Chronicles of the Clayton

Fess up Lee. Them are your nightly PJs.

My draft was at the edge of failing today. I called the wife, had her go to the basement and crack the load door open an 1/8 inch. Here are before and after pics of the mano reading.

I got a screen shot just before I called to make the adjustment. The second screen shot is two hours later.

Edit - it's 2:00 I just got home. Did a mano test thru the primary air at the ash pan door and it matches the pipe reading, this is with the load door still cracked 1/8 inch open.

This nut size is doing just what I was hoping. It slowed down to a crawl. To the point that the blower isn't kicking on at all. OAT is 70, inside is 71. Over the load door got down to 168 degrees.

I'm seriously considering having a ton of nut size on hand in the future for warm weather burns.

Wow Lee! Looks like you're in creeper gear. How long will it sustain that draft? 70* oats, and 70* inside?! How perfect is that? How much fuel have you burned (in one day) at that low a setting?

joeq wrote:How long will it sustain that draft?

Just before I called my wife at 11:00am, it was on the edge of failure at -.005. I even saw it fall closer to zero just momentarily. After cracking the load door, it crept back up to -.0175 to -.020. It stayed there just fine till I got home, then I did a quick ramp up and cool down just to make sure the fuel bed was burning evenly. I thought perhaps there were a dead spot or 2 after running it down that low. But that wasn't the case, the whole bed lit up nicely with an even glow as seen just under the top layer of coal.

The reason for the mano test under the grates (when I got home) was to see if there was any trading of air intake going on since I had the exhaust diverter door closed (which wasn't helping my draft problem of course). The mano reading under the fuel bed matching the pipe proves to me that wasn't the case which is what I was hoping for. This is another fine attribute of using a barometric damper. The baro doesn't influence the volume capacity of the flue pipe, so cracking the load door didn't influence the primary combustion air intake at all. Instead, it allowed more heated air mass up the chimney to help move the draft along, which in turn kept the primary air coming in. I was zooming in on the mano (in the above pics) so it didn't show the temp readings. Basically what I saw was the furnace temp fall and the pipe temp increase after cracking the load door.

joeq wrote:How much fuel have you burned (in one day) at that low a setting?

My fuel economy with the stove size during warm weather burns hasn't been very stellar to say the least, not what you'd expect anyways. I've been averaging 35-40 pounds a day with it. Keep in mind that I was filling it full and heaping it in the center (100-110 pounds total in the fuel bed after loading) and overheating the house even with the primary air nearly shut off. Another contributor to the burn rate was the excessive secondary air I often use to maintain draft during warm weather burns. With the stove size coal, my thinking is that with the bigger spaces between the coal pieces, secondary air is sinking into the coal bed and contributing to primary combustion. Many people have reported that they need less primary air with stove size, and I think this is the cause. Especially those that have fixed secondary air intakes. With the nut size coal, there isn't nearly as much of that going on. SO, with all that said, the nut size is better at having the secondary air do it's job as secondary air.

For the next few days, I'm gonna "force" myself to only add 20 pounds a day which will result in a shallower coal bed (with more like 50-60 pounds total in the fuel bed after loading). The nut size will cope better being shallow than the stove size. I realize the "V" shaped fuel bed gets a bad rap, but here is a good example of where it will come in handy. A 50 pound layer of coal at the bottom of the "V" will be much deeper than a 50 pound layer of coal at the top of the "V". I just started using the nut size on Monday evening.

By doing side by side comparisons with coal sizing like this, I'm seeing the attributes of each in quite a dramatic way. It's allot of fun and very educational.

Thanks for the questions

I did manage to have a temporary draft failure this morning. The outside temps went from 40 degrees to over 60 degrees in what seemed just a few minutes. I hadn't yet opened the exhaust diverter door or added any secondary air after the over night run. The stove wasn't prepared to handle the quick increase of outside temperature. In a matter of minutes, the pipe temp fell from 130 down to 111 degrees. A clear sign that it was being fed from the wrong direction. I went downstairs and found the mano reading on the wrong side of the zero.

I opened the exhaust diverter door and then opened the ash pan door. Almost immediately the mano showed negative pressure that built up to -.02. This is interesting because to me it suggests that the fuel bed does in fact create it's own draft without the help of the chimney. How else would it get the draft moving the right direction if it couldn't help push it up the chimney during a draft failure? I already had an inkling of this from past measurements above and below the fuel bed which showed a -.005 stronger in the ash pan area. This observation reinforces those findings.

How cool is that? You're monitoring your draft in your stove pipe, "and" below the grates? Do you have 2 manometers Lee? I'm sure you have a picture somewhere above, but to me, it all looks like Frankenstein's lab! I guess the lower one would be informative to how restricted your coal bed is, as in "ashed up". be curious to know what the temps are down there.
And also, have heard the stories of stove sized compared to nut sized coal, and the burn characteristics. Can you confirm in your stove, that stove size burns hotter, but faster, than nut size?

joeq wrote:How cool is that? You're monitoring your draft in your stove pipe, "and" below the grates? Do you have 2 manometers Lee? I'm sure you have a picture somewhere above, but to me, it all looks like Frankenstein's lab! I guess the lower one would be informative to how restricted your coal bed is, as in "ashed up". be curious to know what the temps are down there.
And also, have heard the stories of stove sized compared to nut sized coal, and the burn characteristics. Can you confirm in your stove, that stove size burns hotter, but faster, than nut size?

No, I just have one manometer but the probe is easily slid out of the pipe so I can check other locations. When the fuel bed gets ashed up it does show a weaker reading under the grates.

Yes, the stove size can burn hotter/faster than the nut size if you need it to. That's all controlled with the combustion air setting.

I didn't think it would pan out but for the last 3 days I've only put in half a bag of nut size (20 pounds). Running in crawler gear thru the warm weather. Shake and load at 24 hours. After shake down there is still a healthy bed of coals to add fresh to. Coal depth about 6-7 inches after loading.

One more day of this, then it's back to the stove size for the cooler days ahead. House temp stayed comfortable even with it going over 70 degrees outside.

Feeling impressed...

You should!

Thanks Joe, here's a look at the fuel bed over the last few days, as compared to when I really load it.

Note the condensation where the pipes come thru the back of the fire box. I see drips onto the left side secondary air pipe too.

I see where you mean Lee. Did you clean it up in the 2nd photo? Looks good. Is that a full bed in the lower photo, or can you pack it higher?

joeq wrote:I see where you mean Lee. Did you clean it up in the 2nd photo? Looks good. Is that a full bed in the lower photo, or can you pack it higher?

The lower photo is from last year during colder times but while I was still doing 24 hour burns. That coal depth is my norm for a moderate 24 hour burn. When I switch to 12 to 15 hour burns (when heat demand exceeds it's ability to keep up for 24 hours), I don't pack it quite so high.

As for the condensation, it will subside once I can run it hotter. That's why it looks cleaner in the lower picture.

I see, (said the blind carpenter)

Looky what I found in the next town over across the boarder on my bread route. She has 10 tons out back and rain checks for 30 tons of rice.

What can you use 30 tons of rice for? "Pork fried"?