[Bldg-sim] ASHRAE 90.1 Baseline building question

[Bishop, Bill]

Chris,

I assume you're doing an ECB model using 90.1-1999 to meet a local
requirement.

I interpret 90.1-1999, Section 6.3.6.1 differently. (For those without
it handy, the wording is, "Individual fan systems that have both a
design supply air capacity of 5000 cfm or greater and have a minimum
outside air supply of 70% or greater of the design supply air quantity
shall have an energy recovery system with at least 50% recovery
effectiveness.") The criterion to evaluate is for individual fan
systems. The ERV is not the fan system, the four rooftop units are the
fan systems. So, you only need to model heat recovery if one or more of
the rooftop units has 5000 cfm or greater of supply air and at least 70%
OA. You're saying the rooftop units have less than 50% OA (and I would
think they're much lower than that), so the baseline systems do not need
energy recovery.

I'm curious, how would you prorate the heat recovery effectiveness? I
frequently model air handlers as having their own ERV when they actually
receive OA from a common ERV.

Regards,
Bill

William Bishop, PE, BEMP, LEED(r) AP | Pathfinder Engineers & Architects
LLP
Mechanical Engineer
 
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Please strive to live sustainably.
        
-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chris Jones
Sent: Wednesday, September 22, 2010 7:25 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] ASHRAE 90.1 Baseline building question

The project has 4 rooftop units, and one ERV that provides OA to the 
four roof top units.  Except the ERV only provides 50% of the minimum 
OA for each of the four rooftop systems.  DOE2.2 and DOE2.1e do not 
seem to handle heat recovery in a make-up air system using the 
OA-FROM-SYSTEM command.  The way I typically handle this arrangement 
is to prorate the heat recovery effectiveness and the ERV fan power 
to each of the 4 roof top systems.  The 4 rooftop systems have 
typical OA % for an office building - less than 50%.  My 
interpretation of 90.1-1999 Section 6.3.6.1 is that the ERV has more 
than 5000 cfm and more than 70% OA (the ERV is 100% OA), therefore 
the Budget building ERV requires heat recovery at 50%.  To model 
this, the Budget building will have prorated heat recovery at the 4 
roof top units - again because one can't properly model a make-up air 
system with heat recovery using equest (DOE2.2) or DOE2.1e.

Does this make sense?

And thanks for all the help provided by this group!




Chris Jones
14 Oneida Avenue
Toronto, ON M5J 2E3.
Tel.  416-203-7465
Fax. 416-946-1005


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