[BLDG-SIM] Chilled water loop and/or Chiller size

[Anna Zhou]

Hi,All,

I am doing a project with ONE central chiller and was letting eQuest
(DOE2.2) to auto-size the chiller capacity. What I found is that the chiller
is sized (from report PV-A) almost TWICE as large as the building system
peak load (from repoert SS-D). As a result, the chiller and chilled water
loop can never run at above 50% load (from report PS-D).

I tried to diagnose this problem just by building a 2-story office boiling
model (20,000 sqft each story) and used most of the eQuest defaults as
inputs, and ran under California climate zone 01 (coldest) and 13 (hottest).
Comparing the results seems indicating the chiller size does not change much
(about 800 kbtu/h) while the system load is about 380 Kbtu/h and 700 Kbtu/h
for the two climate.

Since the chiller is always running at very load part load, the electricity
consumption is not reasonable. If I choose to use two chillers, the sum of
the chiller capacities is still way larger than the system load. but one of
the chiller will almost not run throughout the year.

Can anybody tell me what's the problem here? Is there a keyword that's
important in calculating the chilled water loop size but not made explicit
by eQuest?


Thanks a lot!

Anna Zhou
Energy Engineer
GeoPraxis, Inc.
205 Keller Street, Suite 202
Petaluma, CA 94952-2886
Phone (707) 766-7010
Fax (707) 766-7014
annazhou at geopraxis.com
www.geopraxis.com

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