Understanding the EKO Air Adjustments

[Eric Johnson]

I hope somebody else does, because I sure haven't figured it out yet.

I'm going to post a picture and tell you what I think I know. Then hopefully you other EKO owners can verify it or dispute it.

Primary Air Inlets:
Control the flow of air into the firebox.
What are the consequences of letting too much air in?
Too little?
Is there a recommended setting?

Secondary Air Tubes
Deliver secondary combustion air to the nozzle or nozzles
What are the consequences of letting too much air in?
Too little?
The recommended setting is 3.5 turns for each tube

Blower Air Inlet Slider
Controls the total amount of air available to the boiler
What are the consequences of letting too much air in?
Too little?
The recommended setting (according to the dealer) is about 1/4-inch in warmer weather, expanding to an inch or more when it gets colder

What I don't have a good feel for is how these settings work in harmony, and how you would go about finetuning the three different settings to try to dial in the combustion process. Do you do it when the boiler is hot or cold? Can one setting negate another one?

I'm am also dimly aware that the air settings help determine, to some extent the stack temp, and therefore the efficiency of the heat transfer. And obviously the proper mix is important to get the cleanest burn.

I learned the other day that the secondary air tubes have a series of holes drilled into them to deliver the right air mix to the nozzle. I'm picturing something like a natural gas burner. Cozy Heat Dave tells me you can see the holes with a flashlight, but I haven't looked in there yet (shy, I guess).

Here's two photos that will hopefully get us all on the same page when trying to figure out which gizmo we're discussing. If I've got the name or function wrong, please speak up.

Note that I glued a couple of modified (shortened) wire nuts to my secondary air adjustment screws to make them easier to adjust. It's not perfect, but it's better than fooling around with a little screwdriver. Of course, now you can't get a crescent wrench in there to set the retaining nut. I use an 8mm open-end wrench now. A couple of 8mm wingnuts would be just about perfect.

 

[Nofossil]

Had a long talk today with someone who really understands the chemistry and physics of wood combustion. Still have 'stoichiometric' and 'adiabatic' bouncing around my brain. His analysis bears out what I had thought, and I've refined my goals for experimenting with thermocouple and oxygen sensor experiments.

Basically, the blower inlet controls the total amount of air avaiable to the system, which determines the maximum burn rate and heat output for the system. The combination of primary air flow rate and nozzle cross-section determines how much actual combustion happens in the primary chamber. The critical adjustment is the secondary air inlets. The goal is about 60% to 70% more air than you would theoretically need, since not every oxygen molecule will find something to combine with. It's much better to have too much than too little secondary air.

If you can measure secondary combustion temperatures, you want to adjust the secondary air to get the highest temperature, or just a bit more than that.

As soon as I get instrumentation in place, I'll file some reports.

 

[mack7]

So on the secondary air adjustments which way allows more air in, screwing them in or out? I notice on mine that the rear nozzle does not ignite many times and the front is always cranking and my air adjusters are set the same. I think I remember Eric saying the right one is the front nozzle correct. Eric when you say 3.5 turns is that from all the way in or all the way out?

 

[Eric Johnson]

Alright! Another EKO 60 owner.

I think I was wrong about front and back nozzles being independently tied to the secondary air controls. They both play a critical role in keeping both nozzles supplied with fresh air.

Turning the screws clockwise cuts the air supply; counterclockwise opens them up. For the 3.5-turn setting, crank them all the way in (clockwise) until they won't turn anymore, then back them out 3.5 turns to be at the recommended setting.

If one of your nozzles doesn't catch, it's probably either that it's cooler than the other one, or possible blocked by ash or wood that hasn't caught on fire yet. I've found that you can fix that by stirring things around with a poker (hopefully a more substantial one than was shipped with the boiler) or the provided hoe, and then throwing a few more chunks on. They they should both light off pretty good.

If you ever try to turn one of those adjusters and it won't turn either way, don't try to force it. You'll just break off the end of the adjuster. If that ever happens, just post it and I'll explain what's wrong and how to fix it.