anyone running with OUT a barro?

anyone ever vent outside air in to feed the fire? i feel like this would be awesome lol

ratherbeflying wrote: ↑

Fri. Jan. 18, 2019 4:17 pm

anyone ever vent outside air in to feed the fire? i feel like this would be awesome lol

EPA wood stoves have outside air kits for that purpose.

Flow vs pressure = mpd vs baro

Two examples:

• MPD/Thermostatic flap: A typical drinking straw with your finger covering some of the bottom with the covered end in liquid. Draw on the straw a hard as you like and you regulate the amount of liquid by varying the size of the opening. A varying amount of liquid moves up the straw only as fast as the opening at the bottom allows and the amount of vacuum on the straw. Worded another way, flow volume and velocity is regulated by the opening size at the entry hole regulating how much liquid exits out of the top.

• Baro: Ever use a straw with a hole in it? Same straw in the same liquid but unrestricted at the bottom. Poke a hole in the straw above the top level of the liquid. Air entering the hole reduces the vacuum lifting the liquid up the straw. Make the hole bigger, you need more suction to get the same amount of liquid to rise the same distance. The hole in the straw changes the vacuum at the top level of the liquid regulating how much liquid exits out of the top.

For us the goal is to keep the hot combustion gasses (BTUs) inside the stove as long as it takes for it to transfer the heat (BTUs) to the room. We don't want hot gasses (BTUs) going up the chimney.

so it sounds like both a baro and a mdp would both be beneficial, its not better to have one or the other its better to have both it seems like... throw a bi metallic in the mix and all those things together should add up to saving a decent amount of coal compared to not having any of them.

Placing a barometric damper in line with an MPD seems like asking for the MPD to clog up. Any savings are going to be measured in low single digits as a percentage over the long haul of a winter season in my opinion.

lsayre wrote: ↑

Sat. Jan. 19, 2019 11:01 am

Placing a barometric damper in line with an MPD seems like asking for the MPD to clog up. Any savings are going to be measured in low single digits as a percentage over the long haul of a winter season in my opinion.

why would the mpd clog up? so you dont think either would be beneficial at all? lol

ratherbeflying wrote: ↑

Sat. Jan. 19, 2019 12:07 pm

why would the mpd clog up? so you dont think either would be beneficial at all? lol

I'm wondering the same. I've seen it happen with wood, but not with about 40 years of using different types of hand-fed coal stoves.

I've gone a couple of years between pipe cleanings because I forgot. That two years equals burning over 6 tons of coal. The pipe was about 1/3 full, but only in the bottom of the pipe. The pipe walls and the MPD still only had a light coating of fly ash. The pipe and chimney clean out had a couple of 5 gallon buckets of ash.

My view is that there's too much exhaust gas velocity going through and around an MPD to get fly ash to stick in any quantity enough to be a problem. Unlike wood exhaust, coal fly ash is very dry and has very poor bonding ability. As it tries to build up on the surfaces inside the pipe the velocity has to increase even more, so it very likely self-limits how much will stick.

Even if the MPD is mounted in a horizontal section of pipe - which is not the best place for it if there's a choice. The high velocity of the exhaust gases created by having to speed up to go around the plate keep it fairly clear.

Paul

With a barometric damper there will no longer be high velocity exhaust gasses to keep it fairly clear.

Sunny Boy wrote: ↑

Sat. Jan. 19, 2019 12:35 pm

I'm wondering the same. I've seen it happen with wood, but not with about 40 years of using different types of hand-fed coal stoves.

I've gone a couple of years between pipe cleanings because I forgot. That two years equals burning over 6 tons of coal. The pipe was about 1/3 full, but only in the bottom of the pipe. The pipe walls and the MPD still only had a light coating of fly ash. The pipe and chimney clean out had a couple of 5 gallon buckets of ash.

My view is that there's too much exhaust gas velocity going through and around an MPD to get fly ash to stick in any quantity enough to be a problem. Unlike wood exhaust, coal fly ash is very dry and has very poor bonding ability. As it tries to build up on the surfaces inside the pipe the velocity has to increase even more, so it very likely self-limits how much will stick.

Even if the MPD is mounted in a horizontal section of pipe - which is not the best place for it if there's a choice. The high velocity of the exhaust gases created by having to speed up to go around the plate keep it fairly clear.

Paul

a couple 5 gallon buckets of ash in only 2 years?? how long is your horizontal pipe section?? my pipe is horizontal for about 3 feet, my clean out was about 2 inches of ash in the bottom of it but my vertical pipe/chimney doesnt seem to have anything at all on it, i cant imagine it ever really building up there??

ratherbeflying wrote: ↑

Sat. Jan. 19, 2019 1:33 pm

a couple 5 gallon buckets of ash in only 2 years?? how long is your horizontal pipe section?? my pipe is horizontal for about 3 feet, my clean out was about 2 inches of ash in the bottom of it but my vertical pipe/chimney doesnt seem to have anything at all on it, i cant imagine it ever really building up there??

The horizontal section is about 5 feet.

I've got a small firebox on the range, so a 6 inch stove pipe is well oversized compared to some of Glenwoods parlor stoves that have a bigger firepot and use a smaller diameter pipe. However, I've found that horizontal section has about the same level of ash in the bottom of the pipe for one year as it does for two years. So that amount of ash left in the bottom of the pipe is getting the pipe closer to all the range needs in cross section for it's exhaust volume flow. When the pipe is bigger in cross section, the exhaust gases can slow down, which lets fly ash drop out of the exhaust stream.

