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.