I thought *kitchen duct* should be ridgid galvanized 18 gauge material ?
Had a mechanical guy come out and offered to do it aluminum-said it would not rust…..I assume he’s referring to el cheapo stuff..
Any advice fellas
I thought *kitchen duct* should be ridgid galvanized 18 gauge material ?
Had a mechanical guy come out and offered to do it aluminum-said it would not rust…..I assume he’s referring to el cheapo stuff..
Any advice fellas
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Replies
FWIW, it's going to br 4" H x 13.5 W.
Goes vertical about 6 up, the goes horizontal ontop of the cabs 3' then makes a L for about 2' and makes another L straight to the outside of the exterior wall.
Seen a lot of stovetop fires where the cheap aluminum melts and allows the grease fire burn in the cabinets or attic. Seen galvanized ones hold up and limit the spread of hood fire.
you've seen alot of hood fires?
jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
you've seen alot of hood fires?Insurance company wanted to know if fires were arson. I should have called them kitchen fires. It was very obvious that people forget they were cooking something on the stove. My reports observed melted aluminum that dripped down on the stovetop from the corrugated aluminum ducts.
Most were stovetop fires with hoods over them. Only saw 2 real Hood fires in restaurants, they didn't have fire suppression systems, their hoods contain the grease fire.
OK, the OP says 4"x13.5" duct. You talk about corrugated aluminum. 'Splain to me what rectangular corrugated duct looks like.
DG/Builder
Stupid me I miss, the prefab rectangular duct. Still the steel duct will not melt as fast as aluminum. Did you ever see a garage fire where the shell of the car remains with a puddle of the aluminum engine on the floor?
In a residence, there is no requirement (in most building codes that I am aware of) for the kitchen exhaust hood/duct/fan to meet any standard.
The reason being is that, as defined in the mechanical codes, residential cooking equipment is low temp, and the fumes are never heavily grease laden, such as you would see with a commercial deep fat fryer. Grease ducts, as required to serve a commercial Type I hood (for high temp, grease, with fire suppression) shall be no less that 16 ga steel, with all welded seams.
Advice? If you have a commercial kitchen in your house, you should retain the services of a licensed PE in your area to design and specify all the components necessary, and be prepared to pay handsomely for the equipment, its not cheap. Else, regular "standard", as in 20 guage, galvanized sheet metal would work well.
I took a Mechanical Code class from a guy who contracted HVAC and cooking ventilation jobs in San Francisco, places such as restaurants, McDonalds and sit-down dining establishments etc. He was the owner of the company and an engineer who did CAD prints and specs for cooking hood etc. then installed them. This was his thought on hood venting. Use stainless if possible and galvanized steel if not using stainless. Round vents are better than square. When venting hoods, don't use any horizontal piping (anything less than 45 degree). When you put the pieces together, install the in such a way that grease drippings, that condense inside the pipe, stay inside the pipe and don't run down between the joint sections and onto the outside of the flue. this last rule is accomplished by joining the top section of pipe "inside" the lower section of pipe. This is sort of contrary to most assemblies that I've encountered but I tend to agree with his suggestions and advise that others follow the above rule.
Since grease buildup can be significant inside the pipe, the potential for flue fire exists and if the flue is not made of at least 22 gauge steel or stainless then your setting yourself up for potential problems. I would suggest against using any aluminum and if your guy suggests using aluminum, then I think you should get someone who's done flues before and knows what they're doing rather than just the run-of-the-mill HVAC contractor or sheet metal guy picking up weekend work.