Install a Barometric Damper on a Stoker Stove/Furnace?

BIG BEAM wrote:What should I set it at?
Hotblast says min .05 for anthracite.

I puzzled over that, too. You may have to experiment with different settings. My Harman manual says .06 to .10. Lot's of people said set it at the lower limit, but for me the stove wouldn't burn well or consistently below .08. Also made a difference whether I was burning nut or pea coal -- apparently it takes more draft to suck the air through pea because the smaller pieces pack tighter together.

for me the stove wouldn't burn well or consistently below .08.

Were is the coal you are burning from?

I'm sitting here trying to wrap my brain(small as it is) around this.The only thing I can figure is if the baro opens and the air starts to move slower through the fire maybe the oxygen in the air has more time to (linger) around the fire making for the same heat with less input air.In other words more of the oxygen gets used with a slower draft vs a faster draft where some of the oxygen passes through the fire and up the chimney.

Is there anyway to mesure this? will CO levels go up or down?

I never saw my baro move that much set at .05,maybe on a windy night if it's 15 or 20F outside.I did see it one night last year when it was -12 or -15 stay open about 1/2 way.I moved it to .08 that night just to see what happened and it opened a little then would close and open again.Maybe my chimney is just border line.
DON

BIG BEAM wrote:What is a good stack temp? On a cold night mine will run 400 or 425 tops(magnetic thermometer 12" from furnace on top of pipe)On a normal day 20 or 30F it's 200-225.
DON

On a cold night my stove will be 550* over the fire temp and with the baro set at .04 on the manometer my stack temp will be around 160* on 20* to 30* days the fire will be 350* and it will be down at 120* you can just about keep your hand on the pipe.

Big Beam!
I am the resident anti-baro guy here. Using a Harman hand fired with a very precise air intake valve (damper), I don't see that much of a difference using a baro.

I have an installed baro & manometer. Typically if I set it up at .07, the baro will be closed. If I lighten up and reduce the draft, yes the manometer will read .05 and my stack temps drop BUT so does my heat output. WTF? The only time I see it necessary is when we have a drastic change in temps. Lets say, from 40F to 20F or any 20F drop overnight. High winds do not affect my set up as my flue is better than 30' tall. Baro simply slows down draft or I should say helps keep a steady draft maintained. Simple as it is. But many disagree with my simple approach to a simple device!

Hi Big Beam, think about consistancy. You adjust your air intake to your furnace to give a certain amount of air for a given amount of draft.. If the draft keeps changing, how can you give a consistant amount of air to the fire?? An anology would be to try to keep your car/truck's speed constant with the throttle pedal, but the engine's power kept changing independant of the throttle pedal.

You want a consistant amount of draft, so you can give a consistant amount of oxygen [combustion air] to the fire.

Here are the two most agravating situations I use for illustration:

At 9PM, the wind is howling, the weather is cold,[very strong draft] and you set your air intake at a setting to keep the fire from burning too fast with the strong draft. AT 3AM, the wind drops, the draft drops, and the amount of air to the fire is reduced.. the heat is too low, and you wake up to a cool house, or maybe enven a cold house because the fire went out for lack of air.

Or:

At 9PM the wind is calm, the weather is mild, lets say 35*, so the chimney draft is a bit lower than average.. you set your draft to the fire to keep the fire going, because if you reduce it too far, the fire will go out without a decent draft.. At 3 AM, a cold front comes through, the wind picks up, the outside temp drops to 20* and the available draft in the chimney increases drasticly,, The furnace has the air set for low draft, so the added draft pulls a lot, too much, air through the fire, the fire burns too hot/too fast.. So you either get awakened by an over heated house at 5AM, or at 7AM you wake up to a cold house because the fire burn out, too fast.

With a Baro hooked up, you would have roughly the same draft all the time, [except when you have very little draft to control]. Your air settings will be much more consistant, more inline with heat output desired, rather than compensation for the weather and draft..

Consistancy is what it's all about. Big fireboxes like your Hot Blast are particularly sensitive to too little or too much air, that is a big pile of coal you are trying to control.. you need as much consistancy as you can get.

How much a baro appears to work is not the issue,, if it is set to control draft at say .05", but the chimney due to current weather is only pulling .04", the flapper will not move.. but if it is a gusty cold day, the flapper would be working quite a bit to keep the draft over the fire consistant. Without the baro, the air getting pulled through the fire would vary from slight to way too much..

Hope this helps.. Greg L

Harmans run a lot more draft than the average. I'm not sure why, maybe it has something to do with the configuration.

I'm starting to get this but I never had any of the problems that you guys are talking about(over heating or under heating).My baro never goes higher than .08 so maybe that is why it doesn't do much.I even had a manual dampner never used it either.Let me explain my chimney.

It's 24' high with a 12" X 18" flue for the fireplace and a 12" x12" ID flue for the cellar furnace.It has a 9"thimble and I reduced the smoke pipe to 8" for about 5'.Then it splits to 6" to my oil furnace and 6" to my coal furnace.Yeah I know you're not supposed to hook them up together but I feel safe with it.I don't even adjust my air intake that much.In the fall oct. nov.I have the air about 1/4 open for superior coal or 1/3 for mystery coal.In the cold weather the air is set at 3/4 for superior coal and wide open for mystery coal.The air over fire is off all the time(mine is manual).Maybe my draft is like I said before just border line or the way I look at it perfect.

I suspect your oil furnace is allowing a lot of unregulated air to go up the chimney, this is limiting your total maximum draft.. In effect it is like an non adjustable barometric damper, allowing air into the flue. with a 24' chimney and a Hot Blast running full open, you should have over .10" of wc.

Coal burners with smaller stoves can fine tune their coal use with a consistant draft and a good coal burning stove.. Many can watch the weather forcast for the night, tweak the air control on the stove,and hit it right every time.

Greg L.

I am posting a pic of my flue setup I would like some of you veterans to let me know if I should improve upon it. Your advise is extremly valued. thanks.
This forum is excellent!

mark.

Nothing wrong with that setup unless you want to swap that galvanized pipe for black stove pipe. Will that baro be in the way of you filling the hopper? If so you can just spin it around some. Other than that the install looks fine.
edit: maybe put a "T" before the elbow so that you can easily vac out the pipe during the winter. Or I suppose it could go after the elbow and you could snake your vac hose in there.

1st time coaler wrote:I am posting a pic of my flue setup I would like some of you veterans to let me know if I should improve upon it. Your advise is extremly valued. thanks.
This forum is excellent!

mark.

The only thing that I see is the baro should not be right on the top your unit you should be at least 12' above where the
flue comes out of the stoker look and read the link below you will read how to set up correctly

http://fieldcontrols.com/draftcontrol.php

Recommended Locations for Field Draft Controls
For gas-fired equipment, the preferred location of the control is on the bull head tee. This location provides maximum relief of downdrafts with minimum positive pressure. (See Fig. 1, Dia. A-C)
With oil or solid fuels, the bull head tee is not recommended, so locate the control as shown. (See Fig. 1, Dia. D-J) These locations are acceptable for gas units as well. Except on forced draft systems, locate the control as close as possible to the furnace or boiler, at least 12" beyond a stack switch on oil-fired units, and at least 18" from a combustible ceiling or wall.

I don't see where it says the baro can not be right on top of the appliance. I have seen others from the forum do it that way but that does not mean it is the correct way.

The configuration marked "J" in your link seems to show the baro right on the furnace.