[bldg-sim] need a reality check for modeling fan energy of a 100% CV reheat system

Peter Simmonds peter.simmonds at ibece.net
Mon Jun 5 07:05:06 PDT 2006


Tom, there are several ways to accomplish this.

Use a VAV system with return fans and set the economizer to 100% OA

You could also set the specifics of the exhaust system as a dedicated
exhaust, but watch the fan power on this one.

You could also increase fan static pressure to emulate two fans.

 

Peter Simmonds Ph.D.

Associate
IBE Consulting Engineers

14130 Riverside Drive Suite 201

Sherman Oaks, CA 91423
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f:    (818) 377-8230
m:  (818) 219-1284
IDEAS FOR THE BUILT ENVIRONMENT <BLOCKED::http://www.ibece.com/> 

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From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Thomas
White
Sent: Saturday, June 03, 2006 8:10 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] need a reality check for modeling fan energy of a
100% CV reheat system

 

Hello everyone:

 

I'm modeling a 400,000 sf hospital with 100% outside air and constant
volume reheat system. The priority is infection control and not energy
savings, so the total ventilation load is HUGE. 

 

Here's my question. I've input all the CFM values for each supply air
handler (about 500,000 cfm combined), but -- strictly speaking -- there
is no return air since all air is exhausted. So, how do I account for
the kWh of all the exhaust air handlers? The exhaust air handlers run
about 2/3 the CFM of the supply air, with the difference made up by
exfiltration and a multitude of special-purpose exhaust fans (in the
labs and so on).

 

I figure my only real option is to treat the exhaust air handlers as
electric loads in the building. They don't contribute to the heating and
cooling loads, but they are a significant energy use.

 

Can you think of an alternate way to model exhaust air fans to account
for their energy use while eliminating any energy use for return fans?

 

...Tom

 

 

Thomas J. White, P.E.
Associate

Lead Engineer, Energy Services

LEED(r) Accredited Professional


 <http://www.glumac.com/> 

________________________________

320 SW Washington, Suite 200
Portland, OR 97204-2640
T.  503.227.5280  F. 503.274.7674  D. 503-345-6246

Thinking. Inside the building.
http://www.glumac.com <http://www.glumac.com/> 

 

 

 

 
 
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