Stove Vs Stack Temperature

 
Mountinpie
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Post by Mountinpie » Sat. Jan. 25, 2014 7:08 am

Hi,
I'm new to coal burning this year with a Harman Mark III. I have a two story home with the stove in the basement. This gives me roughly 40 feet of new masonry chimney. I began by burning a bit of wood early this winter and had a manual pipe damper for that. Heated the entire house just fine. I recently switched to coal and installed a barometric damper (removed the MPD). When burning coal with the primary damper wide open, the baro also swings wide open, stack temperatures hover around 300*, stove temp around 550* and I can't even keep the basement warmer than 76*. In some cases, I can get the stack to about 450* but thats just after loading and with the ash pan door open. Somehow it seems i'm loosing too much heat from this thing. Even the owners manual says that normal operation should not require the damper to be open by more than one full turn. I need to run wide open. Any thoughts? Are my stack temps higher than they should be? Thanks.


 
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Post by Rigar » Sat. Jan. 25, 2014 7:13 am

...you may need to adjust your draft...
do you have a manometer?
..then adjust your baro accordingly
...do you know your stoves recommended draft requirement?

 
Mountinpie
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Post by Mountinpie » Sat. Jan. 25, 2014 7:29 am

I haven't purchased a manometer yet. The manual says that the chimney must be capable of a minimum 0.06" draft when the stove is burning. I believe my problem may be too much draft. Even closing the baro a little bit causes lots of secondary air flow around the glass door as I can hear the "whistling", even on a calm (but cold) day. If I have so much draft, is it possible that I'm losing most of my heat up the flue or even through the baro?

 
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Post by Rob R. » Sat. Jan. 25, 2014 7:55 am

If you have too much draft, the stove should look like a blast furnace with the air inlet opened all the way. Try blocking the baro with foil and see what happens.

 
titleist1
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Post by titleist1 » Sat. Jan. 25, 2014 8:16 am

If your baro is open all the time, you either have too much draft or the counter weight is set incorrectly. A manometer would give the actual draft number and is very helpful to have. I had a Mark III running for many years and in my installation I settled on a draft of .04 for best temp output. Even in the coldest weather my spinner knob was never open more than 2 rotations. With the spinner wide open like you have I would have been sending a lot of heat up the chimney and would have been reloading about every 6 hours. My chimney is only 18' of insulated SS double wall, not as tall as yours.

Closing the baro will cause more draft to come through the stove, either by the spinner knob or the gaps around the door window.

Regarding stove / stack temps, for comparison I would get to 300* on the stack if the stove was up at 700*. Your setup will give different ratio between the two probably but it gives you an idea of what you might see.

I would try closing up the spinner to about two turns, let the baro open up, make sure you have all the ash cleared from the firebox with a good shakedown and watch the temps over the next hour or two before making any adjustments. You may need to scrape along the front, sides and back of the firebox to get all the powdery ash that the grate shaking doesn't clear. I would have to do that about once per week, maybe more often in the colder weather like we have been having.

 
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Post by lsayre » Sat. Jan. 25, 2014 8:20 am

If the baro is opening up at too low a draft setting, then perhaps there is no draft remaining to pull air through the coal bed and make heat. I agree that a manometer is required to set it properly, and that he should cover it with foil and see if he gets more heat.

 
Mountinpie
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Post by Mountinpie » Sat. Jan. 25, 2014 8:46 am

Thanks folks. I'll be purchasing a manometer today (if I can find one) and will post back. Thanks for the advice!


 
titleist1
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Post by titleist1 » Sat. Jan. 25, 2014 8:48 am

Get a couple CO monitors if you don't already have them! We like our forum members to breathe good air and get an alert if some bad air is happening!

 
Mountinpie
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Post by Mountinpie » Sat. Jan. 25, 2014 8:56 am

Yes sir, have one near the stove and another on the sleeping level. Thanks for looking after us!

 
titleist1
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Post by titleist1 » Sat. Jan. 25, 2014 9:08 am

Mountinpie wrote:have one near the stove and another on the sleeping level
AWESOME! Good to be safe!

Grainger may have the Dwyer Mark II Model 25 in stock if you have one of those nearby. You can usually find them on eBay too. One of the members here had one for sale in the past week, don't know if that is still available.

