Improving draft in a basement wood stove

[dave11]

I just put in an Englander 30-NC in my walk-out basement, and all seems fine, except the fire seems a bit starved for air with the door closed and the air inlet fully open. The folks at Englander reviewed the overall situation, and feel the most likely cause is insufficient draft. Mike, a member here on hearth.com (stoveguy2esw), also gave me some advice, but before I made any major changes, I wanted to ask for some more opinions.

The house was built in 1951 and isn't that tight overall. There are three flues in an external chimney, one for the basement fireplace, one for the upstairs fireplace, and one for an old furnace, which is no longer used. The sweep opted to drop a 6 inch SS liner down the unused flue, because it was in great shape, and because it avoided making any changes to the basement fireplace. The stove now sits about 3 feet to the side of the basement fireplace.

There are two 90 degree elbows, and a short horizontal run of about 2.5 feet. It's about 25 feet to the top of the chimney.

The sweep tested the draft with a puff of ash, in the middle of summer, and it went right up. He said there would be no problem with draft in the winter, though it's safe to say that's a guess on his part. If I take the stove apart, the draft I feel with my hand seems fairly robust, though I know that's not very accurate.

The fire starts great, and roars away if I just keep the door open a hair. If I seal the door, the fire visibly fades, and flames come and go at the edges. If after a while I crack open the door, all the logs burst into flames again. I'm no expert, but to me this seems the fire is starved for air.

Opening a nearby window seems to make no difference.

I'd really like a way to prove where the problem is, before I do anything about it. I know draft can be checked with a manometer, and I have access to one, but it seems to me the reading is only valid when the liner/flue are hot, which would require the stove to be going. Measuring it when cool will lower the draft reading, won't it?

And if opening a ground-level window makes no difference, does that also mean an outside air kit will make no difference?

 

[oconnor]

Draft is related to a few factors, and you seem to have taken care of pressure by noting that opening the window doesn't help. That leaves flue size and temp, and your flue size is adequate, but those 2 x 90* elbows knock off an effective 10 feet from your flue height, and then the horizontal run makes it worse again.

Can you get away with 2 x 45 degree elbows and not have a horizontal section? Post a pic of your settup so we can understandf the situation a bit better.

What temps are you getting when you burn? That will help is identify how truly "dry" your wood is. Just for a test, give my fire lighting thread linked below a try and let me know if you get better results or no change.

Brent

 

[dave11]

I'm not at home, so I can't take a pic, but basically there is a 2 foot vertical run coming up out of the stove collar, then a 90 degree toward the wall, a 2.5 foot horizontal run into the wall, another 90 degree going upward, then about 25 feet straight to the top of the chimney.

But the install manual allows up this sort of arrangement; in fact, they show a diagram that uses this same configuration. So I don't see why it should be that.

 

[DAKSY]

Your manual says the minimum VERTICAL run straight up is 25 feet from the floor to the cap.
Your 90s have decreased this considerably.
Replace em with 45s or increase your chimney height.

 

[Corey]

Sounds like that should be tall enough even with the 90º elbows. Couple of quick thoughts - make sure you have a good coal bed before closing the air down too much otherwise it's pretty easy to put the fire out. Second, I'm guessing the liner goes all the way down and directly connects to the stove - make sure that is hooked up right with no gaps or loose fittings - and since this is in an old furnace flue, make sure there are no other holes in the flue which could be letting air in and cooling down the liner. Since you're in the basement - make sure other appliances such as clothes dryer, forced air furnace, vent fans, draft fans, etc aren't causing negative pressure problems. You also might try directing a small fan down the stairs to give some positive pressure to the basement. We've had a few reports of low draft due to hot air rising up the stairs and fighting the stove for hot air rising up the flue.

 

[dave11]

I had reviewed the manual before I purchased the stove, and while it does say the max vertical run is 25 feet, they make no reduction for 90 degree elbows, and in fact show two 90 degree elbows in their install diagram.

I'm confused as to how extending the chimney would help things--isn't the problem that the top of the chimney is already too far away?

The 90 degree elbow in the room could I think be changed to 2 45 degree elbows, but the other one is inside the wall, and barely fits, so could not be replaced.

 

[Wet1]

Generally speaking the longer the chimney, the stronger the draft.

 

[dave11]

cozey heat--that's a good idea about the fan. I had been closing the door to the upstairs, because I can feel air drafting that way and lowering the pressure in the basement, but a fan would be a good try.

But does anyone know about the OAK? If opening a window makes no difference, is an OAK also not going to work?

