Can I use a waste oil heater to heat water or heat my house?
I'm having trouble starting my heater, what should I do?
Where can I get a conical burner and precision needle valve assembly?
Where can I get a nice oil filter like that shown in the article?
What about smoke, odor, and soot?
Frequently Asked Question:
Can I use a waste oil heater to heat water or heat my house?
Answer:
Hot water and home heating
Waste oil heaters can be used to heat water -- either for use as hot water or to heat your home using radiators. There are two ways of doing this. One is to heat a tank of water and the other is to heat water that is pumped through piping that is then run through either a hot water tank or through radiators in your home. But there are many things to consider carefully before doing either of these.
Safety is essential! An oil heater gets very hot and can easily boil the water in a water tank or in water-circulation pipes. Of course, boiling water produces steam, which can cause an explosion. So it is absolutely essential to install a "pop-off" safety valve that will vent the tank and/or tubing in case the pressure rises too high. These are always used in all water heaters so are readily available at reasonable prices.
Additionally, you should install a safety, shut-off, solenoid valve in your oil supply line. This should be controlled by a thermostat in your water system so that the valve will automatically turn off the oil supply to your burner if the water temperature exceeds a safe level -- probably around 190 degrees F. It should have a second thermostat to turn off the oil if the fire goes out unexpectedly (such as from strong, gusty winds disrupting the draft in your flue).
The surface temperature of an oil heater can exceed 1,000 degrees F. So it is essential that you use safe installation practices. You should follow the safety guidelines for wood stove installations. Specifically, this means that the heater must be at least four feet (1-1/2 meters) from any combustible surface. It must sit on a non-combustible surface like concrete, steel, or tile. The flue must be insulated where it goes through the roof, and the rafters and other combustible surfaces in the roof must be shielded by sheet metal.
Always assume the worst because Murphy's Law assures it will happen. All mechanical devices will eventually fail. So think about what will happen when something like your water circulating pump fails and the water in the piping in your heater doesn't move while being exposed to the intensely hot flames inside the heater. Will your safety systems provide adequate control? If the pop-off valve opens, will water flood your basement? If the fire goes out unexpectedly, what happens to the oil flow? Does it soak your carpets or contaminate ground water supplies? What happens to the system if the power suddenly fails?
These safety issues are not trivial! Please deal with them competently and responsibly. Failure to do so could result in your injury or death, or worse yet, how would you feel if one or more of your family members were injured or killed due to your negligence? What if your house burns down?
Controlling the heat
The biggest problem is how to control the heat when heating water -- particularly when using a recirculating hot water heating system in your house. If you have too much fire, the water can boil. Too little doesn't give you enough heat. This is a serious problem when heating your home with hot water radiators as they need to be fed water that is close to boiling to get adequate heat, but the water must never actually boil or you will get an explosion. So the temperature range is very narrow and you really need to have some sort of automatic regulation of the oil flow to hold a fairly precise temperature.
My heater is designed to work manually, like a wood stove, where you keep an eye on it and adjust the temperature yourself. This works just fine for heating a shop or garage where precise temperature control is not an issue, you are heating only air, which can't explode, you are present in the room most of the time, and you don't heat it 24 hours per day. But the situation is different when you want to heat your home or water heater precisely and continually.
Automatic temperature regulation is not an easy problem to solve. I had one reader say, "I used a P.I.D. controller sampling the stack temperature and pulsed a Walbro electric fuel pump for a diesel engine . . . worked great." Personally, I have not tried his system. It sounds like it could work well, as long as safety is kept in mind. What happens if the P.I.D. controller fails or the temperature sensor burns out and the fuel pump stays on?
I have successfully built and tested a motorized valve that can be controlled by an analog, operational amplifier or digital microprocessor using a thermistor for a temperature sensor. But I have not developed the electronics yet. So I cannot provide you with a finished and tested system.
You are on your own here. I ask readers who develop a reliable and functional system to contact me with details of their design so that I can share it with others.
Cleaning
The next issue is cleaning. Cleaning the burner in a shop or garage isn't much of a problem as my burner is extremely easy to clean and most users don't use their shop or garage continually or even every day. But if you want to heat your house with a waste oil heater, it must be cleaned every day, which is a major headache if you want to use the heater continually.
