Combustion gas analyzer reading off Greenwood boiler

From memory: I would think your draft is towards the top of the desired setting. I know the owner's manual show .05-.07 for draft. The 560F stack temp makes me feel like you could choke it down to the .05 number and recover more heat.

I hope you will try this, it would be great to see those numbers too!!

Choke it down is great, but wouldn't it put out less heat. Since it is -16.

ihookem said:

Choke it down is great, but wouldn't it put out less heat. Since it is -16.

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Decreasing the draft should slow the rate at which the combustion products pass through the heat exchanger -- giving the exchanger more opportunity to recover heat before it goes up the flue.

I have a GW 100,love it so far. Where can i measure draft on the chimney. I have insulated ss 8 inch pipe I am not to keen on drilling into that stuff just for a draft measurment. I am only running 2 four foot sections but this is enuff to get me at or just over the peak of the shed. Stove is set 8 inches off grd on concrete pad and with the t at the rear of stove the total height of chimney is just under 12 ft w the weather cap. Thanks

what brand and and model of combustion analyser are your readings from, does it offer the calculation, based on wood parameters, my testo 327 with your readings calculate a much lower effiency% the calculation testo uses is flue gas temp minus supplied combustion air temp, divide that number by the co2 value, then subtract that number from 100. with your, 560 deg- 70deg=490/7%co2=70, 100-70=30% combustion effiency. the high o2 reading and high stack temp might indicate too much draft, if draft was less, the o2 might be lower 6/8% range and stack temp would be lower increasing effiency. high burn garn numbers 251deg-55deg=196/13%co2=15.08, 100-15.08=84.92% combustion effiency

Deere10 said:

I have a GW 100,love it so far. Where can i measure draft on the chimney. I have insulated ss 8 inch pipe I am not to keen on drilling into that stuff just for a draft measurment. I am only running 2 four foot sections but this is enuff to get me at or just over the peak of the shed. Stove is set 8 inches off grd on concrete pad and with the t at the rear of stove the total height of chimney is just under 12 ft w the weather cap. Thanks

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Do you have even a short bit of non-insulated going from the boiler to your insulated flue? If so, make a small port there (draft should, as I understand it, be uniform within the flue, except at/ near the top). I'd tend to think, though, that it's very unlikely that only 8 feet of 8 inch pipe would be at risk of creating too much draft.

You could slow the draft inducer fan down. Most have a speed control, if not use a motor type of dimmer switch.

try the o2/co2 temp readings without the inducer after the hx tubes have been cleaned about 45 minutes into burn, apply the math and let us know the results, i am hoping we will be happily suprised

AlaskaWoodburner said:

The only way to reduce the draft will be to add a barometric dampner. I was also going to try cleaning the heat exchanger tubes and see if it lowers the stack temperatures much. I have not cleaned the back tubes since last spring and they could certainly use it.

I drilled a hole about 20" up from the tee and about 24" below my draft inducer fan. I have the draft fan wired to a timer so I can turn it on for 20 minutes or so to get it burning hot again after adding more wood.

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if you can remove a section of chimney pipe that will also lower draft, also you can install a flap like the old wood stoves inside the pipe up close to the boiler.