Baro and manual dampers

Again.... baro controlled MPD... Boom!

“Automatic stove draft control, no room air heat loss up the chimney”

W, sorry bud but I gotta question that one. I've benn running wood, oil/kero & coal equipment for over 50 yrs & done PROPERLY, I've NEVER had a CO problem. I have read of a BARO sticking open & it not working well, as well as MPD problems. These were unfortunately ignorance based situations sadly

warminmn wrote: ↑

Wed. Feb. 14, 2018 11:00 am

For whatever its worth I am not going to recommend a MPD above the baro for safety reasons. One of those "dont try this at home" statements. We dont need to read in the paper about someone getting CO poisoning from following this advice..... I do realize you all have CO detectors and know what you are doing. Many people dont.

OK, I said that. Carry on now if you must Interesting theories.

Sunny Boy wrote: ↑

Wed. Feb. 14, 2018 10:57 am

There is no way you can feed air to both the stove and the baro without making up that additional air usage that the baro needs from outside the house. Baro's can not "create" air inside the house. What they do is bypass the excess air the stove would have used to burn hotter. But they still need that additional air to come into the house or they could not work.

I'm sorry, but you totally misunderstood what I was saying here,

Lightning wrote: ↑

Wed. Feb. 14, 2018 10:42 am

There is house stack effect to consider and what effect an operating baro has on the neural pressure plane. For cold air infiltration to occur, warm air must leave the house at the top level. It's possible that some of that warm air destined to leave the house at the top level is rerouted thru the baro door, keeping any extra cold air infiltration that would be thought to be caused by the baro very minimal.

I'm not implying the baro creates it's own air to use, I'm saying it uses the cold air infiltration that is already happening if it weren't part of the equation. Like this,

Cold air infiltration = warm air exfiltration

Also that,

Cold air infiltration = warm air exfiltration minus what the baro uses.

What I'm saying is the warm air exfiltration is split between warm air leaving the upper level and the baro usage due to movement of the neural pressure plane in the house, not the chimney system. I know it sounds like a lot of horse pucky but take a minute and think it thru..

Lightning wrote: ↑

Wed. Feb. 14, 2018 11:25 am

I'm sorry, but you totally misunderstood what I was saying here,



I'm not implying the baro creates it's own air to use, I'm saying it uses the cold air infiltration that is already happening if it weren't part of the equation. Like this,

Cold air infiltration = warm air exfiltration

Also that,

Cold air infiltration = warm air exfiltration minus what the baro uses.

What I'm saying is the warm air exfiltration is split between warm air leaving the upper level and the baro usage due to movement of the neural pressure plane in the house, not the chimney system. I know it sounds like a lot of horse pucky but take a minute and think it thru..

The baro is allowing the draft to pull the same amount of air out of the house... just that the baro is splitting where the draft can pull the air from.... some thru the stove,some thru the baro. Take the baro away & the draft will still pull the same amount of air... but now it has to pull all of the air thru the stove.
That is my K/Q=Z formula Very easy.

warminmn wrote: ↑

Wed. Feb. 14, 2018 11:00 am

For whatever its worth I am not going to recommend a MPD above the baro for safety reasons. One of those "dont try this at home" statements. We dont need to read in the paper about someone getting CO poisoning from following this advice..... I do realize you all have CO detectors and know what you are doing. Many people dont.

OK, I said that. Carry on now if you must Interesting theories.

I agree, I wouldn't want anyone that didn't completely understand what is going on to suffer a tragedy.

freetown fred wrote: ↑

Wed. Feb. 14, 2018 11:12 am

W, sorry bud but I gotta question that one. I've benn running wood, oil/kero & coal equipment for over 50 yrs & done PROPERLY, I've NEVER had a CO problem. I have read of a BARO sticking open & it not working well, as well as MPD problems. These were unfortunately ignorance based situations sadly

Yep, ignorance based situations. I am only speaking of a MPD above the baro, and a novice could have problems from lack of understanding or not having a CO detector. You just never know what a novice may try to set up vent wise, some crazy horizontal upside down setup just waiting for problems. MPD below the baro is fine.

I just didnt want a newbie reading this and thinking it is the way to do it. I trust that the posters in this subject know their stoves and setups well and can get by with it.

