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[Bender]

Hi all,

This is my first post for me here, but I've read as much as possible trying to learn the tricks of successfully running an O 250. Mine is a bit unique. I bought it secondhand from an ex-dealer who had it sitting around for a few years. Said he had used it for half a season and decided he needed something larger. It didn't seem to have a lot of signs of use and the price was right. 

Searching the postings, I believe JTS717 and I bought the stoves from the same guy. This is his post (http://outdoorwoodfurnaceinfo.com/forum/index.php?topic=6847.msg55901#msg55901) The airbox design on his is different than mine, but other than that, the two are very similar.

The main differences between mine and the newer models seems to be:
-Firebrick. Newer models have a LOT more than mine.
-Vertical tubes. Mine has only two large tubes coming up from the reaction chamber (about 3" diameter).
-Air delivery in the firebox. Mine is delivered through dime sized holes in 2 air channels that run back-to-front, about 6" off the bottom of the firebox floor.
-Nozzle. Mine is steel (or cast iron) and has 3 large openings in it, about the size of an index finger, which run side-to-side.

I'm good about cleaning it and maintaining a 2 or 3" of ash/coals, and I generally burn good dry hardwood.
I run the air box settings about 4 or 5 turns out.
I upgraded the blower in the off season, which provides more CFM than the original.
I also just installed the siliconized door gasket because the original was leaking quite a bit.

I'm stumped though because it's still not gasifying very well. With the firebox temp at 185+, I can open the main firebox door for a minute and the fire will start burning strong, close it and watch the blow torch in the reaction chamber. This will fire strong for about a minute or two and then snuff out. When I open the main firebox door, the fire has died down and has been mostly replaced with smoke. Burn times at 10 degrees outdoors will be 2 - 3 hours for it to gain a 5 degree differential.  It seems to me that it must still be starved for air. 

I've thought about closing off one or two of the nozzle openings to see if that helps and possibly adding more firebrick in the next off season. I was also considering drilling a 1/4" or larger hole in the airbox and using a magnet to close a portion of it to see if, when the blower is on, the fire would actually suck additional air in through it, or if the blower would just push air out of it.

I appreciate any advice!

[coolidge]

Look at your air inlets in the box closely, I bet there is creosote clogging them off.

[Bender]

Look at your air inlets in the box closely, I bet there is creosote clogging them off.

Last year I did notice some creosote dripping from the air box and had to clean it out, but haven't noticed it this year yet. Before I fired it up this year I did have a look at the inlets and they seemed ok, but thanks, I'll have a look at them again.

I'm attaching a pic of my air box innards. It's laid out horizontal whereas the new ones are roughly the same shape, but vertical. The only adjustable air disc is the center one which supplies the air below the nozzle. The 2 side discs have the bolt heads welded over to the disc. I don't they they intended them to be adjustable, but I could be wrong. I haven't seen the internals of a newer model air box. Are they similar?

[coolidge]

The two on the sides would be my first step, can they be removed and cleaned?

[slimjim]

A trick I learned a while back to remove creosote in bent tubes or hard to reach areas is to cut a section of fish tape used for pulling wires, slide a piece of 1/2 inch copper about 6 inches long over the fish tape,
( use the copper to hold on to the tape and guide it ) then put the cut end into your cordless drill, ( use caution and work slowly ) run the tape into the area to be cleaned gently and turn on the drill, the end of the tape will bang around and loosen the creosote.

[Bender]

The two on the sides would be my first step, can they be removed and cleaned?

I couldn't get a wrench on them, but maybe a vice grip. I can't tell if they're threaded, like the center one, or not. I'll give it a try though. Thanks!

[Bender]

A trick I learned a while back to remove creosote in bent tubes or hard to reach areas is to cut a section of fish tape used for pulling wires, slide a piece of 1/2 inch copper about 6 inches long over the fish tape,
( use the copper to hold on to the tape and guide it ) then put the cut end into your cordless drill, ( use caution and work slowly ) run the tape into the area to be cleaned gently and turn on the drill, the end of the tape will bang around and loosen the creosote.

