Basement Stove Backdrafting

[kamill]

Hello all. I've been doing an incredible amount of research on this issue and the closest thread I can find that relates to my house is this: https://www.hearth.com/talk/threads/carbon-monoxide.172462/#post-2312430

To provide some backstory, we purchased this home in the Spring and the sellers left a stove from the 1920's. We exchanged it through a buyback program and got a Pacific Energy Super Classic 27. It is a ranch style house with a partially finished basement where the stove is installed. It was originally installed in our basement like this with doublewall pipes:


When the stove is cold, there is a good amount of cold air rushing down into it, so it makes lighting a fire pretty difficult. We usually use a torch to heat up the flue so we don't smoke out the basement. Once it gets going it drafts fine but if we don't run the fire 24/7 as it dies down and the flue gets cold, it'll reverse the draft and spill CO into the basement upwards of 50-75ppm. It's not backdrafting any smoke, just CO from uncombusted coals. The house is pretty tight so I installed an outside air kit in hopes that it was a negative pressure issue.


The fire does feel like it's running better with the OAK so I loaded it up for an overnight burn, got the stove top temp to 650 and closed down the damper to ~5% at 10pm. I woke up at 4:30am and my CO detector was showing 25ppm and when I opened the stove it jumped to 60 while I was raking the coals. I think the problem was only getting worse and if I had gotten up later it would have been much higher. There is also a radon mitigation system relatively far away in the basement. The house has 2 bathroom fans and a range fan, but they aren't being run at night, only after reloading the fire in the morning. The attic access is in the garage which is sealed off from the house, no other roof openings.

I'm starting to think the issue might be with the chimney or the basement just isn't designed for a woodstove, which would be sad. Here is what the chimney looks like:


Any input would be great!

 

[moresnow]

What are the wall vents next to the stove. That could be big trouble for performance and code! Is there a 6" stainless liner in the chimney? Add these details.

 

[weatherguy]

So theres no liner in the chimney just piped into flue?

 

[jatoxico]

You can try air sealing upstairs, especially things like attic stairs. Truth is though this problem is not always solvable. You describe a worst case scenario, draft reversal even with a warm stove with fuel in it.

Stack effect is the search term for here and google.

 

[Ludlow]

Nice house. the OAK running up like that almost defeats any benefit. Can you run a pipe to the end of the house at grade with the stove inlet?

 

[begreen]

Getting rid of the sharp 90 and softening it 45s will help. What is the stove pipe connecting to?

• Is there a 6" stainless steel liner in the chimney or just clay tile?
• Is there a cleanout door?
• Is this flue being shared with anything else?

Is there an attic or whole house fan or other open ceiling vent to the attic?

 

[kamill]

Getting rid of the sharp 90 and softening it 45s will help. What is the stove pipe connecting to?

• Is there a 6" stainless steel liner in the chimney or just clay tile?
• Is there a cleanout door?
• Is this flue being shared with anything else?

Is there an attic or whole house fan or other open ceiling vent to the attic?

There is just clay tile afaik, that's what I was told during the home inspection. There is no attic or whole house fan, ceiling fans in every room (6 total), 2 bathroom fans vented outside, and 1 range fan vented outside. There is a clean out door, it's right behind the stove. This is the only item using this flue.

@moresnow the vents lead to the unfinished side of the basement

The entire basement sits at this level so I can't run the OAK differently

 

[begreen]

It would help to know what the flue tile ID size that the stove is connected to.

Looks like the wall vents are to assure combustion air to the boiler.

 

[moresnow]

It would help to know what the flue tile ID size that the stove is connected to.

Looks like the wall vents are to assure combustion air to the boiler.

At least its not a forced air furnace return. I am not certain how much combustion air a boiler sys requires? Potential make up air competition? I wonder if the cleanout door is sealed or needs to be? Guessing a liner install is in the near future. What say you Begreen?

 

[kamill]

I don't mean to derail this thread but now that I went over to check out the furnace I saw the seal on the pipe into the walk has chipped off. Being new to this I'm not sure how big a deal this is? I'm actively using the furnace for oil heat while troubleshooting the wood stove.

