I'm the original owner of an HS Tarm OT50. There's very little documentation available for the refractory lining for the oil burner fire chamber. (Well, I've found a hand drawn parts list for the OT35 and OT50 that shows roof/floor and side walls items 103 and 102 and maybe a nozzle wall or target wall 351, and a newer Braxi list for OT28 MK2 and OT35 showing the refractory target wall (bagesplasten) and oil nozzle wall (olieplade) but no other refractory. There's almost nothing left of the original refractory and I expect that it really should be done. Its clear enough that there was never a pre-formed chamber to just drop in place. Do I need to chase down Tarm parts or do I just buy a generic target wall and a roll of 1/2" waterglass and go to town? Should I add the refractory for the nozzle cone? I'm sure its hardly news, but the oil burner seems to light off better and there is a small but definite efficiency improvement from running the nozzle at 140psi using a smaller nozzle to achieve the same firing rate as at 100psi. As for the wood side - I used wood on and off over the years. I think the most sucessful fires were very hot with very dry wood with a high heat demand, or a small enough fuel load. The point being that the wood needs to burn down to coals with ample air Once the Samson controlled damper gets less than 1/2 onch open the fire efficiency was poor unless it has already gone to coals. I never owned the shaker grates, but adding a few ash shovels of nut anthracite to a load of wood fairly low in the chamber seemed to improve the burning efficiency for an overnight burn when the draft regulator would have to come into play. I think the hot coals and coal ash tended to act as a refractory to encourage more efficient burning of the wood gasses at the base of the fire (in downdraft mode). Every so often I ponder lining the wood chamber with something, but I haven't burned wood for 3 or 4 years other than to get rid of stuff too ugly or irregular or noisy for the fireplace. (leftover kiln dried wood scraps pop too much while watching the Celtics - I keep thinking 'there goes another knee'...) Has anyone had any benefit from lining the lower part of the wood chamber with 1/2" fire brick?