Hitzer 50-93 Overfriring

So I picked up a 4 year old Hitzer 50-93 this January and Installed it.
New to coal burning, so far love the heat and the duties of maintaining it.

Info:
Hopper gasket replaced, all others passed dollar bill test.
2200 sq ft ranch home built in mid 60s and well insulated.
Stove is located in mostly finished basement.
Chimney is SS rocket outside of home 18' tall
Using cheap baro because that's what was used on the stove when I got it, and recommended from last owner.
Manometer installed, reading .05-.06 baro open about 1/3.
Magnetic temp sensor on pipe right below baro and top right corner of stove.
Variable speed controller for blower (usually set at half speed or a bit less).
I ash down and fill every 12hrs.
Normal temps pipe: 180-225 stove: 350-450 nut coal
pipe: 150-200 stove 350-450 pea coal
2 CO detectors in basement.

I started with Kimmel nut coal cause it was bagged and I only had to drive 5 miles to get it.
I burned for about 3 weeks with no issues, thanks to all the info on this forum. Then one morning I emptied ash pan, It had a medium burn going, shook it down till I had coals in pan,(rear flap was open calling for air) and within 10mins or less the stove pipe started to rumble and temp shot up to 550. It filled basement with paint smoke. I shut the back flap, opened the basement door and nervously waited for temps to come down. Once temps dropped to under 200 I adjusted dial rear flap opened and it happened again only reaching 500. So now I'm late for work and I continue to do this till pipe stays at an unnerving temp so I can leave (about 2 hours).
It was fine for a few days, no issues, then all of a sudden one morning it happened again. I let it burn out, shut it down, cleaned everything, checked everything, started a new fire.
It was fine for a few more days, I went to pick up some coal and *censored*, they sold out of nut. I grabbed the last 5 bags of pea and have been using that. I found pipe temps to be lower with same stove temps. Then just this morning, shakedown ad pipe temps shot up to 400.
Can anyone tell what I might be doing wrong? I'm sure it is me and not anything else. Anything I can do to avoid this? I hate being late for work and thinking about the damn stove all day.

Sounds like you are doing things right. I'm afraid the only thing I can offer is that the bi metallic thermostat seems to be reacting too slow to the stove heating up. The ash pan door is sealing properly? I would suggest closing the bi metallic combustion air opening and running it manually. It does have manual combustion air controls on the ash pan door, right?

Hello
One possibility that I can think of..Are you running your blower 24/7? If so you may want to shut it off when you are doing a shake down until the stove comes back up to temp. Leaving it running can cause the damper in the back to open way up while the stove comes back up to temp. and it can get stuck in the open position causing the run away fire.
More will chime in soon with their experience and knowledge:)

Yes it does have ash door vents. Now more than ever I double and triple check that the doors are shut properly since the first runaway.
I did forget to mention that I do shut the blower off before emptying the ash pan and leave it off till the flapper cycles once.

600 degrees on the pipe is a bit unnerving. Panic shouldn't set in till around 900.. yer doing the right thing by cutting combustion air when it gets hot but the bi metallic should be doing that for you. Hopefully more with expertise on these will chime in...

I agree with what everyone has told you so far. When you go to tend your stove, and see the back flapper opened up, shut the fan off. This way the fan doesn't continue to cool the mass of the stove. Empty your cool ashes from the previous tending. If needed, leave the ash pan door open till the existing coals get good and hot. (NEVER EVER leave the room with the ash pan door open. Stay in the room, and baby sit the stove. Should you need to leave the room, close the ash pan door). Once coals are glowing good and hot, close the ash pan door. Top off the hopper, and wait for blue ladies. Once you see blue ladies, turn the fan back on. Wood stoves run stack temps at 450* - 550* all the time. Like mentioned, when temps reach 800* - 900*, you need to be paying attention.

With good gaskets the only places for air to get in are the manual vents on the ash door and the thermostat flap.
First check the manual vents by shining a flashlight on the back of the open door to check for leaks through the sliding vents. Sometimes that inner plate does not fit tightly. If OK I would suspect the thermostat coil or sticky flap.

Thank you everyone for your knowledge. I have just not seen pipe temps that high in the first three weeks of burning coal. I got a bit paranoid. I will try a few things over the next few days and post my results.

Sounds like your damper door is getting stuck open. After you shake it down, I don't leave the house until that door closes.

What happens sometime is you shake it down, the stove calls for a ton of heat and opens it wide. When it's open wide is when it can get stuck. I find the only Time it calls for that much is when a new bed is establishing. Once it hits that once, any time it opens over the next 12 hours should only be an inch or less.

I've never had the door get stuck open unless it's open to almost horizontal. Definitely scary the first time though. My stove body hit 700 and I wasn't home, talked my wife through fixing it
Over the phone.

Was the chimney your tied into ever used for wood fires? You could have had a good old fashioned chimney fire.

Front ash door vents...
Check to see that no slop is in the handle...
No coal stuck in the top hopper door gasket...
Small piece of coal blocking the rear flapper from closing...
You got air comming in from somewhere...

Lightning wrote:600 degrees on the pipe is a bit unnerving. Panic shouldn't set in till around 900.. yer doing the right thing by cutting combustion air when it gets hot but the bi metallic should be doing that for you. Hopefully more with expertise on these will chime in...

900F surface temp on the surface of single wall will be a meltdown on internal temps with triple wall chimney as you transition. It will cause close to 2000F internal temps. If it goes into a big masonry lined chimney them ass of it will probably soak up the heat and not go over temp on bricks and tile before the stove settles back down.

I have a wood stove with a magnetic and internal probe on the stack and if the magnetic on is 300 the probe is 600.

Scottaw wrote:Sounds like your damper door is getting stuck open.

I put the Hitzer thermostat and air intake on my Harman stove a few years ago, and had a similar problem with the intake door sticking open. I called Hitzer and they told me the clearance at the hinge is critical. If the hinge is too far back toward the stove body, then when the door opens its top edge can slide ever so slightly back and the back of the door can bind against the top edge of the air intake tube. In fact Hitzer told me some stoves had been shipped with the hinge bolt hole out of position by a small amount, causing the binding problem.

Try lifting the chain by hand and pull it gently back toward the stove, then release it slowly to see if the door binds. It doesn't take much adjustment to fix it. In my case I removed the hinge bolt and found one just slightly smaller diameter in my odds-and-ends jar. That allowed the hinge to sit a bit farther out and it fixed the problem. I suppose you could instead drill out the bolt hole in the hinge to allow a little more play when you reinstall it.

Good luck, and let us know what you find.

Can you answer why are you messing with the dial on the back of the stove at tending time? Here is how I tend my stove, it is only my 2 cents, it works for me and might not work for someone else.
Stove is running body temp 3 to 350* and the pipe temp is 150 to 175, I open my MPD, shake the stove good, open ash door remove pan and put into ash receptacle, go back to the stove open load door and load stove and close load door, go get my ash pan slide it in and by now the pipe temp is starting to come up, I leave the ash door open slightly till pipe temp reaches 400*, now I close the ash door leave the MPD open for about 20 minutes then close it, stove settles out in approximately 45 minutes back to 3 - 350*. Stove body may rise to 375 to 400 then settle back. I never touch the dial on the rear unless I want more or less heat for the next 12 hour run. I also agree with "NorthernMaine" about running the fan during tending, leave it off till the stove settles out.
Again this is my way of doing things and only my 2 cents, also I never seem to have any puff backs.