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[coolidge]

Had some time in Oct. to do a few things to my 250.
1) Added another row of firebrick(1") in refractory chamber.
2) Made a new nozzle with 1" firebrick ( 1/2" wide, length of original)
3) Glued a piece of EPDM to blower flapper
4)Reset all air settings to 1.5 turns out.
5) Turned air disk on blower completely in, used aluminum tape to cover half the remainding opening.


 Wood usage. 3/4 cord in a month.
 Boiler tubes MUCH cleaner.
 Small amount of fine ash.
 Shooting for 5 cord this year.

[martyinmi]

OK...you've peaked my curiosity.
Why the extra fire brick in the secondary burn chamber?
With the rubber attached to the flapper, does the fire go out if idle time happens to be 4 or 5 hours or more?
Is the 1/2 inch width at the bottom of the nozzle? If so, that's about 4.75 sq. in. of area.(In the neighborhood of 4 sq. in. from the factory)
Do you still get the blue with a hint of orange in your secondary flame with your air inlet settings that low and the nozzle area that large?

I've went in the other direction this year with mine. Our buddy karlk cast me a new nozzle that displaces a little over 2 sq. in. (down from the factory cast 4 sq. in.) I've opened both air inlets all the way.
So far I love the way it functions. I get almost zero smoke ever. The secondary burn flame looks nearly perfect at all stages of the burn. It appears to be using less wood.

The only drawback to what I've done so far appears to be the reduced btu capacity of the boiler when a quick recovery is needed. Intertech's (one of the test facilities the EPA uses) report shows peak BTU output at well over 200K on our boilers during full gasification. Based on the calculated lengthened recovery times with the new nozzle, I believe I've reduced mine to a bit less than half of that, which is exactly what I was looking for. My home will never require close to 100k BTU/hour.The BTU output for a 12 hour full burn should remain roughly the same or maybe even a bit higher because of the increased efficiency. My EGT's have dropped from 300*- 450* plus, down to about 260* after a good cleaning to around 325* after a couple weeks of running. The boiler cycles much less frequently, as cycle times are about twice as long. The good folks at the hearth forum tell us that we gain approximately 1% in efficiency for every 25* drop in EGT. I'm guessing that I'm gaining conservatively (I love that word!) 2%, probably closer to 3 or 3 1/2% more efficient after two weeks burning between cleanings because of the smaller nozzle. I've not noticed hardly any change in the cleanliness of the heat exchange tubes- maybe a bit less debris in the tubes and a bit more in the secondary burn chamber, probably resulting from less velocity and fewer CFM's going through the smaller nozzle.

BUT......you've put the gears in motion inside my melon, my friend!

On a side note-
If anyone needs a new nozzle for their 250, I'd encourage you to send karlK a PM. He can make you about anything you want and he is cheaper that the folks at P&M.

[jreimer]

Are these modifications on the older model 250 or the newer 250?  I have the newer model and some of these air settings are confusing.

If I turn my air disc all the way in, it is completely blocked, and 1.5 turns on the air settings is next to nothing.

I've been fiddling with mine as well, and would gladly trade some output for efficiency.  Do I need to go with a smaller or narrower nozzle if I turn down the air settings?  It seems tough to sustain gasification when you turn the air down too far.

[martyinmi]

My 250 was manufactured in '11, so I guess it qualifies as a newer model.
If you want to play with the nozzle in yours, pm karlK on this site and tell him what nozzle size you'd like and I'll bet he'll be able to make you one.
That fellow is a masonry magician in my book! I've simply explained to him what I wanted over the phone and a perfect nozzle appears on my deck via Fed Ex or UPS.
As far as air settings are concerned with my smaller nozzle, I leave everything wide open. There are only so many CFM's that will pass through a given opening with X amount of pressure. There are variables of course, but we are not dealing with squeezing the highest volumetric efficiency out of a small block Ford head. In time, as the nozzle erodes away, I think I'll need to squeeze off some air flow.
If I had the extra money, and more importantly, the extra time, I'd love to buy a vfd and play around with loosely based Lambda controls.
There is a few guy who frequents the hearth forum who has employed Lambda controls on a Garn boiler. He maintains that he has achieved 90% PLUS actual, not theoretical, efficiency. To put that into perspective, most gassers function in the upper 70's and lower 80's where efficiencies are concerned (based on a tad over 6k available btu's from a pound of 20% mc wood). His is probably about 10% (or more) more efficient than the average gasifying OWB or European styled IWB.
It's hard for me to justify spending a couple thousand dollars on high tech controls to maybe improve efficiencies 5%.
Momma would not be happy with me when she saw the credit card statement.

[slimjim]

Experimenting is great guys, thats how stuff gets done in the field, I can't see how almost eliminating the air from the blower will help and may throw the squirel cage blower off balance but, hey if it works for you great, Coolidge did you ever replace your pipe, Marty did you try the upgrade door gasket, and what became of our conversation on the mixing valves.

[martyinmi]

Richard,
   I sent an E-mail about the cost and availability of 3 mixing valves to Rory. He hasn't got back to me yet.
All three of us 250 owners in this area bought enough gasket material to do both doors. I've not changed mine out yet, as it isn't leaking. The other two have. One guy had zero issues changing his, and loves the new silicone impregnated rope. The other guy got his a$$ kicked when he changed his out, but he did finally make it work. Haven't talked to him in a week or so, so I suppose no news is good news.
Two of us now have made boxes with doors that we've mounted on the front. We have zero condensation on the ledges now.
We call them "External Loading Doors".

[coolidge]

Experimenting is what it is and seems to be working, for me anyway.
I added the firebrick just cause, they were laying in the woodshed waiting to get broken.
The EPDM flapper? My boiler runs for about 15 minutes in the morning(645 ish) them not until 2 to 3 in the afternoon with temps around 40. I was out there when it had a cycle time in the afternoon, no visible coals, didn't rake them around though.It was just over a minute from when the blower started to gasification.

I do have more blueish flame now than I did before, the flame is just long enough in full swing to hit the refractory on the bottom.

Slim, not shure what pipe you are talking about.

[slimjim]

Coolidge, we spoke in the spring, I thought you said you were going to change or add some pipe to your stove, Marty, I will speak with them tommorow

[coolidge]

No I never did, I was going to move the stove so I could heat the shop with it too. I just put a Rinnia in the shop for now.

[jreimer]

Coolidge and Marty, what type and size of wood are you burning in your stove?

Coolidge, how did you make your own nozzle from firebrick?  Did you cast it or assemble it?  Have any of you had any issues with ash plugging up the nozzle when you turn the fan disc in for lower air pressure?

[slimjim]

If you guys need anything let me know, we are trying to stock a few of everything mechanical as sometimes it's faster for me to ship.

[coolidge]

jreimer,    I cut some to fit laying flat. Assemble them too fit the opening of the old nozzle.

As Marty has said, he had karlk I believe cast him one. I do have a new one from P and M but have not had the time too tackle that noisy messy job.