Mr. heater exhaust vent

[rclore]

Hi, this is my first post so wanted to say hi to everyone. I just purchased an
80,000 btu mr. heater. I had a older house furnace there previously and it had quit working. The old furnace had a 5in.pipe duct going through the wall. It had the the double walled pipe in a pipe that is still in good condition. The new heater 4in. duct lines up perfect with the old pipe going through the wall. Can I just get a reducer to go from 5in. to 4in. Right now it is a straight shot to the back of the heater but my manual says it bad a minimum length of 5 ft. Mine is only about 36in.Can I do it luck this or do I have to add a couple 90 elbows with a straight piece to get it to longer than 5 ft. Sorry for the long question.
Roy

 

[Pruittx2]

That horizontal run needs to be 5 ft, and cat 3 stainless.

 

[rclore]

Thanks. I wasn’t sure if I could reuse what’s there. It’s galvanized but in good condition.

 

[pbon]

Not up to code today. But it worked pretty well before the code change. The typical SS horizontal vent kit costs about $300 and has 5’ of pipe with a 45. Angle the heater at 45 and use the 45 elbow and space the heater out from the wall just the right amount and it works. I just installed one. Took some trial and error to locate the heater. The exhaust pipe must end 12” past the outside wall and be a certain distance from roof overhangs and windows or doors.

 

[rclore]

Yea that’s crazy expensive for only 5 ft. of pipe. I would need a 2-90 elbows anyhow because of where mine has to go through the existing 5 in. vent. My gas line, electrical, and hole through wall won’t work for turning it 45 degrees. Thanks for the reply.

 

[38Chevy454]

Yes, that SS vent pipe stuff is expensive. Went through that with my 80K Mr Heater unit installed. The good thing is the SS should never corrode, so however many years form now if the heater is replaced, the vent pipe should still be good.

 

[rclore]

Sorry for asking the same question but when I look at this stainless steel kit no. F102860 it only comes out to 31 in. in length, 37 in. with the elbow. How is everyone using this to get 5 ft. out of it. Are you buying 2 kits? Can I just run this straight out the back of the heater and right through the wall without any elbows because I really don’t need them. Or do I have to get 2 elbows and extra pipe to offset the heater to get this 5 ft. minimum length?
Thanks for any replies.

 

[pbon]

I bought and installed one and the centerline measures out to about 5’

 

[rclore]

Do you know what that part no. is? Because the F102860 only has 2 straight pipes, 1 that’s 12 in. and 1 that’s adjustable from 6 in. to 19 in. That’s the only kit that’s stainless steel and made for horizontal mounting. What am I missing.

 

[pbon]

That the description is not perfect and you are not adding everything up right. You have accounted for 31 inches. The 3 to 4 inch adapter is probably 9 inches, the elbow is probably worth 10” and the exhaust tee is probably worth 10 inches. Anyway, it works and just barely makes the recommended 60 inch minimum and Mr. Heater sells it as a kit for this purpose. My adjustable section is fully extended to make the 60 inches the way I added it up.

 

[rclore]

Thanks for the reply, I’ll give it another look.

 

[julietbaney]

You can run those radiators at a lower temp and will have programming flexibility on the temperature. Research your condensing boiler choice. Go with a manuf that actually MANUFACTURES the boiler and has proper tech support for it. B-W does not build a condensing boiler. I think they, and a number of other companies, private label the Korean Kiterame unit. I am not certain of that, so please confirm prior to decisions. You could eliminate the chimney by going hi-eff. You could also simply drop a proper size liner or a new B-vent down the existing chimney. If you can install a boiler this too would fall in your capabilities.

 

[oldeck]

What is the purpose of the horizontal length being 5'?

 

[Gizzi]

What is the purpose of the horizontal length being 5'?

The manufacturer has probably determined that a 5 ft length will establish proper draft and combustion. Too short of a flue pipe could end up allowing too much oxygen to the burners and not a good fuel mixture.

 

[Showkey]

zombie warning………Very old thread:

The instruction may vary slightly ……but……..MR Heater says:

The minimum horizontal vent length is 3 feet (914mm).

3 feet minimum is easy to achieve 8-12” unit from the wall plus 5-8” wall thickness plus least 12” out past the wall.

6’ in my instructions is clearance to corner and clearance gas and electric meters.

 

[Jason Steel]

zombie warning………Very old thread:

The instruction may vary slightly ……but……..MR Heater says:

The minimum horizontal vent length is 3 feet (914mm).

3 feet minimum is easy to achieve 8-12” unit from the wall plus 5-8” wall thickness plus least 12” out past the wall.

6’ in my instructions is clearance to corner and clearance gas and electric meters.

Any guess as to why it needs to be 6 feet from the corner? I understand the minimum run length but I don't get that. Currently looking to have the 50k BTU Big MAXX installed in my finished garage and am kind of particular about how it'll look.

 

[pbon]

Interesting. The 5’ exhaust kit will make 6’ from the corner plus 18” sticking out the wall a problem. Buy some extra pipe if strictly following instructions.

 

[fitter30]

Cat3 meets spec for the flue gas is acidic. Galvanized would rot out in no time. Pay close attention to the instructions for pitch of the flue.

 

[Aileron]

Any guess as to why it needs to be 6 feet from the corner? I understand the minimum run length but I don't get that. Currently looking to have the 50k BTU Big MAXX installed in my finished garage and am kind of particular about how it'll look.

If the 6' is meant for the oulet, It may be for backdraft of wind whiping around a corner. If its for a elbow inside, 6' may be a bit excessive.