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Electrically fired Boilers?

Posted: Thu Aug 27, 2020 5:21 pm
by TriangleTom
I've been thinking the last few days about the possibility of a small, electrically fired boiler for use running a small engine in the workshop or at home. The chief advantage I can see in firing a boiler electrically over chemically would be much lower operating costs as well as the ability to run it inside when there isn't a suitable outdoor location or outdoor running is precluded by the weather.

It seems like it would be possible to construct such a boiler relatively inexpensively. A 6" diameter section of flanged schedule 40 steel pipe paired with a 1500W immersion heater should offer rugged construction for a smaller, lower pressure (~100 PSI) boiler that, when paired with a thermostat and an SSR, should be relatively easy to manage in terms of controlling the pressure.

Now, the question is is this a practical, possible, or safe idea? Or would I be better served harnessing the hot air escaping from my ears? :lol:

Re: Electrically fired Boilers?

Posted: Fri Aug 28, 2020 8:52 am
There's nothing wrong with being slightly bonkers: steam involves eccentrics everywhere!

Conventional domestic immersion heaters are not designed to take any significant pressure, and I don't know what would happen if they were subjected to it. However, if you ran one through a 1:1 isolation transformer (such as those used on building sites) , had a good current trip in the supply line, and had a good earth connection to the "boiler", nothing too catastrophic should happen if the heater gets crushed, and it may just carry on working.

I would be happier working at low voltage: 12 or 24 volts say, and using commercial wire-wound ceramic coated resistors as heater elements. They are very simple and robust.

I'm afraid I can't remember the source, but I have a memory of some people many years ago using low voltage and then the water itself as the resistive heating element. I suspect the usual brown gunk we put in for boiler corrosion protection would bring the water resistivity down enough to be useful.

Then we have a thread elsewhere about Espresso coffee pumps, and I know many boiler inspectors are occupied in inspecting and checking Espresso machines. There may be some ideas or bits in the machines which could be helpful.

PS I've remembered a bit more about direct water heating: some engine-testing brakes had generators and then variable water-element resistances to absorb the engine power. May they're still used. The resistances were variable by immersing live and neutral plates further, or less far, into a tank of water, and the waste heat escaped harmlessly as steam. No doubt there were also quantities of Hydrogen and Oxygen escaping with the steam, which could be dangerous I suppose.

Re: Electrically fired Boilers?

Posted: Fri Aug 28, 2020 12:08 pm
by DetroiTug
Hi Tom,

Should work fine with standard electric hot water heater elements, may have to use a different thermostat. The elements themselves are rated for at least 150 psi as that is the PRV rating. Although, the temperature may be an issue at near 400 degrees.

Of course it will be the issue of generating steam in an adequate amount over time for the demand. Most likely would be a very low PPH. Electrically generated heat has low efficiency. Would be ok for intermittent steam supply.

Of course, all boiler safety applies, relief valve, sight gauge, blow down etc.


Re: Electrically fired Boilers?

Posted: Fri Aug 28, 2020 4:59 pm
by Rainer
In Germany you could buy electrical heated steam engines for children.
Even with the dangerouse 220 Volt 50 Hz what is usual in German households


Re: Electrically fired Boilers?

Posted: Fri Aug 28, 2020 5:08 pm
by Rainer
And see what happened in World War II:
The Swiss Electric-Steam Locomotives ... isselc.htm

Some more technical info here - In german only: ... lokomotive
In short:
they used 20 Volt on the heating elements
because the water pipes were also used as heating element...

Re: Electrically fired Boilers?

Posted: Fri Aug 28, 2020 6:14 pm
by fredrosse
The easiest way to get some steam generation in the home is with a range cooking burner or electric stovetop element. For this you can use a pressure vessel as you describe, but without the time and expense of setting up the heating system.

To get a little perspective here, our steamboats need heat input ranging around 100,000 BTU per hour (29kW), and typical hobby steam engines need around 1500 BTU per hour (440 Watts).

A typical range top gas burner is 10,000 to 15,000 BTU per hour (2.9 to 4.4 kW). If not in the kitchen, then you can buy a similar output gas burner using butane cylinders for portable service. These burners are generally OK to use within the house without an outside vent stack, just the same as used when cooking food.

Your pressure vessel needs to have a reliable way to sense water level , I have used small radiator vent valves as "try cocks", and a gauge glass would also be recommended. A safety valve set at 100 PSI is definitely required, along with a pressure gauge. Hydro statically test the boiler to at least 150% of the maximum working pressure (150% of safety valve setting). 4 inch schedule 40 pipe is strong far beyond 150 PSI steam service, depending on how the pipe ends are configured.

If you go this route, please correspond here to get good advice about the details of your project.

Re: Electrically fired Boilers?

Posted: Fri Aug 28, 2020 6:27 pm
by fredrosse
Water seeded with salt, or other chemicals making it electrically conductive, has been used to produce variable resistance for loading generators. Two electrodes are submerged in a tank containing the water, and the area of electrode submergence varies the resistance. Yes, hydrogen comes off one DC immersion plate, and Stociometric Oxygen comes off the other one, an invitation for some fantastic fireworks.

This type of resistor was used to load the generators of US nuclear submarine power plants decades ago, and the gasses were isolated from mixing, and vented to atmosphere. Probably not such a good choice for a home boiler setup, as much of the electric input energy goes into making the Hydrogen and Oxygen, not so much for heat into the water unless you combust the gasses under the water level.

Re: Electrically fired Boilers?

Posted: Fri Aug 28, 2020 6:32 pm
by fredrosse
"Conventional domestic immersion heaters are not designed to take any significant pressure, ...."

Actually, domestic immersion heaters to make household hot water are typically rated for at least 100 PSI, and easily take significantly more pressure without problems.

Re: Electrically fired Boilers?

Posted: Sat Aug 29, 2020 5:36 pm
by Lopez Mike
I wouldn't worry too much about using propane in a decent sized room. There is a propane stove in my kitchen with four burners and an oven and at the holidays all are running full tilt. I do use the hood fan once in a while but mostly to get rid of the stink from my entertaining cooking blunders.

My shop boiler is a simple VFT about 8" in diameter and fires off of an ordinary 20 pound bottle. I open the door to the outdoors if I think of it. My shop monoxide detector hasn't sounded off yet.

I've run it at model exhibitions in larger rooms for hours and hours with no complaints or symptoms of derangement. Other than the usual obsession with silly little steam engines.

Re: Electrically fired Boilers?

Posted: Sat Aug 29, 2020 6:28 pm
by Kelly Anderson
I had installed an electric water heater element in a washout plug hole in the bottom of the steam drum in Reciproca's three drum Blackstaffe boiler, and successfully raised steam in my garage in order to test a tiny LBSC injector I had built.