Florence Hot Blast Tricks

Hey guys here is a video of the Florence 153. This year I've decided to burn strictly anthracite. In the past I've burnt a good bit of bit coal. But this year I'm only burning anthracite. So I was trying to figure out a way to increase efficiency of the burn and burn times. Since anthracite really only like under fire air with very minimal over fire air, did a simply trick to the stove. The hotblast design is the best burner for a wide range of fuels but not the best for anthracite. The designers of these stove have a small port in the back of the firepot that sucks air from the ash pan up and around the fire out the gas ring. You can adjust the amount of air some what by the back secondary air control. But you cannot shut it off or reduce it enough for anthracite. So here is what I did. Under the ash pan, I stuck a small piece of steel wool in the hot blast port. This drastically reduced the suction of the over the fire gas ring. I did not completely close off the port and the gas ring still burns off the gases.

So now almost all of the primary air is going through the coal bed allowing a more efficient burn for anthracite. My primary air control was reduced by 50% really slowing the burn. I will post another video of a firepot I have at the shop so you can see the port. Simply remove the steel wool of you want to burn wood or soft coal.

https://youtu.be/6G8I5hTURCI

The designers of these stove have a small port in the back of the firepot that sucks air from the ash pan

No, it takes outside air, just saying.. and I don't understand why you cannot shut it off...??

Hey Grumpy you are correct that the back air adjustment take in outside sir. But if you take a mirror and look inside your ash pan in the back. You will see that the gas port is always open to the ash pan. It always is sucking from the primary air in the ashpan up the back of the firepot to the gas ring. This allows secondary air always over the fire. You can increase the secondary air by adjusting the back control but you can never shut it off. When I get to the shop I'll post a video of the port in the firepot.

Please do, this is the over air intake, I don't see how it takes air from the ash pan,, maybe your stove is different or modified.

What a beautiful stove. Next time could ya' give us more than a couple of minutes to look at it.

OMG that's a beautiful stove, I wouldn't be able to leave the house if I had one of those. I believe you did the right thing by blocking or least cutting down those secondary air bypasses. I did this with my furnace and it made a night and day difference with heat consistency and overall efficiency.

Hey guys here is a quick video of what I was talking about. Sorry for the poor quality of video. Hope this helps explain the secondary air function of the Florence stoves

https://youtu.be/UOTGacn8mxk

What a great looking stove!

Yes, beautiful stove.

Thanks for that, I never noticed that, I wonder if my #77 is the same, I'll take a look next tare down..

For what it's worth - here's a couple more pics of that area...
I have my Florence 68 apart doing a simple re-furb to use at a lake cabin we have.
It actually had a hair-line fracture right in the "hotblast" channel. I drilled the ends of the crack and poured a refractory liner in the fire pot. Hopefully it'll last another 40 or 50 years...

I have some concern about the liner not pre-heating the secondary air but my hope is that once the liner heats up it will still work well enough.

Nice job casting that liner.

What about boring out a series of holes down to the surface of that secondary channel to expose it to higher temps ?

Or drill and install bolts through the liner into the channel so that bolts being exposed to the heat will transfer heat to the channel like a heat wick ? Much like cooling fins do to extract heat from high heat area and transfer it to a low heat area.

We do a similar thing by sticking 16D nails into potatoes to bake them faster. The nails pickup and transfer heat more quickly to the middle of the potatoes. They bake in about half the time,... and more evenly.

Paul

Thanks!
I like the bolt idea. Maybe put like 4 1/4" bolts in there?? Like a reverse heat-sink...I like it!
I tried to keep the refractory as thin as possible where the secondary air goes up next the the firepot. It's kind of hard to tell but it's only about a 1/4" or maybe 3/16" thick in that area.
I may see how it does as is first. I think it would be easy enough to add those if I determine them to be necessary.
Thanks for the idea Paul!

Steve

That is a particularly neat job. How and what you used for a form as well as the technique used, would be of interest to me and others

Ky Speedracer wrote:Thanks!
I like the bolt idea. Maybe put like 4 1/4" bolts in there?? Like a reverse heat-sink...I like it!
I tried to keep the refractory as thin as possible where the secondary air goes up next the the firepot. It's kind of hard to tell but it's only about a 1/4" or maybe 3/16" thick in that area.
I may see how it does as is first. I think it would be easy enough to add those if I determine them to be necessary.
Thanks for the idea Paul!

Steve

Having bolts sticking into the firebed will certainly absorb more heat, but it might also affect how well the coal and ash move downward in that area.

Maybe using "carriage bolts" with their larger diameter heads and have the heads sit flush with the face of the refractory will increase the heat absorbing ability over regular sized screws/bolts, but not interfere with how the coal moves ???

If the refractory is as thin as you say, the square under the carriage bolt heads may be thick enough to set the bolts the right distance to have the bolt head be flush. I think those squares are about 1/4 inch thick for a 3/8 carriage bolt.

Paul