 

[dave11]

Generally speaking the longer the chimney, the stronger the draft.

In general, I also thought that, but then why does the manual list a max vertical run of 25 feet?

 

[dave11]

Generally speaking the longer the chimney, the stronger the draft.

In general, I also thought that, but then why does the manual list a max vertical run of 25 feet?

Ooops, I'm partly wrong. The manual says the TOTAL flue length should not exceed 25 feet. Though I'm still not sure why.

 

[Todd]

How have you been building your fires? How large are the splits? Maybe you just need more time to get use to this stove and the relatively warmer weather may be contributing to the draft problem. Try useing lots of kindling and smaller splits.

 

[dave11]

I just installed the stove, and have only built two fires in it. The wood was well-seasoned cherry, and with the door open a hair, the fire was roaring, so I didn't think it could be a problem with the wood or how I was building the fire. Its true that it wasn't that cold on the days I built the fires, in the 40's, but shouldn't that be cold enough to get a good draft?

Actually, i'm not totally convinced yet the draft is the problem. I wish there were some other way to prove it.

 

[Corey]

Generally speaking the longer the chimney, the stronger the draft.

In general, I also thought that, but then why does the manual list a max vertical run of 25 feet?

Ooops, I'm partly wrong. The manual says the TOTAL flue length should not exceed 25 feet. Though I'm still not sure why.

Flue height is good to a point, but the further the flue gas is from the stove, the cooler it gets. At some point, it is cool enough it won't rise anymore. If that point is still inside the flue, it would be like putting a cap on. (Actually it will get cool enough to not create a 'good' draft and if it's still in the flue, can cause a problem) In technical terms the cooling is called 'lapse rate' - you sometimes see it from industrial stacks where the smoke will rise to a point, then just blow horizontally in the sky - it's become the same temperature as the air and doesn't rise any more. But that is usually a pretty long ways - the MFR may be more concerned with overdraft and not being able to shut the stove down enough, thus the reason for the 25' max flue.

If you opened a window in the basement, that should eliminate any issues I mentioned with vent fans, dryer, negative pressure, air rising up the stairs, etc and would also indicate an OAK won't solve your problem. Is this liner install insulated?

It may take 30+ minutes of burning before you have a good coal bed and can close the air down to truly operating levels. Also, the draft will grow stronger as the outside temp drops and creates a bigger difference in temp between it and the flue gases.

 

[wendell]

I have almost the exact same chimney set up and I am quite sure inadequate draft is not your problem and an OAK would be unlikely to make any difference.

Are you sure you are using your primary air control correctly? It sounds like it is shut down too much so when you close the door, the fire can't get enough air.

 

[dave11]

The liner is only insulated at the top five feet or so. I pushed the sweep, who has a very good reputation, to insulate the whole thing, but he said it wasn't necessary, and would be very hard to do because of the tightness of the space. The 6 inch liner barely fit even without insulation. I can't recall the dimension of that flue, though it's rectangular. 11 X 7? And there were spots where the mortar and tiles bowed inward.

I know insulating it would likely improve draft, and keep it cleaner, though I'm not sure if it can be done at this point.

 

[laynes69]

I thought the same thing with my new furnace. Its draft sensative, big difference from the old furnace. I found I was cutting the damper off too soon, before the firebox was up to temp and things charred. When the firebox is hot and live I can shut down the damper and get a nice burn.

 

[dave11]

I have almost the exact same chimney set up and I am quite sure inadequate draft is not your problem and an OAK would be unlikely to make any difference.

Are you sure you are using your primary air control correctly? It sounds like it is shut down too much so when you close the door, the fire can't get enough air.

Wendell--I agree with you. My first thought was that the stove was somehow malfunctioning or miscalibrated, which was also the remark made by the sweep, when I told him recently about the problem.

But I've talked with a couple of folks at Englander who seem convinced that the stove itself is not the problem. Apparently this problem has come up before, and has been solved by increasing the draft of the flue. Apparently the stove is designed to restrict air flow, even with the air inlet fully open, which apparently is what helps make it so efficient. Cracking open the door a bit increases the burn, but decreases efficiency, and negates the stove's design.

So it may not be that the draft in the flue/liner as installed is abnormally low, but that it is simply not great enough for this particular stove.

I wondered if the air channels inside the stove might be partly blocked, and went looking for them, but they are inaccessible for the most part. I also tried blowing air through the stove's air inlet, but it's hard to tell how much should be getting through, and in what pattern.

