I’m going to assume that the vendor you talked to at the fair was a commercial horizontal burner manufacturer like Reznor. What’s he/she is talking about is the steel housing that is generally called the combustion chamber. It’s what you bolt your oil burner up to. In a commercial unit it is elongated, in a residential forced hot air unit, is horizontal. Therein lies the challenge. We’ve talked about adapting a siphon nozzle oil burner to an existing residential Hi-boy type before (meaning vertical) combustion chamber (forced hot air) and the inherent problems that this creates.
The Hi-boy vertical chamber (on a forced hot air system- not a boiler) is roughly 12 inches (305 mm) across as opposed to most all the commercial waste oil chambers I’ve looked at which are long and horizontal. That’s why you don’t see all the waste oil companies jumping to make oil burners for the residential market. They have to sell you a complete system where there oil burner is mated to their furnace/boiler. They know that if they sell you just the oil burner and you put in your furnace/boiler and it torches a hole in the back of your steel chamber, you are going to be calling them back. There are three parts to building a siphon nozzle burner system. The first is getting the oil burner built, the second is adapting the way your specific burner behaves in your combustion chamber, and last is the collection of waste veg oil/ motor oils.
This is a general overview that encompasses the whole process. That’s why I suggest putting in refractory or furnace bricks at the back of the combustion chamber. In others words, I have taken out the original Koawool combustion chamber liner and replaced it with a wall of refractory bricks to “catch” and shape the flame before it hits the back of the wall of the combustion chamber. (I also have lined the floor of the chamber as well since my flame cone is only inches from it.) If you are over-firing the chamber then try reducing your siphon nozzle size and increasing the psi, while experimenting with shaping the flame cone with your bricks. This should decrease the length of the flame cone while making it hotter.
I’m a newbie and certainly no expert, I talked with a guy that sells the waste oil furnaces, I was looking into costs of maybe replacing my boiler unit, not something I really want to do. Anyway he suggested I simply buy their burner and modify a plate to extend their burner further away from the back firewall. He did suggest I only attempt this in my boiler and not the forced air unit in my shop. I do hope to keep learning from the list, not sure if this is helpful or not? I do find it somewhat difficult to read through the threads and pick up a definitive method of converting. In passing I did mention WVO to a buddy of mine that plays with heating units he said a few years ago he modified his oil burner with an injection pump to burn waste motor oil. We didn’t have time for details but probably should try and pin him down again sometime soon.