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

Gerald Pde geraldpde at yahoo.com
Wed Jan 31 07:11:28 PST 2007


John,
It might be that your CHW loop is on "Standby" mode
which might require for your loop to be always loaded.
Try setting it to "Demand" and see if that makes any
difference.

Gerald



--- "Aulbach, John" <jaulbach at nexant.com> wrote:

>  
> 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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