Question about Insert Leak, Fresh Air Intake, and Improving Efficiency

[jdlev]

Hi Guys,

Couple questions I was looking for some help with:

High Temp RTV Sealant to Seal Insert to Extension?
I installed a Century CW2900 Wood Insert close to 2 years ago along w/ an insulated chimney liner. Just did my initial burn w/ a creosote log and learned an important lesson. Always do a small burn first to check for leaks. When the creosote log started to smolder, the heat from the fire dissipated enough that there was no longer an adequate updraft creating a wonderful smell in throughout the house. Between my insert and liner, I have an extension to get more of the insert into the room (to hopefully allow more heat transfer into the room). Worked well last year, but this year between the insert and extension there's a leak. Now I know the insert can get really, really hot, so I wasn't sure if the black high temp rtv fireplace sealant could hold up to that kind of heat? Is that what I should use to fix the leak? If not, what is recommended...should I just get rid of the extension and connect the liner directly to the insert. That was my original configuration, but it only allowed about 3" of the insert to protrude into the room, so the heat transfer was diminished.

Fresh Air Intake?
I've got a problem. We have a big house, and even if we've got a roaring fire going, we inevitably always get some smoke in when we restoke the fire. Tried everything I've read on the draft thread, but still have issues. Wasn't sure if maybe a fresh air intake would alleviate some of those issues. It wouldn't be a simple install to get a 2 or 3" pipe into the chimney...not even sure where to begin as a DIYer. But maybe it'd be worth it if it could keep the house from smelling like a campfire?

Keep Less Heat From Escaping?
Here's a picture of my insert.

It has a liner of what I think are 1.25" ceramic bricks. It includes a blower, but doesn't seem to move a ton of air through a shell that surrounds the firebox. There has to be a way to drag more heat out of this thing. It seems like right now, 80% plus goes out the chimney. Is there not a way to improve the heat transfer between the insert and the inside of the house? Maybe some ac coils wrapped on the sides w/ a box fan and small pump to move the water?

Easy Starters?
Right now, I'm using a propane torch to get the fires going. We had the same problem as before...smoke leaking into house. Even w/ adding a heater and opening a door to make sure the house had positive pressure to allow the air to rise in the chimney...we'd still get backdrafts...wind or no wind. I'd really like to add a propane starter, but don't want to do anything dangerous. Are there any aftermarket starters you can add to your insert to make starting a fire easier? I typically use the firestarter sawdust things...which work ok, but an easier starter would just make using the fireplace more convenient.

 

[begreen]

Definitely do not use silicone on the flue collar. It's not meant for that high temp and may add to smoke and smell in the house. The problem sounds like weak draft. Describe the installation in detail starting with the flue.

• Is there a full length stainless liner connected to the stove?
• Is the ss liner insulated?
• Was the chimney completely cleaned including smokeshelf before installing?
• How tall is the liner from insert to chimney cap?
• Is the liner 6" round?
• Is this an exterior wall chimney?
• What floor is the insert on and how many floors in the house?
• Does the insert spill less smoke with a nearby window cracked open an inch?

 

[jdlev]

Hey BG

• Self installed liner. Connected top of liner to cap, and sealed the cap to the top of the masonry of the chimney w/ the high temp black sealant.
• Pulled the insert further into the room to aid heat transfer. That required I add the extension. Before the insert was connected directly to the liner. The extension looks like duct work, rectangular in shape, with one box that slides inside the other to allow the insert to sit more inside the room.
• I think the error I might have made was I don't remember blocking off the area between the fire box and the chimney itself while only allowing the liner to come through. The liner just hands down from the cap at the top of the chimney that it's attached to and runs all the way down to the extension and into the insert. I can't remember the name of it, but I seem to remember there needed to be something that blocked off the main chimney from the firebox with a hole cut through the sheet metal to allow the liner through? I didn't think that was all that important since the top of the chimney was sealed w/ the black goop by the cap?
• 25' long x 6" wide (want to say 8" w/ the insulation added?)
• It's a flexible insulated liner, and I'm 99% sure it's stainless.
• I can't remember when the chimney was cleaned, but I believe I did have it cleaned prior to stalled. I can't say for certain because it's been about 2 years, but I've had at least one cleaning just before or after the installation.
• The insert is on the first floor of our home with a vented crawl space below. In the crawl space, the chimney extends straight down and looks like it's a sealed section of cinder block (no vents or anything...just a rectangular cinder block base).
• I believe the base of the chimney is lined w/ brick upon which the insert sits.
• Chimney isn't connected to outer wall.
• I haven't tried cracking a nearby window open.

