Baseheater Temperature Control Questions

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BPatrick
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Post by BPatrick » Sun. Dec. 08, 2013 10:35 pm

This a question regarding temp controls with an mpd on a baseburner. If you had the lower ash pan door open on a baseheater in baseheater mode will the temps in the stove rise. Much or does the fact that the stove is in baseheater mode slow down the stove and keep it from running away. Also, is the mpd a precaution for winds and overdraft or does it aid in stove temps. In the same senario where the lower ash pan is open, does opening the mpd make the stove temp rise, even though it is in baseheater mode.

 
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Post by dlj » Sun. Dec. 08, 2013 10:45 pm

BPatrick wrote:This a question regarding temp controls with an mpd on a baseburner. If you had the lower ash pan door open on a baseheater in baseheater mode will the temps in the stove rise. Much or does the fact that the stove is in baseheater mode slow down the stove and keep it from running away. Also, is the mpd a precaution for winds and overdraft or does it aid in stove temps. In the same senario where the lower ash pan is open, does opening the mpd make the stove temp rise, even though it is in baseheater mode.
Basically consider that the stove pipe is a lot longer when in baseburner mode. The draft is slowed down, so if you close the damper and open the bottom door you may have more fire than can be easily removed from the stove depending upon how much draft your chimney has. Opening the bottom door will always make the temperature rise in the stove.

The MPD helps in stove temps. I've forgotten to close the MPD and basically just sucked the heat right out of my stove...

With all things being equal, in baseburner mode and all the air feeds the same, I can raise and lower the temperature in the stove according to how the MPD is set. I'll often just tweek my damper to change stove temps instead of changing air feeds. I have good draft on my chimney so my MPD is running 7/8 to completely closed all the time except when I'm opening doors and feeding coal, or heating up the stove...

dj


 
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Post by coalcracker » Mon. Dec. 09, 2013 1:15 pm

BPatrick wrote:This a question regarding temp controls with an mpd on a baseburner. If you had the lower ash pan door open on a baseheater in baseheater mode will the temps in the stove rise.

YES

Much or does the fact that the stove is in baseheater mode slow down the stove and keep it from running away.

would run hotter in regular mode, than in baseheater mode- but either way opening the door would run hotter than the door closed.

Also, is the mpd a precaution for winds and overdraft or does it aid in stove temps.

both, but with a clarification- modern stoves that are airtight, can run without any mpd or baro damper at all. The ash door vent controls everything with one control, instead of 4 controls like the old stoves had. Any above fire vents on many new stoves are fixed and nonadjustable.

In the same senario where the lower ash pan is open, does opening the mpd make the stove temp rise, even though it is in baseheater mode.
the stove temp will drop with the mpd open, all other factors being the same. Putting the stove in baseheater mode is going to spread the same BTU of energy over a larger cast iron surface, there would/should be a temp drop as the extra cast iron is going to act like a heat sink. Put a torch on a small bolt, it gets cherry red. Put that same torch on an engine block, the whole engine block will NOT get cherry red, it's much bigger than the bolt

if you open the ash door on a coal stove, and the mpd is open, that's like tromping the gas pedal to the floor in a car, she's wide open full throttle.

if at this point you put the stove into baseheater mode, that would tend to slow it down a bit, because a baseheater has a number of 90 degree bends in the circuit inside the stove, in addition to a 180 degree bend. Let's count them- out the back, then (1) straight down, then (1) 90 forward underneath the stove, then (1) 180 backwards again, then (1) 90 straight up- that's (3) 90 degree turns, and (1) 180 degree turn.

that is going to slow the flow of gases down, because of all the turns. Beyond a certain angle, airflow deflects erratically and creates turbulence, and will slow down. This is a big deal with airflow and gas flow- and one reason why a Chrysler Hemi was such a good engine, the valves and ports are canted so the flow angles are less steep, increasing flow.

so your baseheater with all these bends in it, is a considerable restriction to flow, and that would slow the draft down noticeably.

it's interesting to point out, that most modern stove manuals state, no more than (2) 90 degree bends should exist in the run of stovepipe. In that respect, the baseburner breaks that rule, because it has at least 3 90's, in addition to a 180 degree bend. Just something to think about.

if you close the mpd, that's going to slow down the chimney draft in either mode, normal mode or baseburner mode.

the mpd aids in overdraft condition but also has the effect of raising stove temps at the same time.

the absolute lowest you could run your stove, would be all the draft settings and mpd closed, and in baseburner mode. That would be just crawling along. You'd need a good draft to keep it going at that setting, and depending on how airtight it is, or if it had a weak draft, it may go out.

the baseheater option it basically giving the stove more radiating surface into the room. To get all that surface as hot as the top of the stove, you'd have to crank it up a higher, because that extra surface is going to have a cooling effect if the draft settings stayed the same as in normal mode.

 
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BPatrick
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Post by BPatrick » Mon. Dec. 09, 2013 1:54 pm

Thanks for the information. I have a couple of really old antique stoves that were completely torn apart and completely restored and even added gaskets. I would agree that when a stove is airtight, you can control the temp with the ashpan door. I would want to be able to control the over fire air though, as I am a firm believer in burning off the combustion gases, otherwise they are up the pipe. You need enough air mix and I wouldn't like not being able to control that on a newer stove. I'd hate to waste BTU's.

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