Improving draft in a basement wood stove

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?

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.

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.

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?

Wet1 said:

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

Click to expand...

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

dave11 said:

Wet1 said:

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

Click to expand...

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

Click to expand...

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

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.

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.

wendell said:

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.

Click to expand...

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 said:

dave11 said:

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.

Click to expand...

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.

Click to expand...

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.

oconnor said:

dave11 said:

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.

Click to expand...

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.

Click to expand...

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 said:

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.

Click to expand...

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?