[bldg-sim] Package VAV w/reheat Versus CHW VAV w/reheat

Aulbach, John jaulbach at nexant.com
Mon Jan 29 13:36:55 PST 2007


 
Hi all:

I swear this continued comparison will send me to an early grave.

ASHRAE 90.1 requires a building less than 5 stories and between 75K -
150K floor area to have a package VAV/reheat as its system. There are
those designers that like the CHW VAV system better. There is a penalty
of having a running CHW pump in that case.

However, I just did an eQuest comparison between the two systems, all
things equal (I hope). The CHW system space cooling used 60% MORE energy
than the package system. In the dead of summer, the CHW beats the
package. But in the winter, there seems to be a false load the chiller
is seeing, as the package cooling is almost nil, but the CHW system is
still has 2/3 of the summer usage.

I THINK I have CHW reset correctly programmed for the CHW system.

ANY IDEAS ???

John R. Aulbach, PE, CEM
Project Manager
Nexant, Inc.
100 North Barranca, Suite 820
West Covina, CA 91791 USA
Phone: 626-430-9054
Fax: 626-430-9060
email: jaulbach at nexant.com
 

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