 

[oconnor]

I just installed the stove, and have only built two fires in it. The wood was well-seasoned cherry, and with the door open a hair, the fire was roaring, so I didn't think it could be a problem with the wood or how I was building the fire. Its true that it wasn't that cold on the days I built the fires, in the 40's, but shouldn't that be cold enough to get a good draft?

Actually, i'm not totally convinced yet the draft is the problem. I wish there were some other way to prove it.

Just a few things as I have read thru the entire posts above

This is by definition a draft problem - if the stove isn't getting enough air into the firebox to burn the wood, then there is not enough draft. Opening the door makes it easier for the fire to burn, as it was constrained by lack of air. The only thing that will get it more air in the firebox is more air leaving the chimney - aka draft.

So from there, you can increase draft by increasing effective length, or adding more heat to the flue - both will result in more air leaving the flue. Removing the two 90 degree elbows and the flat run will remove what is essentially a bottleneck in the flow up the flue. The 5 ft per elbow is just a rule of thumb that translates each elbow into roughly equivalent height.

The second item is heat produced - there has yet been no mention of how hot the flue is actually getting. If the flue is not getting hot, then there is going to be reduced draft. Once a blocked flue is counted out (yours inst blocked as it is only your second fire ), then wet wood is my number one suspect when it comes to a fire not burning when the door is closed, with splits being too larger being my number two. There are thousands of posts on here of folks with seasoned wood proving to be wet wood in the end.

That is why I recommend you give the test of fire lighting in my link below a try - the wood I used in the test was not ideal dry, and the flue was only a 5 inch flue, so if you can get a good hot fire going with that trick, then you will have overcome the draft issue. Beyond that, straighten the flue by changing the elbows and then buy a thermometer to help gauge if the fire is getting hot.

 

[dave11]

I just installed the stove, and have only built two fires in it. The wood was well-seasoned cherry, and with the door open a hair, the fire was roaring, so I didn't think it could be a problem with the wood or how I was building the fire. Its true that it wasn't that cold on the days I built the fires, in the 40's, but shouldn't that be cold enough to get a good draft?

Actually, i'm not totally convinced yet the draft is the problem. I wish there were some other way to prove it.

Just a few things as I have read thru the entire posts above

This is by definition a draft problem - if the stove isn't getting enough air into the firebox to burn the wood, then there is not enough draft. Opening the door makes it easier for the fire to burn, as it was constrained by lack of air. The only thing that will get it more air in the firebox is more air leaving the chimney - aka draft.

So from there, you can increase draft by increasing effective length, or adding more heat to the flue - both will result in more air leaving the flue. Removing the two 90 degree elbows and the flat run will remove what is essentially a bottleneck in the flow up the flue. The 5 ft per elbow is just a rule of thumb that translates each elbow into roughly equivalent height.

The second item is heat produced - there has yet been no mention of how hot the flue is actually getting. If the flue is not getting hot, then there is going to be reduced draft. Once a blocked flue is counted out (yours inst blocked as it is only your second fire ), then wet wood is my number one suspect when it comes to a fire not burning when the door is closed, with splits being too larger being my number two. There are thousands of posts on here of folks with seasoned wood proving to be wet wood in the end.

That is why I recommend you give the test of fire lighting in my link below a try - the wood I used in the test was not ideal dry, and the flue was only a 5 inch flue, so if you can get a good hot fire going with that trick, then you will have overcome the draft issue. Beyond that, straighten the flue by changing the elbows and then buy a thermometer to help gauge if the fire is getting hot.

I did check the temp with a quality IR temp gun, though i'm not sure if they're completely reliable, as the built-in fan was running, which blows air across the back and top of the stove at a fairly strong rate. The sides got up to 425, but the top of the stove never got above 300. The t-connector at the wall, which is about 3 feet from the stove, got up to 230. Since the fan is interfering with figuring how hot the stove is getting, I can retake the readings with the next fire.

One of the elbows cannot be replaced because it is behind the wall, and though it's accessible, there's no room to replace it with 2 45 degree elbows. The other elbow is actually a t-connector, with the third arm covered, to allow access to the bottom of the liner for cleanout. There is no way to eliminate the short horizontal run.

I'll give the test in your link a try with the next fire.

 

[dave11]

I just installed the stove, and have only built two fires in it. The wood was well-seasoned cherry, and with the door open a hair, the fire was roaring, so I didn't think it could be a problem with the wood or how I was building the fire. Its true that it wasn't that cold on the days I built the fires, in the 40's, but shouldn't that be cold enough to get a good draft?

