[Equest-users] CW Loop reset

[James Hansen]

Something interesting that I noticed with your model (that is sort of
besides the point):  most of your PIU systems have ~ 2600+ hrs when the
zones are undercooled, yet your BEPS report only shows 7.5% hours unmet
load hours....interesting.

 

To the actual problem at hand:  it would appear your chilled water and
condenser water loops use the SAME reset schedule...this can't be right,
can it?  You're basically forcing your heat rejection loop to be at 63
degrees during the summer, which is why you have such high heat
rejection power consumption #s.

 

Maybe fix that first?

 

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 Mike
Hall
Sent: Monday, April 05, 2010 7:12 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] CW Loop reset

 

Hi All,

 

I am modeling a VAV system using water cooled DX air handlers on four of
five floors.  24/7 load spaces use CHW fan coil units and the entire
fourth floor uses chilled water VAV air handler.  Each DX VAV has an
economizer coil so hours in the winter when the CW temp is low enough
the internal zone receives free cooling.  The entire chilled water loop
also has a water-side economizer so all the chilled water equipment can
recieve free cooling.

 

As seen by the elec consumption graphs I'm having a problem with the CW
loop control strategy.  Either the loop operates at the commanded
setpoint of 85 deg.  Which means there is no free cooling.  Or when I
try to use OA-Reset the cooling loads during the winter are met via
free-cooling but during the summer the chiller barely runs and the
cooling tower tries to meet the load of the CHW loop.

I was able to find the way to disable the error caused by condenser
water below 65 deg thanks to post from board veterans like Mike TIllou,
Steve Gates, John Albach, and others).  I do not know what else to try.

Thanks,
MH


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