Manual Damper in Double Walled Stove Pipe?

 
Ossa
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Post by Ossa » Fri. Sep. 01, 2017 5:34 pm

Not trying to resuscitate the "Manual pipe dampers, how, why, when?" thread...
I've read through that and don't find an answer to my specific question...

Is there any reason that installing a manual pipe damper is a problem in double walled stove pipe? I'm not talking the actual installation; I've just done it with no problem at all. I've got one stove installer telling me he removes a baro damper whenever he encounters one on a solid fuel stove installation. I've got the people who sold me the stove telling me to install a baro damper and not use a MPD in a double walled pipe, as though it's OK in single walled, but not in double walled.

My coal stove is a Efel/Surdiac/Bayard Harmony III. I've got a long, straight all-metal chimney with a huge and healthy draft. I've had trouble with nut coal (all I can conveniently get in VT where I live) burning too hot. I've got the damper on the back of the stove just cracked about 1mm and it still sucks like mad and burns hotter than we need. I'm hoping a MPD will help calm things down.

Thoughts?
Thanks!


 
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Post by Lightning » Fri. Sep. 01, 2017 5:39 pm

My advice would be to install a manometer to measure the negative pressure of the chimney draft. They are cheap and easy to install and are a huge help with getting your draft under control once you install a damper, whether it be a MPD or barometric.

 
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Post by Lightning » Fri. Sep. 01, 2017 5:47 pm

Also, I just wanted to add that a healthy draft pressure will help insure that you aren't losing more heat up the chimney than necessary due to any unknown or unregulated secondary air leakage into the stove.

 
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Post by Ossa » Fri. Sep. 01, 2017 5:50 pm

Lightning wrote:Also, I just wanted to add that a healthy draft pressure will help insure that you aren't losing more heat up the chimney than necessary due to any unknown or unregulated secondary air leakage into the stove.
Got it. Thank you! So no downside regarding the MPD in double walled pipe from your perspective?

 
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Post by Lightning » Fri. Sep. 01, 2017 5:54 pm

Ossa wrote:Got it. Thank you! So no downside regarding the MPD in double walled pipe from your perspective?
Quite honestly I've only dealt with an MPD in single wall pipe. I would imagine, but not sure that, there is a MPD specifically designed to fit double wall pipe.

Does the outlet on your stove go directly into double wall pipe? There is no single wall pipe in your installation?

 
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Post by warminmn » Fri. Sep. 01, 2017 5:57 pm

I used the same stove for a few years. Lightnings advice is good.

By double wall do you mean 2 thin stove pipes or one of the double walled insulated ones? I know its fine with the thin walled ones. They even sell them with a damper installed.

I tried both a baro and manual damper at first, and if you want to, you can install them both for experimenting. You can always tin-foil over the baro or leave the manual damper open after you figure out how you want to run it. I really didnt see the need for using both at the same time, but if you are going to burn any wood in it you will want the manual damper with the baro closed off.

I ended out just using a manual damper but you can go either way if burning just coal. I know i wasted a pound or two of coal a day as my manometer always read high but the stove was so much more responsive I didnt care.

There is no right or wrong, its what works best for you.

On another note, if this was one of the new old stock stoves that were sold as new a few years ago (and likely is), you need to replace the original gaskets. The originals are dry-rotted, or junk anyway. That could be why you are over firing, it could be leaking air around the bottom seal. Also do a candle or smoke test around the whole bottom area checking for leaks (it will draw the smoke in). Mine benefitted from some caulk in odd spots near the legs.

I also made a slicing tool from an old hacksaw frame, that had a good curve in it and worked better than the tool that came with it. I used to open the side door (at least mine had a side door) and rake the crap out of the coal to get more ash out maybe once a day.

There are other mods you can do but first get it working well. I did quite a few. The glass panes I replaced with a solid piece, I enlarged the grates openings, Im sure things I cant think of now.

 
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Post by Ossa » Fri. Sep. 01, 2017 6:03 pm

Lightning wrote:
Ossa wrote:Got it. Thank you! So no downside regarding the MPD in double walled pipe from your perspective?
Quite honestly I've only dealt with an MPD in single wall pipe. I would imagine, but not sure that, there is a MPD specifically designed to fit double wall pipe.

Does the outlet on your stove go directly into double wall pipe? There is no single wall pipe in your installation?
All double walled. I found MPDs installed in a section of double walled pipe, so I know manufacturers make them. I installed a cast iron damper in an existing section of double walled pipe. I can't see any difference from the pre-installed approach.


 
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Post by Lightning » Fri. Sep. 01, 2017 6:11 pm

That's sounds good to me. Warninmn has a lot of great advice too about checking gaskets for leaks with smoke tests and the dollar bill test around doors. You don't want unregulated secondary air robbing heat with it as it goes up the chimney.

Does that stove have a bimetallic thermostat on it? Or is the primary combustion air completely manually controlled?

 
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Post by Ossa » Fri. Sep. 01, 2017 6:56 pm

warminmn wrote:I used the same stove for a few years. Lightnings advice is good.

By double wall do you mean 2 thin stove pipes or one of the double walled insulated ones? I know its fine with the thin walled ones. They even sell them with a damper installed.

Two thin pipes within one another. No insulation.

