Barometric Damper

Post by **ONEDOLLAR** » Thu. May. 14, 2015 2:07 am

Craig.
Just an FYI if you didn't know. The colder it is the better Anthracite burns. When temps are 50f and above, maintaining enough draft to keep the fire going can become an issue. So if you are happy now with the stove and the heat it is producing with temps in the mid 40's or so, you are going to LOVE it when temps drop even more. And of course a MPD will also help considerably.

How cold does it get in you part of SA?

Craigza · Post by **Craigza** » Thu. May. 14, 2015 6:20 am

ONEDOLLAR wrote:Craig.
Just an FYI if you didn't know. The colder it is the better Anthracite burns. When temps are 50f and above, maintaining enough draft to keep the fire going can become an issue. So if you are happy now with the stove and the heat it is producing with temps in the mid 40's or so, you are going to LOVE it when temps drop even more. And of course a MPD will also help considerably.

How cold does it get in you part of SA?

Ta OD,

We can get to 24degF here in JHB although that is rare. Mostly we are around 32degF in our deep winter.

Cheers,

Craig

Post by **Lightning** » Thu. May. 14, 2015 6:29 am

One Dollar, he's got a barometric damper and manometer on the way.

Craig, your price is around $ 230 per ton, pretty good! And your consumption seems really good too. Being the stove is upstairs, it's likely being influenced by positive pressure from stack effect in the house. I'm wondering if a manual pipe damper would be a better option for this situation.

Craigza · Post by **Craigza** » Thu. May. 14, 2015 7:09 am

Lightning wrote:One Dollar, he's got a barometric damper and manometer on the way.

Craig, your price is around $ 230 per ton, pretty good! And your consumption seems really good too. Being the stove is upstairs, it's likely being influenced by positive pressure from stack effect in the house. I'm wondering if a manual pipe damper would be a better option for this situation.

Hey Lightning,

Positive pressure from the stack effect? Please explain? And please elaborate as to why a MPD would be better?

Cheers,

Craig

Sunny Boy · Post by **Sunny Boy** » Thu. May. 14, 2015 7:18 am

Craig,

Stack affect.
The higher up you go in a heated house, the more that the air pressure increases ever so slightly. The house itself acts like a larger chimney. If there is air leakage through the outside walls, the affect is even stronger than it would be by natural indoor convection. The pressure differences are too slight for you to feel, but it can have an affect on how well a stove and chimney system work. A good mano can show it.

Likely, they don't recommend the MPD if your stove is sold primarily as a wood stove. Some folks have a tendency to over choke a wood stove with the MPD trying to slow the fire down to make it last longer. That increases creosote build up.

Not the case with coal. You can run it with much lower chimney temps, thus keeping more heat in the house, with no worry of clogging the chimney system.

Like a baro, an MPD can help in controlling the draft and keeping heat in the stove - instead of sending it up the chimney. And, the mano will help you get the most efficient damper settings with either an MPD, and/or, a baro.

Baro, or MPD, each has it's pluses and minuses. Only you can decide which best fits your stove set up and life style.

Paul

Craigza · Post by **Craigza** » Thu. May. 14, 2015 7:48 am

Sunny Boy wrote:Craig,

Stack affect.
The higher up you go in a heated house, the more that the air pressure increases ever so slightly. The house itself acts like a larger chimney. If there is air leakage through the outside walls, the affect is even stronger than it would be by natural indoor convection. The pressure differences are too slight for you to feel, but it can have an affect on how well a stove and chimney system work. A good mano can show it.

Likely, they don't recommend the MPD if your stove is sold primarily as a wood stove. Some folks have a tendency to over choke a wood stove with the MPD trying to slow the fire down to make it last longer. That increases creosote build up.

Not the case with coal. You can run it with much lower chimney temps, thus keeping more heat in the house, with no worry of clogging the chimney system.

Like a baro, an MPD can help in controlling the draft and keeping heat in the stove - instead of sending it up the chimney. And, the mano will help you get the most efficient damper settings with either an MPD, and/or, a baro.

Baro, or MPD, each has it's pluses and minuses. Only you can decide which best fits your stove set up and life style.

Paul

Ta Paul,

Well I am waiting for the baro. I will install that and see what that gives me. I am not sure that I need the MPD just yet though.

Cheers,

Craig

ddahlgren · Post by **ddahlgren** » Thu. May. 14, 2015 7:51 am

I have both and use according to weather warm MPD open or more open and colder more closed windy closed down tight. It can get so windy here that when I was burning wood it could blow the fire out and pretty exciting when it relit
Made you relize why there are 3 screws in every pipe joint

Post by **Lightning** » Thu. May. 14, 2015 7:52 am

Craigza wrote:Hey Lightning,
Positive pressure from the stack effect? Please explain? And please elaborate as to why a MPD would be better?
Cheers, Craig

Sure.. When the temperature in the house is warmer than outside, the house develops a "stack effect" (similar to what goes on in a chimney) and promotes air infiltration/exfiltration that naturally occurs in the home. In the house there will be a neutral pressure plane (NPP). The NPP is normally located horizontally around the mid section of the structure. At the NPP the pressure exactly equals the pressure outside. Below this plane the pressure is slightly negative compared to outside, and above this plane the pressure is slightly positive. This is easily demonstrated when its cold outside, if you open a window upstairs and downstairs you'll notice air coming in at the downstairs window and air going out at the upstairs window. This is the main bone of "house stack effect".

