wood stove chimney basics

[smoked out]

The thermometer is on the sloped portion. Could only get it to 725. I HAD great secondary burn doing it MY way - Add wood, after it catches fire, close vent but leave it opened about an inch. Even had that neat hovering flame in mid air. Doing it the Kuma way, I only  got secondary burn once in the last few days. Their way, shutting it completely, the temp dropped too low before there was room for more wood. Seems to heat up the attic more than I'd like too - creaking noises up there when it's 6 or 700. And it gets waay too hot in here & smells like cooking metal. Kuma says their way prevents creosote...that getting it to 700 gets out the water & that the inside temp needs to be high if you want the gasses to burn - less pollution outside & less wood needed supposedly. Not so sure if I used less wood their way. Today, with the stove cooled down to 490 there was smoke outside - doing it Kuma's way.
The wood I'm using was split in late Sept, a month or two later than last year. Last year's was rained on before delivery. Plus about a week after stacking it in my shed (2 sided), the shed became a terrarium & rained down on the wood. It's VERY wet here from Oct to June... except this year has been real dry.

How about I compromise & get it to 500 & then leave the vent opened an inch? Would this be good to prevent creosote? Is pitch THAT bad that it would clog it so much & so fast this year? A friend of mine is so against pitch that she pulled a flaming log out of her stove. How low should I let it get before adding wood ? I only have a 9 1/4 inch clearance. BTW it DOES NOT take 16" logs like Kuma states unless the log is up against the glass. Had to put the 16's at a diagonal last year & then pay to get a cord of the fat ones split narrower.

[John Raabe]

A hotter fire is a cleaner burn, but I don't think I have ever gotten my stove to 700ºF. Measuring about 12" up from the stove outlet with a magnetic thermometer on my single wall black pipe it is normally running about 350º when everything is up to temp and the burn is stable. When first getting it hot in the morning it can go as high as 500º.

If you are running at 700º it must be roaring like a locomotive firebox and I'll bet you can see the stove or pipe glowing red somewhat in a darkened room.

Make sure your clearances and shields are keeping any combustible materials (including the studs behind drywall) from getting too hot.

[Squirl]

I may be a little confused.  It was only split this year in September?  Then you used it from October to December?  When was it felled?  Split wood normally takes 6-9 months to properly air dry.  Split in spring, burn in winter. A few rain storms on the wood makes little to no difference.  The thing split wood needs most is time, and being covered helps.

Sappy wood isn't horrible, but it means you are probably burning softwoods high in sap content.  That means they are higher in creosote causing compounds.  The extra maintenance of this wood along with the lower BTU content is why hardwood firewood sells for a premium.  People at high elevations and far northern climates only have softwoods to burn.  They just have to keep their fires hot the whole time and clean their chimneys more often.

[MountainDon]

Burning wet wood is the bane of wood stoves and their chimneys. That should never be done if at all possible to avoid. Wood cut this past summer through fall can not dry out enough in most locations to be used for fires this winter; it won't provide as much heat and it will cause chimney issues. If burning un-seasoned wood is not avoidable then have the chimney inspected/cleaned part way through the heating season.

I've always been at least a year ahead, cutting trees in the fall and winter and stacking it to be burned the next winter. At present we're burning wood that was cut in 2009.  Most is pine as that is the predominant wood here in NM. Most of that wood was not split until recently, some of the smaller pieces aren't split at all (anything under 4 inches or so). It had years to slowly dry so when it was split makes no difference in this case. Of course split and stacked wood will dry more rapidly.


I use an infrared thermometer and have seen peak stove top temperatures of 550 F under hottest burn conditions; maybe 600 once or twice. The black pipe about 4 feet above stove top reaches 300 Fat times. Creosote build up is manageable with a daily hot burn.

[smoked out]

JOHN RAABE - The pipe doesn't glow at 700 but it's a double wall. Wonder how much lower the temp is on your pipe vs the sloped part of my stovetop. Tried moving the thermometer back & forth between my spot & 12" up pipe - 400 on pipe while 620 on stove - but not an accurate test without 2 themometers
SQUIRL - It was felled in spring. Took the vendor from then to the end of Sept, maybe Oct, to finish splitting it. I put about 30 pieces a day in the shed- the top of the pile that was in the sun. I was already burning by time they split the last of it & I stacked the dryest of the newly split in the shed (in the area I had been taking from) - the rest went under a tarp. The condensation under the tarp rendered the wood sopping wet & it's virtually unusable this year - it's the condition of last year's wood & growing green & black stripes. Unusual for here, it's been dry out since & the tarp has been off for at least a month. Next summer I'll find another way to stack & cover it. So the older wood is no longer in reach for awhile but what I'm using is dryer than last year albeit a bit greener.
I bought Doug Fir [ almost a hardwood :-) ] & a got a couple cords of something they call piss pine around here. Haven't used much of the latter - it's good for a cold start or to bring a dying log back to life if I closed the vent too far.
MtDon yes, wet wood is bad, that's why it's strange that my chimney fared better last year than this year... & burning hotter this year.This year I bought almost 2 X what I'll need... so that next winter I'll have seasoned wood.

