How I converted a portable “torpedo” space heater to burn waste oil.
Modify your heater at your own risk. If you make a mistake you can be electrocuted or cause a fire.
I did some reading online about burning waste vegetable oil (wvo) in a torpedo heater, but I had a hard time finding success stories. Brian Miller had good luck. He has plans on his blog about his conversions. There is a link to his site on my blog. Basically he welded a sump to the fuel tank and installed an electric heater to warm the fuel. The sump is deeper than the fuel pick up tube, so the element can not run dry and over heat. Of course he needed to make some adjustments to the air/fuel pressure screws.
I think his system looked very promising, but I wanted to try something simpler. Instead of using heat to thin the waste oil, I wanted to see if I could get my heater to fire on a blended fuel. It ran well at 10% wvo/90% heating oil, but the flame became unstable around 25% wvo. I adjusted the air pressure screw and stabilized the flame. I raised the blend to 40% wvo and I was unable to get a steady flame by adjusting the screw. It would start and run, but the flame sounded like it was breaking up. After a few minutes it smoothed out on it’s own. I think the fire tube warmed up and created a more complete burn by reflecting heat back into the burning oil.
At 50% it would light and run with a sporadic flame until the cad eye safety shut it down. I slid the top cover forward to see what was happening inside the burner. As the fan was exposed behind the cover the flame would smooth out. If I slid the lid back to cover the fan, the flame would break up again. It appeared that the fan was providing too much air for the thicker fuel. The flame was slowly pushed away from the nozzle until it burned out leaving only raw fuel spray. I had no way to adjust the flow of combustion air into the fire chamber, so I slightly flattened the fan blades to attempt to reduce the air flow. After a few tries I was able to restore a steady flame. I still had a rough, broken flame during a cold start, but 8 out of 10 times it would warm up and become steady. A couple time times the safety would time out and shut down the heater. It would start up and run on the second or third attempt, since each restart added a little more heat to the combustion chamber. It does smoke quite a bit on a failed start as the unburned oil is sprayed onto the warm fire tube.
I increased the blend to 60% wvo and the ignition problems got worse. Eventually the igniter gummed up from the thick fuel and fail. It blew the fuse on the control board when it failed. I replaced the fuse and upgraded the igniter to a heavy duty universal replacement HVAC igniter with a lifetime warranty. It was pricey, but I thought it should be able to handle a hard life in and oil burner compared to the easy life of an igniter in a gas fired heater. I wired the igniter to stay on for a couple minutes instead of a couple seconds. I thought it should help to stabilize the flame until the fire tube warmed up. It worked, but the igniter failed after about 10-20 start up cycles. Once again the bad igniter blew the fuse. I replaced the parts and tried again, but the second igniter died just as fast.
Since it failed on a Saturday night I could not get a third igniter. I needed to use the heater in my garage on Sunday so came up with a different way to ignite the flame. I drilled a 1/2″ hole through the heater and into the combustion chamber just below the igniter bracket. The hole is big enough to fit the tip of a plumbers propane torch into the fire box. I knew this trick would work. I used it to start space heaters that I salvaged in the past. It was a simple way to get them running without spending and money for new parts.
I insert the burning torch into the hole and turn on the heater. It fires right up and runs, but the flame sounds broken up. I hold the torch in place for a couple minutes until the fire tube heats up and the flame smoothes out. Most of the new heaters use plastic parts on the nozzles. Make sure you don’t point the torch directly at the nozzle. It should be angled toward the end of the tube so the oil can spray through the “pilot light” igniting the oil.
I can burn a 60%-70% wvo fuel mix with these simple and cheap modifications. I would have liked to be able to use the electric igniter, but the plumbers torch pilot light allows you pull a heater from the trash pile and convert it without putting any money into it. Most heaters are thrown away when the igniter fails, but the rest of the heater is still good. I have a small build up of thick gummy oil on the bottom of the fire tube. It doesn’t seem to be growing and it doesn’t drip out of the heater. It appears that the flame just burns off any new deposits. Most of it formed while I was fooling with the igniter. I have now run my modified heater for several hours and overall I’m happy with my results. I have cut my fuel costs by over 60% and I have now saved enough fuel to offset the cost of experimenting with the new igniters. Now it’s just money in the bank. I plan to add a conventional heating oil furnace (when I find a free one) to my garage and convert the burner to run on 100% waste oil. You can see details for converting a becket burner to waste oil on my blog or here in my other articles.
I don’t have any specific instruction for adjusting the heater. It takes a bit of trial and error. It’s like adjusting a carburetor by ear. Make one small adjustment at a time and watch how it effects the flame. You should be able to pick up on it quickly. I blend my fuel in 5 gallon fuel can. I can see the fuel level through the can, so I fill it a little over 1/2 way with wvo, top it off with heating oil and shake it up. I just “eye ball” the amounts, I don’t go crazy measuring everything. If the heater has been sitting for an extended period, I will rock it a few times to make sure that the fuel hasn’t separated.
Modify your heater at your own risk. If you do not know what you are doing, than don’t touch the heater. I am not responsible for your mistakes or any damage you cause.