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Creosote Build Up

Started by westyswoods, December 17, 2012, 07:40:16 PM

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westyswoods

This will be lengthy so bear with the detail.
I purchased a Portage and Main ML30 OWB this fall, finally got it set up with first fire the day before Thanksgiving. The stove sits under a shed roof twenty feet from the building it heats. Shed is open on three sides and the stove has two sections of stack with one protruding through the roof line, three plus feet above roof line.  Chimney is the one P&M provides with stove. This stove heats 2000 sq. foot shop/apartment area with ten and twelve foot ceilings. Heat source is in floor hydronic which icks up heat from a plate heat exchanger. The two systems are separate and don't mix. Hydronic heat is pressurized while OWB is an open system.

P&M is a forced air induced system which is activated with an aquastat. The whole intent is to completely shut down or temper any fire when heat is not called for. I have my stove set for water temp of 180 on top end with a differential of ten degrees. Stove kicks in at 170 out at 180.

When this stove was first fired considerable condensation occurred. This is to be expected at fire up as all materials need to get up to temp so moisture is driven off.

BEFORE WE GO ANY FURTHER I NEED TO STATE I DO NOT BURN WET OR GREEN WOOD. I have dealt with and sold firewood for well in excess of twenty years. I know the difference.

The moisture problem continued, with water actually dripping from fire and ash doors. I colud not get them to seal. Adjusted door to no avail. Contacted P&M spoke with Bryan who has been great in trying to help figure out what is going on. He sent two new gaskets which I have replaced and stove is now sealed.

One would expect the problem to be solved not so. The by products of combustion have turned the entire inside of this boiler into a tar/cresote coated chunk of steel. Let me again repeat not just a small section where one might expect it could be a little cooler. It is coated front, back, top, bottom to the point chunks a hanging.

I am at a loss for what is going on.

Besides the fact this toxic brew inside the stove will radically reduce the life and make it less efficient, especially when it becomes glazed, which it is becoming. The process off stoking the firebox is anything but safe. I am not referring to backdraft or flash over. The toxins in creosote is extremely harmful. When opening the door to feed if fan has not been running to purge, it is a stand back and let the cresote filled air clear. I have seen other P&M's which is and nothing like this.

I have several theory's which may be causing the situation, but thought I would let the members of this forum start picking it apart.

Please any and all suggestions and or questions are welcome.

I looked at five different OWB's before settling on P&M. IMHO they were by far the best designed and built, I still believe so. Just need to figure what is different about this set up.

Thanks In Advance
West

BTW Burlkraft stopped by today checking on the elderly, showed him the inside, he commented something to the effect of it being a tar pit.

Stay Safe and Be Healthy
Westy

beenthere

West
I would expect the creosote (have it in my boiler) on the steel wall of the burn chamber that has water jacket on the other side. That water is max 180 deg which will condense smoke and wring out the creosote. I'd be surprised if it were different, but haven't poked inside any OWB's.  And maybe I'm not thinking of as much creosote as what you are finding in yours.
May not help to have had such warm weather that we've had since Thanksgiving either.

Sorry to hear of the problem.
Yours seemed to be such a cool setup that you were assembling for heat. Hope someone has a better answer.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

westyswoods

Beenthere,

Thanks for the response. I agree some creosote is expected, also right on with the weather factor. It is my understanding that any water temp above 160 should condense the smoke and as you state, wring out creosote. Not happening here.

Yes you would be surprise as to amount being formed. I will attempt to upload some pics if I can remember how. They don't show true problem but can get an idea.

Thanks Westy,
Stay Safe and Be Healthy
Westy

thecfarm

Sounds like my Heatmor, just about the same settings,

P&M is a forced air induced system which is activated with an aquastat. The whole intent is to completely shut down or temper any fire when heat is not called for. I have my stove set for water temp of 180 on top end with a differential of ten degrees. Stove kicks in at 170 out at 180.

