What to use to seal venting to stove?

[madge69]

Hi all...

Last year was our first year with the pellet stove and initially we noticed a slight smoke smell upon startup. We placed tape on all the joints of the venting and that seemed to do the trick for last year. However, we've used our stove a few times so far this year and the startup smoke smell is back. I'm pretty sure it's coming from either the appliance adapter or where it attaches to the stove. The tape I have is rated to 260F, and I have some hi-temp silicone rated for 500F--intermittent. I figure I was safe applying the 260F rated tape to the outside of the double-wall venting, but right at the adapter is probably the hottest part of the whole setup. I'm wondering if that 500F silicone is the way to go (could be difficult to apply to the backside), or should I be looking for something even higher temp rated?

Please let me know what you think.

Any idea on exhaust gas temperatures or the temperature of the metal at the outlet of stove?

I'm running a VistaFlame VF100 (Enviro EF3) currently using a blend of Okies/NEWP.

Thanks...

 

[lbcynya]

You can find Permatex High Temp RED RTV at most automotive stores. This will work great. Use it generously. Here are the spec's:

TYPICAL ENVIRONMENTAL RESISTANCE
Temperature Resistance Typical Values
Continuous, °C (°F) -54 to 316 (-65 to 600)
Intermittent, °C (°F) -54 to 343 (-65 to 650)

 

[SmokeyTheBear]

Nothing less than 500°F sealant should be used at the adapter.

There are many sealants that can be used just be certain that the maximum continuous rating is no lower than 500 °F (this gives a bit of leeway too allow the system to shutdown because the exhaust blower should thermal off and the stove shut down due to loss of vacuum).

 

[tjnamtiw]

Rutland makes a 500 degree RTV sealant that many of us use. It can be purchased at ACE hardware and others. That sounds like what you have. The downside is that it's a beech to get off. Others additionally or instead of the RTV, use a metal foil tape with a very aggressive tack. I got mine from McMaster when I was ordering some other stuff. http://www.mcmaster.com/#metal-tape/=ek4yx5

In my experiments with improving heat transfer efficiency in the tubular heat exchanger last year, I found using a contact pyrometer that my exhaust temp, if I remember correctly, hovered around the 140 degree range. FYI. Can't speak about your stove, though. Don't trust readings using a IR non-contact meter. Very unreliable.

 

[timjk69]

I used high temp clear. Looks alot nicer than the red stuff and never had a problem with it even right at the stove outlet.

 

[jdempsey]

I use the clear also. From rutland. You cant even tell its on there unless you are close.

I had to seal every seam with alot to keep that crap from leaking. Dont be stingy with it. Pile it on.

 

[Papelletguy]

There is something called mil PAC. Get it from your dealer or online. It cures but does not get completely hard and is rated for way higher temps than anything previously mentioned. The stuff I think is a derivative of something they used to use in steel mills. It is black in color and can be applied like caulk. I would also suggest scrapping your pipe and redoing it if you used the cheap duravent stuff (like I did). It just leaked everywhere. No amount of tape or sealant could have stopped it. That stuff is JUNK I went to my dealer and bought the duravent PRO piping. It is all welded seams instead of crimped, has o ring seals, and is made to way higher tolerences. The difference is night and day. Seriously. It's worth the extra cost and annoyance, IMO. If you use the pro pipe you won't have to tape anything just run a small bead of rtv or mil PAC on the lip inside the female end and push together. Done deal for many years.

 

[madge69]

There is something called mil PAC. Get it from your dealer or online. It cures but does not get completely hard and is rated for way higher temps than anything previously mentioned. The stuff I think is a derivative of something they used to use in steel mills. It is black in color and can be applied like caulk. I would also suggest scrapping your pipe and redoing it if you used the cheap duravent stuff (like I did). It just leaked everywhere. No amount of tape or sealant could have stopped it. That stuff is JUNK I went to my dealer and bought the duravent PRO piping. It is all welded seams instead of crimped, has o ring seals, and is made to way higher tolerences. The difference is night and day. Seriously. It's worth the extra cost and annoyance, IMO. If you use the pro pipe you won't have to tape anything just run a small bead of rtv or mil PAC on the lip inside the female end and push together. Done deal for many years.

