Why are fire boxes small and not large?

[zandstrafarms]

Sounds crazy i know, but husband wants to know why arches use such small fire boxes and not a huge furnace? Why not make fire box full length of 6ft or 4ft or whatever your arch is.

My guess was it helps airflow upward to chimney and because most wood splitters don't split greater than 20in. , lol.

What's the real answer?

[Sugarmaker]

You may need to review a lot of arch sizes to get a picture of this. example: a 4 foot long arch has a lot of firebox area, due to its short length. And the normal wood length is 18 to 24 inches long approx 50% of the arch length. Big arch say 12 foot long. Wood may be 3 foot long, about 1/4 the length of the arch. Just may not be practical to cut wood 9 foot long and or get it in to the arch. The narrowing of the big arch at the back acts like a portion of the flue system using the heat from the fire to heat the rear pan as it passes to the chimney. Nothing says you could not have fire under the whole thing. Just may not be practical as you get bigger arch.
I have seen older oil fired arches with guns at both ends.
My 2 cents:)
Regards,
Chris

[TerryEspo]

Having a fire under the total pan would just be a waste of wood.
There is a science behind the arch design.
There is much heat passing under the pan as it flows toward the chimney.
Obviously the longer the run the cooler the fire air will become.

Fire box size is calculated for performance and efficiency for the size of pan that is going on the unit.

Hope that helps.

Terry