I'm not sure how relevant it is, but there is an old propane line that comes into the chimney. It was actually used for propane logs. It's still in the fireplace next to the insert w/ the valve off. The valve under the house that fed that line is also off. I'm guessing the old line couldn't be used to add some sort of a starter to the insert? Certainly wouldn't want to make the insert into some type of bomb if the propane failed to ignite or one of the kids turned on the valve at some random point (I've got a 3 & 4 year old that can't keep their hands off stuff, lol)

Maybe I just need to reseat the extension into the insert and make sure the connection from the extension to the liner is tight?

 

[bholler]

Ok no you cant put a gas starter in an insert. It simply is not allowed. To fix your setup pull the insert install an insulated blockoff plate and insulate the old firebox then throw out the offset box and install the liner directly to the stove. Those boxes are draft killers and lead to many problems

 

[begreen]

What he said about the offset box.^^ That most likely is the cause of this problem.

 

[jdlev]

Hey Guys...got an update for you.

Tried pulling the offset box, then got a 6" galvanized coupler to go directly between the insert and liner and sealed it with lava lock RTV sealant. Tested it with a small amount of cardboard and one of the nugget starters...seemed to work flawless and didn't see any smoke. Test it a second time today, this time with a small twig fire to get things going w/ 2 nuggets...seemed to be going well...opened the door to add some wood logs to the top, but they must have been damp because they started to put the fire out. About the same time, smoke starts coming back down the chimney from around the insert.

I tried to the seal the old damper hole using a piece of floor tile and some sheet metal...but it's far from perfect. I had to cut out the old damper to fit the 8" tube through two years ago when I installed the insert, so it's cut in a strange fashion since I had to use a grinder and didn't have an oxy torch.

I'm still not certain where the smoke is coming from, but it really looked like it was falling back down through the chimney in between the liner and chimney around the insert.. To me, that would have to come from a leak somewhere up the liner? That could cause issues w/ the draft flow...especially if the heat from the fire dissipates.

I don't know...any other ideas?

 

[bholler]

Hey Guys...got an update for you.

Tried pulling the offset box, then got a 6" galvanized coupler to go directly between the insert and liner and sealed it with lava lock RTV sealant. Tested it with a small amount of cardboard and one of the nugget starters...seemed to work flawless and didn't see any smoke. Test it a second time today, this time with a small twig fire to get things going w/ 2 nuggets...seemed to be going well...opened the door to add some wood logs to the top, but they must have been damp because they started to put the fire out. About the same time, smoke starts coming back down the chimney from around the insert.

I tried to the seal the old damper hole using a piece of floor tile and some sheet metal...but it's far from perfect. I had to cut out the old damper to fit the 8" tube through two years ago when I installed the insert, so it's cut in a strange fashion since I had to use a grinder and didn't have an oxy torch.

I'm still not certain where the smoke is coming from, but it really looked like it was falling back down through the chimney in between the liner and chimney around the insert.. To me, that would have to come from a leak somewhere up the liner? That could cause issues w/ the draft flow...especially if the heat from the fire dissipates.

I don't know...any other ideas?

Ok you cant use galvanized or rtv. Do you have a full stainless liner from the insert out the top? Is it sealed at the top? If you have those things the liner has to be compromised in some way. Regardless the system should not be used untill it is properly inspected by a pro

 

[jdlev]

Found the problem.

Bit the bullet and got up on the roof (not fun on a 3 story house). Offsets might be draft killers, but they're nothing compared to a 95%+ clogged rain cap. We have a stainless square roof cap up top with the diamond wire mesh frame to keep birds/rain out. I'm guessing the soot combined with some creosote to form the sticky substance that clogged the rain cap - even though the diamond wire mesh isn't small, and it has an extra 2-3 inches of completely open space just below the cap. We did burn a lot of pine last year, which no doubt led to some creosote build up, but burned the recommended amount of creosote logs of logs of 2 per season. Just scraped out any creosote I could out of the cap and just replaced it. Draft is obviously 10,000% better in the test fire I just started, and so far no smoke.