Again, your confusing the issue with bringing up stack effect and neutral plane.

They are not a factor when discussing baro verse MPD control of the exhaust side as to which uses, or saves more heated room air, because they effect the pressure on the intake side too.

The change in stove temps is what will effect stack effect and neutral plane the most. And, the point of this baro verses MPD is to reduce, or remove, that stove's effect by maintaining a set temperature by controlling of the exhaust side.

So, if the stove temp is stable than it's effect on stack effect and neutral plane and in/ex filtration caused by it is a constant, so then where does the additional air needed for a baro come from ? Does it come from dense, higher pressure cold air pushing in, or lighter warm air leaking out ? Guess which wins that push-pull contest. Here's a hint, remember our talks about does hot air really "rise", and where does the energy for convection air movement come from.

Paul

windyhill4.2 wrote: ↑

Wed. Feb. 14, 2018 11:36 am

The baro is allowing the draft to pull the same amount of air out of the house... just that the baro is splitting where the draft can pull the air from.... some thru the stove,some thru the baro. Take the baro away & the draft will still pull the same amount of air... but now it has to pull all of the air thru the stove.
That is my K/Q=Z formula Very easy.

Except you left out,.... that increased air through the stove would make it run hotter. That's what we're trying to prevent by either, not needing the extra air with an MPD, or bypassing the air to the stove pipe through the baro.

That extra airflow into the stove is what the MPD prevents by restricting the exhaust.

If you want to see a good way that works, jam a potato in the tail pipe and try and start your car.

Paul

Sunny Boy wrote: ↑

Wed. Feb. 14, 2018 12:00 pm

Except you left out,.... that increased air through the stove would make it run hotter. That's what we're trying to prevent by either, not needing the extra air with an MPD, or bypassing the air to the stove pipe through the baro.

That extra airflow into the stove is what the MPD prevents by restricting the exhaust.

If you want to see a good way that works, jam a potato in the tail pipe and try and start your car.

Paul

I had an MPD in my stove pipe when i was burning wood in my Schrader, the MPD did not prevent the stove burning hotter when the wind gusts roared over my place.

I don't need to argue on this issue, nor do i need edifying on this issue.... EXPERIENCE is the best teacher & it has taught me well.

Sunny Boy wrote: ↑

Wed. Feb. 14, 2018 11:55 am

So, if the stove temp is stable than it's effect on stack effect and neutral plane and in/ex filtration caused by it is a constant, so then where does the additional air needed for a baro come from ? Does it come from dense, higher pressure cold air pushing in, or lighter warm air leaking out ?

I am willing to meet you half way Paul I suspect that a portion of the baro air use is extra cold air infiltration and the other portion is warm air exfiltration that has been rerouted thru the baro meaning that half of the air volume the baro uses is additional cold air infiltration.

Because there is not really a way to prove or disprove either viewpoint.

Dave, not to doubt your experience, but your throwing in wind gusts and wood stoves is just adding variables that only confuse the issue, like I said.

My point is simply, which uses more heated room air, the MPD, or baro.

Lets try to stick to that so we can make it clear, so others are not confused into thinking it's an opinion instead of actual, provable science.

BTW, believe it or not, coal stoves are so slow to respond to changes in intake and exhaust pressure caused by wind gusts that there is not as much effect on the stove as the constant baro air bleed does.

While guys are watching the mano bounce up and down on a windy night and thinking WOW, ...... go look at how the blue ladies are not reacting to those wind gusts. The mano is far more sensitive to such slight pressure changes than the firebed ever could be.

Those Blue Ladies reactions are the real proof of what's happening in the firebox and that's what matters, not wild swings in mano readings.

Paul

Lightning wrote: ↑

Wed. Feb. 14, 2018 12:21 pm

I am willing to meet you half way Paul I suspect that a portion of the baro air use is extra cold air infiltration and the other portion is warm air exfiltration that has been rerouted thru the baro meaning that half of the air volume the baro uses is additional cold air infiltration.

Because there is not really a way to prove or disprove either viewpoint.

