How to Convert an Oil Heater to Burn Waste Vegetable Oil WVO or Waste Motor Oil WMO

How I converted a standard home heating oil burner into a waste oil heater for about $300.

Please don't attempt to modify your heating system if you do not know what you are doing. You can cause a fire or explosion that may destroy your home or get someone killed. I am not responsible for anything that you do. This is just an explanation of how I modified my Becket burner to run on waste vegetable oil or waste motor oil. Modify your heater at your own risk.

There are two basic ways to convert a burner. You can build a pressure burner or a syphon burner. A pressure conversion is considered to be a bit more simple and cheaper to build, but normally requires more frequent cleaning. A syphon burner requires more extensive modification and closely resembles commercial built waste oil burners. They are considered to be more reliable and run longer between cleanings.

I decided to get my feet wet with a pressure burner. I figured that I could keep it for a spare or use it in my garage if it worked and I upgrade to a syphon burner. If I couldn't get it work reliably enough or if it was a complete failure, I would limit my loss because a pressure conversion is cheaper.

Most guys recommend that you get a second oil gun to modify or go one step further and add a second boiler to your system. If the wvo burner should fail your current burner can kick in to prevent you from waking up to a freezing house or worse yet a nagging wife. Used heaters or just the burner guns can be found on craigslist or eBay. You can contact several local HVAC companies. Many of them remove perfectly good oil burners because the homeowner wants to convert to gas heat. The old units are of little value to them. The scrap price is just a couple dollars per hundred pounds of steel. You might score a free heater if you can meet them at the job site to haul away the old heater. Check with your locals scrap yards and scrap collectors. Some heaters have deeper fire boxes than others. Look for the deepest one you can find. A boiler or furnace with a swing open door will be a plus. It allows you to inspect, clean or adjust the burner and fire box easier. But, as they say, beggars can't be choosers. If you find a unit in good shape take it.

Burning waste oil in a heater is similar to burning it in a vehicle. Waste vegetable oil, WVO, is thicker than heating oil or diesel fuel. In order for it to ignite and burn cleanly it must be thinned to be properly atomized by the nozzle and ignited by the electrodes. The oil is heated to thin it and allow it to flow better. Most conversion increase the pressure to the nozzle to help break the oil into smaller droplets to burn better. When the pressure is increased the flow of fuel increases and raises the btu out put of the burner. In order to offset the increased heat most guys drop one or two nozzle sizes. The increased pressure combined with the slower ignition of the thicker fuel can cause the flame to increase in length. If it gets too long it can touch the back wall of the fire box and will burn through it. That's why heaters with a deeper fire box are better candidates for a conversion. Some guys have added a thick piece of sacrificial steel or stainless steel to the back of the box. Some guys have extended the front of the fire box, effectively making a deeper fire box. I have a Tarm dual fuel boiler it can burn heating oil and it is also a high efficiency wood gasifier. I was lucky enough to be able to adjust the flame to what appeared to be a good clean burn with the flame just kissing the target wall. As my nozzles clog or oil thickens from a lower temp the flame grows and touches the wall causing it to glow and letting me know that a problem is appearing long before the burner shows signs of increased smoke or rough ignition.

I began my conversion my spending a lot of time on line reading about the success and failures of others. The best place to educate yourself on converting a burner is the altfuelfurnace Yahoo group. There are other sources out there, the Yahoo group is hands down the best place to be. It's more of an old school bulletin board than a modern forum, navigating the site and locating information can take some getting used to. They do have helpful information for a beginner in the file section. Almost any burner can be converted, but some are better candidates than others. Those details are listed on the altfuel group and I do not need to repeat them. I just going to show how I built my first burner.

The short description of a pressure conversion is to add a heater block inside the blast tube. It contains a cartridge heater and thermocouple. You need to add a pid, an electronic brain to keep your heater block at the correct temperature. The thermocouple tells the pid how the temperate of the block. The pid cycles the heater on and off to maintain the correct temp. I knew that some guys had a problem with ignition because the oil in the heater block was up to temp, but the nozzle was not. The burner could not ignite because it would spray cold wvo until the hot oil reached the nozzle. The excess cold oil can collect in the fire box causing soot as it burns off and it can cause the nozzle to clog. I did some searching a located small band heaters that could fit around the nozzle. I thought this should solve the problem by warming the nozzle and the block at the same time.

