Category III Horizontal Vent

[k-os]

I recently (yesterday) had a Mr Heater Big Max 50,000 BTU heater hung, vented, and hooked up to gas in my garage. I had bought the CAT III vent pieces from Menards along with the below thimble. Note that the company I had doing the work agreed to using materials I supplied, along with I would be paying for any other materials they provided.

Thimble

My understanding is that clearances for single-wall CAT III vent is 6". With the thimble in place the outside "square" of the thimble satisfies that requirement and the inner section of the thimble essentially treats the vent as a double-wall, requiring minimum 1" clearance.

The installer chose to install a horizontal vent with B vent, which I know is not correct and I've contacted them about.

Is my understanding of the thimble use with the CAT III vent correct?

Thank you.

 

[danski0224]

The instructions for the wall thimble will specify clearances.

You may need to go to the vent product manufacturer website.

This process will remove assumptions.

 

[k-os]

From what I’ve found the thimble and vent manufacturer specifies a 6.5” diameter or square cut-out in the wall for the thimble. Still waiting to hear back from the company that did the install. Talked to them this morning and the said they would look into the clearances for it.


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[fitter30]

Cat3 should be stainless with a 1/4" per ft pitch back to the furnace.

 

[danski0224]

From what I’ve found the thimble and vent manufacturer specifies a 6.5” diameter or square cut-out in the wall for the thimble. Still waiting to hear back from the company that did the install. Talked to them this morning and the said they would look into the clearances for it.


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So, you are unwilling to at least look it up for yourself and rely on the contractor that failed to install it right the first time to check it for you?

That makes perfect sense.

 

[Showkey]

Interesting........in my area I go to the home show each year.
Garage heaters are popular and are installed in 80% of the new homes in the show.

Each year I look at the garage installs and HVAC and water heaters with interest.

All the garage heaters are installed with B vent.......no matter the orientation. This is 10-12 builders using multiple heating contractors. Obviously these building at new and inspected. So appears not everyone in on board with CAT III.

My personal garage heater was B vent and was 20 years old when I moved in. It was paper thin from rust and corrosion. I replaced with B vent and then a few years later replaced with CAT III when I replaced the heater. The new B vent was pretty rusty for only 3 years of use. Both the new heater and CAT III were the Menards ........same pipe and thimble as the OP.

Now a few years later that CAT III pipe looks perfect with no rust or corrosion as you would expect from SS.

 

[k-os]

So, you are unwilling to at least look it up for yourself and rely on the contractor that failed to install it right the first time to check it for you?



That makes perfect sense.

I'm not following. I just posted that I found the manufacturer installation instructions. I'm relying on the contractor to correct the issue. If they are working in HVAC all day, everyday I expect them to be able to do this job correctly and up to code.

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[thammel]

I installed my reznor UDAs a few years ago and the instructions specifically called out type 3 stainless vent pipe. I did a horizontal run and the type 3 was not cheap at all. It cost a lot but will last forever.

Tom

 

[finn]

I installed my reznor UDAs a few years ago and the instructions specifically called out type 3 stainless vent pipe. I did a horizontal run and the type 3 was not cheap at all. It cost a lot but will last forever.

Tom

The rules changed a number of years ago.

I have two identical BM hanging heaters in different buildings. The first one allowed B vent for a horizontal exhaust. The second one, purchased a couple of years later, specified the more expensive Cat lll.

There are a number of threads here on this.

 

[k-os]

I took out B vent out yesterday, patched the old vent hole, and replaced the siding. Because of the 3” to 4” adapter the vent won’t come out in the same location. They’ll be coming today to install the Cat III vent.


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[bobbyjean]

20 years is pretty good,guessing it was made in the usa then,wonder where the b-vent of today is made.{yes i can look it up but its late and i'm lazy}
codes have changed and stainless should last "forever" ..............
at three times the cost i think it should$$$$$$

 

[k-os]

The correct venting was installed yesterday. I just have to get the old hole in the wall on the interior side patched, paint the thimble on each side, and get some vinyl trim around the thimble on the exterior.