It is hard to clean the burner when it is hot. But you don't want to turn it off and let it cool for an hour before you clean it. So if you want continuous operation, you really need to have two burners. You can then exchange them quickly without having to shut down the heater for an extended cool-down period.
This process can be done by turning off the oil and while the flame is dying out, you clean the previous day's burner, which would of course be cold by then. Then open the heater and lift out the hot, smoking burner using pliers and drop it in a flame-proof container, like a steel bucket with sand in the bottom and put on a steel lid. You would then take the cold burner you just cleaned, set it in the heater, fill it with kerosene, and light it. Since the burner would be cold, the risk of an explosion from hot kerosene vapors would be minimal.
This process could be completed in just a couple of minutes. The result would be essentially continuous operation.
Self-cleaning burner
But no matter how quick and easy the cleaning process is, having to do it every day to keep your house warm is a nuisance. To really solve this problem requires a self-cleaning burner.
I have been experimenting with just such a heater in my shop. Initial tests have been successful and if I can get reliable, long-term, unattended operation, I plan to use waste-oil to heat my home next winter.
My home uses a propane-fired water heater that circulates hot water through baseboard radiators. While I could use a waste-oil heater to heat the circulating water, the complexity, reliability, and safety problems as described above are very troubling and I don't want to risk it. So instead, I'm going to convert a wood stove to waste-oil operation and put it in my great room. By using a wood stove rather than a water tank, the cosmetics of the heater will be nice enough to place it in a fine home.
I plan to run the heater at a more or less constant output level (using manual adjustment) so that it does about 90% of the heating. I'll continue to use the propane system (which is reliable and thermostatically controlled) as needed to hold the desired temperature automatically. Since the propane system will be used very little in such a system, my propane costs will drop dramatically.
By operating the oil stove manually and only for heating air, it will be safe and easy to use. By leaving the propane system intact, it will not only maintain the house temperature automatically, but I'll have a propane back-up system in case the waste-oil heater has a problem -- and I'll have an oil heater to back up the propane system if it fails. By using a self-cleaning burner, I'll not have to clean it daily. Like a wood stove, I'll only have to shovel out the ash every few weeks.
Efficiency
If you choose to use the oil heater to heat water, remember that efficiency is important. For example, wrapping copper tubing around the heater will not transfer heat to the water nearly as well as having the tubing inside the heater where the flames will come into direct contact with the water tubing. Of course, you must insulate the hot water piping until you get it to the location where you want to extract its heat.
Another consideration is soot. Oil heaters make soot that gradually coats all interior surfaces of the heater and flue. If you have water pipes inside the heater, they will become coated with soot. If the tubes are close together, soot can collect between them and clog the flow of hot gases through the heater and flue. So keep the water tubes at least 3 inches apart.
Gas water heaters use their flue pipe to heat the water. This pipe goes through the tank, is surrounded by water, and contains a turbulator to more efficiently extract the heat from the flue gases. Unfortunately, gas flue pipes are only 4" in diameter, which is too small for an oil heater. Also, the turbulator will quickly become clogged with soot. So you need to use a larger flue and possibly a heat exchanger to heat a water tank.
Soot is soft, delicate, and easy to clean. A blast of compressed air will do the job. But expect a mess when you do so. For this reason, you won't want to clean the heat exchanger or piping inside the heater very often. So leave plenty of room for soot to accumulate.
More about self-cleaning burners
You are probably wondering how I've managed to make my waste-oil heater self-cleaning. The basic process involves rotating the burner continually at about 5 RPM under a stationary scraper blade just above its surface. This scrapes off the ash as fast as it is formed and the burner stays clean.
Of course, this sounds easier to do than it really is, and I've found it quite difficult to obtain long-term, reliable operation for many reasons. These include bearing failures due to the fact that the bearings have to operate in Hell's Kitchen without any lubrication. Finding a suitable scraper blade is tough because it has to live in the oil flames and gets so hot that it bends, breaks, or simply disintegrates. There are also clearance problems due to large amounts of expansion of the parts as the temperature varies. And there are problems keeping the gear motor cool since it is mounted directly under the hot stove. So my self-cleaning heater is a work in progress.
