Econoburn primary air adjustors

[cumminstinkerer]

As promised in another thread here are the pics of my primary air adjustment screw, I'm sorry the photo is a little fuzzy. The two round discs are the factory installed secondary air flow adjustors. the issue I and some others have had is very high flue temps and short burn times. After a lot of playing around I did a couple quick experiments with tape blocking off part of the rectangular holes ( the primary air tubes leading into the upper chamber). The results of the quick tests proved favorable and prompted me to make a real adjustor. I actually looked very hard at how the EKO boilers are setup and how guys were modding their adjustors, I decided on the screw type coming out through the front do to the confines of my install. I simply drilled two holes in the cover over the center of the tubes and welded nuts to the back side, a piece of 1/4 all thread for each, and piece of 10ga mild with a hole through it in the center, a nut on side facing the tube with a tack. I am still tuning but have found that if run between 3 and 5 turns out from closed on the new adjustors and 3 turns out on the secondary screws, my burn time jumps from 1-1.5 up to 2.5-3 hours, I see no loss in heat output from the original design. My flue temps dropped down from mid to high 500's into mid 400's. Like I said I am still tuning a bit, trying different combinations of air to settings and seeing what each does. Bear in mind mine is the smallest econoburn, it is a 100, there is another member on here with an identical boiler that did not have the high flue temp issues so clearly there is some variable that we can't physically see. The top pic is the back side of the fan mounting plate with all four adjustors installed, the bottom pic is what the air channels look like behind that plate.

 

[mark cline]

Last winter , Cumminstinkerer and I had been talking back and forth on primary air control. I came up with a slightly different type of control. In a nut shell, my design used a door hinge ,tack welded to the boiler face and a threaded rod , to screw in and out to open and close the opening.
My results have been favorable in reducing my flue temperatures from the 850 range down to 600 -650 , now keep in mind my Econoburn 300 is considerably larger than the 100 . Although my results are a great improvement over the previous winter , I’m still trying to reduce the flue temperatures to the 450-500 range if possible. I had started with weighing my wood per load and can raise my 1500 gallons of storage , 70 F in a 6 hr burn time with about 200 lbs of maple and ash (17% MC). A few pictures of my setup, Econoburn 300 , 280 gal expansion tank , 3 -500 gallon insulated hot water storage tanks, all before the system was plumbed together .

 

[salecker]

Hi Mark
Here is a picture of the angle iron i added to the bottom end of my turbulators.I did this to each one and saw a dramatic drop in my flue temps.
I am thinking of doing the same to the top of them,effectively trying to keep the gasses in contact with the flu tubes a bit longer.

 

[mark cline]

I had thought of that modification this morning when I was emailing Bruce about his gift to me of the saw blades to make the cutters. How many turbs did you modify out of your total count of tubes ? I think my 300 has 5 tubes , I was thinking at least one angle at the mid point of the turb on each tube. Too much? I’ll have reread the thread . Thanks

 

[salecker]

On mine i put one on the bottom of all 6
Don't forget the fact that all i burn is dry Spruce.
The only time i have seen high flue temps this winter is after the reload.

 

[mark cline]

With my adjustments of the fan volume, cutting back on the primary and the barometric damper, my flue temps are 550-650 after a reload and getting 7 hrs total burn time . Heating my storage from 120 to 190+ with 200 lbs of maple , ash , cherry and beech . I will be doing something with an angle welded to the turbs but just not sure exactly what at this time. Was thinking about mid way up the turb on all tubes . Going to do a little more research. 😎

 

[brenndatomu]

You guys are on the right track for sure...those factory flue temps are insane!

 

[SSweet9c1]

This is great info.. I've been thinking for years that 500+* flue temps is BTU's wasted... I've joked about buying some sort of used fuel oil boiler and modding it so my chimney flows through it! lol I've never had ANY creosote build up in my chimney... Lots of ash goes up it, I'm thinking maybe that's too much airflow going through the whole thing...
Great info! Thanks!
Jon

 

[mark cline]

If you have this pie shaped louver on your blower , it will cut back the air and lower your stack temperatures. I run mine at 1 1/4” open , this plus the barometric damper cut my flue temperatures from 800 to 550 .

 

[SSweet9c1]

The upper bolts/wingnuts I've never seen before (never looked!) I'm wondering if this is air flow control?

 

[mark cline]

That’s your secondary air control, usually 2-2 1/2 turns out or open .

 

[SSweet9c1]

So you are saying, back the wingnuts off, turn them in all the way then back them out 2-2.5 turns?

 

[mark cline]

Yes , but count the number of turns in so you know where you are now. Recommended setting is 2 1/2 turns . Do you have the pie shaped louver on your blower?

 

[SSweet9c1]

So they were out probably 7-8 turns. I set them in to 3 for now, will give it a day and see what happens...

 

[mark cline]

You may see a difference , but if you can restrict the flow into the blower , that’s where you will see a difference.

 

[SSweet9c1]

Hey, I finally got around to taking the cover off my blower, will adjust the pie down to 1.25" and see what happens :D

 

[TCaldwell]

Reducing mass airflow = reduced btu output, so naturally the flue temps will go down, extending burn time, not a bad idea if you have limited storage.
If you reduce primary air alone, boiler output will go down, secondary will be over aired reducing flue temps, incomplete combustion causing lower efficiency.

 

[mark cline]

I had reduced my pie opening to 1” a few weeks ago and it lowered my stack temperature to 450 after a reload and holds about 400 . When I get back home from Florida , I’ll reduce my secondary air to 2 turns out . I’m very satisfied with the way my Econoburn 300 is working with my settings that I have now , but always looking for improvements. Before you make any adjustments, write down all your settings so you can go back if things don’t work out.