Can i use Double wall Cat 3 piping for horizontal install?

[1SickTSI]

Getting ready to install my Big maxx 50000 btu and i will be doing the horizontal exhaust install. My question is can i use the double wall cat 3 galvanized
pipes instead of the single wall stainless steel ones that come with the big maxx pipe kit? I can get the double wall ones so much cheaper in my area.

Unless i am wrong the image below on the left looks like single wall to me. And the double wall Galvanized one is on the right which has an aluminum inner liner

 

[Gizzi]

Horizontal install must be stainless steel. Double wall galvanized is called B vent, which is not permissible in most locations for horizontal installs.

 

[1SickTSI]

Horizontal install must be stainless steel. Double wall galvanized is called B vent, which is not permissible in most locations for horizontal installs.

so all of this info is bogus?

 

[1SickTSI]

i guess i am just confussed lol i will shop around and see how cheap i can get the stainless steel ones for. I will only need roughly a 4 foot long piece and thats it, well other than having to put something on the end of it.

 

[Gizzi]

so all of this info is bogus?

Big Maxx heaters have a section in the install manual on horizontal venting requirements. Code typically refers to manufacturer instructions for vent categories other than type 1. Mr Heater states the heater is rated for cat 3 vent pipe in horizontal configurations, so you need to use stainless vent pipe.

 

[gmcgeo]

can it be done, Yes.

Should you... no.


Go by manufacture specs. If it tells you to run cat 3 ss..... then that's what you have to do. per the manufacture specs.


Prior to buying or installing, i usually find all this out before having the unit. this way i know if i can afford it or not.

 

[Bert_]

so all of this info is bogus?

It can run nearly horizontal for a distance, but you can't just terminate a horizontal run outside the wall. It needs a vertical run to pull the exhaust up.

B vent needs to operate in negative pressure because it's not sealed. Cat III has gaskets and can be positive pressure.

 

[PoorUB]

The big deal between B-vent or stainless was not the sealing or possible leaks with the joints in B-vent, but corrosion resistance. B-vent will rot out in maybe ten years depending on the conditions.

I have an 80% furnace in may garage and after 15 years the "per code", vertical B-vent was rotted out. Horizontal is worse yet because condensate in the exhaust will just lay in the bottom of the vent and rot it out.

 

[Bert_]

I have an 80% furnace in may garage and after 15 years the "per code", vertical B-vent was rotted out. Horizontal is worse yet because condensate in the exhaust will just lay in the bottom of the vent and rot it out.

That's surprising. The b vent for my house furnace and water heater is probably 40 years old. It was put in for a natural draft furnace so that should give an idea of the age. It is in fine shape except for the top foot or so which is still solid but the outer wall is beginning to rust.

Around here I see a lot of b vent used for horizontal venting. While it's not right, the pipe seems to hold up fine. Maybe not quite as long as a vertical vent like is intended, but the only ones I know that needed replaced were 20 years old.

 

[PoorUB]

That's surprising. The b vent for my house furnace and water heater is probably 40 years old. It was put in for a natural draft furnace so that should give an idea of the age. It is in fine shape except for the top foot or so which is still solid but the outer wall is beginning to rust.

Around here I see a lot of b vent used for horizontal venting. While it's not right, the pipe seems to hold up fine. Maybe not quite as long as a vertical vent like is intended, but the only ones I know that needed replaced were 20 years old.

When I was doing HVAC service I replaced a lot of B-vent I know was not twenty years old.

In my experience B-vent that is run though walls seems to hold up fairly well. Exposed B-vent rots out faster. I assume the vent that is enclosed stays hotter longer and dries out faster. Exposed, like in a shop situation, or sticking out of a of a roof rots much faster.

On my shop furnace the b-vent inside the conditioned space was bad, but when the vent hit the cold attic it was terrible! The difference was obvious.

 

[Showkey]

The B vent on my shop heater vented horizontal ( not installed by me) was paper thin and galv. Single wall elbow had perforation holes. Unknown use by the prior owner. Suspect it was less than 10 years old.

 

[1SickTSI]

I will just need to go roughly 5 feet horizontal, heater will be 2 feet from the wall, then from what i read it needs to extend 3 feet out? On the end of the pipe i may use one of those T's i see alot of people using.

So i will get the T below and make sure i have 5 foot of the pipe below?

 

[finn]

I seem to recall the code changed a number of years ago.

What was once allowed by code isn’t anymore.

Goes by the date the heater was manufactured.
Just my recollection,

 

[PoorUB]

I seem to recall the code changed a number of years ago.

What was once allowed by code isn’t anymore.

Goes by the date the heater was manufactured.
Just my recollection,

It goes by the date of installation, not the equipment manufacture date.

I have never had an inspector worry about manufacture date of equipment, only the category type of the venting required.

 

[finn]

It goes by the date of installation, not the equipment manufacture date.

I have never had an inspector worry about manufacture date of equipment, only the category type of the venting required.

Could be. It’s been several years.

There’s also a catch involving manufacturer’s installation instructions, and any unit manufactured after the cutoff date would have new installation instructions reflecting the new code requirements.

Almost a Catch 22.

Moot point , I guess, as it’s been several years, so it’s unlikely that anyone would be installing a heater eight or ten years old.

 

[PoorUB]

Could be. It’s been several years.

There’s also a catch involving manufacturer’s installation instructions, and any unit manufactured after the cutoff date would have new installation instructions reflecting the new code requirements.

Almost a Catch 22.

Moot point , I guess, as it’s been several years, so it’s unlikely that anyone would be installing a heater eight or ten years old.

No catch 22. The local code enforcement has final say.

Old heaters get taken down and move quite often.

 

[gmcgeo]

local code always has final say.