You would think all that junk inside would burn off. I forgot how hot the inside of mine is suppose to get. Some very high temperature is all I can remember,enough to burn cresote. I use mine to heat my hotwater in the summer and notice no diffeance on the inside than when it's 10°.A kinda dumb question,you don't have a leak in the OWB?
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

westyswoods

Not a dumb question at all. It is one of the possibilities we are looking at. The leak would need to be into the fire box and I assume at the very top of or above water level. I have been keeping track of water level and there does not seem to be any loss. Not to say there is not as even a pinhole leak has the ability to produce massive amounts of vapors. If memory serves me correctly there is a 1700 to 1 factor when water is converted to steam, it may even be 17000 to one. Thirty four years since learned that one.

I am set up to pressure test but the stove needs to be shut down before doing so.

Thanks Westy
Stay Safe and Be Healthy
Westy

martyinmi

Three of us bought P&M Optimizer 250's and we all have the same issues, although not as bad as yours sounds. Ours are gassers, no obviously not the same breed as yours. We've noticed that by jumping the off limit parameter to 190-195 degrees that our creosote is reduced by about 50% or so.
If you check the inside immediately after it cycles, does it appear that some of the creosote has bubbled up,burnt, then flaked off? From what I've seen, that is completely normal for a non gasser to do. My FIL's CB 6048 operates just as you describe yours does. He set his high shut off temperature to 190*.
It sounds like you know what you are doing, but I'll ask anyway. You did use one upper port and one lower, didn't you? In the event water is not moving properly inside the jacketed area you could be getting layers of different temperatures, which could potentially give you false temperature readings on your aquastat. I prefer to not divulge how I know that scenario can happen :-[ :-[ 

Keep us posted!
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westyswoods

High port = output
Low port = return

There are times when this boiler will start to bang, always after fire door has been open and coals have really taken off, temp increase.

Sounds like when we were kids and had the old steam radiators. They used to get air locks in them, difference being they are closed systems.
Stay Safe and Be Healthy
Westy

beenthere

The manual or P&M say anything about trapped air in their open system?  Someone mentioned the problem of filling an open system with water and not getting air out of the pumps by flushing water through them before operating. Again, likely the manual should address that on startup.

Not knowing for sure what is causing this, but suspecting that there isn't enough demand for the hot water that this unit can produce in a very short time. The water temp gets to the low set point and the stove fires up, but the high set point is reached almost immediately and the unit goes into shut-down.
Just isn't burning hot for long enough time to get a cleaner burn thus the overload of creosote and tar.

Can you experiment and run it for awhile at full bore by supplying it with unheated water (tap water if cold water won't bust something) and just dump all the hot water it produces?
The idea being to see if it will burn clean and burn off the 'tar' pit.

Seems the company techs would be familiar with this problem too, and if it is what I suspect then they would have run into it with other warm weather start-ups. So I may be far off base here.

Banging might indicate some real hot spots causing boiling and steam, and smacks of poor circulation.
For the old steam systems, I think banging was water condensing in the steam pipes and getting banged around by the steam flow. 
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

albirk

mine is the same way can't wait for cold weather so the stove will kick on more often like once an hour not once every two or three hour

westyswoods

Beenthere,

Great suggestion. Need to look at just how I can do this while keeping the water temp up but yet above that condensation point.

I need to document cycle time. In talking with reps this was never mentioned. It has been in the back of my mind that this stove may be over sized for my system. I designed and installed the hydronic infloor to be very efficient. With the plate heat exchanger the heat side may not be requiring enough BTU's from supply side (stove). I cranked thermos up and have it 88 degrees just for this reason. Pex is embedded in five inches of concrete with two inch high density blue board for insulation. Once heat sink gets up to temp not much is needed to maintain. Can put an in line thermos on return at furnace to check.

