I have the largest heaviest Wolf hood hanging from an extension. I can relate that the extension is pretty hefty, and should be tied to real framing structure above it. (I suggest GRK type structural wood screws for good strength, at least in the corners.) The hood is then bolted to this extension as you note. I believe the hood would be difficult to bolt to it if it were necessary to put free nuts above the bolts. This is because the hood will have a sheet metal top. The nuts should be welded in place on the extension after alignment with the hood through holes, or if the steel is hefty enough, tap the steel. ("Only three threads matter.")

I see no reason why your approach would not work, given minimal analysis or good experience in strength of materials. You will be trading time for money, and because you won't start out with the tooling required to assure alignment and fit, this time may be significant.

This is the time to also plan the path of the duct through the framing.

Installation of my hood required use of a hydraulic lift used for installing ceiling sheetrock, due the the weight of my hood and only two guys, one of which was me. I think four regular guys could hold it in place while a fifth inserted the bolts, or just the two guys who delivered my 48-inch Sub-Zero, but the latter pair would likely get angry if it took very long to get the bolt holes aligned for bolt insertion.

Also, my peninsula not yet present. If one has to work above an existing counter, hood support and reach to the bolt locations may be difficult, or at least require some planning and temporary support structure.

My delicate hood (made for Wolf by Independent):

kas

Thanks Kas

That looks the same basic model (absent bar and obviously slightly shorter. I like you comment on 3 threads - straight from Shigley. No idea who makes them for Wolf now - Independant seems to have been swallowed some years ago without a real trace.

Well I pulled the trigger on the hood as the price was to good to pass up - $660 with the internal blower. I also picked up a new in box remote external blower (Wolf 1500CFM 804701 $300). Figure I can resell whichever I don't use. Calling around to get prices for the duct covers was the usual - you should be sitting down - 2' version $1079 1' version $800. I'm going with the frame as described above. Will have to see if I splurge for 80/20 or just get angle iron or box tubing - I have a mig welder and a oxy accet torch so no problems, also a full machine shop so any mitering etc is easy.

I'll have to decide on the internal or external blower - probably go external. the space it will go in is new construction so framing can be dealt with easy enough. The duct length will not be all that long - cathedral ceiling about 10' plus the roof joists means all of about 4' of duct (not enough to put in a silencer), straight shot up with slight bend to avoid the peak...

I realize these are heavy but its not really a challenge compared to the machine shop stuff I have moved single handed - 2000# bridgeport, 3500# lathe, biggest thing is 4000#, use the egyptan method - lots of cribbing block things up in small steps till you get it positioned add bolts remove cribbing all set.

Paul

Sounds good; don't forget to include a way to get inside the cribbing to insert the bolts.

You will also need to consider an MUA system for your flow rate. Wide open windows will probably not be pleasant in MA year-round.

The actual goal is to not disturb the rising and expanding plume -- just replace its air -- thereby allowing the hood to do its job of capture and containment. If the velocity is high in front of the range there could be induced turbulence at the plume edge that causes mixing of the plume into the room. Fortunately, a study of the merits of different approaches to adding MUA to a (commercial) kitchen found the under range introduction approach to be one of the better approaches (at least in comparison to some edge of the hood schemes.. And anyway, who has a wall to allocate to a giant laminar diffuser such as is typically used for commercial hood testing.

I read on this forum from someone that one of the big name range companies had a note in their instructions to not add air under their gas range for some reason I never learned. You should check your installation manual to ensure you aren't in that category.

kas