That's a cool trick! I'll definitely give that a try. Thank you.   

[mlappin]

I’m not sure how tight you’re bends are, but on the waste oil boiler I built i use one of those rods for pulling wire and they can also handle a drill bit that came with it being chucked in the end of them. I simply took a wire cup brush and replaced the round shaft with an old allen wrench then ground a slot in it so it would lock in the end of the rod, the heat exchanger tubes in mine come up, make a 45 go a little further then make another 45.

[Bender]

I’m not sure how tight you’re bends are, but on the waste oil boiler I built i use one of those rods for pulling wire and they can also handle a drill bit that came with it being chucked in the end of them. I simply took a wire cup brush and replaced the round shaft with an old allen wrench then ground a slot in it so it would lock in the end of the rod, the heat exchanger tubes in mine come up, make a 45 go a little further then make another 45.

I don't think the bends are too severe in these tubes, but I will put that idea into the bag o' tricks too. I appreciate the advice.

[mlappin]

I’m not sure how tight you’re bends are, but on the waste oil boiler I built i use one of those rods for pulling wire and they can also handle a drill bit that came with it being chucked in the end of them. I simply took a wire cup brush and replaced the round shaft with an old allen wrench then ground a slot in it so it would lock in the end of the rod, the heat exchanger tubes in mine come up, make a 45 go a little further then make another 45.

Oh yah, I also chuck the rod in my 18volt drill.

[Bender]

The two on the sides would be my first step, can they be removed and cleaned?

I was able to loosen the two side pipe threads and clean out the pipes using a 1/4" cable with the end frayed a bit. You can see by the pics how much crusted creosote came out. I don't think there was a complete blockage anywhere, but it's definitely breathing better now. The air box was bone dry though and looked exactly as it did when I cleaned out a couple of months ago.

I have my set point at 195 and a 5 degree differential. This morning it was down to mostly a bed of coals after a 12 hour burn and water temp was at 168 degrees. I loaded it half full with dry, split cedar. The fire took off quickly with the door open. I checked it again an hour later and the temp was still at 168 with a good fire going in the main firebox, but nothing other than light smoke in the reaction chamber. Opened the firebox door to get the fire burning hotter, closed the door and got the blow torch in the reaction chamber, which lasted for about 2-3 minutes.

I think I've got sufficient air delivery now. I left the discs for the two side air pipes open 7 or 8 turns and I can see a strong air flow feeding the fire, but I'm still scratching my head as to why it won't maintain the secondary burn in the reaction chamber. Nozzle design not restrictive enough? Not enough refractory material?

[slimjim]

Perhaps to much air?

[Bender]

Perhaps to much air?

Could be... The thing that has me confused is why it runs really well for the first few minutes after having the firebox door open. It's like spraying ether into a carburetor. The engine runs great while it's burning the ether and then goes back to sputtering after it's burnt off.

I'll try turning the outside discs in to reduce the airflow a bit and see what happens.

Is the (center) air flow to the nozzle supposed to to create a venturi effect? Since that setting is adjustable with the airbox sealed, I have played with that quite a bit, but haven't seen it make much of a difference.

Thanks!

[coolidge]

Factory nozzle?    Try closing the outside ones right up to 3 complete turns out. 3/16 to 1/4 inch, way too much air.    Check inside the firebox also at those air ports.

[Bender]

Factory nozzle?    Try closing the outside ones right up to 3 complete turns out. 3/16 to 1/4 inch, way too much air.    Check inside the firebox also at those air ports.

Yep, factory nozzle, but a prototype - made of cast iron or steel. Borrowing from JTS717's picture, it looks like the image below.  I have them open about an inch each now, so that could be it. It's going to be around 20 below tonight, so it'll be a day or two before I give that a try. At least once a day I make sure the air ports are open.

Just thinking... The new blower that I put in this fall supports running at variable speeds. I haven't installed a controller for it, so it's just running full-tilt now, but if I am putting too much air into the firebox, adding that controller would be an easier test than opening the air box each time. I think the controller's only $20 or so, so I might have to put that on my christmas list.