Actually, i'm not totally convinced yet the draft is the problem. I wish there were some other way to prove it.

Just a few things as I have read thru the entire posts above

This is by definition a draft problem - if the stove isn't getting enough air into the firebox to burn the wood, then there is not enough draft. Opening the door makes it easier for the fire to burn, as it was constrained by lack of air. The only thing that will get it more air in the firebox is more air leaving the chimney - aka draft.

So from there, you can increase draft by increasing effective length, or adding more heat to the flue - both will result in more air leaving the flue. Removing the two 90 degree elbows and the flat run will remove what is essentially a bottleneck in the flow up the flue. The 5 ft per elbow is just a rule of thumb that translates each elbow into roughly equivalent height.

The second item is heat produced - there has yet been no mention of how hot the flue is actually getting. If the flue is not getting hot, then there is going to be reduced draft. Once a blocked flue is counted out (yours inst blocked as it is only your second fire ), then wet wood is my number one suspect when it comes to a fire not burning when the door is closed, with splits being too larger being my number two. There are thousands of posts on here of folks with seasoned wood proving to be wet wood in the end.

That is why I recommend you give the test of fire lighting in my link below a try - the wood I used in the test was not ideal dry, and the flue was only a 5 inch flue, so if you can get a good hot fire going with that trick, then you will have overcome the draft issue. Beyond that, straighten the flue by changing the elbows and then buy a thermometer to help gauge if the fire is getting hot.

And Brent, I follow what you're saying, but I'm still confused as to how you can be certain this is a draft issue. What if, for example, there was indeed a partial blockage of the air intake within the stove, say a dead mouse or stray piece of packing material or whatever--wouldn't the stove behave in the same way as mine is doing? Or am I not grasping this correctly?

 

[BrotherBart]

For one thing, turn that blower off. Get the stove burning well and up to operating temp before you even think about starting the blower. For one thing on the 30 the blower blows around the flue collar cooling the exhaust. For the second thing, it keeps the firebox from getting hot enough for good combustion if it is running too soon.

Turn the blower off, crack the door until you get a good burn going and then don't turn the blower on until you get up to something like 450-500 on the stove top.

The stove and the flue aren't getting a chance to warm up to operating temp.

 

[dave11]

For one thing, turn that blower off. Get the stove burning well and up to operating temp before you even think about starting the blower. For one thing on the 30 the blower blows around the flue collar cooling the exhaust. For the second thing, it keeps the firebox from getting hot enough for good combustion if it is running too soon.

Turn the blower off, crack the door until you get a good burn going and then don't turn the blower on until you get up to something like 450-500 on the stove top.

The stove and the flue aren't getting a chance to warm up to operating temp.

Hmm. I was starting to realize that as I was reading all the advice that has been coming in. It's a good thing there are websites like this to give a clue to all of us greenhorns.

So the blower is still a good idea, but just not until temps are high enough, correct? And the blower should be turned off or cut back if the firebox temps drop too low?

 

[Yagminas Masonry and Wood-heat]

I find a lot of newer stoves are starved for air and are pretty finicky buggers in general. If it draws well with the door cracked then the chimney is fine. I've had to modify air intakes in the past just to get a little more roar out of 'em. Also, if a stove was 100 percent efficient...there would be zero draft. To me, wood-stoves thrive on being a little in-efficient.

 

[BrotherBart]

Hmm. I was starting to realize that as I was reading all the advice that has been coming in. It's a good thing there are websites like this to give a clue to all of us greenhorns.

So the blower is still a good idea, but just not until temps are high enough, correct? And the blower should be turned off or cut back if the firebox temps drop too low?

You bet. Just let that bad boy get up to temp and get a draft established before turning on the fan. Good rule of thumb is to only run the blower on high at high stove temps. I cheat sometimes but only because I know what a high and a low burn look like in the stove.

And my feet are cold. And it is first thing in the morning. And I want some heat and I know the price in chimney crap I will pay for it by turning on the fan too soon.

But I never turn it on until a good draft is established and the burn is rocking.

 

[xman23]

Brother Bart is correct. We all go thru this, thinking something is not working right the first few burns. The draft gets far better the hotter the stove and chimney gets and the colder it is outside. My draft is good but when I want the quickest hotest fire, I leave the side door open for 1/2 hour or more and 2 reloads. Only when the stove has a bed of coals and is filled with burning wood do I need to close down the air. One other thing, It's hard to tell if the wood is dry enough. To maintain the burn with wet wood you need a real hot fie and bed of coals.

Tom