I can tap into the two ports not yet used to increase circulation if need be. One of the selling points of this stove was the round configuration of firebox which should prevent just such a problem.
Stay Safe and Be Healthy
Westy

thecfarm

Another idea,turn the blowers off and have it heat the house. Turn off the blowers to the OWB so no air can get into the fire box.The water temp will drop down. drop it down to 120-140,I would think. Than turn the blowers back on. It will have to run for a while to get the temp up to 180 and than check the creosote  inside.
If you had a leak,the water level would be down. I had a small drip on the back side of one of my lines coming out of the OWB.It was on back side where I could not see it and by the time it cut down to the ground it had evaporated. I was starting to think I had a hole in the OWB.
I experimented with green wood,cut it in the morning,burn it at night,with both soft and hard wood.No difference in creosote. Just smoked more and used more wood.The inside looked like I was burning dry hard wood.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

doctorb

Hard for me to tell if anything is "super" wrong here.  With an efficient stove having long cycle times between burn cycles, creosote is going to build up.  With my 2300, I just burn (fans on) with the door open during loading and the fire burns upward, melting and burning it off.  With a tight system and all airflow going down through the coal bed (I am presuming that your stove is a gassifier) what's left behind in the firebox is the residue from when the blowers turn off at the end of the cycle.  My OWB firebox always looks black.  I agree that, as the weather gets colder and the cycle times shorten, this will be less of a problem.  If you look at FF threads regarding the use of OWB's iin the summer to provide DHW, they had increased creosote problems too.  I think the reason for their creosote build-up is probably the same as yours.
My father once said, "This is my son who wanted to grow up and become a doctor.  So far, he's only become a doctor."

thecfarm

You said chunks are hanging down. How thick?   Mine has some flakes of cresote hanging,just about like thick paper in places hanging down.I would say about as big as my hand.Some places are bare and some have pieces hanging down. It's very brittle too. When I open the door there is no smell of creasote,not alot of smoke either. I don't have to wait for it to clear like you said.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

r.man

I have had bad creosote problems with mine and saw it in a friends although the owbs were not P and Ms.. Was always due to lack of air coming into the firebox. If your system is reasonably efficient and the weather has been warm you may have an air problem that is going to become obvious in the cold weather or it might be cycle time. I am not familiar with your air system, is it a blower and if so does it also have a damper closing the opening when the blower is off? I would be taking a quick look at these components to make sure nothing was left unhooked, backwards, bent etc from the factory.
Life is too short or my list is too long, not sure which. Dec 2014

thecfarm

I have the flaps,on my blowers. The one at the back is the worst for getting clinkers into it and keeping it open just a little. There is a tray before the flap to catch the stuff but that gets filled and than into the flapper it will go. 2 ways I can tell it's getting air. I open the feed door and the coals are glowing red. Should be all black,like the fire has gone out. And there is smoke coming out of the stack on idle. Should be just a little and I do mean a little when it's not cycling.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

beenthere

For clarity on the P&M design, here is a link with a video.
http://www.portageandmainboilers.com/wood.html
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

ga jones

I've owned 2 owb from 2 different manufactures and have seen many others. Heatmor mahoning hardy free heat machine friends of mine.I've loaded all of them for them at different times. I've never seen one that wasn't full of creosote. I have not seen the inside of a gasser. But all the non gassers build up. The only one I've seen that was clean inside was one that my friend burned coal in. If you widen the differential to the max you will burn off some of it.however not to the extremes you have.the only times I've seen that much was in a cracked one.also burning green wood in warm weather
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gspren

  This is my 3rd year with my P&M ML30 and it isn't near as bad as you desribe. I have my high at 180 and a 4 degree diferential so it kicks the blower back on at 176. I know that that sounds close but when the blower kicks off at 180 temps climb to about 185 and when the blower kicks on at 176 temps often drop several degrees before starting up again so I still have about a 10-15 degree swing, works for me.
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

gspren

 How often and how much wood do you put in at a time? I find mine works best when I aim for twice a day loadings and put in just enough to get through to the next loading. If you look in 2 hrs after loading things might be wet but the last few hrs before reloading things are dried out.
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

albirk

Westyswoods one ? do you burn the same size wood you sell to people with inside stoves when i went to the OWB the splitter stays in the shed a lot more (12" down no split it still drys for 2-3 year )i no if it was split it will dry better but i put the OWB so i can burn larger blocks my thinking if i can load it in the truck i can load it in the stove i also have found loading twice a day helps i'm lazy when it comes to splitting i will make shorter blocks so i dont have to split

westyswoods

Thanks to all for the thoughtful responses. Quite sure we've got the problem narrowed down to couple of choices.

