How Barometric Dampers Function, Why Use a Barometric Damper

lsayre wrote:

Richard S. wrote: Correct, only a baro on stoker.

What about the case of the AA and AHS Anthratube type stokers, which stoke via electronic ashing, and are otherwise somewhat similar to hopper equipped hand fired units in their basic functioning (sans for the draft inducing fan)?

My chimney doesn't draft enough on its own to warrant an MPD even if it was permitted, but I figured I'd ask this anyway. My baro damper only opens when it is extremely cold outside, and/or if there is a wind of more than 5 MPH (7 MPH seems to do it) blowing across the top of the chimney. Far and away mostly it is wind causing it to open.

My guess would be not smart (sounds like the cyclonic action, draft inducer, centrifugal heat absorber are all things that require this strength of this forced draft to function well).

@ lightning... Im sorry for the wording/explanation of the primary purposes of MPD vs Baro's (trust me... I was not of these opinions prior to being in a test facility to see and hear the rational) I just thought it was enlightening enough for me to try and share, if you view my former posts regarding Baro's/MPD's you will see my opinion differed vastly from the description here. So when you are quoting me in this thread its not me personally that your conflicting with (so don't beat me to hard ), I can kinda see why designers and manufacturers and those who helped to bring the entire coal stove industry back in the USA during the oil crisis steer clear of public forums now though

lsayre wrote:
What about the case of the AA and AHS Anthratube type stokers, which stoke via electronic ashing, and are otherwise somewhat similar to hopper equipped hand fired units in their basic functioning (sans for the draft inducing fan)?

My chimney doesn't draft enough on its own to warrant an MPD even if it was permitted, but I figured I'd ask this anyway. My baro damper only opens when it is extremely cold outside, and/or if there is a wind of more than 5 MPH (7 MPH seems to do it) blowing across the top of the chimney. Far and away mostly it is wind causing it to open.

I'm not all that familiar with the internal operation of the AHS, sounds like a question for Yanche. I'll pm him.

The issue with a mpd in a stoker with forced air is you're going to create positive pressure. I know in my stoker that's almost guaranteed to cause flue gases to be forced into the room.

dcrane wrote: and manufacturers and those who helped to bring the entire coal stove industry back in the USA during the oil crisis steer clear of public forums now though

The reason they steer clear is becsue it's double edged sword..... You get really good advertising for free but now you have to deal with your customers publicly and they aren't interested in doing that. I've offered invitations to all of them, their choice not mine.

dcrane wrote:I should ask the question "why do you use a MPD"? Your answer should be to control the heat of the stove (if your using it for some other purpose let me know, im all ears?)
next question... "why do you use a Baro"? ....after answering that you will then realize these items are for 2 different purposes

once you realize this fact you will then also realize its like comparing ball point pens to frying pans.

Dear Mr. Crane. What we have here is a failure to communicate. I can almost see what your confusion is, but not quite. Let me try to answer your two questions above.

Why do you use a MPD? You say to "control the heat of the stove" which is correct. What you seem to fail to comprehend is that when you "control the heat of your stove" by using an MPD, you are slowing down the draft by restricting it. You are limiting the draft.

Why do you use a baro? Well you didn't actually answer that one but please allow me. "To control the heat of the stove." A baro does that be allowing air to be introduced into the vent which reduces the draft on the stove. You are limiting the draft.

In both cases, its all about the draft of the stove. The over the fire draft. You can reduce by restricting it with an MPD or reduce it by introducing air into the vent. Both reduce draft, both control heat in the stove.

If you bring up ball point pens and frying pans again, I may have to use profanity.

In Dave's defense, he did fully credit someone else with the posted dissertation that has everyone up in arms. If Dave is confused, then he was guided in that direction by the person to whom he gave credit.

lsayre wrote:In Dave's defense, he did fully credit someone else with the posted dissertation that has everyone up in arms. If Dave is confused, then he was guided in that direction by the person to whom he gave credit.

I'm not up in arms....yet. But posting information that is just plain wrong is well....wrong. I don't care where he got his wrong headed information. I'm hoping Dave is going to come to the Meet N Greet later this year. I'm going to buy him a beer and we will talk draft and dampers for hours.

who's Dave? well anyways... Im trying the MPD with a Baro after it this upcoming season... the purpose of my MPD as always is to get the heat in the stove and radiating to the living area.... the purpose of the baro will be to save coal (no matter how much I use my hand to cover the bowl of that tobacco pipe... when I suck all my air is going through that bowl), no matter how much I reduce my MPD and turn down my primary air (all that draft is still sucking through my coal bed)... with a baro it wont be!

Now thats all im posting here, someone better be buying me a pepsi at the meet after this beating Im on my way to Conn. to hook up with Beamerboy and try to swap out his blower for him so I have to head out... PS. someone send me a link to williams 3rd vid if they can find it please, I enjoyed his first 2 very much but cant find the 3rd. TY

coalkirk wrote: Manual and barometric dampers BOTH are draft limiting devices. They do the same thing but they accomplish it differently. A baro limits draft by allowing room air to be drawn in the vent pipe. A manual damper limits draft by partially blocking the vent pipe. Both limit draft.

