Barometric Damper Adjustment Error

Originally I setup my baro by feel, I had a feeling it might have been a little off but "close enough". I had it set a bit tight to prevent a loss of draft, I was worried that the gasses would escape into the house. To do it right I ordered a manometer from matthaus and I checked my settings. Holy crap I probably sent a half ton of coal up the chimney. The specifications are .02 over the fire and .045-.05 12" from the base in the stack. I was at .11 over the fire and almost .3 in the stack. I adjusted it to specs and right away I noticed the pipe cooled off considerably. Before when the stoker was on the pipe was about 250 degrees, when the boiler was idling the stack was just hot enough where you could touch it but you couldn't keep your hand on it, probably 180-200. Now when it's stoked up you can touch it without getting burned but not for long, when the stoker is off you can put your cheek on the pipe it's pretty much lukewarm. What was weird was when I started adjusting the baro, the thing would flap open and closed rhythmically, you could tap your foot to the beat. It took about a minute to stabilize and now it sets about 1/3 open mostly all the time. What causes it to flap, a reversal in the flue gasses?

Amazing what a little device will do. I wasn't too surprised mine was a bit high (.06-.07) until I got the damper adjusted correctly, now perfect at .04, on a really warm day (40-50), it will drop to .02, .03.

I helped another guy on here and his was .12 or so with a SWG power venter. They set his Baro up to like .08 as far as it would go. No wonder he was using so much coal and not getting enough heat out of the stove.

Most of the time when mine is flapping, there is wind blowing or something...

e.alleg wrote:.... What causes it to flap, a reversal in the flue gasses?

It seems with my power vent that it flaps when I get close to the set point of the baro. I just reduce the speed on the power vent till it stops. With a natural draft it is an indication that you are getting some kind of variation, either wind as Dave said, or could be combustion air from the stoker, this changes the static pressure in the stove which in my experience seems to change the draft.

I'm glad to see that the manometer paid off Ed!

it works great, and even better I can talk with the Europeans about having 2.7mm draft and I actually know what I'm talking about

based on a 24 hour burn it looks like I'm saving about 30# a day by having that baro flapped open all the time. I should have my manometer paid off in about 2 weeks at this rate

e.alleg wrote:based on a 24 hour burn it looks like I'm saving about 30# a day by having that baro flapped open all the time. I should have my manometer paid off in about 2 weeks at this rate

Wow, ......that's impressive.

Same thing this morning, coal consumption is down at least 20%. This isn't typical, a baro usually saves 10% is what I heard, but it turns out that I have a very strong draft that was sucking the heat out. I noticed that before the ash pan was cool to the touch, cold almost. Now it is warm which means that the a lot more heat is staying in the boiler.

hmmm,... I'm not convinced I have this thing figured out yet. I mounted my manometer permanently today so I can watch it occasionally. I set the draft perfect at .05 with the stoker running the other day and saved fuel. It was 20 degrees outside with a steady breeze. The problem is today was 32 degrees and no wind, the draft (all measured in the pipe) was down near .02, over fire draft was next to nothing. I knew it was low because usually when I open the fire door the ash-dust gets sucked in, today it just kind of sat still. I adjusted the damper so that the draft is back to where I like it, .02 over the fire and .05 in the pipe.(about 2 full turns in on the weight) Now the problem is when the stoker kicks on and the pipe warms up the draft is back up near .1. My baro is a "draft-o-stat" from the 50's, do they ever go bad where they don't regulate like they should? It does swing freely and I made sure that it is perfectly level.

Get a Field Controls Type RC Barometric damper.

Hi E.alleg, your chimney is doing what chimneys do. With more heat differential between the outside temps, and the hot gasses in the chimney while the stoker is making heat, the baro will have to open more to keep the draft from being too high.
But when the stoker is at an idle, not making much heat, and the outside temps are warmer, you will have less draft in the chimney, The baro if set for say .05 in the chimney, and the chimney is only pulling .04, then the baro flap will be closed.

If you have draft when the stoker is idling, and it increases when the stoker fires up making heat, and the baro keeps the the Maximum draft at your target setting, then that is all that can be done. Personally if it has when idling some draft over the fire, and at least .02 in the chimney, and increases to .05 [your set point] when the stoker fires up, that sounds perfect. Having a lot more draft when the stoker is idling is just pulling heat out of the boiler.

Greg L

Ok I spent some quality time tonight with my barometric damper. At idle the draft is about .04 and the damper is open about 1/3 of the way. As soon as the stoker kicks on the flap closes up tight and the draft goes up to .12 after the stoker has been running for a few minutes the baro bounces around a bit and then settles open to about 1/3 again and stays that way until the stoker turns on again. It seems like the damper is working backwards to what I envisioned it doing. If I set it when the stoker is running to .04 draft then when the stoker shuts off it is .01 or less, it's hard to see on the scale but makes me nervous and the flapper is wide open. I don't really know what could go wrong but somehow I think mine isn't working right, I might have to spend the $40 on a new one. The alternative is to wire it open about one inch and leave it at that, that keeps the draft at .06 but when the wind blows it won't compensate.

I was just checking a Fields Control RC damper. If it is mounted upside down it will hang open. I don't know what it would do during firing. The larger segment of the flapper door should be toward the bottom and the smaller segment, which has the weights mounted on it, should be toward the top.

Ebay has 7" RC for $16.30 shipped. Item number: 110205174033

Is your baro mounted in a TEE at a turn? They are designed for installation on a straight run. Maybe that could cause this behavior?

I don't have an EFM, but that should not make a difference. My damper hangs open about a third of the way almost constantly at this time of year. When the stoker runs it will do a little flutter when the blower first starts, as if you were to bump it closed with the flick of a finger, but it quickly returns to its partially open position. At times it may move back and forth but never fast, its just a smooth motion. The only time it shuts quickly is when I open the ash door or open the fire door because this breaks the draft. I am using a Fields RC.