I tried both a baro and manual damper at first, and if you want to, you can install them both for experimenting. You can always tin-foil over the baro or leave the manual damper open after you figure out how you want to run it. I really didnt see the need for using both at the same time, but if you are going to burn any wood in it you will want the manual damper with the baro closed off.

No wood. Coal only.

I ended out just using a manual damper but you can go either way if burning just coal. I know i wasted a pound or two of coal a day as my manometer always read high but the stove was so much more responsive I didnt care.

There is no right or wrong, its what works best for you.

Thanks. It's very frustrating when supposed 'experts' (the installers) offer diametrically opposed opinions with no room for any other way...

On another note, if this was one of the new old stock stoves that were sold as new a few years ago (and likely is), you need to replace the original gaskets. The originals are dry-rotted, or junk anyway. That could be why you are over firing, it could be leaking air around the bottom seal. Also do a candle or smoke test around the whole bottom area checking for leaks (it will draw the smoke in). Mine benefitted from some caulk in odd spots near the legs.

It is definitely NOS. I never would have bought the stove if I realized the company had changed hands so many times and is now defunct. The bottom of the stove cracked last heating season and I was lucky enough to score another one on ebay with cracked glass, nothing else wrong for $250! And 75 miles away! I tore that one down and and put the bottom on the 'new' stove. At the same time I re-caulked all the joints. I'll still do the candle test though!

I also made a slicing tool from an old hacksaw frame, that had a good curve in it and worked better than the tool that came with it. I used to open the side door (at least mine had a side door) and rake the crap out of the coal to get more ash out maybe once a day.

Good idea on the thinner knife. I also rake from the top to get the ash out and keep the air moving.

There are other mods you can do but first get it working well. I did quite a few. The glass panes I replaced with a solid piece, I enlarged the grates openings, Im sure things I cant think of now.

Thanks for the response!

 
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Post by Ossa » Fri. Sep. 01, 2017 7:02 pm

Lightning wrote:That's sounds good to me. Warninmn has a lot of great advice too about checking gaskets for leaks with smoke tests and the dollar bill test around doors. You don't want unregulated secondary air robbing heat with it as it goes up the chimney.

Does that stove have a bimetallic thermostat on it? Or is the primary combustion air completely manually controlled?
It has a bimetallic thermostatic damper.

 
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Post by Lightning » Fri. Sep. 01, 2017 7:22 pm

Theoretically speaking, a stove with a properly working bimetallic thermostat 'shouldn't' require a damper since the thermostat regulates combustion air based on heat output of the stove. The exception would be with the stove connected to a chimney with an unruly draft. Which brings back to the manometer installation. :)

 
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Post by Lightning » Fri. Sep. 01, 2017 7:32 pm

Just to elaborate on that, it's my thinking that the bi metallic thermostats are designed to function best within a specific range of negative draft pressure. For example, between -.02 to possibly -.10 inches of water column. Above or below these measurements would have symptoms of either a slow sluggish fire that doesn't produce enough heat, or a fire that burns too hot and won't idle back when you want it to.

 
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Post by Ossa » Fri. Sep. 01, 2017 7:48 pm

Lightning wrote:Just to elaborate on that, it's my thinking that the bi metallic thermostats are designed to function best within a specific range of negative draft pressure. For example, between -.02 to possibly -.10 inches of water column. Above or below these measurements would have symptoms of either a slow sluggish fire that doesn't produce enough heat, or a fire that burns too hot and won't idle back when you want it to.
I think my draft may be considered unruly. I have a Tee out the back of the stove, about 12 ft straight up to the top of of the cathedral ceiling, then up to the ridge line of a 10/12 pitch roof. I'm guessing it's about 25 ft straight shot total. The house is at the top of an open hill where the prevailing winds come up the hill. I've had times when the stove damper has pulled itself shut when it's cracked open about 1/8".

So, given all this, is there any downside or safety issue with the MPD in the double walled pipe?

Point taken on the manometer and draft measurements. I'll follow up on that. I know there are a lot of threads on here that deal with that.

 
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Post by Lightning » Fri. Sep. 01, 2017 8:06 pm

Yeah I'd dare say you have an exceptionally strong draft by the sounds of it. As for the MPD in a double walled pipe, I don't see why or how it would be any less safe than a single walled pipe. Perhaps somebody with more experience with double wall pipe would chime in.

 
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Post by warminmn » Fri. Sep. 01, 2017 8:54 pm

Yep, I agree about it being fine to use the MPD on your double wall.

No installer has used the stove you have in your house, with your chimney and coal, so they do not know how to use your stove in your house. try a few different things and figure out what works for you. Your results may differ a lot from mine and thats fine.

I ended out cracking my grate in I think the 4th? year I used it. Its the shallow ash pan. It should probably be dumped twice a day to keep air space underneath the grate. I was careful but still cracked mine. That side door is wonderful. Many stoves could benefit from having one.

If you search this site for this stove, you will find a lot of great advice. my posts were a learning experience as it was my 1st coal stove, so probably trust my later posts more :lol: But several posts from other owners too.

If you have your stove where you can enjoy the fire view, I used to like pulling the hopper and burning stove sized coal in it, banking it towards the back and piling it high. Very pretty, kind of looks like charcoal burning.

Its a pretty decent stove, but needed a deeper ash pan. Its much better looking than most modern stoves are. Im too far away from coal country to find a used stove but given the chance I'd get another grate if it was cheap, but not at the prices Ive seen.


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