I have not published my work on the self-cleaning heater at this point because I'm still problem-solving and it will take many more months of work before I have all the problems resolved and have proven long-term reliability. Also, this system requires precision machine work to make the bearing housing needed to rotate the burner precisely under the blade and the drive shaft system must be adapted to the gear motor.
Gear motor used to rotate burner
When I get all these problems solved, I'll probably offer a kit of parts to those who may be interested in a self-cleaning heater because few readers will be able to build the parts themselves and getting a local machine shop to do a small, one-off project like this is tough.
I'm only mentioning the project so that those who have the tools and inclination can experiment with self-cleaning heaters themselves. I only ask that those readers who are clever enough to make such a system successfully share their experiences with me so that others can benefit from their work.
To help interested readers move along in this direction, I'll mention a couple of potential solutions to some of the problems outlined above. With regard to bearings, forget using any sort of ball or roller bearing. At temperatures of nearly 1000 degrees, such bearings blue, lose their temper, and fail.
Obviously, you cannot use rubber seals (which melt), or any sort of oil-based lubrication (which chars). Because the bearing turns slowly, they should survive without lubrication. But I've found that their bearing cages lose their temper and fail, which either jams the bearing or the balls fall out. Cageless bearings might prevent the balls from falling out, but that wouldn't solve the problems of bluing, annealing, and general failure.
Currently I'm using solid brass bushings to support the steel shaft. These seem to be holding up well, but they squeak when hot. I've put powdered graphite in them to silence them, but without any seal to hold it, the graphite soon disappears and the bushing squeaks again.
My next step is to try solid graphite bushings. But these are expensive and require a polished shaft as any roughness of the shaft will cut into the relatively soft graphite. So my search for a suitable bearing continues.
The scraper blade needs to be stiff and sharp. It also must be installed at an angle to the burner disk in order to direct the ash up and over the side of the burner. The scraper blade needs to be tiny (1/4" square maximum) so that it doesn't accumulate much ash on itself as the blade doesn't get cleaned. Although there is nothing that cleans the blade while in operation, I was pleasantly surprised to find that it only accumulates about a half inch of ash before most of it falls off by itself. So the blade is semi-self-cleaning.
Mild steel of such small dimensions looses most of its strength in the intense heat. It then bends and won't hold a sharp edge. So I switched to a section of piston ring (which is made of nodular cast iron with very sharp edges) with great results initially, but I found that after 3-4 days of burning, the ring's nodular cast-iron degrades, fails, and breaks away from its holder. See photo.
I tried a piece of ceramic tile, which took the heat well, but it was too brittle and eventually fractured. Currently I'm using a piece of 1/4" square cobalt tool-steel that is used for cutting tools in lathes. This finally seems to be handling the job as it has not failed in over a week of continuous operation. See the photo.
Piston ring scraper blade
Cobalt tool steel scraper blade, recently in operation
Anyone who is seriously interested in experimenting with a self-cleaning heater may feel free to contact me to discuss issues. Otherwise, readers should check this website from time to time to check on the progress of this project and the possibility of a kit of parts.
Keep warm
-- Roger
Question:
I'm having trouble starting my heater, what should I do?
Answer:
There is really only one reason that a waste-oil heater goes out soon after you light it -- the burner isn't hot enough to vaporize oil. The burner must get up to a high temperature before it will vaporize oil and develop a self-sustaining flame.
This problem will be worse with a steel burner than with an aluminum one because it is harder to heat steel than aluminum. You should be able to get most burners hot enough by doing the following:
- Be sure that your burner is COMPLETELY FULL of kerosene before lighting it.
- As soon as it is lit and you have closed the door, turn on the oil to whatever produces a "medium" heat setting.
Now I understand that with a new heater, you don't know exactly what "medium" is yet, so make a guess. The idea here is to replace some of the kerosene that burns away with oil so as the burner gets hotter the fuel will change from relatively easy-to-burn kerosene to harder-to-burn oil. Obviously, the fire will go out once the kerosene is burned away if you don't feed it some oil.
However, don't flow large amounts of oil when the heater is cold as the oil will tend to cool off the burner too much and the burner isn't hot enough to vaporize large amounts of oil at that point. So start with a relatively slow oil feed.