Most of us have our stoves downstairs in the negative pressure area of the home's stack effect (below the neutral pressure plane). But since the chimney's stack effect is stronger, there usually isn't a problem of a flue gas reversal (draft failure) as long as we keep enough heated air mass going up the chimney.

Now lets apply this to a barometric damper that will be located upstairs in the positive pressure area of the home's stack effect (above the NPP). The barometric damper functions because of very small pressure differences between the inside of the home, outside of the home and the pull of the chimney's negative draft pressure. My hunch is that the barometric damper will also try to satisfy the positive pressure at the top of the house by letting an excessive amount of air thru its door to go up the chimney. I might be going out on a limb here a little ways but it all makes perfect sense.

Post by **Lightning** » Thu. May. 14, 2015 8:02 am

Craigza wrote:Well I am waiting for the baro. I will install that and see what that gives me. I am not sure that I need the MPD just yet though.

Absolutely, do try it.. There are members here that are die hard manual damper and others that believe the baro is the supreme draft regulator. Myself, I am a baro believer. A baro keeps the draft pressure steady. This in turn will give you a steady heat output on a manually controlled stove because of the steady incoming combustion air supply that is a result of the baro.

ddahlgren · Post by **ddahlgren** » Thu. May. 14, 2015 8:09 am

I think a lot of that is controlled by how tight the house is with my 1874 one it has so many leaks hard to believe pressure difference could be found. All I know for sure is with stove going it takes about 2 days for drafts to go away once plaster walls heatsoak. The old guys that built houses then built them for coal and constant heat input compared to central heat with little bursts every now and then. It is kind of odd when I think that my boiler is rated for 100,000 btu/hr and the Crane 404 puts out around 25 to 30,000 on i's best day maybe 40,000 at take it to the grave yard temps. On a typical 20F day I am burning enough coal for a net 20,000 BTU input and walls warm and more comfortable. Go figure.

Sunny Boy · Post by **Sunny Boy** » Thu. May. 14, 2015 8:11 am

The stack affect can vary a bit side-to-side depending on how the house is sited and what's around it.

My fireplace chimney - on the prevailing winds side of the house - likes to back draft when first starting.

The only way to prevent it is stuff crumpled news paper up into the damper plate opening, close all the doors to the living room and put a rug over the furnace cold air return floor register. Then I can light the paper to warm the chimney, without it drawing back down the chimney into the house. And it is prone to puffing back unless I keep a good strong draft going and close the fireplace doors.

Down-wind end of the house, I've never had to pre-warm the kitchen chimney before lighting the range. And the range never has smoke leakage through the top plate gaps right after lighting. Even with a cold chimney in winter, it always draws immediately. That chimney shows very slight draft even when the stove is out in summer.

Paul

ddahlgren · Post by **ddahlgren** » Thu. May. 14, 2015 8:19 am

mde me look at the mano at zero and air dead calm. about 65 inside and out as well.

Post by **Lightning** » Thu. May. 14, 2015 8:28 am

Craig, It will be a tough call.. It won't show up on the manometer once the barometric damper is set to regulate the draft pressure since it (the manometer) will be influenced by the higher pressure above the NPP. BUT, what you will notice is that the baro door is nearly wide open most of the time. But don't worry, there is an app for that..

What would need to happen is a control of flue gas volume after the barometric damper. Being that you are an engineer and I can tell you have good wit about you, I will suggest this...

Craigza · Post by **Craigza** » Fri. May. 15, 2015 7:04 am

Hi all,

Many thanks for all the replies. I am waiting for the baro and stuff to arrive. I think the package should be here today. T-Piece is ready - off to pick it up.

Cheers

Craig

Craigza · Post by **Craigza** » Mon. May. 18, 2015 12:31 pm

Hi all,

So all the kit from overseas has finally arrived. I installed the T-Piece this weekend. The baro is in the horizontal position roughly 24" above the stove. I have set the slide manually to 5. Whatever that means. I have topped the stove up and am getting it up to temp. I have one gauge on the top right front corner of the stove. The other is sitting roughly 18" up the flue before the baro T.

I can see the baro opening and closing. I can also hear the air being sucked in. I do not have the mano installed yet. I will need to get some fittings first - the ones that came with the mano are plastic. Not sure if I can install those.

The temp on the stove is ~300degF and the temp on the flue is ~175degF. I am waiting for the gauges to settle as I was firing pretty hard to get everything warmed. I shook too much and hat to restart the fire.

So, what should I be looking for from here on in. I know that the manual says I should look at 0.05. Someone stated in an earlier post that 0.02 - 0.04 is what I should be looking at. What is the benefit of setting the baro to that pressure?

Cheers,

Craig