OWB explosion

[redytorace]

Are you sure they are exactly the same? Maybe wood is more prone to something like this when it is shut down, than coal is? Therefore their wood units might have small differences to avoid it? Like say a bigger hole? Or something else?

Also I would be pretty leery about the strength of the firebox after many of these episodes. IMO it would take a lot of firebox flex to blow water out the top - it's not likely designed to take any of that. So each one would be working on a weak spot somewhere, making it weaker. Bending till it breaks kind of thing.

I can't see any major difference in design between the two that would cause this. I don't know if wood or coal is more prone to something like this?? My dealer/installer has been burning the same stove for a few years now and also burns wood in his during milder temps. He has never had this happen, and has never heard of if happening before. I'm waiting to hear back from the manufacturer.

 

[Deleted member 117362]

I have had one and seen two run away burns on owb's. Solenoid sticks and fan, draft door remains open, allowing for that burn, water starts boiling, causing banging in water jacket. Water will shoot out top vent. If you do not catch it in time, you may be rebuilding outside of stove, replacing ruptured pex lines and electronics. My solenoid had a burr on it, filed burr and it's fixed, but I do have a spare one now. Plus pump, aqua-stat, stove rope and fan.

 

[lefturnfreek]

Ok, then go to smaller loads and tend to it more often.

I’m north of 50 and I haven’t fired my boiler yet but I have to do the same thing, start small then work my way up to full load of 4fts then drop back again in spring.

 

[panolo]

I don't see how load size should factor into it if the stove isn't boiling over. I mean the premise is that once it reaches temp that it cuts the air. Shouldn't be boiling over in that case if it is working properly. Mines been loaded for two days because of the milder temps.

I think it's not evacuating the gas and smoke and when a little oxygen mixes and the flame goes you have the ingredients for a mini explosion. Has to be an air or design issue. Boiling over is super easy to tell as the steam and water kinda goes everywhere.

 

[lefturnfreek]

That’s right, I never said it was a boil over issue, it’s a explosive smoke situation.

When you have too large of an amount of burnable material, going from mildly out of control from burning in mild temps, then having the damper close leaving all the coals to out gas from going from a burning state to an oxygen starved environment and add air as the damper opens .... boom...

 

[Marley5]

From my own experience, I've experienced a flash fire from opening the door immediately after the stove reached temp and damper shut.....only once as it took several weeks to get my beard back.

I also load the boiler all the way to ceiling on days I'm away for 14hrs and yet to experience the internal explosion.

If it wasn't for the damper serving as a pressure release valve, the stove may come apart.

I'm wondering what temp the stove read when this occurred and also find out what temp the dealer keeps his stove set at and follow suit.

 

[09sseddo]

If it was my boiler I think I would put a time delay in series with the fan. This would let the damper door open for a few minutes before the fan kicks on. On mine I have a two stage stat that accomplishes this same idea.

 

[Marley5]

If it was my boiler I think I would put a time delay in series with the fan. This would let the damper door open for a few minutes before the fan kicks on. On mine I have a two stage stat that accomplishes this same idea.

You may be on to something.

 

[Marshy]

Sounds like a classic case of puff back. The firebox is getting saturated with highly combustible gas from a slow smolder of newly loaded wood on hot coals. Google the term pyrolysis. Once the firebox is full and enough oxygen or heat is introduced you get a subsonic combustion called deflagration. It can be damaging but, not as much as sonic explosion but could still permanently damage the boiler.

You either need to change you burning habit or how it's being operated.

 

[user 194142]

Sorry for the long post, but I have a important question for the OWB owners and I appreciate any help. Last year I had a Heatmaster C375 installed. It has a solenoid that opens a draft door and a fan that kicks on when it calls for heat. Twice so far (once last spring and once this fall) there has been a violent explosion inside the firebox. So violent that I heard it from inside the house and it blows water out the top of the stove and soot/ashes out of the draft door and into the fan. Both times it has happened within 10 minutes of loading the stove and within 2 minutes of the fan kicking on. I'm assuming it is from smoke and gasses building up inside the firebox..and once the fan kicks on and gets the fire going, the flame ignites the smoke/gasses which causes the explosion.

The major issue is each time this happens, the explosion blows coals/ashes/soot into the draft door chamber and all that debris in there prevents the draft door from closing. Air freely enters the stove and it will burn out of control unless I free up the draft door. Luckily I was home both times this happened and I was able to get the draft door freed up and closed, but my concern is that if this happens when I am NOT home, the fire will burn out of control and overheat/boil the stove.

Both times this happened the outside temp was only in the high 30's/Low 40's so the stove sits idle for several hours at a time. Has this ever happened to anyone or does anyone have any suggestions to prevent it from happening?? Thanks in advance for your help.

 

[user 194142]

I have a MF7000 HeatMaster, three weeks old and did EXACTLY the same thing right down to when it was filled. The back door compartment was covered completely with ash and jammed up the fan to the point it quit working. Manufacturer sent an email but no response. This is pathetic in my opinion. I had a Empyre for 18 years prior to this piece of junk. Not a moments problem until I wore it out.

 

[user 194142]

Sorry for the long post, but I have a important question for the OWB owners and I appreciate any help. Last year I had a Heatmaster C375 installed. It has a solenoid that opens a draft door and a fan that kicks on when it calls for heat. Twice so far (once last spring and once this fall) there has been a violent explosion inside the firebox. So violent that I heard it from inside the house and it blows water out the top of the stove and soot/ashes out of the draft door and into the fan. Both times it has happened within 10 minutes of loading the stove and within 2 minutes of the fan kicking on. I'm assuming it is from smoke and gasses building up inside the firebox..and once the fan kicks on and gets the fire going, the flame ignites the smoke/gasses which causes the explosion.

The major issue is each time this happens, the explosion blows coals/ashes/soot into the draft door chamber and all that debris in there prevents the draft door from closing. Air freely enters the stove and it will burn out of control unless I free up the draft door. Luckily I was home both times this happened and I was able to get the draft door freed up and closed, but my concern is that if this happens when I am NOT home, the fire will burn out of control and overheat/boil the stove.

Both times this happened the outside temp was only in the high 30's/Low 40's so the stove sits idle for several hours at a time. Has this ever happened to anyone or does anyone have any suggestions to prevent it from happening?? Thanks in advance for your help.

I have a HeatMaster MF7000 3 weeks old and it did the EXACT same thing!! The only difference is that mine introduces air into the bottom from a fan on the back. Prior to this one we had a Empyre 450... not a moments problem in 18 years.
I e-mailed HeatMaster and in no uncertain terms told them what I thought of their OWB stovesa and demanded to know what happened.... no reply. The stove integrity has no doubt been comprimised now and I want this one replaced at their expense.... what a piss poor design.