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Cabin/RV size WVO/WMO/BD boiler
Hello all,

We have some very rural property and we're going to put our small camper on it eventually.

Longer term, we'll be building a small cabin (something like 12x12 or 12x16).

I rebuilt the camper and insulated it about as much as you can do with a 2x2 frame. The cabin will be much better insulated. Our camper is a 16 footer, which works out to around 8x14 of floor space, taken up with a fair amount of cabins, appliances, etc. I figure that the camper and the future cabin will have pretty similar heating needs, the larger cabin with good insulation being similar to the poorly-insulated camper with a smaller footprint.

Anyhow, I like the idea of an outdoor boiler. I have the space, it keeps the fire away from the living quarters, and it gives me some flexibility. It would also not take up much space in the cabin or in the camper and I could probably retrofit the existing camper furnace to blow through a heater coil piped into the outdoor boiler without much difficulty.

We have a lot of wood, but wood's kind of difficult to control and that led me to WVO/WMO/BD - essentially an oil-burning system.

Googling, I keep ending back on this site, so I thought I'd post here for suggestions.

We are in a valley, but have a few neighbors on the ridge above. I don't want to generate any foul smells. I like the clean burning and non-clogging characteristics of a babington burner, even though it's more complicated than a pan.

There's a bunch of info out there on building a house-sized oil boiler or furnace, but very little on the small scale I need.

What I was thinking was to use something like this:

as the boiler. It's about 2' long and 1' in diameter.

Could also use an oil air compressor tank, or a couple of BBQ propane tanks welded together. It would be mounted horizontally.

Inside that mount a smaller tank, such as is used for vehicle air bag systems.

This one is 8" diameter and 22" long


I suspect I'd want to mount the inner tank on the lower portion of the outer so that the heat radiating upward would be exposed to the greatest volume of fluid.

Within that 8" chamber, I'd mount a small burner. The space between the two tanks would be filled with either water, a water/glycol mix, or oil that would be pumped to a radiator inside the cabin or RV. Fluid would either be at atmospheric temp, or slightly pressurized like an automotive system. I figure I can use an automobile heater core for the exchanger inside the sturcture, with a full-size automotive radiator and fan as a means to dissipate heat quickly if things get out of hand or if I can't throttle down the burner sufficiently on low-need days.

The whole assembly would be inside a doghouse-type structure to protect from the elements.

I have a bunch of questions, but am curious what you think so far about the concept. Despite reading everything I can get my hands on, this is still new ground for me.
Registered: May 06, 2010Reply With QuoteReport This Post
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An interesting project, I have been thinking about something similar for an off-grid motorhome.

THIS LINKS TO my long running "3rd oil heater so far" discussion detailing the development of a reliable heavy-oil drip burner space heater stove. This same concept could be used to heat water by adding a water jacket, or even just wrapping a few coils of copper tubing around the stove casing. This stove is built from a 100 pound propane tank but the concept can be scaled up/down. the motorhome stove will be built using something similar to the air tank you have shown, only mounted vertically. It may be possible to build an even smaller one using, say, an old dry powder fire extinguisher canister, some of these are 8 inches in diameter and 24 inches tall. The surface area of this small container won't radiate heat as well as a larger tank but if the exhaust stack is also used to radiate heat it may produce enough heat. The small stainless steel nut cups available in the kitchen gadget section of home improvement stores should work as the tiny burner assembly, yet to be determined.

I have built and used a couple of drip burner stoves for the last 8 winters, they burn well, with any amount of heat you need, the heat is adjustable, and can be run reliably unattended on only a small amount of 12 volt electricity. They are not quite as clean burning as a more sophisticated and complicated pressure or siphon burner but they work just fine and with 100% reliability if built right. There is sometimes a TINY amount of odd aroma from the chimney if you are within maybe 50 ft of the house but there is such a small amount of smoke that it dissipates within a couple feet from the top of the chimney.

THIS LINKS TO a short 2-page discussion here of a nice commercial Babington burner oil burner that would be perfect if they were ever made available, they were developed for the military but some were sold for home heating in Scandinavia but nobody seems to has found any in the U.S - Bummer.

THIS LINKS TO a great and extensive discussion here named "military heaters on ebay", this is about drip burners modified from military tent heater pot burners. Many are using them with heavy oils and there are detailed discussions and info of a couple of outdoor water heater units used to heat small houses.

The problem is that I have not yet found any SMALL heavy oil burners that really have a reputation for working. Another problem is that the commercial or home-converted furnace oil burners require a fair amount of external power for high pressure fuel pumps, air compressor, oil heaters etc. There are versions of these that work fine but they are all considerably larger thah you need as they are modifications of normal home oil burners. Check out for the best info and parts availability for doing your own conversion, the info there is condensed from years of posts on the yahoo oil burners discussion group and the info works. I have built two heavy oil burners using there basic siphon type burner assembly with electric heater block.

These burners produce a lot of heat so need to be switched on/off as needed, this takes a controller but these are available from normal furnace burners, One of the problem areas is getting them to re-light reliably, thus the need for preheating the heavy oil to help it ignite.

One of these burners is going into a water heater similar to what you describe only bigger. A friend hear has a 50 X 75 insulated shop with pex tubing in the concrete floor slab, it is costing him several thousand dollars per winter to heat it using propane and a big new on-demand water heater, we are going to add a waste oil burner in parallel with the propane heater.

