Combustion Air Flow Question

DennisH · Post by **DennisH** » Mon. Feb. 21, 2011 8:57 am

Greetings from the Upper Peninsula of Michigan. This is a great forum, and I have been studiously reading prior to operating my new Yukon Eagle IV wood/coal add-on to my existing propane furnace.

I've had the coal furnace fired up continuously for four days now. No problem getting the coal fire started and keeping it going. Got the knack of shaking, banking, etc. However, there is one procedure that everything I've read says is a big no-no, but so far has been working great for me. My ash pan, when fully shut, has no draft/combustion air fitting. The unit itself has a "electronic" damper on the front of the furnac, just below the firebox, but I have no visual way to see whether it's functioning properly or not, as it is tied to the the thermostat. Furnace is in basement, thermostat one level up in great room.

The operators manual says, that once a good, hot fire is established, whether wood or coal, the ash pan door must be fully closed. However, when I do that, even with the thermostat set far above ambient room temp to create demand, the firebox cools to a point where not enough heat is generated to trigger the fan blower. Fire doesn't go out, but it just doesn't burn very hot. What I've done, and with frequent checking over the past four days, is leave my ash pan cracked open about a finger width (1/2 inch). When I do that I get a nice, hot, very controlled fire, particularly with the coal. Plenty of heat, house is warm, everybody is happy.

While I'm not an expert on coal furnaces or fires by any means, I'm not stupid, and I understand combustion and thermodynamics very well. Seems to me that I'm simply making up for what may be a design flaw. My logic says there should be a draft/combustion air fitting in that pan, to bring good air flow from beneath the grates, and all I'm doing is making one of my own by leaving the ash pan cracked. I have watched this like a hawk for four days and have seen no evidence of over-firing, runaway combustion, excessive flue temp, etc. I believe I'm being safe, but I harken back to every post I've read in this forum that the ash pan must absolutely be closed once a hot coal bed is established.

Comments from anybody with more experience than I or similar practice would be greatly appreciated.

DennisH
Bark River, MI

titleist1 · Post by **titleist1** » Mon. Feb. 21, 2011 9:13 am

Welcome to the forum!!
I agree with you it seems like you are creating draft access that should already be built in to the ash door with a slide damper or spinner knob or bi-metal damper control or etc. etc. etc......

Could you post a pic of your rig featuring the ash pan door?

fastcat · Post by **fastcat** » Mon. Feb. 21, 2011 9:20 am

Well first off I think I would be figuring out why the electronic air flap isn't doing its job as it should. As you know just one mistake doing it your way could turn your house to ashes. When you turn the thermostat up high does the air flap open at all? If not change the thermostat, if this doesn't cure the problem look into the electronics, something is not functioning properly. I will keep my fingers crossed for you keeping that door open. I'm sure someone will be jumping in very soon that is running something similar to yours.

dlj · Post by **dlj** » Mon. Feb. 21, 2011 10:02 am

It does sound like the electronic damper is not working correctly, whether or not it is large enough... If you put your thermostat to something well above the temperature of your house, it should be opening up that damper. Then you can go downstairs to look and see if it's opening. Photos of the door and electronic damper would help...

dj

DennisH · Post by **DennisH** » Mon. Feb. 21, 2011 4:53 pm

Thank you all for your comments. I've posted pictures of the outside of my ash pan, as well as the electronic damper control. I cannot visually see inside the cover of the actual electronic damper to verify whether the damper is open all the way or not, based on the demand signal from the thermostat. Spoke with a factory rep today, and he said that people do indeed drill holes in the face of the ash pan to increase air flow upwards through the grates and the bottom of the coal bed. Said covers should be fabricated for those do-it-yourself-drill holes where possible. Won't void warranty if I do that. O.K. Got that. (Next thought: Why isn't there a field change or something to make modified ash pans available???!!) My flue gas temps are around 425-475 degF, so that's just about ideal. I re-adjusted the manometer reading through my draft control damper in the flue pipe to ensure a nice 0.03 inches while I had the factory rep on the phone. What I'm going to do is rake, shake and build up a good hot bed of coals again, and close the ash pan all the way, but not latch it shut and see how that does, now that I've fine tuned the barometric pressure.

