Hotdawg 45k BTU Attached Garage Install Venting Questions

mikeyy

I am installing a Hotdawg 45k BTU into my attached garage in Colorado (Denver metro area), I plan to use 3" B Vent parts using an adjustable wall Thimble thru a 2x6 wood frame wall with a horizontal termination. My questions are...
1) Their are many wall thimbles to choose from, some 3" wall thimbles are 9" square and imply that I need to frame in a square opening around the ≈3" round passage for the B-vent tube, Other 3" wall thimbles are round with an outside diameter of 7" which leaves much less air space between the ≈3" round passage and any combustible material.
The distance between the 3" vent output and the wall is about 10".
The question is: Which wall thimble should I use for this installation, the round one is much less expensive but the square one allows more air space around the B-Vent passage thru the wall?
2) Should I put some kind of "high temp" insulation in the airspace between the B-Vent passage and the normal batting insulation?
3) Should the termination be attached to the wall or should it be extended XX inches beyond the wall. This wall has a 24" eve about 15" above the location where the vent will exit the wall?
Thanks for any help...

EBEBRATT-Ed

There should be venting instructions furnished with the heater.

There are many manufacturers of B vent. Pick a good one, Hart and Cooley or whatever and stick with all parts from the same mfg. Do not mix & match parts from different mfg. Follow venting and clearance instructions furnished with the heater and the b vent and you should be fine. Keep the fiberglass insulation away fro the B vent. With the thimble you will be fine.

The eve 15" above the outlet may be too close. It should tell you in the venting instructions. If not, I would try to extend the vent

rick in Alaska

You don't want that exhaust venting that close to the overhang. There will be a lot of vapor in the exhaust in the wintertime, and it has a tendency to float right up in to the overhang, and cause moisture issues. And, if the overhang is vented from under it, those wet vapors will attack your roof sheathing.
Extend it past and it will solve a lot of issues.
Also, all the thimbles are listed for the proper clearance, so any one will work. Don't put any insulation around the b-vent as it passes through as they use that clearance for cooling to maintain the clearance listing.
Rick

kcopp

I was under the impression that if you side wall vented you needed to use stainless steel.

John Mills_5

That seems to be what many are saying. We've done a couple brands where they require stainless steel for side venting. B-vent is leaky (I know, it's a garage) and should be used for vertical venting where there is a draft to keep the flue negative.

This is what Lennox/Allied Air says about their garage heaters: If the LF24 unit heater is to be horizontally vented, a
positive pressure may be created in the vent. The unit
heater, when installed with horizontal venting, will
perform as a category III appliance. I noticed supplyhouse.com had a stainless steel vent kit for demand water heaters that would work for these little unit heaters.

John Mills_5

Modine says the same thing about the Hot Dawg: Horizontal vent configurations are Category III. For residential
installations, this requires the use of an agency approved
(UL1738) Category III vent system.

EBEBRATT-Ed

As with any appliance the installation instructions need to be read and followed.

Many times the equipment is hung or set and then the instructions are read (or worse they are not read at all). The instructions need to be read first to eliminate any hang ups.