 

[kennyp2339]

Reverse draft There are a few things you can do but it may only help when in the burning season.
1st question, when you were buying the place did the basement smell like old fireplace? This will determine of you have a stack effect issues year round, if it didn't then you may just have a pressure issue when it gets cold out.
Cold air is more dense so it sinks, warm air being less dense rises, pressure will always seek to equal itself out. What does all this have to do with wood burning? Everything.
First thing that needs to be determined is the size of the masonry flue, 6x6, 7x7, 8x8 what ever it is, and its orientation of exposure to the home, north, south, east, west, and length, but judging from the pics your +16ft. The size diameter will tell us what type of volume your running, a stove that has a 6" flue outlet that gets connected to a 8"x8" flue may not have enough volume to compensate and can only work properly when super hot to get the proper exhaust volume. Visa versa a stove that has a 8" flue outlet connected to a 6" chimney may have to much volume in the firebox and cannot get enough volume out to keep burning.
Orientation to the house would be good insight because a north west exposure is about as bad as it can get since northern side wont see as much sun (minimal radiant heating) west side for prevailing winds that will just suck more heat away.
A 6" insulated liner connected from the stove T to the top cap is the best way to go, as BG mentioned getting rid of the 90deg elbow and installing (2) 45 deg elbows to make the transition into the chimney cause less turbulence which equals better flow.
Depending on your overall height and draft (tested by a meter, .05"h20 seems to be the set chimney draft standard while the stove is running on high) you may need to add a anchor plate to the top of the existing chimney and a 3ft section of class A pipe with a fairly restrictive free cap (no mesh to clog up)
You OAK setup is not advised and can be dangerous, not only is it supply cold air to a cold stack, but in the event the stove looses draft embers can go through the oak and start a fire which would vent directly to you sill plate (house framing)
I suggest you call you local certified chimney guy and let them test the chimney draft and make suggestions.
But a insulated liner, replacement of the elbow to 45's seems to be in order here.

 

[kamill]

I popped open the clean out door and the flue is definitely clay and it measures 12"x8"

@kennyp2339 I'm not entirely sure what you meant by the chimney orientation so I made this crude drawing

I'm really considering just getting a pellet stove insert for the living room as the house is only 1400sqft and liners don't appear to be very cheap

 

[kennyp2339]

I popped open the clean out door and the flue is definitely clay and it measures 12"x8"

@kennyp2339 I'm not entirely sure what you meant by the chimney orientation so I made this crude drawing View attachment 236182
I'm really considering just getting a pellet stove insert for the living room as the house is only 1400sqft and liners don't appear to be very cheap

Flue is way to big for your stove, the issue is that it takes a lot of heat to maintain the temp inside the flue to keep things going in the right direction, once the burn enters the decay stage the coals don't produce enough heat and the chimney cools cause the denser air to seek its bottom which is your basement reversing the draft.
A insulated liner is the answer and they don't break the bank.
When considering a pellet stove remember that the pellet stove needs electric to operate, and pellets cost $$$, and the stoves need regular clean outs / burn pan scrapings, so pick a stove with the best reviews and easiest clean out method, plus takein account of the noise, top end stoves are made pretty quite though from what I understand.
A few years back home heating oil was in the $4.00 a gal range, it was a cold winter and the cost of pellets shot sky high also, supply and demand so keep that in mind.

 

[weatherguy]

Pellets stoves ain't cheap either, liner will be a lot cheaper.

 

[kamill]

Any suggestions on liner brands and diameter? Can a stainless steel liner be run through the existing clay one?

 

[begreen]

I popped open the clean out door and the flue is definitely clay and it measures 12"x8"

@kennyp2339 I'm not entirely sure what you meant by the chimney orientation so I made this crude drawing View attachment 236182
I'm really considering just getting a pellet stove insert for the living room as the house is only 1400sqft and liners don't appear to be very cheap

Yep, there is problem #1. You are feeding a stove that requires 28 sq in flue into 96 sq in.. I will bet the manual warns not to do this. This setup needs an 6" insulated liner. Yes it can be run inside of a clay pipe. Woodland sells Champion which is a relabled Ventis liner. This would work if the ID is a true 8". but verify that. If the actual ID is 7" x 11" you may need an insulated oval liner.
https://www.woodlanddirect.com/Chim...n-Pre-Insulated-Easy-Flex-Chimney-Liner-Kit-6

FYI, a good pellet stove is not cheap either. Is there a possibility of moving the wood stove upstairs instead?

