The furnace is about 75K btu but he was probably running about triple that or even more with the oil pressure, air pressure and nozzle size he had installed. He had a huge shop to heat, so by 'overfiring' I mean pumping way more btu's through the heat exchanger than it was ever meant to handle. And he had the furnace set to run all of the time when it was switched on, throw a wall switch on the furnace and heater and pumps started and ran until it was manually turned off, he didn't run it through a thermostat so it would cycle. I want my setup to work 'normally' where I set a temp on a thermostat and the furnace kicks on and off to maintain it, so when I move everything over to a 'new old furnace' I need to make changes to the wiring, just not sure what changes I'll need to make. And not sure if the pump setup he is using will work for me, or how to trigger it, I need to move my drip pan evaporator style heater first then I can get started on modifying and installing the new furnace. The good story is that I posted on CL and have about five or six candidates so far for a replacement furnace, which gives me some options. A front chimney would work great for me, so I'm going to try to hold out for one, hopefully one of my candidates have that.