Author Topic: homemade WMO conversion for wood stove  (Read 565 times)


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homemade WMO conversion for wood stove
« on: February 14, 2020, 11:52:51 am »
I was appealed to say the least, when I watched the YouTube video where a man converted a wood stove into a waste oil burning furnace. The idea is that you can burn used oil on a metal plate by blowing air on the fire like a forge.  In the video the man used plumbing hardware and simple fluid power science to improve a machine and leach free thermal energy from waste oil that would usually cost money to get rid of.  This seemed like a project I could enjoy building with a bonus of not having to deal with wood anymore, not to mention the benefit of getting rid of my used oil.

Ask anyone who knows me, and they will agree that this kind of project is right up my alley. I could put all this stuff together with one trip to the hardware store and for less than fifty bucks and after one evening of tinkering I could have free heat for my man cave.  I anticipated a positive outcome for the build as the concept development and trial and error had been done already by the YouTube Guy.  He laid out a few parameters that I tried to follow as close as possible. First the plumbing schematic was straight forward, put a copper tube inside of a steel pipe, both pipes are plumbed into the stove and turned down into a stainless-steel pot. The copper tube is hooked to the oil reservoir the outer steel pipe is hooked to a blower. Second was the lighting instructions. He started the fire by splashing some Kerosene into the pot and throwing in a flaming paper towel then turning on the oil and the blower then poof it was running.

With the local hardware store and some hillbilly style scrounging I came up with enough ¾ steel pipe and copper tube to put this thing together. I used an old machine oiler and a ball valve for the oil reservoir and an old green house blower (60cfm) for the air supply. Two trips to the thrift store provided me a stainless-steel pot and overflow catch pan.  I wound up with about three days of gathering and thirty dollars in this project, so it was time to put it all together and give it a try.

With guidance from my new You Tube mentor and a few friends, I was ready to light her up and get some free heat out of this thing. This is usually the climax of most of my projects as I am known as the type of guy who would get a go-kart project three quarters finished and jump on for a premature, no brake, funnel full of gas in one hand, and beer in the other hand type ride. But not this time! I had bought the right stuff and done the research. Following the instructions, I splashed the Kerosene into the pot, lit the paper towel and turned on the oil and the blower and It was off to a good start, but I couldn’t keep it running. The next night I picked up some diesel fuel and tried it again this time it took and it raged for an hour and burned about 2 quarts of used oil, all the while only getting the room (100 sq. ft) up to a sweltering 49°F. I even started cutting the oil with gasoline and I could practically touch the stove without burning my hand. It made a cool sound like a forge and a lot of flames, but all the heat was going out the pipe. When I tried dampening the flue it would choke out the flame. I tried more air, less air, more oil, less oil, opening the air vent closing the flu and visa-versa.

 I guess what I am asking is there anything I should try before I rip this POS out and go back to burning wood?


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Re: homemade WMO conversion for wood stove
« Reply #1 on: February 18, 2020, 01:30:11 pm »
I dont have any recommendations for you but wanted to say you have an interesting project going and I would hate to see you scrap everything and go back to wood.  But, if there isnt a good way to achieve a good burn and use the heat efficiently versus sending it out the exhaust, maybe this style of heater just wont work.  It sounds like you have a creative side to you and I would encourage you to give some other things a try before giving up.

I have heard of people dripping old dirty oil, stuff beyond being able to be used in a pressure or siphon system, into a wood furnace.  This is used in conjunction with wood.  You woudl probably still be in the same situation with heat going out the exhaust.  Heat extraction before going out the exhaust is probably where you will have to concentrate.


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Re: homemade WMO conversion for wood stove
« Reply #2 on: February 18, 2020, 06:41:35 pm »
  Can you link us to that youtube  video
You can't put it on the internet if it isn't true!


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Re: homemade WMO conversion for wood stove
« Reply #3 on: March 02, 2020, 09:04:19 pm »
I guess what I am asking is there anything I should try before I rip this POS out and go back to burning wood?

Oil has a learning curve.  It requires heat to work.  Most people get the burners started then freak out the flames are too big and shut it down when they sould keep it going, let it heat up and settle and go from there.

Getting oil to burn is not the trick, controlling it is.  If you are not getting enough heat, it comes down to two things and 2 things only:
 1. You have too much air for the amount of oil you are burning.
2. You don't have enough oil flow.

The 3rd is a combination of both.

If you have control of the air and the oil flow then you can do anything basically. You can have a small gentle fire or you can have a clean burning raging inferno.  It's just a matter of balancing the two.  You have to learn how to read the fire.  Having too much oil will also make a fire burn cold. You want the oil to change from a liquid to a gas. It's gas that burns not wet stuff. For that to happen you want the burn chamber to be at very least 350oC for engine oil.

Hard to say without seeing any pics of your setup but Rather than force the air down onto the opil pool which largely cools it, I like to have the air spin around the  bowl it's burning in unless one has a very tall vessel that the fire will heat as it escapes and transfers the heat back to the oil pool. Having a tall vessel also allowed the pipe with the incoming air to be preheated which helps a lot. I also feed the oil into the air pipe so it also has a chance to preheat to a gas at least boiling off the more volatile components in it which means it is burning as soon as it exits the pipe and imparts more heat to the burn vessel.  Spinning the fire also sends it outwards to the heater in this case to warm it up

One thing i see a LOT of people do which puzzles me is they duct the flue out of the building as soon as possible.  In a shed the best thing to do is run that flue from one end to the other inside the space you want to heat. There is a lot of energy and a lot of surface area to transfer the heat to the air in there and it increases efficiency dramatically. Throwing all the heat straight out to atmosphere is stupid really. The longer you can keep it in the building to radiate the warmth you are doing the whole exercise for, the better.

If you are not getting enough heat, simply turn up the burn. You may have to increase your air and oil rate but that should be no big deal.
If you can see in your burn chamber and there is very little oil or the fire goes out or drops within 10 seconds of shutting the oil off, you are probably running lean or too much air.  If you shut the oil off and the thing continues to burn pretty much the same for the best part of a minute or more, you are too rich.  Smoke can indicate this but I can also have a litre of oil sitting in a burner and the fire will burn perfectly clean because all the vapors are being mixed with enough air at the top.

Don't ever doubt oil doesen't have enough power. I'm building a waste oil powered spa heater to heat the home with and my biggest trouble is keeping the output down to 20KW ore less.  If I wanted to do 200KW which is what most Olympic size pool heaters are here, I could do that with great ease and ramp it up to 500KW VERY easily.  5-10 Kw is going to keep most homes hot let alone cosy once the place is up to speed so it just comes down to burning enough oil to provide the heat you need.