[BLDG-SIM] another 90.1 ECB question

[Alec Stevens]

Hello,
In light of recent questions to the list on the ASHRAE ECB method, here is one that we are working on: 

The proposed multi-story office building will have a cooling tower serving a condenser water loop.  Each floor has a VAV air handling unit with a water-cooled DX compressor, heat is rejected to the CW loop.  Economizer cooling is provided on the water side via separate WSE coils.  OA is provided to each floor's AHU, but 100% OA is not provided.  The waterside economizer coils can pre-cool the mixed air when the CW temperature is low enough, and can run in series with the DX coils.  

Regarding the base budget building, the system map in 90.1 seems to indicate that a central chiller plant is required for this type of building (System type 2).  However, in general I think we are supposed to use consistent HVAC systems in the base budget building and the proposed building.  I want to know if we can use the floor-by-floor water cooled units in the base budget building so as to be consistent and to not penalize the energy performance of the floor-by-floor DX units compared to a chiller plant.

Also, the language is confusing to us regarding air vs. water side economizers.  In 11.4.3, we are directed to include an economizer that meets the requirements of 6.3.1, where the standard seems to indicate that a system must have either air or water side economizers.  However, in 11.4.3e, the standard seems to say that system type 2 must use airside economizers.  The proposed design seems to meet the requirements for waterside economizers, but I don't want to penalize the proposed design for not having 100% OA capability.  

Your thoughts on the above questions would be appreciated.

Thanks!
Sincerely,

Alec Stevens, PE, LEED AP
DMI
450 Lexington St, Newton, MA 02466
p: 617-527-1525 x105  f: 617-527-6606
e: astevens at dmiinc.com

===========================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20040713/262eaa26/attachment.htm>