The cap obviously must have let out a 'bit' of smoke - but no where near all of it on top of killing the draft (which in turn killed the fire even w/ the damper all the way open). So when the fire died out due to lack of o2 and the heat from the fire dissipated, the smoke must have fallen back down through the chimney. Any minor leaks up near the cap would have pushed the smoke back down into the area outside the chimney...or maybe the 6" connector wasn't perfectly sealed up near the old damper hole, and that's what filled the area just above the insert with a very minute amount of smoke.

Either way...so far, it's been about 10 minutes since I re-lit the wood, and it 'appears' (knock on wood) that the problem is fixed. Fire looks like it's going pretty good now :D :D :D :D

 

[begreen]

Pine is not the reason. Too cool temps in the flue are the issue. When they drop below 250º they begin to condense on colder surfaces like the cap screen and upper part of the chimney. Typically this is from burning poorly seasoned wood, be it pine or oak. Creosote logs just try to soften the accumulations. The are not a panacea. The chimney needs to be cleaned frequently when burning poorly seasoned wood or with a system that loses too much heat before the flue gases exit at the top.

Get the chimney cleaned asap. There are likely creosote deposits still in the chimney. And seal up leaks in the flue system down below. They also cool down the flue gases. Leaky cleanout doors are notorious for this problem.

 

[jdlev]

Ok you cant use galvanized or rtv. Do you have a full stainless liner from the insert out the top? Is it sealed at the top? If you have those things the liner has to be compromised in some way. Regardless the system should not be used untill it is properly inspected by a pro

Well....crap. I was hoping the 6" coupler I used might have been stainless, but it is in fact galvanized w/ the 2 tappered ends inserted into both the stove and the insert (male to female connection both ways). When I said RTV...I meant the lava lock sealant. It says it's for use on wood stoves and inserts...so hopefully that won't cause any issues.

Glad that I kept the offset. Since that is for sure stainless...I guess the best thing to do is have a pro come out, sweep the pipe, put the offset back on, and go from there.

 

[begreen]

Have the sweep bring out a 6" section of ss rigid pipe or liner. That can be crimped on both ends to make a couple.
Lava Lock is just silicone RTV with a 650F rating. The liner and flue will get hotter than that. Don't put anything on it.

 

[jdlev]

Pine is not the reason. Too cool temps in the flue are the issue. When they drop below 250º they begin to condense on colder surfaces like the cap screen and upper part of the chimney. Typically this is from burning poorly seasoned wood, be it pine or oak. Creosote logs just try to soften the accumulations. The are not a panacea. The chimney needs to be cleaned frequently when burning poorly seasoned wood or with a system that loses too much heat before the flue gases exit at the top.

Get the chimney cleaned asap. There are likely creosote deposits still in the chimney. And seal up leaks in the flue system down below. They also cool down the flue gases. Leaky cleanout doors are notorious for this problem.

Ah...didn't realize the lower temps could cause that. There were a lot of times last year when we would use the fireplace during a cold rain...not sure if that would also have that type of impact. We don't have a cleanout door on the fireplace...just the insert. However, there is a small 1" hole that comes from under the house that has the old propane line run through it. Was actually considering capping the line under the house, and then using the hole as a fresh air line since our crawl space is vented pretty heavily.

I forgot to mention...the liner is insulated and stainless steel.

 

[jetsam]

I'd consider insulating the liner, maybe with poured-in perlite or vermiculite.

As begreen said, low flue temps are causing your buildup. Pine doesn't cause creosote.

You can address the problem with insulation, burning hotter, geting dry wood, and sweeping more frequently. Ideally, all of the above.

I'd also try to work out a flue connection system that allowed easy sweeping. I don't think that offset would work for me- but I like to sweep every time the stove goes out, usually a few times a year.

 

[jdlev]

I'd consider insulating the liner, maybe with poured-in perlite or vermiculite.

As begreen said, low flue temps are causing your buildup. Pine doesn't cause creosote.

You can address the problem with insulation, burning hotter, geting dry wood, and sweeping more frequently. Ideally, all of the above.

I'd also try to work out a flue connection system that allowed easy sweeping. I don't think that offset would work for me- but I like to sweep every time the stove goes out, usually a few times a year.

If I could sweep it out myself that would be ideal...the problem there is the insert's height only leaves about 5-6" up top. The insert has the recirculation systems (air pipes on top of the firebox), so I'm not even certain I could get to the liner going through the fireplace insert. The liner itself is insulated. I think BG was on point when he mentioned burning improperly aged wood. A lot of what we burned last year had been cut only about 3 months before.

