Low capture velocity @ lab hood
Low capture velocity @ lab hood
(OP)
Lab hood has had a low capture velocity for years.
Client wants to correct situation.
sash ht-12"
hood-42"wide
Motor is 115v/230v
amps 8.8
direct drive utility set dedicated system to this hood.
average measured FPM is 35 FPM
approx. 6'-0" of ductwork
I believe motor/fan set up is wrong, any comments or advise?
Client wants to correct situation.
sash ht-12"
hood-42"wide
Motor is 115v/230v
amps 8.8
direct drive utility set dedicated system to this hood.
average measured FPM is 35 FPM
approx. 6'-0" of ductwork
I believe motor/fan set up is wrong, any comments or advise?





RE: Low capture velocity @ lab hood
RE: Low capture velocity @ lab hood
Check the following things
1. Condition of the impeller
2. Condition of duct work (leakage into the duct).
3. Position of damper (don't go by the outside marking)
4. Take actual power readings and compare with the theoretical formula BHP = cfmxTP/(6356xeff)
RE: Low capture velocity @ lab hood
Always test the fume hood using the ASHRAE-110 test and include dynamic challenges, sash movement, and thermal loading. Look into what the EPA is doing and copy their PPT testing (full sash open, rigorous test) protocols.
Avoid risk to the owner and yourself by researching the above issues and don't simply keep on defaulting to failed solutions.
RE: Low capture velocity @ lab hood
If you are considering only six feet of duct, then the next thing I would ask is why a fume hood is needed at all? If there is an industrial hygienist available, which should be easy to tell, as the sticker on the hood should have their name or initials, then contact them and ask why a failed fume hood is in use. The sticker should be updated annually, so the person responsible should be around. Before going further, talk to the IH responsible for annual cert; if no such person exists, then don't mess with it. Being it's an in-line fan on a fume hood, it might be good to talk to the maintenance mechanic (after reading the MSDS flle that is required to be maintained for the hood by law, if requirement for the hood exists).
Sounds like someone got chumped, as I've seen before, with an in-line fan. If whomever was there before and put an in-line fan and could not get 100 fpm on a six foot run, why buy ownership now?
RE: Low capture velocity @ lab hood
Andrew Gorton, MSc
Noise & Vibration Consultant
www.PapadimosGroup.com