Coals after 8+ hours!

[Slow1]

Ok, some of you folks take such things for granted, but I was surprised today to find this when I got home.

I left home this morning after loading up - load was sometime before 9a (not exactly sure what time, but it was before 9). I had a good bed of coals and one mostly burned split in there on top of which I loaded three good sized pieces - one of which was a 'monster' piece of 3+ year old oak that I acquired recently as part of a new load of wood. That pretty much filled up the box although there were quite a few good sized gaps in there as the pieces didn't 'fit' well together. I choked the air back slowly to about 1/4 and left it cooking....

Got home about 5:30 and was surprised to find the stove wasn't cold so I took a look inside and started raking the ash around and to my surprise there was actually some glow to the few remaining charcoal bits! Just to see what would happen I piled these together in the front of the stove and sure enough with air open they shortly were lit up into a nice pile that I'm sure I could have used to start a new fire.

So, this was a definite record for me. What changed? Well... two big things and perhaps a third factor come to mind.
1) Better wood - I had a couple pieces of this 3yr oak in there which clearly makes a big difference.
2) OAK input limiter - A few weeks ago I fit a piece of foil over the OAK input such that it covers 1/2 of the surface area. This has clearly tamed my fires and I have seen a significant increase in my heat output as well as the burn times with a corresponding decrease in flue temps while not putting smoke up the chimney (hmmm can anyone say 'overdraft confirmation'?)
3) the minor difference(?) the high temp today was around 45 or so - perhaps warmer temps outside decreased draft enough to help slow burn rate?

Open to ideas and comments - mostly I'm just excited that I may be getting the hang of this stove.. but if factor #3 is the main reason (outside temp) then perhaps my dream for overnight burns when it is cold next year are going to be dashed. Thoughts anyone?

 

[Todd]

I also noticed a difference with my burns because of my OAK. In fact I took it off because my stove is in my finished basement and the Oak pipe ran 8' up the wall and out through the sill plate. I think this forced the cold air down too hard and caused a kind a blast furnace effect at the beginning of the burn and cooled the stove towards the end. I tried a damper in the Oak, but it was a pain and still sucked too cold air into the stove. Yours may be different setup, and I don't really know if the OAK would work better with a horizontal run.

 

[BrotherBart]

Yeah some day we need to start a thread here on hunting down and harnessing the unregulated holes in these stoves that do nothing but get the stoves past the EPA cert test and make them so hard to control in the real world. We know how to give'em air when they need it.

The cat stoves may not have the problem but some of these non-cats are crazy hot burners until you get your hands around their throat.

 

[Slow1]

I also noticed a difference with my burns because of my OAK. In fact I took it off because my stove is in my finished basement and the Oak pipe ran 8' up the wall and out through the sill plate. I think this forced the cold air down too hard and caused a kind a blast furnace effect at the beginning of the burn and cooled the stove towards the end. I tried a damper in the Oak, but it was a pain and still sucked too cold air into the stove. Yours may be different setup, and I don't really know if the OAK would work better with a horizontal run.

I don't actually have the OAK installed - rather I'm simply covering the OAK connector pipe about 50% I plan to create a variable valve of some sort (I've seen pictures here of one someone designed) so I can control the inflow on demand easier than changing different pieces of foil. But for the last couple weeks I've been running with this half covered configuration and been quite happy - it is interesting how different the stove runs, a bit slower on startup (that's when I'd like to have a variable cover wide open) then it runs nice and steady once dampered down. Before I started covering the OAK input I never would see flames at the front of the stove, only in the back. Now we've had some nice pretty flames in the front of the pile which are very nice as well as steady 550-600 surface temps.

 

[gpcollen1]

Why wouldn't you just cut the air back all the way in order to get a longer burn?? Am I missing something? Why restrict the air inlet when you have an air control on the stove?

JUst looking now but VC notes a 2.1 cu ft box and 10 hour burns. To me, this would mean it should definitely give you coals at 8-9 hours - enough to touch off another fire. Packing the firebox is critical to achieve longest burns possible. Taking your time and putting that jigsaw puzzle of wood together in the stove can be very rewarding when it comes to burn time.

 

[Slow1]

Why wouldn't you just cut the air back all the way in order to get a longer burn?? Am I missing something? Why restrict the air inlet when you have an air control on the stove?

Like most (all?) EPA non-cat stoves, the primary air control that is given to the operator is not the full story of air inflow to the stove. With it cut all the way off there is still quite a bit of air available to the fire. At least there is still a 'hole' open for the air - the amount of air flowing in is of course a function of the suction pulling the air through it (i.e. draft on the top) and the resistance to the flow headed in (i.e. the available air to the inlet). So... the basically even with the air control completely shut off I this is still the best burn time I've achieved (even packing the stove 'full' to the best of my ability).

Yes VC lists this as a 10hr burn time - and I am targeting hitting that some day but at the moment I'm celebrating my closest achievement. I expect that I am getting closer and closer... but I don't think I'll ever hit 10hrs without further modification to the draft and/or air supply. Simply packing it full (which I have done) isn't enough here - best I got with that before was around 6 hours (prior to pulling out the roll of foil).

 

[karri0n]

Is this an insert? If it's a free-stander why not just get a pipe damper? With a pipe damper you can probably have some coals in there after 12 hours. On my stove, I could pack it 100% full and close air all the way, and still have not a single black piece in there, just fine gray ash, after about 6 hours. With the pipe damper, I've had coals after about 11 hours when I decided to sleep in on a weekend, and when I got up I thought I was gonna regret sleeping in and wake up to a cold stove, and that just wasn't the case. Nice coals, load her up, off she went!

 

[Peter B.]

I would second karri0n's suugestion for a flue damper. It <does> sound like you may well have an overdrafting situation, and I'm inclined to think modifications to the OAK will only partially address the problem.

Even with my leaky antique smoke dragon and a rather small firebox, I can fairly reliably manage 8 hours or more before there are no longer enough coals to light off again. (But don't misunderstand me, I'm <not> saying all that time is usable heat production.)

Without a flue damper, I think the time would likely be reduced by a third or a half.

Peter B.

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[gpcollen1]

So what kind of chimney/flue and how tall?

 

[Slow1]

I'm not sure of the measurements - I need to get a ladder up there or get the sweep to measure it when we clean it this spring (I'll measure it myself if necessary - I'll be there staring down the pipe if he'll let me near the ladder if you know what I mean, heh). Anyway the setup has double wall SS 6" all the way outside and then through the wall. Inside I have about 4' of single wall up to the bend that goes 90* to meed the SS to go through the wall. If I did the pictures right here you can see the run and perhaps guess the length...

 

[bigdaddybry]

I load her up at around 1am, by 8am she's out. I don't fire her up 'til about 3pm when I get home from work. There's always enough coals left in there to start another fire. No supercedar needed just a few pieces of kindling and the door left ajar for a couple of minutes. Not bad considering 14hrs have passed.