Re: heat wheels: The ACGIH Manual of recommended practice specifically says these should not be used. The following is a quote from page 10-11 of the 27th edition of the book:
"The use of a heat wheel should be avoided where there are hazardous substances in the exhaust air stream since there is leakage between the exhaust and supply air zones. To isolate these air streams, wipers are employed to seal the spaces on the upstream and downstream sides of the wheel. During the operating life of the wheel, seals must be inspected for adjustment and replacement. The casings in the energy wheel lose their effectiveness and need to be replaced after several years. The drive motor and v-belt and chain also require inspection and maintenance.
Care also must be exercised when the exhaust air stream has a high moisture content and the incoming air stream could be lower than 32 F. When it is below freezing outside, the cold incoming air could drop the wheel temperature below the dew point of the exhaust air causing water drops to form. These water drops could then freeze on the wheel causing deterioration of the wheel materials."
But it's the first line of the quote from the manual that is most important: "...there is leakage between the exhaust and supply air zones." Look hard at the mechanical drawings of the heat wheel system. To believe that thing only returns 4% of the contaminated air to the building as the manufacturers claim you'd have to believe that you can assign a section of a Jacuzzi for peeing.
In a message dated 6/21/2011 4:21:44 PM Eastern Daylight Time, kauletta**At_Symbol_Here**NOTES.CC.SUNYSB.EDU writes:
Do any of your buildings have a heat recovery wheel in the HVAC/Fume hood system? Our newest building has a heat recovery wheel installed for LEED certification but new researchers are questioning the safety of this system (energy research).
I do not understand how these systems work. The architect has forwarded some white papers, but these are vague, at best, on chemical safety data &testing.
If you have a heat recovery wheel in a chemistry building -
How did you determine it was safe to use?
Do you have chemical restrictions?
What criteria do you use for restricting chemicals because of this system?
Any help or insight you could provide is greatly appreciated!
Lab Safety Specialist
Stony Brook University
EH&S Web site: http://www.stonybrook.edu/ehs/lab/
Remember to wash your hands!
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