Kitchen Hood Venting & Pressure
Kitchen Hood Venting & Pressure
(OP)
I was hoping someone may be able to educate me on the static pressure differences in venting a kitchen hood up towards the roof or down towards the basement. Why would a blower be warrantied in the first arrangement, but not the second? Much appreciated....





RE: Kitchen Hood Venting & Pressure
Static pressure differences? For each elevation increase of forty feet, there is about a 0.5 in. w.c. pressure drop (depending on where you start - this is approx. sea-level data). It's thermal differences that create a flue, though. With all temps equal, pressure drops through a duct rise should be equal to pressure drops at the same gradients outside the building, creating a static condition, or no air movement within the duct.
I have no clue if this answers what you ask - I don't want to spam you with extra information...
RE: Kitchen Hood Venting & Pressure
We're working at 8000' so I'll assume 48' height change is equal to .5" w.c. change. This means a .08" w.c. increase from the hood down to the basement in my desired ducting arrangement. Do blowers not work effectively when attempting to move air from a lower static pressure area to a higher pressure area? Even in such a small pressure differential? Thanks again....
RE: Kitchen Hood Venting & Pressure
RE: Kitchen Hood Venting & Pressure
RE: Kitchen Hood Venting & Pressure
RE: Kitchen Hood Venting & Pressure
RE: Kitchen Hood Venting & Pressure
RE: Kitchen Hood Venting & Pressure
NOTE: be prepared for a nice cold draft blowing back onto the stove during winter if there's not a good backdraft damper. Hopefully it won't be strong enough to blow out pilots and cause an explosive hazard.
In the end, I personally would bash up a little sheetrock, duct it right and preserve the warranty. But that's just me. If it's your own residential, I think we should be allowed some leniency and to assume some risk - it's our own necks at stake. If you're performing a service for a customer, you should (in fact, you're obliged to) do it the right way without question.
RE: Kitchen Hood Venting & Pressure
RE: Kitchen Hood Venting & Pressure
RE: Kitchen Hood Venting & Pressure
But with increase in static the blower will reduce its intake cfm, thus lowering its exhaust.
How much you will get at the end of the duct?
1. Calculate total static
2. Read fan curves and read the cfm against the calculated static loss on the correct curve.
3. This is the cfm you will get at the fan.
This is how I would do it.... Always looking for better ways....
Vic