[Equest-users] chiller sequencing
James Hansen
JHANSEN at ghtltd.com
Thu Mar 3 12:35:25 PST 2011
This is pretty easy with chiller sequencing.
Make sure to uncheck the "pro-rate" load box for the sequencing.
For the 1st page, with loads up to 150 tons, just put in CH-1.
For the 2nd page, with loads up to 350 tons, put in CH-2 only.
For the 3rd page, with 999 MBH limit (ie default), put in CH-1 and CH-2
with no max load for either chiller.
GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA 22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
www.ghtltd.com <http://www.ghtltd.com/>
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Carol
Gardner
Sent: Thursday, March 03, 2011 3:26 PM
To: Fleming, Joe
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] chiller sequencing
Hi Joe,
The info is actually pretty robust, it just hasn't been covered for
while and no one seems to be using it much. So kudos to you. I am going
to attach a screen shot below, but also refer you to Volume 3 of the
manuals. That's where you'll find lots of in depth discussions. Some of
the commands may be slightly different in name and format but I think
you'll be able to figure them out.
Cheers,
Carol
Volume 3: Topics > Central Plant Components > LOAD-MANAGEMENT and
EQUIP-CTRL > Examples of EQUIP-CTRL and LOAD-MANAGEMENT Sequences
Example 1: Chiller Staging
Assume a central plant has three chillers: 200 tons, 400 tons, and 600
tons. By default, the program will use the 200 ton chiller whenever the
load is in the range of 100-200 tons, the 400-ton chiller for loads in
the range of 201-400 tons, etc.
In this example, this is not the optimum control sequence, however,
because the 200 and 600-ton machines are newer and much more efficient
than the 400-ton machine. The following sequence will optimally load
the newer machines and reserve the 400-ton machine for periods of
maximum load:
CHLR-CTRL = EQUIP-CTRL
TYPE = COOLING
CIRCULATION-LOOP = COOLING-LOOP
LOADS-THRU-1 = 2.4 Millions of Btuh
CHILLERS-1 = (CHLR-200)
LOADS-THRU-2 = 7.2
CHILLERS-2 = (CHLR-600)
LOADS-THRU-3 = 9.6
CHILLERS-3 = (CHLR-600,CHLR-200)
LOADS-THRU-4 = 14.4
CHILLERS-4 = (CHLR-600,CHLR-200,CHLR-400)
..
The spacing between load ranges is for clarity only; as with all BDL
input, spacing has no effect on the meaning of the input.
Some types of equipment, such as chillers and cooling towers, have a
capacity that varies hourly in accordance with ambient temperature
and/or other conditions. Therefore, it often makes sense not to have to
specify a fixed LOADS-THRU range, but to allow the range to default to
the hourly capacity of the equipment listed within the range. If you do
not specify the LOADS-THRU keyword, the value will default to the hourly
capacity. The following is equivalent to the example above, but takes
into account the varying hourly capacities:
CHLR-CTRL = EQUIP-CTRL
TYPE = COOLING
CIRCULATION-LOOP = COOLING-LOOP
CHILLERS-1 = (CHLR-200)
CHILLERS-2 = (CHLR-600)
CHILLERS-3 = (CHLR-600,CHLR-200)
CHILLERS-4 = (CHLR-600,CHLR-200,CHLR-400)
..
Also, while the above input works, it uses more keywords than is needed;
also for clarity. The following input is equivalent:
CHLR-CTRL = EQUIP-CTRL
TYPE = COOLING
CIRCULATION-LOOP = COOLING-LOOP
CHILLERS-1 = (CHLR-200)
CHILLERS-2 = (CHLR-600,CHLR-200,CHLR-400)
..
This input, while shorter than the previous, is also somewhat
overspecified because the default sequencing for the EQUIP-2 list is the
order entered. In other words, the CHILLERS-SEQ-2 did not need to be
listed in this example.
If sequencing is not specified, equipment is started in the order
listed. The following examples are equivalent, and illustrate how
sequencing works:
LOADS-THRU-2 = 999.
CHILLERS-2 = (CHLR-600,CHR-200,CHLR-400)
LOADS-THRU-2 = 999.
CHILLERS-2 = (CHLR-600,CHR-200,CHLR-400)
CHILLERS-SEQ-2 = ( 1, 2, 3)
LOADS-THRU-2 = 999.
CHILLERS-2 = (CHLR-200,CHLR-400,CHLR-600)
CHILLERS-SEQ-2 = ( 2, 3, 1)
In all these examples, CHLR-600 starts first, followed by CHLR-200,
followed by CHLR-400. To force CHLR-600 and CHLR-200 to always start
and run together, give them the same sequence number:
LOADS-THRU-2 = 999.
CHILLERS-2 = (CHLR-200,CHLR-400,CHLR-600)
CHILLERS-SEQ-2 = ( 1, 2, 1)
On Thu, Mar 3, 2011 at 11:58 AM, Fleming, Joe <joe.fleming at tlc-eng.com>
wrote:
How would one sequence chillers in the following way?
Chiller 1 - up to 150 tons
Chiller 2 - 150-350 tons (Chiller 1 is off in this range)
Chiller 1&2 - 350-500 tons
The Load range tab provides a "max load", but I believe that when I move
to step 2 that equest is going to keep both chillers on.
i.e. for an input such as;
Chiller-Seq-Max Load
Chiller 1 - 1 - 150
Chiller 2 - 2 - 350
Should you utilize the different "Load Ranges" here?
The help file for this sections is not as robust as the other help
sections.
Thank You
Joe Fleming
E.I., LEED AP BD+C, BEMP
Mechanical Engineer II
TLC Engineering for Architecture
Your 2030 Challenge Partner
800 Fairway Drive, Suite 250
Deerfield Beach, FL 33441-1816
phone:
954-418-9096
fax:
954-418-9296
direct:
954-418-4591
website:
www.tlc-engineers.com <http://www.tlc-engineers.com/>
<http://www.tlc-engineers.com/>
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Carol Gardner PE
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