Actually a mpd does not limit draft. A measure of draft is with a manometer, when you close your mpd your draft does not drop manometer stays the same. same number means same draft, what you did limit was the volume that could ecscape.

With a baro when you push the flap open more the number on the manometer does go down, a lower number means the drafts has been limited.


Eric

Well there is a good deed to make up for all that malarkey about dampers. I think you may have some C240 H90 O4 NS in that tobacco pipe. Or maybe some C21H30O2.

Coalfire wrote:

coalkirk wrote: Manual and barometric dampers BOTH are draft limiting devices. They do the same thing but they accomplish it differently. A baro limits draft by allowing room air to be drawn in the vent pipe. A manual damper limits draft by partially blocking the vent pipe. Both limit draft.

Actually a mpd does not limit draft. A measure of draft is with a manometer, when you close your mpd your draft does not drop manometer stays the same. same number means same draft, what you did limit was the volume that could ecscape.

With a baro when you push the flap open more the number on the manometer does go down, a lower number means the drafts has been limited.


Eric

Over fire draft, not chimney draft.

dcrane wrote:who's Dave?

Oops, sorry about that Doug.

coalkirk wrote:

Coalfire wrote: Actually a mpd does not limit draft. A measure of draft is with a manometer, when you close your mpd your draft does not drop manometer stays the same. same number means same draft, what you did limit was the volume that could ecscape.

With a baro when you push the flap open more the number on the manometer does go down, a lower number means the drafts has been limited.


Eric

Over fire draft, not chimney draft.

Hate to jump in on such a controversial topic, but I have to agree here. Draft can be measured in more than one place. The fact that the manometer doesn't drop when you close the MPD only means you don't have the manometer tube in the right place.

And just to throw a left handed metric monkey wrench into this:

http://dictionary.reference.com/browse/damper?s=t

damp·er
[dam-per]
noun
1.a person or thing that damps or depresses: His glum mood put a damper on their party.

2.a movable plate for regulating the draft in a stove, furnace, etc.

3.Music.
a.a device in stringed keyboard instruments to deaden the vibration of the strings.
b.the mute of a brass instrument, as a horn.

4.Electricity . an attachment to keep the indicator of a measuring instrument from oscillating excessively, as a set of vanes in a fluid or a short-circuited winding in a magnetic field.

5.Machinery . a shock absorber.

No distinction between manual or automatic. A damper is a damper.

Richard S. wrote:

lsayre wrote:
What about the case of the AA and AHS Anthratube type stokers, which stoke via electronic ashing, and are otherwise somewhat similar to hopper equipped hand fired units in their basic functioning (sans for the draft inducing fan)?

My chimney doesn't draft enough on its own to warrant an MPD even if it was permitted, but I figured I'd ask this anyway. My baro damper only opens when it is extremely cold outside, and/or if there is a wind of more than 5 MPH (7 MPH seems to do it) blowing across the top of the chimney. Far and away mostly it is wind causing it to open.

I'm not all that familiar with the internal operation of the AHS, sounds like a question for Yanche. I'll pm him.

The issue with a mpd in a stoker with forced air is you're going to create positive pressure. I know in my stoker that's almost guaranteed to cause flue gases to be forced into the room.

A manual damper should never be used with a AHS or A-A Anthratube type boiler. The "Anthratube" is a steel cylinder, relatively tall vs. it's diameter. In it there is a stack of ash, burning coal and fresh coal. To get any significant combustion and hence heat output, you must have forced air flow. That comes from the combustion blower. It sucks air from the ash pit up through the "Antratube" and through one side of the hot gas to water heat exchange. Since the combustion fan blades are in the exact center of the hot gas heat exchanger, the second half of heat exchanger has the hot gases blown through it and into the cyclone fly ash separator. From there it is blown out the boiler breach, the stove pipe and chimney. During idle time, i.e. no powered combustion blower, the only combustion air is from natural chimney draft and some thermal heat rises effects. This is no where enough to support anything other than idle fire conditions of an existing fire.

ANY MANUAL PIPE DAMPER WOULD PUT AN OBSTRUCTION IN THE PATH OF THIS PROCESS AND SHOULD NEVER, NEVER BE USED.

You need a barometric damper to regulate the idle draft. This bypasses a portion of your chimney's excessive draft, by allowing that excessive draft to be drawn directly from the room where the boiler is located. This prevents excessive idle heat production by starving the idle fire of excessive air. IF you have a very, very well drafting chimney or regular high wind conditions your barometric damper needs to be over-sized, i.e. larger than the breach diameter. The recommended installation method is concentric flu pipes. This is shown in the A-A installation manual appendix. Method applies to AHS also, and is what I recommend for both AHS and A-A installations.

jpete wrote:Hate to jump in on such a controversial topic, but I have to agree here. Draft can be measured in more than one place. The fact that the manometer doesn't drop when you close the MPD only means you don't have the manometer tube in the right place.

I agree. I see instant change in manometer when altering MPD position, even by a tiny increment.

A question: Under marginal draft conditions and with the MPD set when chimney draft was excellent and now it drops, which type of damper will best maintain maximum draft under those poor conditions? Will the partially closed MPD register less draft than the baro whose flap will be closed under those conditions?

Neither damper will. Dampers are draft limiting devices only. They will never help to improve draft, only limit it if there is too much draft.