Split size - CAT vs Non-CAT is the large split/burn time link changed ?

[Slow1]

In another thread there was a comment about split sizes along the line of "split it smaller to season better ... doesn't matter as much in a CAT stove, but in a non-cat larger splits are needed for longer burns" or something like that. I don't want to threadjack the other thread so I'm posting my question here...

Anyway - this got me to wondering (as I'm now changing to a cat stove) - can I expect nice long burns even with smaller splits with a cat stove? Put another way, is there still an advantage to larger splits or should I be splitting things down smaller across the board?

 

[Todd]

I don't think it makes a difference if the stove is cat or non-cat, bigger splits burn longer and smaller splits burn hotter and shorter in either stove. I like to have a good assortment of different sized splits for my stove and I reload by raking the coals forward, then placing a larger split in the back and a smaller one in front on top of those coals. Then I just pack the rest in. That large one in the back seems to burn forever and leaves a good coal bed after an overnight burn.

 

[karl]

If you can pack them tightly small splits burn just as long, well almost. I burn slab wood, think of 3/4" boards with bark on one side. They pack in the stove very tightly and I get 10 hour burns with them easily

 

[CrappieKeith]

wood is wood.....8000 btu's per pound at 20% moisture content.

 

[Backwoods Savage]

Contrary to some opinions, larger blocks of wood will hold a fire longer than small splits. We find it best to mix them. Our largest are saved for night burning but we still put some small ones in just to be able to fill it better.

We burn mostly white ash, soft maple, elm, cherry along with a little bit of other woods. When filling the stove we like to put in at least one maple in the front of the stove. The largest pieces of wood goes on the bottom in the rear of the stove, then another good sized one on top of that. Then we just fill in with whatever fits best.

Just a caution on using a cat stove. Never burn green wood in it. Make certain your wood is well seasoned and you will be one happy camper for sure.

 

[Highbeam]

I believe that large wood will have a longer burn time, though cooler, than small splits. Sure they have the same btu per lb, but when you burn wood you are burning the wood gas which oozes out of the wood when it is heated. The more surface area of the small splits means more area for gas to ooze out and means more area for oxygen to mix with it and burn.

In a non-cat stove with small splits there is a surplus of secondary air which means that all of this rapidly produced fuel gas can be burned fast and hot in the secondary burn area. It will rocket out of control since the heat of the secondaries will boil even more fuel gas out of the wood. This would be described as going nuclear and a runaway. I pack huge splits in my stove and then fill in with little ones for the overnighter.

On a cat I assume that you can throttle the inlet air so much that you cool the fire to reduce fuel gas production.

 

[ControlFreak]

I believe that large wood will have a longer burn time, though cooler, than small splits. Sure they have the same btu per lb, but when you burn wood you are burning the wood gas which oozes out of the wood when it is heated. The more surface area of the small splits means more area for gas to ooze out and means more area for oxygen to mix with it and burn.

In a non-cat stove with small splits there is a surplus of secondary air which means that all of this rapidly produced fuel gas can be burned fast and hot in the secondary burn area. It will rocket out of control since the heat of the secondaries will boil even more fuel gas out of the wood. This would be described as going nuclear and a runaway. I pack huge splits in my stove and then fill in with little ones for the overnighter.

On a cat I assume that you can throttle the inlet air so much that you cool the fire to reduce fuel gas production.

Wow, great explanation!

 

[Highbeam]

Thanks CF. I think that in an ideal world you could stack the small splits (or lumber) tightly to act as a single large log and get a slower burn.

pook, doesn't the cat burn this CO? If so, it wouldn't be wasted up the chimney but would support Todd's conclusion that "smaller splits burn hotter and shorter in either stove".

 

[summit]

i would think that small splits would work best on a full load in cat stoves, as they are more designed to choke a fire and let the cat eat the smoke (which not always happens). this would provide a better percentage of the limited firebox airflow thru the burning mass, resulting in a more complete combustion on shut down.

 

[DiscoInferno]

I think Highbeam's description fits my non-cat Ultima to a "T", the Napoleon also but somewhat less so (shorter chimney?). I've started splitting larger for that reason, because with the primary all the way off a large load still burns faster that I need it to for the first few hours (all secondary burn at that point). I've only had 2 small fires in the Fireview, so I can't speak to the cat yet. But certainly the heat from the cat doesn't seem able to radiate down to the wood the same, as it's in a separate chamber from the wood. This may allow finer control of the wood consumption rate via the air control. And you seem to be able to turn the air and the burn rate down lower than on my non-cat stoves, but that could easily be a function of outside temp and chimney differences. I'll learn more this winter.

 

[Slow1]

Sounds like you are in a good position to do some experiments then Disco - play a bit and let us know as the winter goes on?

 

[DiscoInferno]

So do any cat stoves provide secondary air to the cat? I didn't see that the Fireview did, but I didn't look too hard. I'm confused, now that I think about it, why a cat stove can get away with seemingly much less air input than a non-cat?

 

[DiscoInferno]

Actually, now that I look closer at the inside of the Fireview it looks like the single air inlet supplies both the base of the fire and the cat. There are holes in the plate that directs the air towards the glass to let some air into the cat. Clever.

 

[Highbeam]

The VC cat stoves have a seperate cat air inlet that is user controllable.

 

[Highbeam]

The VC cat stoves have a seperate cat air inlet that is user controllable.

how does the user determine how much cat air to allow?

From what I understand it is very difficult. Most just set it at a certain place and leave it alone.