[Alan Gage]

I agree with what the others said, 700 degrees is incredibly hot for stove temp and I can hardly believe the manufacturer would recommend you get it that hot (unless there's something special about that sloped section of your stove). I heat exclusively with wood and I've never been able get my stove over 600 degrees and I burn hot with oak and locust almost exclusively.

I'm also surprised that your double wall pipe is running 400 degrees, seems too hot for that as well. I'm suspicious of your thermometer.

To check pipe temperature with double wall pipe you really need a thermometer with a probe (not the magnetic style that you seem to have) that actually checks the internal temperature. The rule of thumb is that the internal temp of double wall pipe 18" above the stovetop will be about twice the exterior temperature of single wall pipe.

I think you're wood is still wet. Do you hear it hissing when it starts to burn? Cut this spring and split in September is simply nowhere near enough time for wood to dry. Wood doesn't really start to dry until it's split, doesn't matter when the tree was cut down (unless you start talking years). Even splitting it in early spring and burning it that same winter is cutting it pretty close in my opinion. The newer EPA stoves, while burning cleaner and more efficiently, are not as tolerant of wet wood where the old smoke dragons would burn it without much issue (so I've heard, never used one).

Unless you get a lot of rain through the summer putting a tarp over your wood isn't really much of a help. And if you let the tarp hang over the side of the stacked wood you're doing more harm than good. The wood needs sunshine and wind to really start drying out. If you want you can cover only the top of the stack with a tarp and and then weight it down so it doesn't blow away. This will keep most of the rain off but still let the air move through.

Here's how it works with my stove (and the one I had previously) with a fresh load of wood. I usually leave the door cracked slightly for about 5-10 minutes, at which point my internal pipe temp 18" above the stove reaches around 600-800 degrees (which would be about 300-400 degrees externally for single wall pipe). Then I shut the door and back the air off a little. If the secondary burn kicks in and the pipe temp is still increasing I shut the air off completely. The internal chimney temp will then maintain 700-800 degrees and the stove itself will eventually get up to 550 degrees. Secondary burn will continue until the wood is done off gassing (30-45 minutes?) After the stove has been running for 5 minutes I don't like to see any visible smoke coming from the chimney.

I like using the chimney temp because it reacts quicker than the stove temp.

There's nothing wrong with burning pine. The sap or pitch doesn't cause creosote build up. The best explanation I've heard for this old wives tail is that pine is so light weight to begin with that when people pick it up and feel the light weight they assume it's dry when it's really not.

I'd try and find someone you know who has some verifiably dry wood you can try in your stove and see how that burns. The stuff they sell at convenience stores isn't cheap but has a good reputation for being dry. You can also find pretty cheap moisture meters ($25) at places like harbor freight that are accurate enough for firewood. You can't check the ends or outside of a piece of wood since these will test dry while the inside is still very wet. You need to split it open just before checking the moisture content with the meter. You'll be shooting for under 20%.

Good luck!

Alan

[smoked out]

Mystery solved. The probable reason for my chimney clogging in 2 1/2 months of burning dry wood hotter that last years wet wood was that the handyman did not do a thorough job cleaning my chimney this summer before burn season. The handyman that cleaned my stove in the summer is the same guy who cleaned it again after the smoke was coming into the house a week ago. Two days ago I got a chimney sweep in to inspect the connections. A cleaning was another $20 so I had him do it. There was a clog a few feet down from the top of the chimney that had an opening about the size of a baseball for smoke to escape. So the handyman was not thorough a week ago & might not have been in the summer either. Regarding Kuma's suggestion to get it up to 700 or 800 & shut it completely - the chimney sweep was appalled by such bad advice & said that when his stove goes into the red he SCRAMBLES to get it down - for fear of fire.
I open the vent, add wood, close the door, & slowly close the vent when it gets to about 375. It sometimes climbs to 500 or 550 after that but no more 700 for me.
No hissing with this wood. Last year was steam & hissing like a frying egg! This summer I think I may put the really moldy wood against the shed &, when it rains, hang a tarp off the shed roof overhang so the wood isn't enveloped in it's condensation. I keep 2 36" diameter wood racks in the room with the stove. When one is empty I refill. A full rack is in the house for approx 52 hrs before it's burned. I don't use the heavier ones - they go on the bottom when I refill again. That's about the best I can do within my budget. Four and a half cords lasted me from Sept 2010 til March. This year I bought 10 1/2 cords so next winter's wood should be much better... unless I switch vendors after I lay into him for sneaking cedar in with the Doug Fir & end up with a worse vendor.   Thanks to all for your input. :-)

[Dave Sparks]

This probably is a good time (now that the blockage is gone) for you to observe the draft when lighting a fire.
Your eyes and ears should tell you all is well. Good Luck!