[Bldg-sim] [BLDG-SIM] Condenser Water Reset in eQuest

[Melissa Crowe]

HI

I just ran into the thread below and I am wondering why the condenser water reset temp min has not been lowered.  When chiller plants have York chillers we reset CWST down to 55°F.  It would be nice to capture/explore the chillers running as designed.   I understand that the DOE2 curves are not fit for lower CWST and  we would have to create chiller curves ...but that's life....until DOE2 produces alternate curves.

Thanks
Melissa

[cid:image001.jpg at 01D02372.92170350]
Melissa P. Crowe, LEED AP
Project Engineer
Engineered Solutions, Inc.
6 Union St, Natick MA 01760
508.647.9200 x225 (P) l 508.652.1936 (F)
MCrowe at EngSolutions.com<mailto:MCrowe at EngSolutions.com>

CAUTION: The preceding email message and any attachments to it may be confidential and/or may contain proprietary information that is entitled to protection from disclosure under applicable law. It is not intended for transmission to, or receipt by, any unauthorized persons. If you are not the intended recipient or such recipient's employee or agent, please do not read any attachments, or print, copy, disseminate or otherwise disclose the contents of this email. If you have received this message in error, please (i) notify the sender by return email immediately that you received the message in error, and (ii) erase or destroy the message.

[BLDG-SIM] Condenser Water Reset in eQuest
Steven Gates steve.gates at doe2.com <mailto:bldg-sim%40lists.onebuilding.org?Subject=Re%3A%20%5BBLDG-SIM%5D%20Condenser%20Water%20Reset%20in%20eQuest&In-Reply-To=%3CMDAEMON-F200608171544.AA4418203pd80001204645%40gard.com%3E>
Thu Aug 17 13:41:20 PDT 2006

 *   Previous message: [BLDG-SIM] Condenser Water Reset in eQuest <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/003229.html>
 *   Next message: [BLDG-SIM] Condenser Water Reset in eQuest <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/032261.html>
 *   Messages sorted by: [ date ]<http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/date.html#32262> [ thread ]<http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/thread.html#32262> [ subject ]<http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/subject.html#32262> [ author ]<http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/author.html#32262>

________________________________

We are checking eQUEST to confirm the issue of MIN-COND-T, and will fix it

if it is missing.







Mike is correct that the capacity and power performance curves were not fit

for condenser temperatures below 65-70F, and the default MIN-COND-T reflects

this fact.  The reason is because the majority of chillers cannot operate

satisfactorily much below this temperature.   For many reciprocating

chilllers, the expansion valve requires a minimum pressure differential in

order to operate and deliver the rated capacity.  Centrifugal chillers may

also be limited.  Recently, we were investigating a 'frictionless'

centrifugal compressor, and learned that motor cooling would be inadequate

if the condenser temperature (and pressure) drops much below about this

value; insufficient liquid refrigerant would be injected into the motor.







If you want to investigate lower condenser temperatures, we recommend that

you inspect the capacity and eir curves in the regime of interest to confirm

whether they yield reasonable results.







The best way to use the DIAGNOSTIC NO-LIMITS override is to first debug your

input at a higher diagnostic level so that the BDL can issue errors,

warnings, cautions.  Once you are ready to run, then set NO-LIMITS.







Depending on feedback we get from people, we can reduce the lower limit of

MIN-COND-T, or change the error checking so that it issues a warning rather

than an error.  As the curves are NOT fit for temperatures lower than about

65F, the lower limit should probably remain the same, but the checking

reduced from an error to a warning.  Comments?







Steve Gates











  _____



From: BLDG-SIM at GARD.COM<http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org> [mailto:BLDG-SIM at GARD.COM<http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org>] On Behalf Of Mike Tillou

Sent: Thursday, August 17, 2006 10:58 AM

To: BLDG-SIM at GARD.COM<http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org>

Subject: [BLDG-SIM] Condenser Water Reset in eQuest











Hi all..I thought I would share a couple of tips on using Condenser Water

Reset Strategies in eQuest . Hopefully some of you will find this useful.



We just finished modeling a chiller plant where we looked at using low

condenser water temperatures ( below 60F ) as an energy efficiency measure.

The project is in a climate with very low wetbulb temperatures .  There are

a couple of quirks I thought I would share about trying to model a strategy

like this.



The Condenser Loop Control tab has several options for resetting the loop

temperature.  If you notice MIN-RESET-T always defaults to 70F.



Issue  #1:  If you reset the Condenser loop MIN-RESET-T lower than 70F (say

65F) and then run an hourly report to check the loop temperature everything

looks like it's working fine.  BUT..if you also check the chiller entering

condenser temperature you will find it never goes below 70F even though the

condenser loop says it should be lower.  This is because the chiller has a

keyword MIN-COND-T that defualts to 70F and cannot be changed from within

eQuest.  You have to change the keyword manually in the input file by adding

the line, MIN-COND-T = 65 underneath the definition of your chiller.





The most likely reason this defaults to 70F is because the default chiller

performance curves were not designed for condenser temperatures below 70F  (

someone should correct me if this is wrong)



If you want to try and model condenser water temperatures below 70F I highly

recommend you create custom performance curves that include data points that

describe the operation of your chiller at the appropriate condenser water

conditions.



That brings me to Issue #2.



The MIN-COND-T keyword has a lower limit of 60F.  In other words even if you

create the appropriate performance curves  and then try to set MIN-COND-T

lower than 60F you will get a simulation error.



You can work around this by using the DIAGNOSTIC keyword "NO-LIMITS".  In

effect this turns off both the Max and Min keyword limits.  You can then

simulate chiller operation with very low condesner water temperatures.



If you use the "NO-LIMITS" keyword do so very carefully.  This is a very

important error checking function of DOE2.2 eQuest.



Mike







Michael Tillou, PE

etc Group, Inc.

PO Box 7, Williamstown, MA 01267

ph. (413) 458-9870 fx. (413) 458-9875



















==================

You received this e-mail because you are subscribed

to the BLDG-SIM at GARD.COM<http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org> mailing list.  To unsubscribe

from this mailing list send a blank message to

BLDG-SIM-UNSUBSCRIBE at GARD.COM<http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org>





======================================================

You received this e-mail because you are subscribed

to the BLDG-SIM at GARD.COM<http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org> mailing list.  To unsubscribe

from this mailing list send a blank message to

BLDG-SIM-UNSUBSCRIBE at GARD.COM<http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org>

-------------- next part --------------

An HTML attachment was scrubbed...

URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20060817/d916ca09/attachment-0002.htm>

________________________________

 *   Previous message: [BLDG-SIM] Condenser Water Reset in eQuest <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/003229.html>
 *   Next message: [BLDG-SIM] Condenser Water Reset in eQuest <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/032261.html>
 *   Messages sorted by: [ date ]<http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/date.html#32262> [ thread ]<http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/thread.html#32262> [ subject ]<http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/subject.html#32262> [ author ]<http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/2006-August/author.html#32262>

________________________________
More information about the Bldg-sim mailing list<http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20141229/9f70b569/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.jpg
Type: image/jpeg
Size: 1517 bytes
Desc: image001.jpg
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20141229/9f70b569/attachment-0001.jpg>