I am doing a interior vent pipe off my pellet stove with black pipe. I bought a tube of the permatex ultra black. It is rated to 500 degrees. Is this enough? I know some say get orange. (550 degree) ... but is the black good enough since it’s rated for 500? I seen some people said their pellet vents only get 150-200 degree.
Pellet stove rtv.... ultra black..... high temp enough.
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A pellet vent pipe has plated exterior metal, it's thin. Inside that is a stainless steel inner pipe and between the two is insulation. The stainless steel is there for fighting corrosion and high temps. I know how hot the outside gets, I have no doubt but that the inside is much hotter.
Gas B vent is the same way, but it has an aluminum inner liner, no insulation in the air space ... and so it's cheaper, lighter, and will not withstand pellet vent inner temps, the Al liner will probably melt.
Black iron pipe is gonna rust fast from the inside due to high temperature corrosive flue gasses and will slowly get hot and stay hot at the stove end, a fire hazard to any nearby combustables I'd say.
I used the orange, it holds up year after year.
Gas B vent is the same way, but it has an aluminum inner liner, no insulation in the air space ... and so it's cheaper, lighter, and will not withstand pellet vent inner temps, the Al liner will probably melt.
Black iron pipe is gonna rust fast from the inside due to high temperature corrosive flue gasses and will slowly get hot and stay hot at the stove end, a fire hazard to any nearby combustables I'd say.
I used the orange, it holds up year after year.
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The black I used had very little odor which was nice for inside the house. 5 years next month and it’s holding up just fine.
Simpson Pellet Vent Pro has no insulation between the inner and outer layer. Not sure about other brands
I replaced some really old Dura Vent in 2017, easily 20+ years or more older. I took the easy way of removal, I used a sawzall I did. Not sure what brand but it has the 4 tabs that fit into recesses and require a 40+ degree twist to full lock ... but it had thin white fibrous fluff like insulation between SS inner & steel outer. I scrapped the outer steel, but found the inner stainless steel looked like chrome on the side facing the insulation but black on the hot gasses side, but the black cleans off easily with solvent like "Brake Clean" & a wrag. I kept it because it's easy to cut with snips, I'll find uses for it. It too is sealed lengthwise with a continuous crimp. I never measured the exterior OD of the Dura Vent but the line is 3" so overall must be near 3.5". I do not know that new or current Dura Vent is so insulated, but I suspect it is. I do know that it is heavier than Gas B vent and thumping a new piece it sounds stuffed, but my wire probe will not get past the crimps near the ends except far enough on the female end between the inner & outer to the crimp, there's insulation there.
Today, as I continued my replacement of the flue with new, I took note of the sealant I used in 1992 to seal the joints for the various sections (the parts you twist to adjust it) of an adjustable elbow between the flue pipe and stove, all orange RTV and still soft. I had smeared it on the exterior of the joints only. It is the hottest place along the vent, pardon the dusty stuff, it's all clean now.
Only other place I used it was outside where the pipe enters the wall thimble-passthrough. I did see my thimble is also insulated some with white fluffy stuff.
![[Hearth.com] Pellet stove rtv.... ultra black..... high temp enough.](https://www.hearth.com/talk/data/attachments/267/267805-86cb19a59b60ff2895826accbf286d2e.jpg?hash=UOVUz99Nqc "[Hearth.com] Pellet stove rtv.... ultra black..... high temp enough.")
I feel like the black will be fine too.
Today, as I continued my replacement of the flue with new, I took note of the sealant I used in 1992 to seal the joints for the various sections (the parts you twist to adjust it) of an adjustable elbow between the flue pipe and stove, all orange RTV and still soft. I had smeared it on the exterior of the joints only. It is the hottest place along the vent, pardon the dusty stuff, it's all clean now.
Only other place I used it was outside where the pipe enters the wall thimble-passthrough. I did see my thimble is also insulated some with white fluffy stuff.
I feel like the black will be fine too.
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I couldn't edit my post (#7) just above, so I'm quoting that part that I would edit.
I have since then torn into some other pieces, all were used some. The inner SS liner is 3" OD, the outer Galvume coated steel shell is 3-9/16" OD, maybe a hair over like nearer 3-5/8". There is no insulation between the inner SS liner and the outer Galvume plated shell other than air space. One newer piece was electrically welded lengthwise, no seams, both inner & outer tubes. The older sections had crimps their whole length and were sealed on ends by a simple wrap of rope seal like a door uses, but the one newest piece used a red O-ring in a formed groove to seal to the next pipe. The newer and older sections were equally compatible on each end.
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