[BLDG-SIM] Condenser Water Reset in eQuest

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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.


[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

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[BLDG-SIM] Condenser Water Reset in eQuest
Steven Gates steve.gates at doe2.com
Thu Aug 17 13:41:20 PDT 2006

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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

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