The range is hooked up to a very tall, brick chimney that has a very good draft. It was originally built for a kitchen coal range. As the ash level in that horizontal section tries to get higher, the velocity inside the pipe has to go up - especially when I have the dampers open and it gets roaring during re-fueling.

And the clean out from two years bears that out. After two years, there is more than twice as much ash in the chimney than just one year has. So it only collects just so much in the pipe, no matter if it's one year, or two than sends the rest into the chimney where it's far larger in cross section, so the exhaust slows down and drops out the extra fly ash.

Plus, I really damper the range way down at night. Because it has so much surface area to extract and radiate heat before it gets to the stove's pipe collar, it will easily cruise along at .005- .007 mano readings. That means the exhaust is moving very slowly through the pipe, which will make it much more likely to drop fly ash.

If I used a smaller stove pipe, and always kept the mano readings higher, I'm sure the pipe would stay clearer.

Paul

Fly ash density varies on the coal source and the quantity varies on the coal's source. Therefore YMMV.

Sunny B - have you taken manometer readings from the pipe on each side of the MPD under the same conditions? Curious what the pressure drop would be.

My setup has a 36” section of 6” horizontal pipe between the stove and chimney. I can tell that it’s ashing up when I can no longer cruise the stove with the mpd fully closed.....

VigIIPeaBurner wrote: ↑

Sun. Jan. 20, 2019 9:28 am

Fly ash density varies on the coal source and the quantity varies on the coal's source. Therefore YMMV.

Sunny B - have you taken manometer readings from the pipe on each side of the MPD under the same conditions? Curious what the pressure drop would be.

Nope, not on either side of the MPD.

Just a test - posted at least a year ago - using the mano in the pipe and a second mano in the stove before the stove collar.

When I replaced the stove pipe this year, I angled most of the horizontal section about 45 degrees thinking it would help reduce fly ash build up. Last warm spell we had back in December I took the pipe down to check. It didn't make any difference.

A half season ( I start it up in September) of fly ash was at the same level as a full season. So the scrubbing action of high velocity exhaust when I get a fresh batch of coal roaring before resetting the dampers, seems to have quite a bit of control about how much fly ash level the oversized pipe for the range will allow before a build up increases the velocity more and carries the excess into the chimney. Kinda neat the way the stove self clears the pipe to what the stove's pipe size limit needs to be.

Paul

VigIIPeaBurner wrote: ↑

Fri. Jan. 18, 2019 6:15 pm

Flow vs pressure = mpd vs baro

Two examples:

• MPD/Thermostatic flap: A typical drinking straw with your finger covering some of the bottom with the covered end in liquid. Draw on the straw a hard as you like and you regulate the amount of liquid by varying the size of the opening. A varying amount of liquid moves up the straw only as fast as the opening at the bottom allows and the amount of vacuum on the straw. Worded another way, flow volume and velocity is regulated by the opening size at the entry hole regulating how much liquid exits out of the top.

• Baro: Ever use a straw with a hole in it? Same straw in the same liquid but unrestricted at the bottom. Poke a hole in the straw above the top level of the liquid. Air entering the hole reduces the vacuum lifting the liquid up the straw. Make the hole bigger, you need more suction to get the same amount of liquid to rise the same distance. The hole in the straw changes the vacuum at the top level of the liquid regulating how much liquid exits out of the top.

For us the goal is to keep the hot combustion gasses (BTUs) inside the stove as long as it takes for it to transfer the heat (BTUs) to the room. We don't want hot gasses (BTUs) going up the chimney.

love the examples, both however leave you with the same result, more liquid (heat) left in the glass (stove) in the same time period. so, with that being said im sure the stove would be much more efficient (using less coal for the same heat output) with a baro (or mano, or both) because for the stove to produce 600* stove face with a draft of .11 must be wasting alot more heat then a stove with a 600* stove face with a .04 draft... anyone agree with this logic?

ratherbeflying wrote: ↑

Wed. Jan. 23, 2019 8:56 am

because for the stove to produce 600* stove face with a draft of .11 must be wasting alot more heat then a stove with a 600* stove face with a .04 draft... anyone agree with this logic?

Your stove requires a "specific" amount of oxygen to produce a skin temperature of 600 degrees. In order to supply that specific amount at -.11, your primary air opening might be at 50% whereas at -.04 it would need to be at 85%. In either case, the same amount of combustion air is entering the stove and in turn that same amount is leaving the stove. This is the component that carries heat up the chimney. There is no reason for more heat to go up the chimney with a stronger negative pressure in the stove UNLESS said pressure is causing excessive air to pass thru the stove that is not contributing to combustion. This is why some stove manufacturers don't insist that a stove has a baro or manual pipe damper when the stove is equipped with a bi metallic thermostat. The thermostat keeps the stove temp steady, whereas with a manually controlled primary air and no baro, the stove temp is at the mercy of the draft pressure.

I still don't believe that a baro, MPD or bi metallic thermostat will save a measurable amount of coal with a modern air tight stove, unless it's over heating the house when used without any of those devices...

Opinions may vary but that's what makes sense to me