Chronicles of the Clayton

So you tried all stove size?
What did/didn't you like about it?

Just did another coal/ash comparison. Getting 13.2%. If the coal is 10% as average is, then I'm loosing 3% unburnt coal in the ash pan. It seems like it should be more considering how thoroughly I shake and clear ash..

Well, last night I got caught pushing the limits a little too hard. I woke up this morning with my remote BBQ alarm sounding with a low pipe temp of 140 degrees. I grabbed the cell phone also on my night stand, tapped the IP cam app and saw my draft was just a hair on the wrong side of zero. Yep, it had warmed up to 40 degrees outside from 32 the night before and I had all the right conditions for a drafting flatline.. Primary air set for a low slow burn, secondaries at 10%, my exhaust diverter door closed (indirect mode) and my basement vents that let outside air come in, were closed.

I went to the basement and could smell a hint of sulfur. I opened the ash pan door, clicked on the flue pipe draft inducer, opened the secondary air and opened the exhaust diverter door and got things moving in the right direction. I only ran the inducer for about a full two minutes, after that the draft was maintaining it's proper course on it's own. I left the ash pan door open for about 5 minutes letting the pipe temp run up to 250 degrees. After closing it, I left the secondaries open at 100% and the exhaust diverter door open and I didn't change the primary air setting. Draft is settling at -.03 now.

On my set up, the flue pipe temp plummets when the draft fails so its a pretty good indicator when I have a draft failure. By the time I got down to the basement (a matter of 5 minutes), it had fallen from 140 degrees to 132.

It seems the exhaust diverter is doing a little too good of a job making the furnace transfer heat instead of it going up the chimney. I haven't had a draft fail this year before installing it. With the mild temps outside, I should have either had it open or had more secondary air going thru the fire box, or both..

Also noted, my temperature spread between stove and pipe is pretty disgusting with the diverter door open and the secondary air open. Currently seeing about a 45 degrees spread , at the time of draft fail this morning it was around a 100 degree spread.

CO alarms didn't register any CO in the house. All is good now. But if I hadn't been home, the wife would have been pissed if I had to walk her thru all that process of reestablishing the draft! I know better now to make sure I have adequate secondary air set for conditions outside.

Lee, perhaps it would be best to not push the limits of reduced draft so far. As for KingCoal the safety margin of draft has been reduced with your new modifications. The main advantage that he has is over you is that formerly he was complaining of having a powerful vacuum cleaner of a draft that needed two MPD's and a baro damper just to tame it, so his margin of safety was potentially not compromised by his modifications as much as yours was. Safety first! A few pounds of extra coal burned per day is well worth it to maintain a safe draft level.

Yes, I agree. My exterior block chimney is influenced by outdoor temperature fluctuations. When its cold out for a period of time and then warms up, my chimney remains colder than the air outside. This condition reeks havoc with drafting. I'll be more careful.

Glad that you had the monitoring situation under control. You seem to have found the lower end of the envelope you have been working with. Many times we go nuts with calculating the upper range and seeing how low we can go and forget that the laws of thermodynamics and gas laws are called laws for a reason. When you go up against the laws and try to work around them, you will fail, every time.

What you experienced though wasn't a fail. It was finding a set point. Now you know with your current configuration at what point you will loose draft. So the lesson learned is stay above that point at all times. IMHO, don't beat yourself up with always having the maximum spread between heat output and pipe temps. With the Clayton, you gotta have a goodly amount of heat going up the chimney simply due to it's design. I usually run with a 200-300 degree spread. My stoker had a completely different spread.

It ain't a Baseburner where your going to get a 5-1 or more spread between sidewalls and the pipe. Neither is my stove. I can get 2/1 easy and If I get a 3/1 spread I am ecstatic.

The one and only true test is

Are you warm?

blrman07 wrote:Glad that you had the monitoring situation under control. You seem to have found the lower end of the envelope you have been working with. Many times we go nuts with calculating the upper range and seeing how low we can go and forget that the laws of thermodynamics and gas laws are called laws for a reason. When you go up against the laws and try to work around them, you will fail, every time.

What you experienced though wasn't a fail. It was finding a set point. Now you know with your current configuration at what point you will loose draft. So the lesson learned is stay above that point at all times. IMHO, don't beat yourself up with always having the maximum spread between heat output and pipe temps. With the Clayton, you gotta have a goodly amount of heat going up the chimney simply due to it's design. I usually run with a 200-300 degree spread. My stoker had a completely different spread.

It ain't a Baseburner where your going to get a 5-1 or more spread between sidewalls and the pipe. Neither is my stove. I can get 2/1 easy and If I get a 3/1 spread I am ecstatic.