The heart of the conversion is the heater block. Better conversions use machined aluminum blocks to replace the J-tube in the burner. I picked up a 12" length of 1"X1" aluminum square stock at my local welding shop. It was a left over end piece so it was cheap. My first heater was a 350 watt unit with a thermocouple,tc, built in. I purchased one cartridge heater and 2 band heaters from PPE supply. There's a link to their site in the files section on the altfuel group. Since I don't have a machine shop, I held the aluminum in my vice, cut it to length and drilled a hole for J-tube to pass though. I also drilled a hole to insert the heater cartridge. You should use heat transfer paste when building the heater block to allow the heat to pass from the heater to the block, to the J-tube and finally to the oil.

Lay out the heater block carefully. There is limited room inside the blast tube. There needs to be room for the electrodes and the cad eye. The block must also clear the squirrel cage and the high voltage springs. I was able to get my block pretty close but I still needed to use a file it down to add a little clearance in a few places.

I bought a cheap PID on eBay. I found that getting one from over seas was cheaper than getting one local. The PID is a computerized relay or switch. The TC tells the PID the temperature of the heater block. The PID controls a relay that powers the heater. The heater draws too much energy to be wired directly through the PID and requires a relay. Nearly everything on the PID can be programed. You set the low temperature where you want the heater to turn on and you set the high temperature where you want the heater to turn off. You can also set how fast the PID will cycle your heater relay. The PID has alarm contacts that can be set to open or close at different temperatures. The alarm contacts open and close the thermostat contacts on the primary control on the oil burner which turns the burner off and on. Detailed instructions for programming a PID should come with your unit and additional help can be found on the altfuel group.

I have the unit wired through the aqua stat on the boiler. It will call for heat when the boiler temp drops to 160 degrees and stop the call for heat when it reaches 185 degrees. When the temp drops and the boiler calls for heat the aqua stat sends power to the oil burner. The PID, heater, heater relay and the primary control are energized. The primary does not turn the burner on at this time because the PID alarm contacts are open. The TC tells the PID that the heater block is too cold so the PID turns on the relay energizing the heater and beginning the heating cycle. When the PID senses that the heater block is up to the minimum temperature, in my case 375 degrees, the alarm contacts close and the primary control turns on the burner. The unit should fire, the cad eye should "see" the flame and tell the primary control that the burner is operating properly. The PID will cycle the relay to keep the heater block temp within the range that you have programed. The burner should continue to fire until the boiler temp reaches 185 and the call for heat stops. The aqua stat will stop the flow of electricity to the burner ending the cycle. I needed to move my cad eye forward into the blast tube as many guys who use wvo burners have needed to do. I tried to paint the blast tube with hight temp silver paint, but it didn't help. The wvo doesn't burn a white as home heating oil and many times the cad eye will not "see" the flame. Moving it forward solved the problem for me.

Of course there are several was to wire a burner. A "cold start" boiler may be wired differently because it does not have a domestic hot water coil and the boiler will be allowed to cool between cycles. The house thermostat will start the call for heat for a cold start boiler and a hot air furnace. The call for heat will end when the thermostat is satisfied and stops the call for heat. I don't think it meets code, but I used a standard outlet and power cords to attach my burner to the boiler. This made switching back to my stock burner much faster. I wired my burner with a power cord for the heater element and second power cord for everything else. This allowed me to tune the PID with out powering up the heater.

I began the heating season using the same wvo that I filtered for my vehicles. You can view my blog or my other articles on this site for details of my filter system. I used a standard home heating oil filter on my burner. It clogged with wax after burning only ten gallons of fuel. I quickly realized that I needed to use a cold filter system for my burner. I pump my vehicle fuel through the filters at 80 or 90 degrees because the heated tanks in my vehicles will reach the same temperature and melt and wax or fats left in the fuel. The boiler fuel was stored in the garage until it was needed to refill the tank in the basement. The fuel temp was around 50-60 degrees. It was cool enough for some fat and wax to solidify and clog my filter. I solved the problem by adding an additional step to my filter process. I cut two holes about 8" around in the top of a clean 55 gallon drum. I hung a 5 micron sock filter in each hole and used the drum to supply my burner. Normally I filter with blue jeans, but a couple filter bags so I used them. I use 2.5 gallon "cubies" to store and move the fuel from the bulk tank in the garage to the drum in the basement. Cubies are the square, thin walled plastic jugs used to sell the vegetable oil. They normally are about 5 gallons, but some of the smaller ones have thicker walls and resist cracking better than the large ones. I pour a couple cubies of my vehicle grade wvo into the bag filters in the drum. To speed the cold filter process I normally keep a couple cubies in the basement to warm up to the basement temp if the garage is near freezing. I can scrap the wax out of the filter bags as needed. usually only once a week, but maybe twice a week during very cold weather. The bags could just be discarded and replaced, but I prefer to clean them. A large ladle works well for me.

