Old BK runs away

Here's my setup:

Old BKK non-certified. 5' DSP to SS class A thru-the-wall and then up about 14'. 8" all the way.

Here's my issue:

When doing an overnight sized reload, I'll push the coals to the back near the air inlet, fill it up tight N/S with mixed hardwoods and set the dial so I can hear some, but not a ton of air coming in. Fans off.

Sometimes the stack temp will go nuclear and I'll end up with a "chimney cleaner". The DSP feels hotter than the stovetop...but not to the point where the class A adapter starts to glow. I don't have a probe thermometer, but this is hot enough to know that it's too hot. When this does happen I crank the dial all the way down and wait a few minutes till things cool off.

Never have this problem on a small reload...just the big overnighters. Stove top temp is usually 400-500 when this happens but sometime it will happen even lower. No correlation really.

I'm at a loss as to why this happens and it's frequent enough to be annoying. I have to watch the stove like a hawk for a couple hours after the reload.

My first thought was the thermostat was bad and/or the damper was sticking. The damper moves freely and adjusts to the temperature of the stove. No perceived issues. This makes sense that it leaves it open because the stove top temp is usually pretty low when this happens.

Bad / going bad gasket? Not sure…it can control it really well except for these big initial loads.

Too much draft...I don't have a damper?

Coals to close to the air inlet?

Something else?

Need some help from the experts.

Thanks.

I suppose air could be leaking at the flue collar...it is not sealed with cement. I could try to use a smoke stick and see if it draws air around it.

There is not nearly enough creosote in the stack to generate this type of heat so it may very well be a form of secondary combustion...

Also, don't know if this matters, but all visible smoke is GONE when this happens...a lot like secondary combustion.

mbutts said:

Am I to understand you have 5' of stove pipe that is horizontal or maybe at a 45 deg angle? If so might be fly ash and creosote in it that needs to be cleaned out. Is ur gasket ok on door? take cover off tstat flapper in back and see if it is closing. If you do not have an air leak anywhere else turning down the temp dial and closing the flapper should shut off all air to the stove.

Click to expand...

Stove pipe goes up ~3' and over ~2' before it connects to the class A.

T-stat flapper appears to be in working order (I pulled the cover and inspected, closes fully and moves freely) and if I turn the dial all the way down it will snuff it out...but I can still hear it drawing air. It takes a couple minutes though.

I'm starting to think it is the gasket or the flue collar leaking. The pipe is pretty clean...not spotless...but not dirty enough to cause this. My current thinking is that the stove is drawing air through the flapper and "somewhere else" resulting in too much air and an excessive flue temp.

I'm going to replace the gasket tonight and go from there. Probably about that time anyway. Next time this happens I'll smoke test the flue collar and see if it is drawing there too.

I was referring to the door gasket that I'm going to replace.

Is there another gasket?

north of 60 said:

To try and help as I had a similar situation as you with a 30yr old BK at a house I was staying at while I was working out of town for 3 month's. Since the highs for most of the time where -30 I wanted to make things right with the stove.
#1 was the door gasket was pretty much compressed and at the end of its time. I had the new door gasket shipped in and replaced it with the new BK era thick wide gasket. In the photo as you can see that in the corners I did not streach the gasket but actually bunched it up in those areas as the stove corner lips are quite square. Now upon removal of the door I found a crack on the stove upper top left hand side. it was long but not separated. After re assembling the door and lighting the fire I noticed better control until it heated up. That crack was opening more than a 16th which was enough for me to see the flames.
Being a pipefitter/welder the next step was easy. Next day I was able to bring the welding rig back to the house and removed the door once again. All was ground down and I heated up the stove area so the expansion and stress in that area was removed.
Filled the crack with 7018 uphand with a filler 3/32 and larger woven cap with 1/8th. Reassembled/ Popped on the door. The stove was once again a new animal under control. The lady of the place we rented from still crosses my path now and again as I go there to do some spectacular fishin. 3yrs and still together.

Click to expand...

Thanks for the detailed response. Do you happen to remember what size that gasket was? The widest I can find around here is 3/4 at the box stores. The local fireplace shop was out of 1". Can't really tell from you picture, but it looks like 1" or more.

My gasket is compressed pretty bad. After she cools down a bit I'll try a dollar bill test but I don't see I'll be able to do that on the bottom (suspect area) since this is the old drop door type stove.

Before I lit the first fire in this stove (4 burning months ago) I gave it a detailed inspection for cracks. I didn't really expect to find any since the stove, while 25 year old, only had a handfull of fires in it before I bought the house.

Negative.

Biggest they carry around here is 1". I'll look into mail order.

