How I built my furnace
Quote from notfeanor on May 27, 2026, 2:52 pmQuestion about the burner distance from the furnace body- so there's mixed propane/air mixture in the entire distance of pipe from the propane injection site to the end of the burner, yes? Is it just the velocity of air from your blower that prevents flashback, and an explosion or flame within the pipe behind the burner face? I'm leaning towards a burner system like this but was thinking of placing the propane inlet much closer to the furnace. I assume this distance is just for proper mixing. What are flashback/burnback? I've seen an improperly made (not mine) forge burner glowing red for the entire distance of the exterior pipe, built on a similar design. It didn't fill me with safety minded thoughts...
Question about the burner distance from the furnace body- so there's mixed propane/air mixture in the entire distance of pipe from the propane injection site to the end of the burner, yes? Is it just the velocity of air from your blower that prevents flashback, and an explosion or flame within the pipe behind the burner face? I'm leaning towards a burner system like this but was thinking of placing the propane inlet much closer to the furnace. I assume this distance is just for proper mixing. What are flashback/burnback? I've seen an improperly made (not mine) forge burner glowing red for the entire distance of the exterior pipe, built on a similar design. It didn't fill me with safety minded thoughts...
Quote from Jerry Martin on June 1, 2026, 3:37 pmMine has a 1/8-inch copper tubing hooked to a 100-pound propane tank with a high-pressure regulator. I run it on about 5 to 8 PSI. I have used a 20-pound tank but had to put it in a tub of warm water to keep the valve from freezing up. The gas line enters the tube about 6 or 8 inches from the outside of the furnace. I have the tubing bent in a zig zag, so it enters the tube and goes down to the center of the tube and then the bend goes to the furnace. I clean up the end of the pipe, so the gas comes out pretty smooth. You have to have enough air to keep the fire out of the tube or it will get red hot. I have a reducing tube in the furnace end that I think has kept the fire from going back up the tube. I have a 1 1/2" tube about 15 inches long with a 1 1/2" to 1 1/4" reducer going into the furnace. The reducer has melted back a lot of the reducer but it still working well.
Well, that's a lot of gibberish... I'm still looking for pictures. Probably easier just to take some new ones.
Mine has a 1/8-inch copper tubing hooked to a 100-pound propane tank with a high-pressure regulator. I run it on about 5 to 8 PSI. I have used a 20-pound tank but had to put it in a tub of warm water to keep the valve from freezing up. The gas line enters the tube about 6 or 8 inches from the outside of the furnace. I have the tubing bent in a zig zag, so it enters the tube and goes down to the center of the tube and then the bend goes to the furnace. I clean up the end of the pipe, so the gas comes out pretty smooth. You have to have enough air to keep the fire out of the tube or it will get red hot. I have a reducing tube in the furnace end that I think has kept the fire from going back up the tube. I have a 1 1/2" tube about 15 inches long with a 1 1/2" to 1 1/4" reducer going into the furnace. The reducer has melted back a lot of the reducer but it still working well.
Well, that's a lot of gibberish... I'm still looking for pictures. Probably easier just to take some new ones.