The one and only true test is

Are you warm?

i agree, it's just another page in the operator's manual you've been building.

i look at the forecast before work and before bed for signs of large swings and set the stove to handle it either way it goes for the next 12 hrs.

so far I've been fortunate. but, as Larry says I have advantageous draft that takes the low side pretty much out of the equation.

blrman07 wrote:Are you warm?

KingCoal wrote:i agree, it's just another page in the operator's manual you've been building.

Yep, plenty warm and thanks for the words of encouragement fellas, all good points.

I'm learning that maintaining a healthy draft is not just a matter of the temperature of the flue gas, but also the amount of flue gas. I've held a draft during warmer outside temperatures with low flue temps but the difference was the amount of flue gas going up the stack, controlled with extra secondary air. It almost seems like there is a pivot point between primary and secondary air that must be followed to keep draft stable. If I turn my primary down low for a low slow burn, then I need to allow more secondary air to maintain enough mass going up the chimney to keep the draft proper. Seems like when I get below that specific amount of mass needed to go up the chimney which is distributed between the primary and secondary air, that's when I see the draft get unstable. I'm rambling again but I haven't been looking at it this way till recently..

Lightning wrote:I'm rambling again but I haven't been looking at it this way till recently..

Your rambles are good because they help to pinpoint the factors. How does mass, volume, and velocity interrelate?

Wanna hurt your brain? I always jump to the engineering tool box for this kinda stuff. I think I sprained mine. I know they correlate and I'll let the brainiacs work on this one. There are enough formulas on this page to keep you plugging and chugging for days.

You can compare the outside vrs inside temps to find when you reach that "bad" point

http://www.engineeringtoolbox.com/natural-draught ... d_122.html

Hey Lightning, why don't you just get an antique base burner? for the wife.
Just a Québecois's joke !
Keep on the good job.

franco b wrote:

Lightning wrote:I'm rambling again but I haven't been looking at it this way till recently..

Your rambles are good because they help to pinpoint the factors. How does mass, volume, and velocity interrelate?

I've been thinking about this. I've learned recently that it takes only 1 BTU to raise the temperature of 55 cubic feet of air by 1 degree. I find this quite interesting. That seems like a lot of air for relatively not very much energy. This tells me that air and flue gas don't carry as much heat as I would have thought. So that said, I wonder..

When I cut back secondary air, I also see my flue pipe temp fall.. does it fall because the flue gas there is cooler? Or I have a better explanation.. it falls there because there is less mass moving thru the pipe at the same temperature. And since there is less air mass, the pipe can loose it to the room easier. Kind of like wind chill effect in reverse.

It would also explain why the pipe at the breech reads 200 degrees with the probe under a layer of insulation and then just 12 inches further up the pipe I can lay my hand on it all day long..

Hey, its taken a few seasons plus some but I'm really getting the hang of this, fellas! It seems that thru a matter of optimum circumstances, I've been able to get 24 hour burn cycles with steady heat output at a pretty hefty burn rate. It's been getting pretty cold out too. I've never attempted once a day tending during this part of the heating season, unless of course it got unseasonably warm. The average high for the last 8 days is 32.5 degrees. The average low over the same 8 days is 22.5 degrees with some nights down to mid-upper teens. Daily coal usage average over the 8 days is 57.2 pounds. I've been doing my shake and load routine in the evening hours. Undoubtedly, as we sink into further into extreme cold I will have to go to twice a day. But for now, its nice not doing a shake and load at 3:00 am before work.

I contribute this success to a combination things. One, being the bigger nut/stove size mix coal I'm using this year. It seems that the coal bed has more "space" for ash instead of choking. Another contribution is the new heaving technique I've been doing with my poker tool. Jabbing the front of the coal bed at a 45 degree angle and pushing towards the back along the topside of the grates. The coal is heaved upward and the ash amongst it falls to the bottom so I can get more ash out on the second shake. Then lastly, the exhaust diverter is really making that firebox quite the coaclear oven.

The pic below is from two days ago when I dumped on a whopping 65 pounds at one tending. I think that's the most I've ever put on at one time. Also, I did put the center section of plate baffle back in to force the hot gases off the coal bed to really hit the water coils. Evidence of this is confirmed by the darkened areas just under the baffle on each side of the firebox.

Lightning wrote: I did another ash/coal measurement today. This time I'm getting 12.7% ash, which is more realistic. My first outcome of 9.6% ash didn't include ash that has accumulated in the firebox nooks since it was measured after a clean out.

Just did another coal/ash comparison. Getting 13.2%. If the coal is 10% as average is, then I'm loosing 3% unburnt coal in the ash pan. It seems like it should be more considering how thoroughly I shake and clear ash..

Coal/ash comparison for the last 11 days 13.8%..
At least its consistent..