Vent for a Mr. Heater Maxx 50 ? (newbie - HELP! ;-) )

[Chucker]

Hi,
So I have a variation on the general questions that get asked on this issue.
Vertical vent vs, Horizontal... I understand the basics: (vertical B-vent) (horizontal cat. 3)....
Two part question... I take it that the difference has to do with heat rising up? - So vertical vent is more "efficient" and safer?
If that's the case, how can they "allow" any length of "vent connector" (horizontal run) to reach your "vent" or "chimney."? ...
and..... My heater is about 4' from exterior wall. Can I run B-Vent (or even single wall vent) through a thimble and out the wall to a vertical "chimney" at that point?
What would be the problem with that? Would the "chimney" have to be anything different than continued vent pipe? What's the difference? (if I were to do that, or run it through the roof, inside the wall?)
Thanks in advance for your thoughts!

 

[fitter30]

Single wall has a minimum clearance 18" and can't be used in a attic area. B vent 1" clearance and can be run in a attic. As to running horizontally a short run 4 ' can use either but in a shop a long run in a cold space single wall could cool the flue gas and cause condensation inside the pipe and rust it out. The manufacturer of the furnace in the install manual of what type of flue material to use is the last word and has to be used for the UL rating.

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[Chucker]

Single wall has a minimum clearance 18" and can't be used in a attic area. B vent 1" clearance and can be run in a attic. As to running horizontally a short run 4 ' can use either but in a shop a long run in a cold space single wall could cool the flue gas and cause condensation inside the pipe and rust it out. The manufacturer of the furnace in the install manual of what type of flue material to use is the last word and has to be used for the UL rating.

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Okay - I hear that. Disregard the single wall but I'm more trying to get at the fact that if I run it straight out the wall and terminate it there (the only unheated space will be in the cavity itself 3.5 inches) it says I need "cat 3" (stainless and all that). --- If I run it vertically through roof I can use B-vent (and it could have a horizontal run of several feet). -- I'm wondering if I can use B-vent, run it out the wall and then, instead of terminating it, run it vertical from there...??

 

[pbon]

The horizontal section needs to be cat3 since moisture could cause rust in that section and 20 years later it could be bade enough to allow C02 into the garage. 15 years ago, you could have run B horizontally out the wall. Today, the code is different and you can’t evade the cat3 requirement by going vertical after the horizontal section. But it’s your house and if no one is going to inspect it, you can do what you want. There are probably still a lot of B horizontals in use without issue.

 

[Chucker]

The horizontal section needs to be cat3 since moisture could cause rust in that section and 20 years later it could be bade enough to allow C02 into the garage. 15 years ago, you could have run B horizontally out the wall. Today, the code is different and you can’t evade the cat3 requirement by going vertical after the horizontal section. But it’s your house and if no one is going to inspect it, you can do what you want. There are probably still a lot of B horizontals in use without issue.

Ok - Thanks. It's interesting though as the instructions don't lay it out that way. Their section on "vertical venting" says class B and talks about keeping the horizontal run as "short as possible" (then gives a table that says up to 25' if just one elbow). - and use a drip t etc.... In any event, it won't be inspected so..... - I appreciate the input!!

 

[k-os]

The other big difference between B vent and Cat 3 vent is that Cat 3 has built in silicone seals, allowing the sections to seal to each other.

 

[pbon]

Ok - Thanks. It's interesting though as the instructions don't lay it out that way. Their section on "vertical venting" says class B and talks about keeping the horizontal run as "short as possible" (then gives a table that says up to 25' if just one elbow). - and use a drip t etc.... In any event, it won't be inspected so..... - I appreciate the input!!

I assume the instructions mean the length of the elbow since you obviously need one to go up. But you do make a good point and I don’t know the answer. I would keep asking and searching. I think if you want to go through the wall horizontally and then up, you must go through the wall and into a chimney rather than use pipe to go up.