Heat shelf in Adobe, Greenwood ,Seton?

[muleman51]

Is there any merit in a shelf of that refractory board on top of the walls below the boiler tubes to make the flow of hot gasses move to the front and up creating a longer path before exiting. I had a shelf in mine for a couple of years before it disintegrated and haven't found a source for a replacement. I'm not sure if it really helped or not. Sometimes I think the heat just stays up on top longer without, then I wonder if the shelf creates more flow over the top and exits quicker and extracts less heat. The shelf idea came from Adobe. Just trying to get the most out of this boiler.

 

[sparke]

I have a shelf on my Greenfire. I am using one of the refractory pieces I had installed over the tubes earlier in the season. This summer I plan on putting secondary air tubes underneath the shelf. This will re-burn any excess gasses as they are leaving the firebox. I had to push the shelf back so only 12" is protruded over firebox because the refractory actually accelerated the fire too much. The tubes stay much cleaner using this method. I am still experimenting wood use and heat output with this method...

 

[PassionForFire&Water]

You can make one from vermiculite board / Skamole is probably easier to source.
If you don't find it I do stock this.
I have 25mm in thickness and 600mm x 1000mm
Temperature wise it can take it, I'm 100% sure

 

[mole]

I have a shelf on my Greenfire. I am using one of the refractory pieces I had installed over the tubes earlier in the season. This summer I plan on putting secondary air tubes underneath the shelf. This will re-burn any excess gasses as they are leaving the firebox. I had to push the shelf back so only 12" is protruded over firebox because the refractory actually accelerated the fire too much. The tubes stay much cleaner using this method. I am still experimenting wood use and heat output with this method...

Sparke,
Does the shelf improve the efficiency? Do you get more heat out of it with the same amount of wood?

 

[sparke]

I have had it on for about 2 weeks. I am still experimenting. When I had the whole firebox covered, the fire was accelerated too fast. I currently have about 12" of refractory extending over the firebox and it is working well. Burns cleaner a bit more heat... The real difference will come when I put secondary air under the shelf. Once there is secondary air the shelf will come all the way forward again. I expect that to make a big difference in efficiency. I am going to change primary/secondary air this summer unless I come into $$$ and buy a Froiling, or Vigas, or Attack, or ... : )