Chimney liner / cap connection - Is this correct?

[TheBaron]

The liner on my newly installed woodstove insert seems to have shifted. The top part of it looks like it has moved up and now the flange that is supposed to rest on the adapter is up. You can see the corrugated liner pretty clearly and it isn't straight. Seems to me that any driving rain, etc could easily work its way in to this joint. See attached pic.

What do you guys think? I think this needs to be fixed, but the Installation contractor says its fine...

 

[Nick Mystic]

What sort of flue liner are you using? When you say, "corrugated liner" are you referring to a stainless steel flexible liner? If so, from your description and photo it would appear that your liner is cut an inch or two too long and when the connection was made to the top of your insert the installer pushed the liner up your chimney to make the connection and this resulted in your rain cap lifting off your top plate. I recently installed a ss flexible liner in my tile flue to hook up a wood stove in front of my fireplace. After connecting my liner to my stove using a T - connector I pulled the slack out of my liner up on the roof before connecting it to my top plate. My first attempt resulted in my pulling the pipe too far up my chimney and this caused my T - connector to tilt upward down in my fireplace opening. To remedy this I only needed to loosen the hose type clamp on my top plate connection and let an inch or two of liner recede back down the chimney. This shifted my T - connector back to the correct position. In your case it appears as though the opposite happened and your pipe is being pushed up your chimney raising your rain cap up off your top plate exposing your flex liner, as you described. My top plate/rain cap system was a bit different from yours because in my case the flex liner is locked in place by a clamp on the top plate, which means if I pushed too much liner back up my chimney it would have lifted my top plate, not my rain cap as seems to have happened to you. The only way my system could end up looking like yours is if I did not lock down the hose type clamp on my top plate and was allowing my liner to "float" coming through the cap (allowing the liner to slide up through the top plate and raise the rain cap with it).

The way this type of liner system is supposed to work is for the weight of the liner to be carried by its connection to the top plate. It is the weight of the liner that holds the top plate down tight to the top of your chimney. The top plate is usually glued in place on the top of the tile flue liner using silicone caulk since drilling holes in clay tile is likely to break the tile. If the top plate is connecting directly to a brick chimney then it can usually be screwed to the chimney brick using anchors. At any rate, it should be a relatively quick and easy fix for you once you understand what is going on. It will likely be just a matter of pulling some slack out of your flex liner. locking it in place with the hose type clamp on the top plate and perhaps trimming off some excess flex liner so that you can position your rain cap back down tight to your top plate. Your cap might even have enough space available to just lower it down a bit further onto your liner and tightening it down. Just be careful you don't end up having the liner stick up into the screen opening portion in the rain cap or you will restrict your draft.

 

[TheBaron]

Thanks Nick - that should be helpful when I get up there to check. Pretty long way up in my case so I was going to ask the installer to come back and correct.

The liner is a stainless steel flex liner, made by Magnaflex. It came as a kit with the adapter and cap as well, so maybe some other folks on here who have used the same system would know if it has a way to lock the liner in place at the top, I would assume it would have to.

 

[Nick Mystic]

I looked up your Magnaflex liner kit and it looks pretty standard in that there appears to be a hose type clamp on built into the top plate that locks the liner in place, but I can't tell from the picture how the rain cap is connected since it doesn't look to have the same type of hose clamp that my rain cap has.If it turns out that your liner is in fact a bit too long and that is what is forcing your rain cap to lift up, then you do want to fix it. Not only might rain be able to get into your chimney, but your liner is also likely leaning against the sides of your clay flue liner in a number of places. When I put my flexible liner down my chimney I found it impossible to make the liner be perfectly straight as I slid it down the chimney. As it went down the curvy nature of the liner had it touching my liner in multiple spots. It wasn't until I connected the bottom with T-connector to my stove and pulled the slack in the liner back up the chimney that I was able to straighten it out and keep it off the clay flue liner. The reason you want your liner to be as straight as possible is to maximize your draft and make cleaning easier. But also it will help prevent creosote from building up inside the ss flex liner at those spots where it is touching the clay liner. The clay tile liner is going to be cold in the winter and since it will make the liner cold in those spots where the two touch it is those cool spots that will build up creosote the quickest.

 

[TheBaron]

Thanks Nick. They are coming after Easter to fix the cap and also have fabricated a better elbow to get rid of the sucking noises caused by the adjustable 45 they installed.

 

[mellow]

That doesn't look like a standard top plate, looks almost home made. Most top plates will have a locking band on them that holds the liner in place.

Another side note that looks like a bit to much creosote on that cap if this is a new install, from the liner pushing up it might be restricting your draft to much, either that or you are burning under seasoned wood.

 

[TheBaron]

This is mostly fixed up now. The elbow they fabricated is much sturdier and has no joints (welded heavy gauge stainless). The sucking noise is gone from the chimney connection, and the cap is now sitting down properly on the flue tile adapter.

I've got about 2 12hr fires worth of wood left, so hopefully that'll round out the shoulder season.

Thanks for the help on this folks.