Roger Sanders' Waste Oil Heater

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Roger Sanders' Waste Oil Heater

Text of Roger Sanders' Waste Oil Heater

Roger Sanders' Waste Oil HeaterSecond EditionAfter five years of use, much experimentation, many upgrades, and hundreds of letters from readers and builders, Roger Sanders has updated his original waste oil heater project with a great deal of new information and options. What follows is a revision of the original article that has far more detail and information based on practical experience.

ContentsIntroduction....................................................................................2 Problem 1: Cleaning.......................................................................2 Problem 2: Low-heat operation....................................................8 Problem 3: Oil-flow stability.........................................................9 Theory of operation......................................................................13 Practical points of operation.......................................................14 - The flue........................................................................................14 - Air tube restrictor ........................................................................15 - Lighting the burner.......................................................................16 - Flame-outs....................................................................................20 Construction..................................................................................21 Burning vegetable oil....................................................................24 Automation options......................................................................26 - Improved starting system.............................................................26 Full automation.............................................................................26 Hot water and home heating.......................................................30 Wood stove conversions...............................................................32 Heating a greenhouse...................................................................33 Sources...........................................................................................34 - Online links..................................................................................35

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IntroductionI built a Mother Earth News Waste Oil Heater (MEN heater) to heat my repair and machine shop, where the heater gets used all day, every day, for about eight months of the year. The MEN heater works as claimed and puts out a lot of heat. I was pleased to find that I could successfully use waste oil to heat my shop. However, after using the MEN heater for several months, I became so frustrated with its problems that I concluded that it is unsuitable for serious, regular use. So I embarked on a journey to design and build a more practical heater. There are three big problems with the MEN heater. These are: 1) Cleaning 2) Low-heat operation 3) Oil-flow stability

Problem 1: CleaningCleaning the MEN heater is a major hassle. Burning waste motor oil leaves deposits in the combustion chamber. Calling these deposits "ash" is deceiving as they can be as hard as concrete and just as hard to remove. Experience reveals that there are actually several different types of deposits. These can be broken down into two basic types that I'll call "ash" and "coal."Photo #1 MEN heater built by Journey to Forever

"Coal" deposits are dark gray (almost black) and appear much like unburned charcoal. These deposits are very hard and must be chipped away from the burner surfaces using a hammer or cold chisel and hammer. They form on the hot metal surfaces inside the combustion chamber where the oil changes state from a liquid to a gas (vaporization). "Ash" deposits are crusty, light, airy, and are easy to wipe away with a gloved hand or putty knife. They mostly are light in color, ranging from tan to light gray, although some are black. For easy cleaning, "coal" must be avoided at all costs, only "ash" must remain to be removed. Vaporization heaters (like the MEN heater) must be cleaned every few hours of operation, depending on the oil used, the contaminants present, and how hard you run the heater. If you use your heater every day, all day, this means that you'll have to clean your heater every morning before you light it for the day. This cleaning ritual is a serious problem with the MEN heater due to its complicated burn chamber. There are many parts and some of them have rounded surfaces, which make them hard to access for cleaning, and they are bolted together. The heater produces heavy "coal" deposits. 2

Photo #2 MEN heater burn chamber

The nuts and bolts inside the MEN heater's combustion chamber become encrusted with coal, making them difficult to unscrew. Once the parts are separated, it is necessary to use a hammer and chisel to break away the coal. Its rounded surfaces are hard to clean because a hammer, putty knife, or chisel only contacts a small area, which forces you to spend a lot of time cleaning small spots, and the parts must be constantly turned to expose new areas to clean. It is much easier and faster to clean flat surfaces. It is necessary to use a drill to clear out the holes in the burner. This dirty, messy, time-consuming and frustrating task gets old very quickly. Others have tried to deal with this problem, like Bruce Woodford. I tried Bruce's forced-air heater, which uses a simple combustion chamber filled with loose bolts to make it easier to clean. This is a simpler design than the original MEN heater, and it is more efficient. It was easier to clean too. I give Bruce high marks for his design. But there were still problems. Shaking the bolts as recommended did a fine job of removing the ash, but the bolts were also coated with coal, and shaking them did not completely clean them. Eventually you have to beat on them with a hammer to break the really hard deposits free, and this was timeconsuming and difficult as they are hard to hold and have rounded surfaces. An easier solution is to replace the bolts, but large bolts are expensive. The cylindrical burner also became coated with coal, and because access to the inside is very limited, cleaning it was difficult.

Another issue was that fishing the loose bolts out of a pile of ash was a messy business. Setting the bolts back into place in the combustion chamber was a fiddly job that tried my patience. I didn't like the noise and complexity of using an electric blower. The heater would not run reliably at low heat settings. All this frustration finally compelled me to design my own combustion chamber and heater. Conceptually, vaporization heaters are simple and easy to design. They work by vaporizing liquid oil upon a hot metal surface. The vapors are flammable, and when mixed with adequate amounts of air, they burn very well. But making a design that doesn't produce coal is very challenging. The heart of the problem is that as oil boils and evaporates from the hot vaporization surface, it leaves behind all the "sludge" from the oil that will not vaporize and burn away. This sludge is turned into a hard mass by the heat of the burning oil. I found that pure, clean, new, oil has few deposits, but used crankcase oil is full of contaminants, detergents, and various additives, which remain behind. This problem is much like boiling water in a pan or teapot. As the water changes to steam, the minerals in the water are left behind as "scale" in the pot, forming hard deposits that are difficult to remove. Commercial waste oil heaters partly solve this problem by atomizing the oil through a nozzle rather than vaporizing it. The contaminants are atomized as well, so they are not left behind in the nozzle. A blower is usually used, causing the contaminants to be blown out the flue into the atmosphere. 3

Photo #3 Bruce Woodford's combustion chamber

The contaminants include toxic substances such as heavy metals (including lead, zinc, cadmium and chromium*) that are better left behind in a burner rather than being discharged into the atmosphere where we can breathe them. So a vaporization heater is likely to be more "green" than an atomization heater. My heater is environmentally sound because it distills the oil, automatically removing heavy metals from the oil before burning it. This heater effectively eliminates airborne, heavy metal pollution. Atomizing heaters have other, major problems. They require compressed air or an hydraulic pump to atomize the oil, the oil must be pre-heated, very well filtered, the nozzles tend to clog with carbon, low-heat operation is not practical, and the pumps, nozzles, and air compressors add a lot of complexity and maintenance issues. Also, they use large amounts of electricity, which is expensive and defeats the idea of using "free" fuel and being environmentally responsible. I like the simplicity, silence, and economy of a vaporization-type waste oil heater, so I focused my attention on making one that is extremely simple, noiseless, requires no electricity, that produces mostly soft ash rather than hard coal, and has only flat surfaces that are easy to clean. I have designed, built, and tested dozens of burners in trying to develop an ideal combustion chamber. There isn't the space in this article to describe all the details, changes, and experimentation involved. So I'll just summarize my findings and describe the burner that solves the problems. After considerable experimentation, I eventually settled on the idea that the simplest combustion chamber was best. This took the form of an open "pot" into which the oil would drip, vaporize, and burn. I tried various types and sizes of pots, with and without different types of internal assemblies. I found they all could be made to work. Of course, some worked better than others. I found an 8-inch cast iron pot (20.3 cm) worked quite well. The nice thing about an open pot is th