I had a hard time maintaining the heater block temp. I thought about upgrading to a hight out put heater, but that would mean building a new heating block. I thought long and hard about the problem. It appeared that the large volume of combustion air that the fan was pushing past the heater block was cooling it off. I was always a hotrod, 4X4 guy and I thought about insulating the heater block with something that could stand up to the 400 degree temps. I used some scrap pieces of header wrap and some of the high temp self sealing tape that I use to build electric wvo heater to insulate the heater block. All was well until one day in February when the heating element failed.

I needed a replacement and I was already considering upgrading to a higher wattage heater. I searched eBay and found a great deal for a few replacements. A company was selling off some new old stock 400 watt heaters for only $8 each. They were 1/2" round, did not have a built in TC and were a little longer than my current heater. Since I paid out about $30 for my first element and I wasn't sure why it failed so quickly, I decided to pick up several of the $8 heaters even though it meant that I would have to fabricate a new heater block. If I lost another heater, I would be set up for a fast and cheap repair to it back in operation.

I built my second block. Even though this one required more care because of the larger heater and the additional tap for the TC. It seamed to come together quickly. I guess the experience of building the first one paid off. My PID came with a TC, so I had one to use as a replacement for the TC that was built into the heater.

Burning wvo does require a bit of time and some of the work is messy, but it definitely beats paying a $350-$450 per month heating bill. I heated my home with a wood stove for several years in the past. I was lucky to have a source of large pallets used for shipping sheet metal very close to my home. They measured about 4'X8' and were made up of 3 or 4 rough cut hard wood 2x4x8's or 3x4x8's held together with cross members made of pine 2x4's. They were easy to break apart and cut to length with either a circular saw or a chain saw. As far collecting firewood goes, I had it made. Because the wood came from pallets it was aged and dried. The pine was easy to light and made great kindling. The hard wood 3X4's would burn most of the night if I stacked them tightly into the fire box. Even as good as I had it with wood collection the wvo was much easier. No heavy lifting was required. Just run a hose and turn the pump. I have an article about building a great waste oil pump on my blog.

Once you work out the little nuances and get a reliable, clean burn you'll be glad you invested the time and money. I got my pressure burner up and running for about $250-$300. By the end of November I hit the break even point. The rest of the winter was just money in the bank. I went through a couple nozzles. I had good luck cleaning them 2 or 3 times, but after that they would not atomize correctly. I started out with a cheap heater relay. The contacts corroded and it failed near the end of the heating season. It's was mostly my fault. For the first couple months I did not have the PID programmed correctly and it was cycling the relay several times per second. After I learned how to set up the PID correctly the relay only cycled every 3-5 seconds. That's a lot of excess wear and the relay probably would have lasted much longer. Since I needed to replace it, I put out the extra money and upgraded to a solid state relay. It should have a much longer service life.

That just about wraps up my first heating season using wvo. I have saved hundreds on dollars in heating costs and gained valuable experience. Next year I expect things to go a bit more smoothly. For an added bonus I am burning a carbon neutral fuel not a fossil fuel so I'm helping to save the environment without sending excess money over seas. Since my boiler produces hot water for showers, it further reduced my energy costs. I have a DIY roof mounted solar water heater and wall hung on demand water heater that I switch to during the warmer months just by turning a couple ball valves. I am planning to reinvest some of my fuel savings into building a syphon burner for next year and saving the pressure burner for a spare or using it in the garage.

Again alter your heating system at your own risk. If you do not have much basic knowledge about heaters I suggest that you purchase Residential oil Burners by Herb Weinberger. It's covers everything you would need to know in a very easy to understand format. I have no connection to him, I just found the book very useful and I am in the HVAC field.