Help Think This Through - Hanging A Grease Hood

[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?

[Zeke]

If you don't have access to the top of the joists, I say it's a good plan.
But, if you can't get above the unit, I don't understand the B & T. I'd be raising it with jacks.

[mgatepi]

+1 on floor jacks

[MBAtarga]

From your drawing - are the threaded rods exposed?
Do you have access to the ceiling (via the attic?) or is this between floors in your home?

[jyl]

No access to topside of joists, this is on first floor of a three story house.

The space between ceiling and hood, including the threaded rods and the duct elbow, will be roughly 20-24" tall. I haven't exactly figured out how high I'll mount the hood, but a tall person needs to be able to stand under the front edge without hitting their head, since the front edge of the hood will be about 6" further into the kitchen than the front edge of the range below. Ceiling is 108" high, front edge of hood is about 10" tall. That space will be enclosed with some sort of light wood frame and panel thingy, details TBA. Maybe I'll mount some shelves or speakers up there.

Jacks - hmm, I should go see what I can rent. I don't think a typical drywall lift can handle 400 lb? The jack will have to lift to about 70" above floor. It is all stairs to get in the house, so renting a jack that weighs as much as the hood would be tough.

[A930Rocket]

I’m not an engineer and did not stay at a Holiday Inn Express, but I think I would use some kind of angle iron/brackets to support your channel with horizontal bolts to the joist, vs relying on a lag screw installed vertically

Also, use a bolt through the side of the channel, with a tube on the inside to prevent crushing it.

Can you install cleats temporarily on the wall, so that you can rest the vent hood on each one as you go up. The front can be supported by a couple of 2 x 4 stiff legs. With it balanced like that, one person can hold it, while the other installs the all thread, etc.

Edit: is there anyway to wall mount it? I saw in the instructions, they have a cleat that screws to the wall, but only holds 250 pounds.

[dad911]

I've used a table lift from harbor freight to lift large heavy wood hoods. Set it where the range goes, lift and block.

[1990C4S]

Unistrut, with their hardware for hangers and threaded rod.

Blocks of 4x4 to lift it.

[908/930]

If bolting direct into the joist I would use 3/8 RSS Structural screws, should be available by the piece at a lumber store vs lag bolts. But, about the extra 150lbs on each joist you are possibly pushing your luck a little there, I'm sure you do not want to open the ceiling but doubling up another 2x8 is probably a good idea. Where is the load in relation to the ends of those joists? What is directly above the location you are installing this?

[Zeke]

Originally Posted by 908/930

If bolting direct into the joist I would use 3/8 RSS Structural screws, should be available by the piece at a lumber store vs lag bolts. But, about the extra 150lbs on each joist you are possibly pushing your luck a little there, I'm sure you do not want to open the ceiling but doubling up another 2x8 is probably a good idea. Where is the load in relation to the ends of those joists? What is directly above the location you are installing this?

He is close to the wall AFA load goes. I can see your point if this was over an island.

When I said jacks, I assumed that some custom blocking/frame work would be required. Also, when I lift something heavy like that, I have braces on hand to hold the weight kinda like the stops on a car lift. Take the hood up 18' at a time with a simple car floor jack. I've done it so I know it will work. Too bad throw away 2 x 4's cost a fortune these days as I've bought as many as 10 for a small job like what you are planning.

Since it was mentioned and you confirmed that you will enclose the portion above the hood to the ceiling, I will 2nd the idea of opening up the ceiling.

Also, you may need to check the specs. Most hoods like to be within 36" of the cooktop. And, as you said, 6" beyond the face of the range. I'm 6 feet tall so I put my hood at about 74" off the floor. That's 2" more than they wanted but too effin bad.

You will find that while cooking you lean over a bit anyway, so I could have gotten away with 72" but I think I would have felt crowded.

[dad911]

60 inch hood you are going to catch at least 4 ceiling joists and 4 wall studs.

2 screws in each, 20 lbs per screw. This is not that big a deal.

[jyl]

Originally Posted by dad911

60 inch hood you are going to catch at least 4 ceiling joists and 4 wall studs.

2 screws in each, 20 lbs per screw. This is not that big a deal.

That’s an idea. The hood only has four hanging points, one at each corner. But I can use some steel bars to add more hanging points. Distribute the load to eight points, 400/8 = 50 lb per point. Plus the wall studs.

[70SATMan]

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.

[jyl]

Originally Posted by 908/930

If bolting direct into the joist I would use 3/8 RSS Structural screws, should be available by the piece at a lumber store vs lag bolts. But, about the extra 150lbs on each joist you are possibly pushing your luck a little there, I'm sure you do not want to open the ceiling but doubling up another 2x8 is probably a good idea. Where is the load in relation to the ends of those joists? What is directly above the location you are installing this?