I think the fireplace is probably going to need a bit of work, and unfortunately, non of it sounds like an easy fix. I had a draft problem (with smoke coming back into the house) at the end of last year. The clogged rain cap no doubt caused that issue. Since i don't fancy getting up on top of a 3 story house to jump on top of the chimney to reach the rain cap, I'll need to access the liner from down below.

Step 1: Fireplace Insert Slide
I just installed a bunch of rails on my deck and have the benefit of some left over aluminum balusters. I used a crowbar to get them under the insert to allow the insert to slide in and out on top of the balusters. Sliding it over the brick would have been nearly impossible. Some type of rail system that the insert could sit on to allow it to be more easily pulled in/out for cleaning would be beneficial. Just have to figure out how to anchor it in place.

Step 2: Chimney Sweep
I think I saw a chimney brush at harbor freight not too long ago. I'm guessing I'll need one that can reach 25' As long as I can keep the pipe clean, I think 90% of my troubles will take care of themselves.

Step 3. Improve Heat Transfer
There is a noticeable difference between the amount of heat transferred into the room when the offset allowed the insert to extend another 14-16" into the room. I'm not a huge fan of the offset since it doesn't provide that direct path up and out the chimney to aid in keeping that crud from collecting and can allow for lower temps - but hopefully, including a monthly sweeping of the chimney will circumvent that issue.

Right now, it relies on air transfers between the firebox and insert shell to blow heat into the room, but the air being pushed through the unit is almost unnoticeable. I'm having my 2nd floor HVAC unit replaced, so I'll have access to some free copper pipe and already have a pipe bender. Would be pretty easy to rig up a heat exchanger on the side of the insert complete with a fan and flow control valve. Would probably just need a blow off valve run out a nearby window for safety, and might work fairly well.

The CW2900 insert is supposedly rated for up to 75,000 BTUs an hour. That might be true, but it sure feels like 95% of that is going out the stack.

 

[bholler]

If I could sweep it out myself that would be ideal...the problem there is the insert's height only leaves about 5-6" up top. The insert has the recirculation systems (air pipes on top of the firebox), so I'm not even certain I could get to the liner going through the fireplace insert. The liner itself is insulated. I think BG was on point when he mentioned burning improperly aged wood. A lot of what we burned last year had been cut only about 3 months before.

I think the fireplace is probably going to need a bit of work, and unfortunately, non of it sounds like an easy fix. I had a draft problem (with smoke coming back into the house) at the end of last year. The clogged rain cap no doubt caused that issue. Since i don't fancy getting up on top of a 3 story house to jump on top of the chimney to reach the rain cap, I'll need to access the liner from down below.

Step 1: Fireplace Insert Slide
I just installed a bunch of rails on my deck and have the benefit of some left over aluminum balusters. I used a crowbar to get them under the insert to allow the insert to slide in and out on top of the balusters. Sliding it over the brick would have been nearly impossible. Some type of rail system that the insert could sit on to allow it to be more easily pulled in/out for cleaning would be beneficial. Just have to figure out how to anchor it in place.

Step 2: Chimney Sweep
I think I saw a chimney brush at harbor freight not too long ago. I'm guessing I'll need one that can reach 25' As long as I can keep the pipe clean, I think 90% of my troubles will take care of themselves.

Step 3. Improve Heat Transfer
There is a noticeable difference between the amount of heat transferred into the room when the offset allowed the insert to extend another 14-16" into the room. I'm not a huge fan of the offset since it doesn't provide that direct path up and out the chimney to aid in keeping that crud from collecting and can allow for lower temps - but hopefully, including a monthly sweeping of the chimney will circumvent that issue.

Right now, it relies on air transfers between the firebox and insert shell to blow heat into the room, but the air being pushed through the unit is almost unnoticeable. I'm having my 2nd floor HVAC unit replaced, so I'll have access to some free copper pipe and already have a pipe bender. Would be pretty easy to rig up a heat exchanger on the side of the insert complete with a fan and flow control valve. Would probably just need a blow off valve run out a nearby window for safety, and might work fairly well.

The CW2900 insert is supposedly rated for up to 75,000 BTUs an hour. That might be true, but it sure feels like 95% of that is going out the stack.

It would be much easier to just remove the tubes and baffle and clean up through the unit.

Do you have an insulated blockoff plate and insulation behind the insert?