Manual Pipe Dampers .. How, Why, When

 
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Lightning
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Post by Lightning » Wed. Dec. 11, 2013 9:24 pm

dbsuz05 wrote:My experience with MDP's so far.... closing it cools cools er' down and opening heats er' up. Check damper door open on windy days and closed on the calm.
Good point.. Many people have the misconception that a MPD "holds the heat in the stove"... :)


 
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Post by Bruce M » Wed. Dec. 11, 2013 10:51 pm

dbsuz05 wrote:My experience with MDP's so far.... closing it cools cools er' down and opening heats er' up. Check damper door open on windy days and closed on the calm.
I have had the exact opposite experience with my stove, could it be when you open your damper it allows more air to be pulled through the stove thus firing the stove hotter.

 
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Post by freetown fred » Wed. Dec. 11, 2013 10:53 pm

I don't think that's a misconception at all Lee. Think about it. I don't know much about physics--but if I did, I'd have to say, it's just physics. toothy -- On warm days, I keep my MPD open & it lets heat out of the stove--YES--heat RISES--during the cold months, I keep it closed to PREVENT the heat from rising & escaping from the stove body. Just sayin.

 
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Post by Carbon12 » Wed. Dec. 11, 2013 11:16 pm

Eh,...ah,....my brain hurts Mr. Gumby. I did not know MPD were supposed to control burn rate. I still might not know that.

 
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Post by Lightning » Thu. Dec. 12, 2013 3:01 am

freetown fred wrote:I don't think that's a misconception at all Lee. Think about it. I don't know much about physics--but if I did, I'd have to say, it's just physics. toothy -- On warm days, I keep my MPD open & it lets heat out of the stove--YES--heat RISES--during the cold months, I keep it closed to PREVENT the heat from rising & escaping from the stove body. Just sayin.
I know right? It goes against the grain of the normal thinking.. And I bet it will open a whole new big yucky slimy can of worms.. :lol: When I close my manual damper, I see a number of things happen. Starting with, the manometer showing a weaker draft. Then shortly after, the flue pipe temp starts to drop, the over the load door temp starts to drop and the burn rate starts to drop. Nowhere do I ever observe an increase in heat anywhere when I close the MPD. So I'm not quite on board with that. I'm sure its a matter of perspective :)

 
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Post by freetown fred » Thu. Dec. 12, 2013 5:34 am

Lee, I would suspect that possibly you need some more under fire air which your mano would jump some with the MPD open, but settle back down when closed--just thinkin out loud my friend--what you're describing just don't sound kosher--Oh yeah, this old farmer knows a little Yiddish--I used to be a pretty worldly kinda guy! :clap: toothy

 
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Post by Rob R. » Thu. Dec. 12, 2013 6:16 am

Bruce M wrote:could it be when you open your damper it allows more air to be pulled through the stove thus firing the stove hotter.
Yes.


 
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Post by Lightning » Thu. Dec. 12, 2013 7:51 am

Rob R. wrote:
Bruce M wrote:could it be when you open your damper it allows more air to be pulled through the stove thus firing the stove hotter.
Yes.
I also agree.

 
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Post by rberq » Thu. Dec. 12, 2013 8:26 am

Lightning wrote:
dbsuz05 wrote:My experience with MDPs so far.... closing it cools cools er' down and opening heats er' up. Check damper door open on windy days and closed on the calm.
Good point.. Many people have the misconception that a MPD "holds the heat in the stove"... :)
Oh, good. I thought it was just me. I installed a MPD this year for the first time (along with the baro), and the MPD just cools the stove. I have stopped using the MPD.

 
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Post by KLook » Thu. Dec. 12, 2013 8:35 am

Carbon+O=Oxidation=Heat. MPD + < O= < Oxidation= < Heat

Kevin

 
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Post by Lightning » Thu. Dec. 12, 2013 2:58 pm

Here's a thread I started about the last few posts if anyone is interested

Manual Pipe Dampers - A Matter of Perspective

 
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Post by Sunny Boy » Thu. Dec. 12, 2013 3:31 pm

Lightning wrote:
dbsuz05 wrote:My experience with MDP's so far.... closing it cools cools er' down and opening heats er' up. Check damper door open on windy days and closed on the calm.
Good point.. Many people have the misconception that a MPD "holds the heat in the stove"... :)
I don't think it is that black and white if it could be measured accurately. It think it does matter how much the MPD is closed for a particular stove's draft, etc. And that the MPD can, "hold the heat in", by helping to fine tune the speed that the hot gasses move through the stove to maximize heat transfer out of the stove and the stove pipe.

And, remember, not all MPD plates have the same size and number of holes in them. What works for one may not work the same way for others. That doesn't mean the hold heat in is a misconception, but very likely, just misapplied.

I've been checking this with actual surface temperature measurements with an IR gun and a manometer in the stack about a foot below the MPD.

These readings are all being done keeping the primary air opening always the same - set to .045 gap with a feeler gauge, and only take when the range is in indirect mode, to be as consistent as I can and remove those as variables. The only thing that gets changed between heat and mano readings is the angle of the MPD.

So far the numbers are showing a narrow range of MPD angle that gets and keeps the hottest part of my stove hotter, while the stack temp will drop some.

With the MPD fully open to 90 degrees the hot end stays in the low to mid 600 degree range. Mano stays about .07-.08.

With the MPD set to about 35 degrees, the hot end plates get up in the low to mid 700 degrees and the stack temps drop 20-30 degrees. And the mano drops to .04.

If I close the MPD just a bit more than that, the hot end plates will very slowly start to get cooler and so will the stack temp.

If I open it slightly more then that 30-35 degree angle say to 45 degrees, the stack temps go up, but the hot end of the stove temps slowly drop back into that 600 degree range.

I'm not saying my tests are proof that it will work with every coal stove, . . I'm just showing that with actual, accurate temperature reading that it isn't a misconception for all coal stoves.

The "hold heat in" saying may be an old wives tail because it may only work for the old style stoves with the longer internal passageways that kitchen ranges, base burners, and back-pipe parlor stoves have.

Paul

 
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Post by freetown fred » Thu. Dec. 12, 2013 5:01 pm

SB, you really do different angles with your MPD? I mean like other then half closed or totally closed? I remember my Father tellin me once on the farm in Bucks Co. Pa--" ya know, the more complicated/ complex the gadgets, the more complicated/ complex the theories--just sayin ;)

 
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Post by warminmn » Thu. Dec. 12, 2013 5:52 pm

I don't know who's right or wrong :lol:

With my surdiac I look at the forcast in the morning before I go to work. The more wind they predict, the more I close my damper before I leave. Yes, I do think it slows the fire down. Ive learned about how to set it to have about the same fire 10-12 hours later using the damper. My air intake is usually the same when I leave. I rarely have it closed more than maybe 75 percent.

 
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Post by Sunny Boy » Thu. Dec. 12, 2013 6:14 pm

freetown fred wrote:SB, you really do different angles with your MPD? I mean like other then half closed or totally closed? I remember my Father tellin me once on the farm in Bucks Co. Pa--" ya know, the more complicated/ complex the gadgets, the more complicated/ complex the theories--just sayin ;)
Just for testing purposes, Fred.

Normally, the MPD is fully open during loading and cooking, about 35 degrees during the day for just heating, and fully closed at night.

Yup, I think your Dad was right. I'm a believer in K.I.S.S too. However, I'm also very curious about how things work. And, how these old sayings get started. I like to see if there is any truth to them, . . so then I run tests.

Maybe it was that I watched too many Mr. Wizard shows on TV as a kid. :D

Paul


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