[Equest-users] Chiller Staging

David Eldridge DEldridge at grummanbutkus.com
Tue May 8 12:35:40 PDT 2012

I had e-mailed the posters off-list, but here is the reply in case it is useful to anyone else.

I'm not sure that would work for determining when one chiller would be on as the load rises, and two chillers would be on as the load falls. The program still only makes the decision based on load without knowing if the load was increasing or decreasing at any time unless that's been added since I looked.

Also the pumping for one vs. two chillers might be important.

If the purpose of the study is to determine the optimal staging, I do think a spreadsheet might be more flexible for your scenario. Use eQUEST to provide the load and building temperature conditions at each hour, and use your own logic to stage chillers and calculate the energy usage. This will be based on an ideal case of known conditions.

However with six chillers of two different types in the plant, the ability to model the proposed sequence is going to exceed the accuracy of the assumptions used to calculate the loads and system response. For an Appendix G type analysis the eQUEST staging might suffice unless the two chiller types are very different, or unless this is an existing building with monitored chiller plant data that you are trying to match.


(Also testing my new e-mail address ;)...old one will continue to forward though.)

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

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Howe, Timothy
Sent: Tuesday, May 08, 2012 10:29 AM
To: Janne Kairento; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Chiller Staging

Quick thought here.  Why not create a custom set of chiller curves which directly models your different stages and associated chiller efficiencies and model as one large chiller.

Timothy Howe, MS, LEED® AP BD+C
Mechanical Engineer
61 Commercial Street
Rochester NY 14614
Ph:   (585) 413-5347
Fx:   (585) 272-1814
Cell: (585) 330-8681

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From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Janne Kairento
Sent: Tuesday, May 08, 2012 11:26 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Chiller Staging


I have building with 6 chillers (2 different capacities) and I would like to model them with 14 stages of operation.  How can I independently control the increment (add chiller) and decrement (stop lag chiller) of an individual chiller stage. I was using equipment control, however, the saw tooth approach does not account for the overlap of plant stages. Thank you for your time.


Janne Kairento LEED AP, EIT
B2Q Associates, Inc.
146 Main Street
North Andover, MA 01845
Office: 978.208.0609 x209
Fax: 978.719.6339
Mobile: 978.210.7397

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