[anesthes]

Installing this heater in my garage. Not a plumber/gas fitter.

I don't have access to the attic space, so I need to do everything either from under the ceiling or above the roof.

Can cut a square out of the drywall and screw the fire stop / support plate to the ceiling ? Or must it actually go inside the attic? I was hoping I can sandwich some strapping on the attic side of the drywall to give some backing to screw the plate to.

In regards to the insulation spacer, I figured I'd just put some 6 or 8" around the Bvent inside the attic from the top to keep insulation away from the b vent. I figure I can slide this in from the roof side.

Does this sound acceptable / code compliant ?

 

[anesthes]

I have never seen a plate like that for a gas water heater. Follow the MFG instructions.

It's not a water heater, it's an 80k shop heater.

That's the plate that came with the Mr. Heater installation kit. The instructions are not super helpful. The product video from the manufacturer has this amazing graphic.

The installation instructions say "refer to local codes".

I found this image online, however I cannot tell if it shows the fire stop attached to the drywall or in the attic space, or if it's even code.

 

[anesthes]

You need a double wall flue from ceiling drywall through the roof.

verify local code addenda.

B vent is double wall.



I have the correct kit supplied by the manufacturer of the heater for a vertical vent. My question is if the fire stop plate can be oriented below or above the ceiling .

 

[anesthes]

How much room between the ceiling and the roof?

About 30".

 

[anesthes]

I would cut a hole near by so you could work up there off a ladder and close the hole fix the drywall later.

I could do that. I'm still curious if the block could go on the ceiling though, as I'd have a 1" hole around the pipe. Seems the inspector would have an issue about a gap around the pipe even if it is blocked farther up, you would think a fire in the garage could spread to framing members in the cavity ?

 

[anesthes]

You can't have a gap around the firestop. It needs to be tight against the vent. (less than ⅛" is fine for tolerance.) It doesn't have to be in the attic space, you can install it on the underside of the drywall. You must maintain that 1" clearance to all combustibles youth, including framing and roof deck. Those tabs are to insure you have that gap at least at the fire stop.

Perfect. So I can cut both the roof and ceiling to slightly larger than those tabs, mount the plate to the ceiling and then put a larger pipe over the b vent to keep insulation and critters out of the "gap" it sounds.

Perfect thank you!

 

[anesthes]

Yes, except you have the wrong fire stop if it's not tight to the pipe. We use those ones because they are cut perfect, and are safety listed making inspectors happy. The gap isn't about critters, it's about keeping fire out for the rated time, a second pipe wouldn't do that.

Got it. The stop fits snug around the double wall pipe. I see that the tabs are for the 1" clearance from that. I thought about putting another stove pipe around the tabs to keep insulation/rodents/whatever out of the 1" clearance space, but if that's not necessary I won't. I'll cut back the insulation and drywall several inches just to be safe.

Is there a trick to marking the roof to cut the hole in the correct spot ? Like it would be great if I could use some sort of laser mounted in the 90* bend that would project the dead center on the roof sheating above so I can line up the hole saw.

Thanks!

 

[anesthes]

Finished this up. called for an inspection. Looks good based on the illustrations in the manufacturer's docuntation. Single wall to B vent adapter, Bvent through the ceiling, about 20" above the roof (4:12), storm collar, rain cap. I cut a square in both the ceiling and roof deck significantly larger than the double wall B vent to allow greater than 1" clearance. I liked the fire stop/support plate design, it has an integrated strap that goes around the bvent, allows you to adjust height from the finished side and then clamp it down. Better than the ones they sell at Lowes.

 

[anesthes]

Passed inspection this morning.

 

[anesthes]

Looks good. Sorry, been too busy to look at the forums much.

I don't see a switch for the electrical. You need something within sight to turn it off.

That's because the ceiling is so tall it wasn't in the frame of the photo.

You can see it in this photo:

 

[anesthes]

Fantastic. I might be in love.... [emoji28]

First bay has my 2 post 'service' lift. The second bay the four post for oil changes and storing two cars. Third bay is for general parking.

Been on this project just over a year. Getting burnt out!