BeGreen said:

Just a guess, but is there any air leakage around the flue collar? This could be creosote burning off in the flue or perhaps, it's secondary combustion occurring too far downstream, in the flue pipe?

Click to expand...

Last night I had another "episode"...actually several small ones. Big load...a lot of air...coming up to temp. DSP gets crazy hot in short bursts.

I pull the cover off the damper thermostat to find everything shut down. When I leaned over I hear rushing air. I thought it was coming through the hole in the damper flap. I temporarily plugged the hole with my gloved thumb and still hear a lot of air rushing. I'm 99% sure it was leaking in around the flue collar. Tried smoke testing it but the pipe and stove top were too hot it just pushed the smoke up and all around. I did see some go between the collar and pipe though.

This morning I took all the stove pipe apart and inspected everything. Pipe is still in good shape. Some minor discoloration but no signs of oxidation. Lots of powdery ash but not creosote until it hits the "up" section of the SS chimney...and very little there.

Brushed out all the ash...reset the stove pipe on the collar with a very snug fit (was pretty loose before). Just to be sure it was sealed I put down a bead of furnace cement on the inside of the collar where the pipe seats against the stove. It is setting up now.

Re-assembled the stove pipe. In a couple hours I will start a small fire to cure the cement. Hopefully this will exorcise the demons. I'll post findings.

BeGreen,

You must be some kind of stove savant, a g-d genius, 160 IQ. You're going to be a general someday. Thanks for the help.

Last night about 7:30 I packed the stove with some elm, cherry, and oak. Big, big load. Set the dial to allow a lot of air in the stove and got things cooking. Normally, after a few minutes the stack would go nuclear (with that much air). Not tonight. Then I cranked up the air even more which would have, without a doubt, set it off prior...but still running great.

Settled in at a stove top temp of 550* and ran all night. This morning at 6:30 there were still too many coals for a reload and the stove top was still 500* +. Asked the wife to toss on a few splits at about 9:00. Pretty good burn time for 20* outside temp with a lot of wind.

I'm trying not to get too excited too quick, but I think this problem is solved. Could have been cleaning the stove pipe, but considering I got only a 1/8 cup of fine dry ash out I really don't think that's the case. I'm feeling pretty good that it was air leaking around the flue collar.

Its like a whole new stove...and a real sweetheart at that. It is a hungry stove, but wood is free...and free is cheaper than a new stove. Maybe someday I'll get a new cat stove but, for right now, I couldn't be happier.

I can't tell you what a relief it is not to have to baby-sit the stove for hours after reload. Walking up and down the stairs to the basement every 15 minutes is no way to live. I'm just embarrassed that it took this long to correct the problem.

Haven't replaced the gasket yet. Thinking I might hold off for a bit. It passes the dollar bill test everywhere...but I couldn't test the bottom.

Yeah...but you have to throw a half cord of wood at it to get it to last that long LOL!

Things are still working good so I'm going to leave the door alone for the time being. The bottom of the gasket looks good. The top corners looked worn but passed the test.

Two nights ago I ran the flue temp up pretty high (on purpose) just to see how long it would take to get it "too hot". There was some creosote on the DSP to SS adapter that burned off (wouldn't brush off) but I was able to quickly get things shut down so I don't think the stove is leaking. I may have a minor leak where the stove pipe connects to the chimney but...I'm not sure...and...don't know how I would correct it even if there were one. Probably worth mentioning I had packed it full of super-dry, very small rounds from the limbs of a red elm tree which undoubtedly lit off very hot and fast.

I was a little concerned but, the more I thought about it, I was intentionally running the stove too hard and that's what caused the small amount of creosote to light off. I wouldn't go so far as to call this a chimney fire, but I could hear it crackling. I went outside and saw one or two small embers come out of the cap. The SS chimney (out an up installation accessible outside) was hot to the touch but nothing to get concerned about.

Last night I ran the stove without trying to "push" it and she ran like a dream. Packed it full of cherry and oak at 7:30...brought stove top up to 550* - 600*...fans on high...dial at 3.25. At 6:30 this morning the stove top measured 550* and there were still too many coals for a reload. Stove is installed in a 1700ft2 poorly insulated basement and heating just as much above the basement (good insulation). Outside temp in the 20's. If I was leaking air in the stove I don't think I could get these excellent burn times.

In my opinion problem solved. I'm going to be much nicer to my chimney now and keep the temps reasonable. I just had to push it to know where the trouble starts. Was my experiment good for the chimney...no. Did it hurt it...highly doubtful. (Side Note: Did a nice job of cleaning it..had some hard creosote in the last couple feet of stack this is gone now! I had been using some Rutland product to break it down and I think the high heat really helped it along.) But now I can sleep much easier at night knowing how hard I can run it without getting into trouble.