 
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Post by oliver power » Sat. Jan. 25, 2014 9:15 am

titleist1 wrote:If your baro is open all the time, you either have too much draft or the counter weight is set incorrectly. A manometer would give the actual draft number and is very helpful to have. I had a Mark III running for many years and in my installation I settled on a draft of .04 for best temp output. Even in the coldest weather my spinner knob was never open more than 2 rotations. With the spinner wide open like you have I would have been sending a lot of heat up the chimney and would have been reloading about every 6 hours. My chimney is only 18' of insulated SS double wall, not as tall as yours.

Closing the baro will cause more draft to come through the stove, either by the spinner knob or the gaps around the door window.

Regarding stove / stack temps, for comparison I would get to 300* on the stack if the stove was up at 700*. Your setup will give different ratio between the two probably but it gives you an idea of what you might see.

I would try closing up the spinner to about two turns, let the baro open up, make sure you have all the ash cleared from the firebox with a good shakedown and watch the temps over the next hour or two before making any adjustments. You may need to scrape along the front, sides and back of the firebox to get all the powdery ash that the grate shaking doesn't clear. I would have to do that about once per week, maybe more often in the colder weather like we have been having.
Exactly how titleist1 has stated. I'll second what he said. Oliver

 
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Post by Mountinpie » Mon. Jan. 27, 2014 7:06 am

OK, I think I'm getting close. Turns out the answer for now was a laser thermometer which told me that the magnetic thermometer on the stack was way off. Instead reading about 150*, it was reading closer to 350*. The higher reading told me that I was burning the stove hot, but it wasn't really producing heat. Now I know that nothing was as hot as I thought. I started from scatch again...cleaned out the stove, etc. and set the baro to open when the stack got to 200*. Now all seems well. I may have some tweaking to do, but I'm getting a stack temp around 250* with a stove temp over 600* on about half a load...much better! That leads to my next question, what is a safe operating temperature on the stove? I see above titleist1 indicated that he could run the stove at 700*. Is it safe to go over that? Thanks all!

 
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Post by titleist1 » Mon. Jan. 27, 2014 7:59 am

the magnetic gauges are known to read low on the stack because of the curved surface. I have a barbeque probe threaded into my stack about 1' up. you should be good with the laser though because my probe gauge reads the same as the laser on the stack. imo your stove to stack temps sound like a pretty good ratio now.

you mention 'half a load'...fill the firebox all the way to the top of the firebrick. filling it up won't cause higher temps just give you longer burn times. the higher temp is controlled by the amount of air coming through your spinner knob. how many turns open do you have it?

700* was about as hot as I would run mine. it would be in really cold weather like the last couple weeks and I may have had the spinner open 2 to 2-1/4 turns to get it there.
My mag stoker I am running now was hitting 710* measured with my laser on the front just above the door the last couple weeks, it's the same type 1/4" construction as the mark III.

 
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Post by Mountinpie » Mon. Jan. 27, 2014 10:40 am

Thanks titleist1! The temps mentioned earlier were with the spinner open two full turns. My laser was reading over 608* (it only goes to 608*) about 2 inches from the top of the stove on the side. The front of the stove and lower on the sides seem to measure a bit lower. Honestly, I only used half a load yesterday because I'm still a little afraid of the thing. I'll fill it to the top today when I get home and watch it through the evening. Hoping to get a consistent 650*+ to heat the upper two floors a bit and am guessing it will take a day or so for the heat to get there. The ups and downs yesterday didn't have much effect upstairs. When I was using wood, it would warm the entire house. No reason to expect different with coal, right?

 
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Post by Storm » Mon. Jan. 27, 2014 11:46 am

George here, welcome to the forum. I too have a new Mark 111 top exit. Learning the balance between spinner and baro adjustment. Even with a manometer I get .04 draft. To .06 it varies top of a sandstone bluff in central Wisconsin. To day it's 12below with a wind 20to 30 mph. Had a Mark 1 before good for the 20x30 family room, but now we heat the whole house with the Mark 111. It takes time only adjust one thing at a time then you know what each thing is doing. I was afraid to fill all the way up to the top of the firebrick. Has no effect on temp just a longer burn time. I run my stove at 450-525 with a stack temp of 250. Good luck G.


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