19, 2013 12:58 PM
To: 'Sunil Nair'; 'David Eldridge'
Cc: 'equest-users at lists.onebuilding.org'
Subject: Re: [Equest-users] Question: Modeling Specific Chillers

Hello Sunil,
It sounds like the manufacturer may be trying to get you a capacity for a given set of condenser and evaporator temperatures.   What you need is the manufacturer to tell you what the full load (and part load) capacities of the machine are with the lift conditions you specified.  So, for higher lift conditions, the machine will have lower capacities.  He doesn’t need to match the capacity you selected the chiller at to all the lift conditions you specify.

If it helps, the spreadsheet I use to generate custom chiller curves can be downloaded from here:


Jeremy McClanathan, P.E., BEMP, HFDP, LEED® AP
19203 36th Avenue W, Suite 200, Lynnwood, WA 98036
P 425-672-1071 | F 425-778-8769
P Please consider the environment before printing this email.

From: Sunil Nair [mailto:energymodel.sunil at gmail.com]
Sent: Wednesday, September 18, 2013 9:55 PM
To: David Eldridge
Cc: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Question: Modeling Specific Chillers

I think I am hitting a roadblock here, trying to get the necessary data to model the chillers. I have gone through the EDR document on simulating HVAC systems and other posts on modeling chillers here on the mailing list. I think I can get the part load data from the manufacturer.

Trying to get the full load data has been difficult though. The chiller manufacturer tells me that if I want the full load capacity at reduced condenser entering and/or higher evaporator leaving temperatures, he can only provide up to about 5% higher capacity than design capacity. Beyond this he will need to change the expansion device in his selection software to get the total capacity. I don't believe changing the expansion device is the right way to go.

I have attached a sample data sheet with various data points that I thought I should get from the manufacturers. The data points I have in the sheet are what will be practically seen in operation here. However they are all lower than the design temperatures of the chiller. I'm not sure if I am going in the right direction with this one.

Any inputs are appreciated.


Sunil Nair

Ab Initio

TMA House, Plot No. 6, 2nd Floor,

Main Road, Wagle Industrial Area,

Thane (West) - 400 604

Ph: +91-22 - 3243 7023

Cell: +91-8879595123
web: www.abinitio.co.in<http://www.abinitio.co.in/>

On Fri, Aug 16, 2013 at 7:25 PM, David Eldridge <DEldridge at grummanbutkus.com<mailto:DEldridge at grummanbutkus.com>> wrote:
You should be able to look at the manufacturer data plotted vs ECWT and load and determine if a single set of curves (one modeled chiller) or two are needed to accurately model power usage by the chiller over the range of load. (if you can get the data)

David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP
Grumman/Butkus Associates

From: Sunil Nair [mailto:energymodel.sunil at gmail.com<mailto:energymodel.sunil at gmail.com>]
Sent: Thursday, August 15, 2013 11:40 PM
To: Busman, Michael R
Cc: David Eldridge; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>

Subject: Re: [Equest-users] Question: Modeling Specific Chillers

Dave and Mike,
Thanks for your inputs.
Yes, I am referring to the multistage chiller where the liquid is flashed to the inlet of the second stage impeller. As you have mentioned this process is internal to the chiller.
My thought initially was I may have to model multiple compressors per circuit for a chiller without VFD. I did not find this option in eQUEST. As I think about it now, my case would be quite different from having multiple compressors per circuit.
I am in the process of obtaining data points for the chiller from the manufacturer so I can input the data points into eQUEST.
I'll keep this thread updated.
Sunil Nair
Ab Initio
TMA House, Plot No. 6, 2nd Floor,
Main Road, Wagle Industrial Area,
Thane (West) - 400 604
Ph: +91-22 - 3243 7023
Cell: +91-8879595123
web: www.abinitio.co.in<http://www.abinitio.co.in>

On Wed, Aug 14, 2013 at 10:56 PM, Busman, Michael R <MBusman at chevron.com<mailto:MBusman at chevron.com>> wrote:

My understanding of an economizer for a multi-stage centrifugal is that some of the liquid refrigerant flashes as it passes through the expansion device.  This flash gas, I believe is introduced to the input side of the second stage impeller.  Since the economizer is internal to the chiller, one set of curves should be sufficient as there is only one mode of operation as I understand it.  You didn’t specify, so I’m assuming you are not referring to a water-side economizer.

I haven’t custom defined a chiller yet in eQUEST, however, it appears that several performance data points from the manufacturer are required for eQUEST to generate the curves if you select this method.  The other is to generate your own curves.  Many years ago when I used to work in VisualDOE, I found the calculation methodology to define chiller curves from the Pacific Gas & Electric web site, which I used to set up a spreadsheet to calculate the curve coefficients.  This was originally set up for constant speed chillers.  A number of months ago I added a spreadsheet tab to handle variable speed chillers.  To create the 3 sets of curve coefficients, at least 10 full load data points at different chilled and condenser water temperatures were required from the manufacturer in order to map the compressor.  There was no max or min limit for the part-load data points as I recall.

If you’d like a copy of the spreadsheet, I can email it to you, however, you might want to check the eQUEST manual or DOE-2.2 reference manuals regarding directly entering data points into eQUEST and let the program figure out the curves for you.

My best,

Mike Busman

Michael R. Busman, CEM
Lead Project Engineer II

Chevron Energy Solutions
A Division of Chevron U.S.A., Inc.
145 S. State College Blvd.
Brea, CA  92821
Direct  714-671-3561
Fax     714-671-3438
eFax   866-420-0335 (Include my Full Name followed by "CAI:MHTZ" on Cover Sheet)
Mobile 310-387-2083
mbusman at chevron.com<mailto:mbusman at chevron.com>

From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of David Eldridge
Sent: Wednesday, August 14, 2013 9:46 AM
To: Sunil Nair
Cc: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Question: Modeling Specific Chillers

When the chiller runs on economizer it will use a separate set of curves and be modeled as a distinct chiller.

One set of curves will be difficult to model both modes of operation.

DSE Mobile

On Aug 14, 2013, at 11:34 AM, "Sunil Nair" <energymodel.sunil at gmail.com<mailto:energymodel.sunil at gmail.com>> wrote:
Hi All,

I have a couple of questions with respect to modeling specific chillers.

1) I am trying to model a centrifugal chiller with an economizer. The chiller in question is a centrifugal chiller running on R123 with an economizer installed to it. Do I just need to get data from the chiller manufacturer and input the curves into the model? Is this the right way to go?

2) How do you model multi stage centrifugal chillers without VFD's?


Sunil Nair

Ab Initio

TMA House, Plot No. 6, 2nd Floor,

Main Road, Wagle Industrial Area,

Thane (West) - 400 604

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