Your getting closer. Like you did with "hot air rising" your giving energy to the lighter air when it's actually the colder, heavier air (and gravity) that is providing the energy to move the air and create those pressure differences. The exfiltration air is powered by that heavy infiltration air, not because the lighter air is able to move on it's own just because it's lighter. If there was no way for cold air to come in the warm air would not be forced out.

If your forcing air into a balloon (aka, cold outside air at higher pressure than indoor air) and you add an addition leak out of the balloon, does that reduce the first leak, or just allow the forced colder air to speed up and move more air in through the balloon to make up for that increase in outlet ? Think, where's the energy (force) coming from in that, air in/air out system ?

And yes, you could prove it by making a sealed model, putting entry and exits points in it, and use air flow meters at each point of entry and exit. Then see what the readings are as you heat the inside and open/close various exits and entries.

Paul

Sunny Boy wrote: ↑

Wed. Feb. 14, 2018 12:34 pm

Dave, not to doubt your experience, but your throwing in wind gusts and wood stoves is just adding variables that only confuse the issue, like I said.

My point is simply, which uses more heated room air, the MPD, or baro.

Lets try to stick to that so we can make it clear, so others are not confused into thinking it's an opinion instead of actual, provable science.

BTW, believe it or not, coal stoves are so slow to respond to changes in intake and exhaust pressure caused by wind gusts that there is not as much effect on the stove as the constant baro air bleed does.

While guys are watching the mano bounce up and down on a windy night and thinking WOW, ...... go look at how the blue ladies are not reacting to those wind gusts. The mano is far more sensitive to such slight pressure changes than the firebed ever could be.

Those Blue Ladies reactions are the real proof of what's happening in the firebox and that's what matters, not wild swings in mano readings.

Paul

I've already been edified by experience... wood stove & coal stove.. high draft affects both. I did observe the blue flames change size when the draft changed...

I don't need more edifying by your ponderification...

I'm trying lol. In your balloon example I'm imagining the cold air infiltration has an advantage because of the size of the openings. Where in a house situation there is resistance on both the in/ex filtration sides as air has to traverse the available nooks and crannies at both the top and bottom of the house. The balloon example isn't a fair comparison.

So let's take a 10×10×10 steel box. Put a 1 sq ft hole in the bottom and a 1 sq ft hole at the top. Let's heat the box to 500 degrees and create a stack effect action. For simplicity let's assume the heated box creates 200 cfm of natural air infiltration and exfiltration thru those top and bottom openings.

Now we shove a 6 inch pipe into the side of the box halfway up to simulate the baro and attach an exhaust fan that moves 200 cfm out of the box. Where is the air going to come from?

Will -
A) 400 cfm come in from the bottom hole and 200 cfm continue out of the top hole?
B) Will 200 cfm continue coming in the bottom hole and zero cfm exit the top hole, or
C) Will the 200 cfm exiting the exhaust fan be shared between the two holes with 300 cfm coming in the bottom and 100 cfm exiting the top hole.

I'll take C for one million dollars please

No really, this is how I would expect the outcome.

Edit - Is anyone getting this or is it still clear as mud

As an added safety precaution when the mpd is installed above the barometric damper you may want to consider the following:

1. Install a second mpd below the barometric damper with an adjustable linkage and set so that when the top damper is shut on an extremely windy day the bottom is open.

2. Attach a second linkage from the top mpd to a spring return motorized damper controller set to open the top damper in the event of a power interuption. (See note #5)

3. On the roof install a wind sock far enough away from the chimney to prevent it from catching fire and not to be influenced by thermals created by the stove.

4. Eight inches below the tail of the wind sock and 4.85 inches in from the end of the sock mount a weatherproof micro switch. When the wind is blowing the upper mpd will be open and the lower mpd will be closed. When the wind dies down the sock will relax and activate the micro switch and reverse the dampers.

In the event of a power failure the spring loaded return on the motorized damper control will open the top mpd and close the bottom.

Note 5. This can also be connected to plc in the event you decide to install a backup inverter, solar array, or emergency backup generator. Also I would strongly recommend inserting a 1-1/2" stainless steel pipe from the chimney flue and extend it to within 3.75 " from the bottom of the micro switch to keep any snow or ice from accumulating and interfering with its preformance.
Wiring diagram and Cad drawings available on request.

Paulie