DennisH · Post by **DennisH** » Mon. Feb. 21, 2011 5:07 pm

What the factory rep wrote to me:
DennisH
Bark River, MI

Re: Combustion Air Flow Question

Postby Keith Nelson » Mon Feb 21, 2011 9:43 am
Some folks have opted for drilling a few holes in the ashpan door for burning coal.Coal ,especially anthricite which needs a steady stream of air to burn since it is so dense and has a high ignition point up over 850 degrees.
A shut off to the holes should also be fabricated if you elect to do this. Your warranty will not be voided.

Coal is a finicky fuel,but it can be burned in our furnaces.

Another option is to strengthen the draft regulator so that the draft speed is a hair faster.
The result will be shorter burn times with wood .

rockwood · Post by **rockwood** » Mon. Feb. 21, 2011 6:06 pm

DennisH wrote:My logic says there should be a draft/combustion air fitting in that pan

You're right.
When you fabricate this draft control in the ash pit door be sure it's large enough to allow the draft you need......Ashpit door 1/2 inch open would let quite a bit of air flow.
If 0.03 is the draft the manufacturer recommends go with that but I personally wouldn't have it any lower than that on a hand fired furnace using natural chimney draft. Setting draft control for a stronger draft (.05-.06) might actually cure the problem you have but I would still add draft control in the ashpit door especially if you're burning anthracite.

fastcat · Post by **fastcat** » Mon. Feb. 21, 2011 8:28 pm

DennisH wrote:What the factory rep wrote to me:
DennisH
Bark River, MI

Re: Combustion Air Flow Question

Postby Keith Nelson » Mon Feb 21, 2011 9:43 am
Some folks have opted for drilling a few holes in the ashpan door for burning coal.Coal ,especially anthricite which needs a steady stream of air to burn since it is so dense and has a high ignition point up over 850 degrees.
A shut off to the holes should also be fabricated if you elect to do this. Your warranty will not be voided.

Coal is a finicky fuel,but it can be burned in our furnaces.

Another option is to strengthen the draft regulator so that the draft speed is a hair faster.
The result will be shorter burn times with wood .

Well for sure they know they have a problem. If I were you I would find a stove dealer and order two air adjusters that go on an ashpan door (spinner type) and then drill or cut your air holes behind them, looks like you have plenty of room on the door. That way you are sure you can adjust your air flow and get it right the first time. See what some others say. I also agree with Rockwood to up your draft to .05-.06 to see if it helps, I do beleive it will.

DennisH · Post by **DennisH** » Mon. Feb. 21, 2011 9:41 pm

Thanks to all of you who made inputs. I will get to it and see if I can find a good way to make some ash pan modifications, as well as adjust draft.

Post by **franco b** » Mon. Feb. 21, 2011 9:56 pm

You paid for a unit that was supposed to be controlled by a remote thermostat and now find you have to convert it to manual operation at your own expense. Something is wrong here.

McGiever · Post by **McGiever** » Tue. Feb. 22, 2011 12:38 am

I am curious of the wiring to this electronic damper.
You say it gets it's input signal from the t'stat.
I'll assume the t'stat is 24 volt...but what volts is the damper?
Where is the source for the 24 volts to the t'stat?
Could you check for voltage signal for damper w/ a voltmeter?

How come the mfg. rep didn't address the question of possible damper malfunction?

If you need help, try scanning your wiring diagram and we will try to help you out.

dutch · Post by **dutch** » Tue. Feb. 22, 2011 9:39 am

here's a link to the manual on the manufacturers webslite
http://www.yukon-eagle.com/pdfs/manual4.pdf

there are 2 different schematics depending on whether there is an
A/C unit involved. at one point, it mentions 2 different thermostats,
large and small? maybe a 2nd is there with the A/C option

at the end, their FAQ section gives ideas where to check
if the fire isn't producing heat, and where to look at voltages
etc in the controller

DennisH · Post by **DennisH** » Wed. Feb. 23, 2011 9:29 am

My unit only has one thermostat associated with it, but I will check the voltages to/from the electronic damper control unit. Thank you for those inputs.

Combustion Air Flow Question

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