If the stove still goes out, then simply refill the burner with kerosene and light it again. Usually the second dose of kerosene will get it hot enough.
CAUTION!
Never fill a hot burner with kerosene and light it as this will cause an explosion. But if your heater is not hot enough to vaporize oil, it won't be hot enough to cause a kerosene explosion either.
You can easily tell if your stove is too hot to light with kerosene. If you put kerosene in the burner and it vaporizes making a lot of white smoke, then DON'T LIGHT IT! That white smoke is explosive. But a warm burner won't make much if any white smoke, so is safe to relight.
Once the heater keeps going on oil, the flame will be weak and rather small. It won't have enough heat to accept large amounts of oil. So let the burner heat up for about 15 minutes before turning the oil up to high. The burner needs to be good and hot before you turn it up high.
You can help "learn" your heater by checking the appearance of the flame by looking down the air tube or though the door window (if you use one). You'll see that the flames over the burner look different depending on the burner temperature and you can "read" your burner's temperature and burning condition by observing the characteristics of the flame.
Specifically, when the heater is first started, the flame over the burner has some blue color (although it will mostly be yellow), is fairly uniform, and appears to be smooth and "leisurely" in its action. But as the burner starts getting really hot, the flames become highly agitated with bright streaks of light shooting radially out from the burner, the flame loses its blue color and becomes an intense white/yellow.
Note that the blue color of the flame is only present directly over the burner. As the flames spill over the edge of the burner, they will be yellow/white.
Be patient. There is a lot of mass in a heater and it takes time to get it hot, particularly when the heater is first started and is just trying to get the burner hot enough to vaporize oil well. Expect that it will take about a half hour to get really hot, and in an hour, it will really be pouring out the heat.
Some readers can't find kerosene and wonder what else they can use to start their heaters. Good options are charcoal lighting fluid, stove oil, and diesel fuel. Note that #2 diesel (what you get from most diesel stations) does not burn as easily as kerosene, so you will need to light it with a small propane torch.
If you are not using one of my aluminum burners, and you find that you can't get the heater started using a single dose of kerosene, then your burner probably isn't deep enough. I specify a 12-degree cone on my burner because I found that a shallower 10-degree cone didn't hold enough kerosene to get the heater started. So switching to a deeper burner should give you sufficient volume to hold enough kerosene to start it on the first try.
Also, many readers have substituted hemispherical burners for my conical design. Besides being harder to clean due to the fact that they don't have flat surfaces, a hemisphere doesn't expose as much dry surface to the flames to get hot fast. So a hemispherical burner is somewhat harder to start than a conical one.
Of course, you can always get any burner hot enough by heating it using a big propane torch rather than filling it with kerosene. The torch I'm referring to is the type that connects to a 20 pound propane cylinder using a hose. These torches are used for burning weeds and melting ice. They put out a great deal of heat.
To use it, simply blast the burner with the torch for a minute or two before starting the oil drip. Once the oil catches fire, you can remove the torch and the heater should be self-sustaining. If the fire goes out, heat it with the torch for a longer period of time. Note that you can keep heating it with oil in the burner.
Question:
Where can I get a conical burner and precision needle valve assembly?
Answer:
Due to significant demand, I have machined, conical, aluminum burners in stock. The price is $50 plus $10 for handling and U.S. shipping.
I also make precision needle valve assemblies. These also cost $50 each, plus $5 for shipping.
Shipping for overseas customers is double the above amounts ($20 for burners and $10 for valves).
Payment may be made by check or money order to my address shown below, or through Paypal using my email address <mailto:rogersanders@wispertel.net>rogersanders@wispertel.net.
Roger Sanders
12054 Deer Trail Road
Conifer, CO 80433
Question:
Where can I get a nice oil filter like that shown in the article?
Answer:
I purchased my waste-oil filter/water-separator on eBay. It is made by COMBU and is their model number 70101. It is a 100-micron filter using a cleanable metal screen rather than a paper element. It is made in Italy, but there is an American address on the label:
COMBU Inc.
2001 S. 21st St.
Parsons, KS 67357
If you can't get a filter though them, then you can "Google" waste oil filters on-line and something suitable should show up. If not, then most any diesel filter should work.