The first being the stove is over sized for the heat load the building requires. As stated in an earlier post this building was built to be very heat loss efficient. I was heating with a 100,000 btu Dunkirk gas boiler prior to installing P&M.

The boiler worked fine although never was able to hold temp in cold weather like I wanted. 1000 dollars a year for LP was big factor for switching.

Monday night at 2200 I went down and loaded stove for the evening, put in about six pieces of oak 6" diameter 30" inches long. Eight hours later went to check on fire load. There was water literally running out of every opening on the front of the stove. Opened the fire door and the wood loaded the night before was basically unburned, a little charring present. Water temp on aquastat was 185, with water temp in building at plate exchanger 180.  There was still a good bed of coals in bottom.
I actually pulled two of the pieces out opening the ash door and let it fire up to around 200. Closed up and let burn down to just coals, five plus hours later. The pure water was gone although there was still much tar based creosote present.

Did not load ad heavy last evening and will see what happens this AM. The temp is supposed to drop this week also as it has been in the forties since firing up.

I spoke with Bryan at P&M yesterday and his suggestion was to increase the heat load. Agree this can be a solution, but how. I believe Beenthere also suggested, the difficulty is with a hydronic in floor hear (5" concrete heat sink well insulated below), the temp holds for a long, long time. Not like forced air where you can just open the doors.

Solution is going to be learning to manage my loading better, I hope. With colder weather coming we will see. Always wanted a little greenhouse maybe build one off south side of shop and heat with forced air.

The other piece being stack height. I have 6 foot of chimney with three foot through roof. Ridge of building runs north south. Stack goes through roof near the east edge so any west winds drop down over peak and cap stratifying the chimney opening. This is should not be an issue when the fan is running as positive pressure will take care of it. During shutdown that lack of draw may be keeping the gases captured. I would appreciate feedback on the chimney as I don't feel like spend a couple hundred bucks on another section without positive results.

A special thanks to all who have replied as your words of wisdom are invaluable.

Westy
Stay Safe and Be Healthy
Westy

gspren

  Westy, in the main door opening where you load the wood is the bottom plate flat or is there a raised area running across, this would depend on when your stove was made? I am not sure how the newest models are but on my ML30 it had the raised area and I had it changed.
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

westyswoods

 It is flat another change I see in my stove versus the You Tube video with Bryan demoing is my stove does not have an air inlet in the center of the back fire box wall. The manufacture date of this stove is 10 of 11.

What was the intent with removal of the lip you speak of?

Westy
Stay Safe and Be Healthy
Westy

gspren

Quote from: westyswoods on December 19, 2012, 03:09:52 PM
It is flat another change I see in my stove versus the You Tube video with Bryan demoing is my stove does not have an air inlet in the center of the back fire box wall. The manufacture date of this stove is 10 of 11.

What was the intent with removal of the lip you speak of?

Westy

  When they removed the air inlet from the back they had a slot come up in the bottom plate of the door opening and a piece of plate bent like an angle iron welded over it to supply air above the coals. This caused condensation from the door to pool up and leak. I removed about the middle half and welded a piece in to fill the exposed part of the slot but still allowing some air in at the sides. I knew they were changing that but don't know how. Does your stove let some air in above the coal bed? The biggest thing I feel is to not put too much wwood in at a time, a half load will last mine more than 14 hrs unless it's really cold out. It shouldn't take too long for you to get a feel for how much to load. Good Luck!
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

Logging logginglogging

I usually take a garden hoe and scrape the lil shelves on the sides on my E-2300 a little each time i reload. This keeps them very clean and allows the ashtrol to be in contact with metal. I do have a hard time cleaning off the shelf of the back wall and usually just scrape  and chip it all off when i clean the stove.
if I had a flatter garden hoe i could probally get the back wall, and mabye ill midify this one or buy one if i see one around.
Keeping the coal bed low and managed helps... dont let morons load the stove when u r not home... like people that come to let your gog out side and feel compelled to jam an entire cord of wood into your stove.

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