 

[kamill]

Thank you all for this valuable information! I'm not sure how the previous homeowners ran their wood stove for 20+ years on this flue liner

 

[begreen]

Thank you all for this valuable information! I'm not sure how the previous homeowners ran their wood stove for 20+ years on this flue liner

Hard to say, perhaps poorly?

 

[Hogwildz]

The prior stove from the 20's may very well have had 8" requirements if any requirements at all. Was prolly constantly fed, and never has a chance to revers draft.

 

[Bad LP]

Hard to say, perhaps poorly?

I was thinking that they didn't run it.

 

[Chas0218]

There is just clay tile afaik, that's what I was told during the home inspection. There is no attic or whole house fan, ceiling fans in every room (6 total), 2 bathroom fans vented outside, and 1 range fan vented outside. There is a clean out door, it's right behind the stove. This is the only item using this flue. View attachment 236173

@moresnow the vents lead to the unfinished side of the basement View attachment 236174

The entire basement sits at this level so I can't run the OAK differently

You need to get rid of that OAK piping and change it to the semi rigid. That stuff you have right now is not UL listed and will ignite at high temps. Also how tall is the chimney? That chimney needs a liner to have that stove working right. If I had to guess it is too big and doesn't heat up enough to properly draft.

 

[Pertzbro]

For what it's worth, I have a unique custom fireplace in the basement with 35+ foot of clay tile and a modern insert on the main level with 25+ feet of liner in a masonry chimney. I turn off my radon system in the winter. I felt that it helped create negative pressure or helped reinforce the stack effect. I wouldnt say it was a cure all for me, but it does seem to help.

Could be a placebo effect - but honestly I'm more worried about reverse draft and a nasty smelling home than radon 5 months of the year.

As stated above - get that thing lined. It will help safety and efficiently by drafting much stronger. You'll notice a huge difference in how your stove operates. I'd go a foot or two above the masonry.

 

[Pertzbro]

Where does your boiler vent to? Looks like that chimney is super wide and the cap on it is full width of the chimney making me believe it has two flues.

 

[kamill]

Where does your boiler vent to? Looks like that chimney is super wide and the cap on it is full width of the chimney making me believe it has two flues.

The oil furnace vents to another flue, there is 3 flues on the chimney. From the inside looking out, the left flue is the oil furnace, the middle flue is an open fireplace on the main floor that we're not using, and the right flue is the basement woodstove.

You need to get rid of that OAK piping and change it to the semi rigid. That stuff you have right now is not UL listed and will ignite at high temps. Also how tall is the chimney? That chimney needs a liner to have that stove working right. If I had to guess it is too big and doesn't heat up enough to properly draft.

When the stovetop is 650 degrees the piping still feels cold to the touch, it connects to the back of the pedestal. I can definitely change it to something more safe but I don't believe it is contributing to the issue. I don't have an exact height on the chimney right now, when we had it swept before this season the sweeper did say that it is too short.

Are there cases where a SS liner is installed and it still cools in the early morning and backdrafts? I'd hate to spend the money only to have the issue remain.

The previous owners definitely used their woodstove. They left over a cord of wood and there is evidence of them cutting down multiple trees on the property for firewood. Here was their stove:

I'm sure they dealt with CO as the peak level on the CO detector they left had a reading of 45 before we even installed the new stove. We can operate the stove 24/7 but I'm just tired of getting up at 3:30 to feed the fire and I'm not comfortable letting it die out. My wife and I work opposite shifts so it's never left unattended and we fuel it every 4 hours or so but that is going to change in January when she switches to day shift.

 

[begreen]

That is an old Franklin fireplace which is much less draft sensitive. Even so, the high CO reading indicates this has been a long term issue.

Are there cases where a SS liner is installed and it still cools in the early morning and backdrafts? I'd hate to spend the money only to have the issue remain.

Yes. If this were my house and I wanted wood heat I would consider the option of selling the wood stove and buying an insert for the main floor fireplace.