Scrap the whole venting for a leak? That sounds a little drastic, but I know what you're saying. I looked at my invoice from the dealer and they charged roughly $400 for all those venting parts! According to the invoice, it is "pellet vent pro", but it still leaks. I'm pretty sure the lion's share of leaks are right at the stove / adaptor. I searched for the mil pac stuff but only came up with software results.

Anybody ever hear of or use this product? "Seal-It-Right by Rutland" (broken link removed to http://www.rutland.com/productinfo/seal-it-right.html)

"Seal It Right is an easy to use sealant for installation and maintenance of direct vent appliances, such as gas burning systems and pellet stoves. May also be used to seal metal flues for wood and coal burning stoves. It flows to create a gasket, yet easily releases for cleaning or inspection. It withstands temperatures up to 800° fahrenheit and does not release harsh pungent odors as with some other high temperature sealants. It becomes tough and flexible with air curing and further hardens with heat. Resists vibrations, cracking, fumes, gasses, moisture and acids formed by gas combustion by-products. Due to its high solids content, it will not shrink or turn to brittle powder."

 

[SmokeyTheBear]

There is something called mil PAC. Get it from your dealer or online. It cures but does not get completely hard and is rated for way higher temps than anything previously mentioned. The stuff I think is a derivative of something they used to use in steel mills. It is black in color and can be applied like caulk. I would also suggest scrapping your pipe and redoing it if you used the cheap duravent stuff (like I did). It just leaked everywhere. No amount of tape or sealant could have stopped it. That stuff is JUNK I went to my dealer and bought the duravent PRO piping. It is all welded seams instead of crimped, has o ring seals, and is made to way higher tolerences. The difference is night and day. Seriously. It's worth the extra cost and annoyance, IMO. If you use the pro pipe you won't have to tape anything just run a small bead of rtv or mil PAC on the lip inside the female end and push together. Done deal for many years.

Scrap the whole venting for a leak? That sounds a little drastic, but I know what you're saying. I looked at my invoice from the dealer and they charged roughly $400 for all those venting parts! According to the invoice, it is "pellet vent pro", but it still leaks. I'm pretty sure the lion's share of leaks are right at the stove / adaptor. I searched for the mil pac stuff but only came up with software results.

Anybody ever hear of or use this product? "Seal-It-Right by Rutland" (broken link removed to http://www.rutland.com/productinfo/seal-it-right.html)

"Seal It Right is an easy to use sealant for installation and maintenance of direct vent appliances, such as gas burning systems and pellet stoves. May also be used to seal metal flues for wood and coal burning stoves. It flows to create a gasket, yet easily releases for cleaning or inspection. It withstands temperatures up to 800° fahrenheit and does not release harsh pungent odors as with some other high temperature sealants. It becomes tough and flexible with air curing and further hardens with heat. Resists vibrations, cracking, fumes, gasses, moisture and acids formed by gas combustion by-products. Due to its high solids content, it will not shrink or turn to brittle powder."

Yes I've heard of it, used it, and happen to have a tube of it sitting within arms length. I haven't had cause to remove anything I've used it for so I can't tell you if it does easily release or not.

I've also used the heavy duty refractory cement, that stuff is good but not something to use on pellet stove venting.

I tend to allow for more than the the manual calls for when it comes to things with fire in them.

 

[ChrisWNY]

I use the clear also. From rutland. You cant even tell its on there unless you are close.

I had to seal every seam with alot to keep that crap from leaking. Dont be stingy with it. Pile it on.

I agree, I used gobs of the Rutland clear RTV high-temp silicone to seal my PL vent air-tight. I have about 8' of 4" PL vent inside my home before it exits outdoors through a thimble. I got tired of chasing small leaks in the vent pipe and eventually just slopped handfuls of Rutland over every seam on the pipe that was inside the house. No more leaks whatsoever. I also used the Rutland silicone on the adapter area, no issues at all (then again my Selkirk 4" PL vent pipe doesn't exceed 150-160°F, at least on the outer wall of the pipe).