Quote:
Originally Posted by jyl
Braintrust, looking for advice so I don't squash myself or another.
Trying to install a 60" commercial stainless steel grease hood in my kitchen. The hood is a model BD-2 from Captive Aire.
https://www.captiveaire.com/catalog/showCatalogList.asp?cattypeid=69
It weighs around 300 lb (the website says it weighs 400 lb - but my son and I were able to lift and carry it, with difficulty, and I don't think we could do that with 400 lb) and is designed to be suspended from four threaded steel rods anchored in ceiling joists above the hood corners.
My joists are not in the right place, and I am doubtful about machine threads in wood joists, so planning to lag bolt steel channel into the joists, open side down. I've found this strut channel 1-5/8" tall by 1-5/8" wide (12 gauge) in steel.
https://www.grainger.com/category/electrical/conduit-fittings-strut-channel-framing/strut-channel-and-accessories/strut-channel
Then use channel nuts inserted in the channel and screw 5/8" threaded steel rod to that
https://www.grainger.com/category/electrical/conduit-fittings-strut-channel-framing/strut-channel-and-accessories/strut-channel-accessories?attrs=Sub-Category%7CNuts%2C+Washers%2C+and+Screws&filters=attrs
and hang the hood from those rods using steel nuts and a couple of fender washers.
The channels will be bolted to three joists, with the bolts at the ends and middle of the channels. The channel will be about 36" long, then hood is about 33" deep. The "rear" (closest to back wall) spring nuts will be about 5" forward of the rear-most bolt. The "front" spring nuts will be about 1/2" to 1" forward of the front-most bolt.
A not-to-scale drawing, side view
To lift the hood up to meet the threaded rod, I was going to rig up a block and tackle, and leave that rigging in place as a sort of backup.
Does this make sense?
I mostly see this sort of channel used to hang conduit, but have seen HVAC units hung from it as well. I found this load table from another strut manufacturer that says 12 gauge steel strut channel on 12" centers can support up to 1,100 lb of load concentrated mid-span, so that seems like plenty.
If I need to worry about the rods and nuts, I could use a pair of rods and nuts at each corner of the hood. But I'd think 5/8" threaded steel rod in tension should be hella strong. Each corner needs to support static 100 lb, or ~200 lb if the nearest one fails, or ~500 lb if some moron decides to do pull-ups from my grease hood.
Thoughts? |
There's a couple of ways to skin this with Unistrut. First suggestion,, don't use spring nuts with the slotted channel, use cone nuts. The springs get stuck in the slots if you're trying to adjust rods and brackets... Total pain. Spring nuts are good if you're using solid strut.
Your diagram is mainly sound but, as has been suggested, get L-shaped Unistrut brackets and then run through bolts through the joists horizontally. Attach the L brackets to the strut using cone nuts. The main issue with attaching to the joists is that once hung, you have no adjustment between those two rails. The only way to get some four way adjustment is to hang two Unistrut cross members from the two rails attached to the joists. That brings your supports lower of course but, that's what I recommend based on the info so far.
Depending on how your hood mounts line up with the slots, you can have the open side of the channel either up or down. My inclination would be to face the open end down so that you can slide your all thread in the cone nuts from side to side to adjust the hood. You'll also need Unistrut flat plate washers, locks and nuts to keep the all thread locked down with no spinning.. DO NOT use fender washers.
Do you have enough height to use a wire rope come along hanging from your nifty, new unistrut frame? It's hard to know what to use to lift the hood without seeing how the rod attaches to your hood and whether you can keep adjusting long rod until you're really close and then can trim the excess off.
Last thought,,,, 3/8" all thread will hold it but, consider the overall length of rod you'll have to determine if the hood will swing unless you're going to attach it to the wall behind to prevent movement.