[BLDG-SIM] another 90.1 ECB question

[Konstantine Babets]

Alec,

 

I think the intent of the code is exactly to penalize an HVAC system (or equipment) that is less efficient than the Code one. The choice of local floor DX unit brings about issues of a less efficient refrigeration, less efficient economizer control (i.e., waterside vs. air side), that must be offset somewhere else in the building, i.e. more efficient glazing...Furthermore, nowhere in the code it is mentioned that the consistent HVAC systems must be used. 

It has been my experience that for the ecb model an air-side economizer should be used.

In general, the situation you have described is fairly common, and unfortunately the proposed design building is thus often penalized.

Konstantin Babets
Jaros Baum and Bolles
(212) 530 9455


----- Original Message ----- 
  From: Alec Stevens 
  To: BLDG-SIM at gard.com 
  Sent: Tuesday, July 13, 2004 12:04 PM
  Subject: [BLDG-SIM] another 90.1 ECB question


  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

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