Wrong Air Intake Setting

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leowis1
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Post Wed. Feb. 27, 2008 8:57 am

Hello Everybody,

I'm starting a new thread because I found another problem with my efm stoker setup. Before I never had a baro-damper installed and I was burning through the coal. After I installed it and used a manometer, I got that problem squared away. However, I was getting a strange positive pressure reading over the fire.

I found that the feed rate was on 5 teeth and the air intake was set to 6. I backed the air down to 5. Can anybody tell me what is the adverse effect of having too much air on a coal fire?

BTW, I did pay the dealer the check over my entire install. He set the teeth and air. It wasn't until I found this board that I realized how screwed up I was. Thanks!

Leo

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coaledsweat
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Stoker Coal Boiler: Axeman Anderson 260M
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Location: Guilford, Connecticut

Post Wed. Feb. 27, 2008 9:18 am

You may just be reading the manometer with the wrong hose? Is it a Dwyer with a siamesed hose? If so, you are probably on the wrong hose.

You should be reading the chimney draft in the stovepipe prior to the barometric damper. If you are reading it in the unit over the fire, that is overfire draft and not chimney draft. They are two different animals. You may get a positive reading with the draft blower running when checking your overfire draft. That would depend on your unit and its setup, chimney, manual pipe damper, etc. A positive draft can be dangerous, so double check everything.

The feed shouldn't impact the draft much, if at all.

Some details would help, I forgot what the details of your install was.

leowis1
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Post Wed. Feb. 27, 2008 1:37 pm

Hi.

I was using a Bacharach(?) manometer prior to receiving the Dwyer in the mail. I did measure the draft in the flue in between the boiler and the damper. The manometer didn't have a negative or postive sign next to the numbers. I'm guessing the flue pipe is negative because my CO detector never went off, the flue pipe is cooler, and air is being sucked into the damper, not pushed out. Anyway, the reading is a little higher than -.01. When I close the damper door the needle shoots up to -.03.

When measuring the draft over the fire, I'm getting positive .015ish. This is when the stoker is running. If I close the damper door, the needle moves up to positive .02. This stuff is starting to look like voodoo. :? Why would I get a positive pressure over the fire?

I double checked the feed rate. The dealer told me he set it at 6 teeth. It was 5 teeth. The air was also at 6. I backed it down to 5. Stoker-man tells me that you can look at the ash ring around the pot to eye-ball an optimul burn. I don't know what I should be looking for? Could an inaccurate air intake setting explain why I'm getting a positive pressure over the fire?

Leo


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coaledsweat
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Post Wed. Feb. 27, 2008 2:36 pm

leowis1 wrote:Why would I get a positive pressure over the fire?
I would consult with the manufacturer. I think its possible a positive overfire draft may be in its design. I run my boiler with a positive overfire draft, but it will only do so when the combustion blower is on and the manual pipe damper is closed. The cause is simply the blower is pushing in more air than the chimney draft evacuates, this increases the pressure in the unit. I would think you draft is set a little low on your damper. Try resetting your baro to around .04 and see if the overfire draft comes down to neutral or goes negative. It won't take much, you're dealing with very minute changes in pressure.

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e.alleg
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Post Sun. Mar. 09, 2008 10:38 pm

I would back the air down or get more draft by closing the baro up some, positive pressure over the fire is bad. That is a sure way to get a CO leak sooner or later, through the hopper or otherwise.

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coaledsweat
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Post Sun. Mar. 09, 2008 11:06 pm

Are you using a manual pipe damper in the stovepipe? That will do what you describe.

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