The boiler will use a 100 pound 14 inch diameter propane tank as the outer housing and a smaller 12 inch diameter 60 pound propane tank as the inner wall of the boiler, this gives about a 1 inch thick water jacket. This will lay horizontally with the furnace burner mounted on a swing-open plate on one flat (original bottom) end, the flue will come out the other, we may eventually add another heat exchanger tank around the vertical flue pipe to add either pre or post heating of the water depends on how hot the exhaust stack runs. If you have too much water around the burner flame the burner space never gats hot enough to burn efficiently, thus the 1 inch water jacket.
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post

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Tim has excellent ideas along this line and has experience, so you can't go wrong there or, if you are pretty handy, you can always get Murphy's waste oil furnace plans whose main advantage is that the entire unit is designed to remain outside and away from the dwelling.

I love the innovations these guys have come up with.

** Biodiesel Glycerine Soap - The Guide
- on 5 continents helping people make & sell soap from the Biodiesel Glycerine.

Location: :-) Great White North eh ? | Registered: December 10, 2004Reply With QuoteReport This Post
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Another thought, although I have not tried this myself. -- Possibly convert an old salvage yard GAS water heater over to use some other source of heat. Almost all the old gas fired water heaters I have gotten from salvage yards have had good water tanks, there only problem was that the gas pilot light thermocouple electrical connection needed cleaning. If some heigh were added to the bottom burner section of one of these water heaters you could use a drip pot heater, a small wood fire, or some version of a pressure/syphon burner for the heat. There are commercial water heater versions that use a normal pressure style home heating oil burner for heat. It would make an interesting project for a discussion.

OR - I have tried this - There are hot water/steam pressure cleaners that use the same type home oil burner to push heat through a big coil of 1/2 inch pipe, they makw a LOT of steam/hot water but will run automatically.

If you use the indoor thermostat to switch a circulation pump on/off to your indoor radiator the temperature of the water stored outside can be about whatever it wants, this reduces the need to tightly control the heat source.
Location: fisher,illinois,usa | Registered: June 03, 2003Reply With QuoteReport This Post
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A mate and I use an old gas water heater with a babbington to heat his wvo for bio processing.

He uses one of those small tankless compressors for the cheap spray guns. The tank is layed on its side for roof space and the output is directed toward another tank to make the most of the heat generated. It works well and will bring 1000L of WVO up about 35oC+ in well under an hour.

I forget what we worked it out at now, it was a while back but I think it was putting about 60KW actually into the oil. Personally I don't like the babbington principle and the need to have a compressed air source. It would be easy to set the output though by way of the amount of fuel and air burned.

Personally I prefer the turk burner style. They will burn anything without preheating the oil and require nothing much more than a common fan ducted ( with a stator) to run for low power applications. They also have a great turndown ratio which would be great for this sort of application.

I have mainly built high output burners of this type ( last one can kick 400Kw out) but I'm now looking at smaller ones for just home heating myself.
The design I'm looking at will use a turk burner to heat water going through a car radiator ( or 2, one stacked above the other) and probably store the hot water either under the house in 44 gal drums or have an IBC or 2 wrapped with house insulation.

The burner could also be placed under an old gas water heater and I have been trying to find one to try this and see if the water heater is capable of absorbing enough heat for this sort of application. I am not sure what output the burners normally do but I assume it would not be high unless the heater was some sort of fast recovery model. A small radiator or car heater core in the flue outlet may aid greatly in the amount of energy the system could absorb.

The 44's could be uninsulated so they can leech their heat passively into the home above or for extra heat the water could be circulated through other radiators either under the house and ducted or in the house itself.

The IBC could act as the thermal mass for circulation if getting under the house was not feasible.

For the burner itself, I'm looking at using old fire extinguisher bottles. The old ones are pretty thick although the newer ones seem a bit the opposite.
In a low output situation like what would be needed in this instance, I think they would take a long time to burn out anyway. It's when you drive the things hard and get them super hot the steel burns away.

The fuel feed system I use is nothing more than a bit of copper pipe going into the air duct so the oil is blown along into the burning chamber. It's not atomized, doesn't have to be, as long as it gets into the chamber. For low power burners, gravity feed is fine. When you get to pushing 40L an hour you need some sort of pump or tank pressurization.

The burner itself is preheated using either LPG, wood or a petrol laced oil supply and once heated, the straight oil is admitted and the residual heat in the burner allows it to change state and go from there. The burners have a pretty wide turn down ratio, far more than any commercial burner I have found stats on.

You can leave the air alone and just vary the fuel to get a pretty good output range or vary the air and fuel with the same burner and get something like 100: turndown ratio. The main thing when going low is to maintain enough heat in the burner and not let the thing get too cooled by the excess air.

It would be entirely possible depending on the location of the burner to run a cable from inside the house to a valve to control the fuel flow for heat output. Better still may be a stepper motor arrangement or a servo like on model aircraft. One would tune the air input to the median value they wanted then just vary the fuel flow.

Automation could also be setup with thermostats where the water reserve ( and I'd have one even just a 44 so the system could be open. ) temp was measured and the burner just cycled from idle to burn and back as required.

A system like this would require minimal energy input and could easily be run on 12V and cheap and easy to build.

This is a vid of a much larger burner I built working on the same concept. Now all I have to do is make a smaller one and package it up! :0)
Registered: July 30, 2010Reply With QuoteReport This Post
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