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Model the system as a VAV system with preheat. Use return fans
instead of exhaust fans. As the system is 100% OA the return fans
act as exhaust fans. Set a MIN-AIR-SACH and MIN-CFM-RATIO schedules
in the system to specify the hours when the fans run at 40%. Use
VSDs on the fans in the building and in the model. This type of
system has been used successfully at the new BC Cancer Centre for thier
lab systems. Where possible, use transfer air from non-lab systems
to provide some of the make-up air for the labs - this will save
considerable energy over 100% outdoor air.<br><br>
<br>
At 09:24 14/04/2005, JRR wrote:<br>
<blockquote type=cite class=cite cite="">You have no option, the fume
hoods have to run 24/7/365. In 1981 University of Maryland College Park
-- Chemistry Department had two grad students recrystalize an organic
compound<br>
using warmed 100% N-Octane as the solvent. They wanted to speed
things up so they<br>
put the beaker in a regular refrigerator ......... The blast wiped out
three lab rooms on the<br>
4th floor. The frig did not have a sealed explosion proof defroster fan
motor..........<br>
The classrooms were empty and the two RAs got the munchies and went
the basement<br>
vending machines for a candy bar, still the sight of their lab coats
riddled with glass cuts.....<br><br>
You can make the fume hoods a separate heating zone, supply them directly
with heat exchanger<br>
tempered outside air, and use two fan speeds occupied and vacant- hoods
closed<br>
john ross<br><br>
Peter Summons wrote:<br>
<blockquote type=cite class=cite cite=""><font size=2>OK , its Friday so
I am allowed to ask for advice and guidance.<br>
Firstly I am using VisualDoe, I am modeling the energy performance of a
200,000 sf building which has 60,000 sf of laboratories. The labs all
have fume hoods so the supply air is balanced to the exhaust air (100%
OA).. Now I have the following problem: a fan system is either on or off,
therefore the lab fans are on 24 hours a day. I would like to reduce the
exhaust flow during unoccupied periods to exhaust air from the fume hoods
at their minimum flow of 40%. Reducing the flow would also reduce the
make up of outside air to balance the flow and obviously reduce energy
consumption.<br>
Am I missing something here or does anyone have a magic trick that will
allow me to accomplish my goal. Simply said HELP<br>
</font>Peter Simmonds Ph.D.<br>
Associate<br>
<font size=1 color="#808080">IBE Consulting Engineers<br>
14130 Riverside Drive Suite 201<br>
Sherman Oaks, CA 91423<br>
p: (818) 377-8220<br>
f: (818) 377-8230<br>
m: (818) 219-1284<br>
</font><font face="Arial Black, Helvetica" size=1 color="#808080"><a href="BLOCKED::http://www.ibece.com/">IDEAS
FOR THE BUILT ENVIRONMENT</a></font><br><br>
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<x-sigsep><p></x-sigsep>
<br>
Chris Jones, P.Eng.<br>
14 Oneida Avenue<br>
Toronto, ON M5J2E3<br>
Tel. 416 203-7465<br>
Fax. 416 946-1005</font><PRE>
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