I have poked around on this website off and on over the past couple of years and have just now decided to start utilizing it. I have so many questions about the different projects that I work on that it seems to overwhelming to even start asking them. So now I am just going to start posting comments about what I am doing and maybe I'll be able to glean what I need to from others.
The project I am currently working on is a waste oil heater based on the original MEN design. Thanks to everyone that has ever published any of their experience with building this and similar heaters/burners. I have read it all. Unfortunately, there seem to be no authorities on the subject and there is very little written about the theories behind the various designs. I can only speculate.
My current design differs from the MEN design and others in the following ways:
Heater is located in a 6'x6'x7' enclosure outside of the house.
A blower for combustion air is used but as a draw through on the exhaust side.
Supply air runs inside the exhaust air duct so there is only one 6" hole in the top.
Cone is fixed and does not adjust up and down.
Burner support has adjustable height.
Burner assembly can be removed without tools.
Fuel controls will be much more complex when I get to them.
I am very lucky to have my little enclosure. It is made of dual wall steel pannels with 2" of insulation in between. The company I work for often has HVAC related items that eventually find their way in the dumpster or at my house. The heater will use 100% outside air for combustion and another set of fans to move the hot air from my enclosure to the crawlspace of my house. My original plan for heating my house was a radiant floor system, then I discovered that a conditioned crawlspace is not only going to be more efficient but it will also be a whole lot cheaper to install and whole lot easier. I will eventually post all of my work on the radiant floor heat system if I can still find it. For now I am just pointing out that a conditioned crawl provides the same type of radiant heat with numerous advantages. All that is required for a conditioned crawl is to cover the ground with 6 mil plastic and insulate all of the crawlspace walls. After that, any source of heat you put down there will radiate up through the floor. This is not a "crawl plenum!" Crawl plenum = bad idea. Much more on this later; I was just explaining what the enclosure was all about.
It appears that most DIY waste oil burners require some forced combustion air to burn clean. My reason for going with a draw through blower is to avoid any possibility of combustion fumes leaking out of the heater. The enclosure will be under positive pressure and the heater will be under negative pressure. Of course, the challenge I will face is to see whether or not I will be able to cool the exhaust gasses enough before it gets to the blower.
The supply air duct is 4" vent pipe coming from outside. It will pass through a 6" to 4" reducer as a way to get inside the 6" exhaust duct. The 6" duct will run to the trunk of a T and the 4" duct will turn 90° inside the T and down into the heater. The other arm of the T will also be fitted with a 6" to 4" reducer providing the exhaust gasses a route to exit. Their will be some heat exchange between the supply and exhaust combustion air which will help cool down the exhaust gasses for the blower. Hopefully, the supply combustion air will warm up enough that it doesn't cool down the dripping oil. The supply air fan for the enclosure will be pointed directly at the duct carrying the exhaust gasses. I hope that the exhaust duct is not something that will have to be cleaned very often.
I did not want to fool with adjusting the height of the cone every time that I needed to clean the burner assembly. Thin sheet metal parts just aren't made to withstand repeated mechanical manipulation. I designed an adjustable base for the burner assembly instead. I used two brake drums, one sitting on top of the other for height. No modifications were made to the lower brake drum. I welded a sheave with a 3/4" bore to the top of the other brake drum. I welded a 3/4" nut to the top of the sheave using a piece of 3/4" allthread for a centering guide. The allthread can now be screwed in and out or up and down through the brake drums. I welded another sheave with a 3/4" bore to the top of the allthread to place the burner assembly on. I drilled two 1/4" holes into the outer perimeter of the sheave and welded some pins into it. The pins fit inside two holes drilled into the bottom of the frying pan of the burner assembly. Now, if I want to remove the burner assembly, I just spin the burner down till it clears the cone and then lift it off the pins. Originally, my plans involved trying to use pipe flanges with threaded rod. It almost works but pipe fittings tend to be cast and it is almost impossible to find a straight one.
I must admit that my plans for oil delivery are still kind of foggy but I intend to have just about every safety that I can think of. It is very hard to find parts that say they are compatible with oil; motor or veggie. Actually, from what I've seen, valve seals are more likely to withstand motor oil than WVO. I have a solenoid valve that I hope will work. I also have thermostats, air pressure switches, and limiting valves. Should any number of conditions fail to exist, the solenoid will lose power and shut off. I am debating on whether or not to reduce down to 1/4 tubing. I will probably just use 3/8" pipe and let the throttling valve do it's job. Although it shouldn't be necessary, I will place a second "limiting valve" closer to the end of the line that will be adjusted for highest allowable flow at hot oil temperature. If it is too restrictive at cold temperatures I will just remove it. Other elements that will be added are a heating element inside the drum in case there is need for a cold start, a viewable sediment and settling trap, and a valved port so that I can pump fresh oil back up to the delivery tank.
A note on throttling valves: The valve I am referring to is like a combination ball valve and needle valve. The ball valve is used to shut it off and inside of that is the needle valve which can be adjusted to limit how much can flow through the port.
I have finally started putting my system together and I am more than halfway through. From this point on I will try to document my work as it goes and if I have the time I will fill in the parts that I've already done.