The joists are 2x10 (nominal). Actual height a little over 9”. Spaced 16” on center. (This is a 110 y/o house, I can’t ever assume standard sizes or spacing.)

The joists are about 12’ long span. Don’t know wood type, whatever they built from in Portland Oregon a century ago - old growth fir or redwood? The load described below is from about 2’ to 8’ along the span, measured from the exterior wall.

Directly above is a clawfoot tub. Hmm. Suppose 350 lb water, 500 lb humans (I dunno, two big people standing in full tub?), 300 lb tub, 400 lb hood, 100 lb other, that’s 1550 lb live load, area 12’ x 3’ (span plus three joists?), so around 45 psf live, say 10 psf dead, a span calculator says L/600 deflection is 12’.

I don’t know if that’s acceptable deflection in a modern house, but in this old place as long as the deflection is “on the charts” I feel content.

[jyl]

Originally Posted by Zeke

He is close to the wall AFA load goes. I can see your point if this was over an island.

When I said jacks, I assumed that some custom blocking/frame work would be required. Also, when I lift something heavy like that, I have braces on hand to hold the weight kinda like the stops on a car lift. Take the hood up 18' at a time with a simple car floor jack. I've done it so I know it will work. Too bad throw away 2 x 4's cost a fortune these days as I've bought as many as 10 for a small job like what you are planning.

Since it was mentioned and you confirmed that you will enclose the portion above the hood to the ceiling, I will 2nd the idea of opening up the ceiling.

Also, you may need to check the specs. Most hoods like to be within 36" of the cooktop. And, as you said, 6" beyond the face of the range. I'm 6 feet tall so I put my hood at about 74" off the floor. That's 2" more than they wanted but too effin bad.

You will find that while cooking you lean over a bit anyway, so I could have gotten away with 72" but I think I would have felt crowded.

Range top about 32” above floor (range is sitting on casters). The hood is what they call a low proximity backshelf model, so the lower front lip (where you’d hit your head) is only 14” below the top surface of the hood, while the rear and sides of the hood extend 24” below the top surface. There are also side panels I can install.

I’m 5’ 11”, call it 6” as a round #, so putting the lower front lip 74” high puts the top of the hood at 84”, leaving 20” from top of hood to 108” ceiling. That sounds tight for a block and tackle.

https://www.captiveaire.com/CATALOGCONTENT/HOODS/BD2/SubmittalDrawing.asp?img=drawings/bd-2

[Zeke]

Nice hood. I expect that it uses a remote fan. I have a semi remote fan (not totally at the end outside, but mid way along the duct). Cuts down on noise considerably.

I would use the end pates if there's an option.



[edit:] I just measured my Wolf range height and it's 36". 32" seems low to me. That's the typical height of bathroom vanities; kitchen counters and counter height appliances are typically 36".

[jyl]

Originally Posted by Zeke

Nice hood. I expect that it uses a remote fan. I have a semi remote fan (not totally at the end outside, but mid way along the duct). Cuts down on noise considerably.

I would use the end pates if there's an option.

Yes, 12” round duct on top. Easiest will be to use two 90 elbows and a 5’ horizontal run to take duct out the exterior wall, then mount a sideblast fan to the side of the house. It’s the garage side so I don’t much care how it looks. Inline fan is also possible, it will be on the other side of the wall. I haven’t calculated the CFMs. Specs say all ductwork has to be welded but I’m going to ignore that, this will see 1% of the use and grease that it would see in a commercial setting.

[greglepore]

Really like the high cfm fantec inlines for this application, along with their muffler...

[Zeke]

Originally Posted by jyl

Yes, 12” round duct on top. Easiest will be to use two 90 elbows and a 5’ horizontal run to take duct out the exterior wall, then mount a sideblast fan to the side of the house. It’s the garage side so I don’t much care how it looks. Inline fan is also possible, it will be on the other side of the wall. I haven’t calculated the CFMs. Specs say all ductwork has to be welded but I’m going to ignore that, this will see 1% of the use and grease that it would see in a commercial setting.

Right. Welded ductwork is only for fire code. Commercial. Use the best high temp tape. The ducts don't get very warm, but if there was a flash fire it would get sucked up into the duct.

I assume if this ever happened you would visit the garage side.

Also, will you use a damper? If not, when not in use the hood will suck air out of your house like a vacuum. To reduce this, use the correct side vent cover oriented in a way that breezes don't pass by and create a low pressure system at the terminus.

On a windy day, I can feel air leaving the kitchen.

The opposite can be true as well under certain circumstances where wind can want to enter the house. That gets complex so I'll leave it at that.

The right cover is important.
https://inspectapedia.com/BestPractices/Kitchen_Vent_Fan_Specifications.php

[mattdavis11]

I now see she is not the only one that knows how to burn groceries. She usually opens the windows, but often too late.

I'd love to have a range vent. See it and saw it, can't be that hard.