Most diesel filters have water drains and use paper filter elements. They use smaller holes in their filters than that normally used in a waste-oil heater filter, but since the oil flow in a waste oil heater is very slow, this should not be a problem.
The paper filter elements cannot be cleaned, so should be replaced annually. This is a small expense that isn't necessary if you can find a screen-mesh filter like the COMBU as this can be cleaned and reused.
I find that annual cleaning of the COMBU filter is adequate. It is easily disassembled by removing a bolt in the top that holds it together. Upon disassembly, I find that the filter is mostly clean. But the filter has blocked a lot of small sediment particles that have accumulated in the bottom of the filter -- and most of that sediment has already been removed since it tends to flow out with the water when I drain it. The filter is easily washed in either a kerosene-filled parts washer or in soap and water.
Question:
What about smoke, odor, and soot?
Answer:
All oil heaters will make some smoke, odor, and soot. However, this is usually not a problem because a heater of my design makes less smoke and odor than a wood stove, and wood stoves are commonly accepted and in wide use.
My heater design is reasonably efficient and once up to operating temperature, it only makes a little smoke. The photo shows my heater when running on "medium" where the surface temperature of the heater is 500 degrees F. Smoke is visible, but you have to look carefully to see it.
Of course, the smoke would be more visible against a white, cloudy sky than when seen against trees or against a blue sky. But generally, the smoke is not excessive.
The amount of smoke varies depending on the type of oil used and the amounts of contaminants in it. Also, the stove will smoke more when cold than when hot, just like a wood stove.
There is more smoke when the heater is run on "low" than when run on "high." This is to be expected as when the burner temperature is lower, the efficiency of the stove is less than when it is running real hot.
The oil has a characteristic odor, but in my opinion, it is not unpleasant. I rarely smell anything, but if there are gusty winds, I'll sometimes smell a little odor in certain areas. Again, this is much like a wood stove that you catch a whiff of odor now and then.
Note that the height of your flue can have a significant effect on these factors. Your flue should extend above the ridge of your roof so that the smoke and odor can rise and be carried away on the wind. If your flue is below the ridge line of your house, then the smoke can be trapped and carried downward into surrounding areas rather than going up and being dissipated in the wind.
In summary, you should expect some smoke and odor. If you live in a situation where this would be objectionable to either your neighbors or government authorities, then you should not build this type of heater. But for most situations, this will not be a problem.
Soot will build up inside your heater and especially inside your flue. Soot is very soft, delicate, and easy to remove.
Soot can build up and become quite thick over time. After burning 600 gallons of oil last winter, I found I had soot almost two inches thick inside my flue. I found that this much soot started to interfere with the draft in my heater and that I had trouble getting stable operation. So if you notice that your heater doesn't seem to be working right, check and clean your flue.
I originally used a wood stove flue cap. This had a screen in it to catch wood sparks. This screen quickly became clogged with soot and I had to remove it. Oil stoves don't make sparks, so this is not a problem. Just be aware that you can't use any sort of filter on the flue.
Because soot tends to accumulate in the flue, you should NOT use a flue with angles in it. I would expect soot to accumulate rapidly in the bends of such a flue pipe.
So use a straight, vertical flue if at all possible. If you must use a bend, then it would be best to use a "T" rather than a 90 degree elbow at the bend. You can then open the end of the "T" to quickly and easily clean out the soot.
Generally, you should expect to need to clean your flue annually. This is easily done with a blast of air. You can used compressed air, a leaf blower, or the blower side of a shop vacuum. You can also use any sort of soft brush or rag on a string. It's easy to do, but expect a mess.
Note that oil stoves that use blowers or that otherwise have strong, relatively violent burning characteristics tend to blow the soot out of the flue so cleaning isn't needed as often (or ever). My stove burns quietly and gently by comparison, so soot accumulates easier.
Soot probably will leave some dark areas on the roof in the area of the flue. This is just like the dark streaks you often see running down the side of a diesel truck from the soot in its exhaust. This can be easily washed off with a hose and a hard rain will also remove most of it.
Back to: Roger Sanders' Waste Oil Heater -- main page
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