Lister Engine Forum
Alternative fuels => Straight Vegetable Oil => Topic started by: mikedell on December 15, 2013, 12:30:07 AM
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Hey all,
Was looking around the net for a decent priced wvo preheater and everything I found IMO was over priced. So I thought Id share a very simple design based on a $80.00 design I found on ebay. It may be crude, but it works very well, and can be built for roughly $30.00 fuel fittings included.
Items needed,
#1 Standard 1 inch T fitting
#2 5-6 inch piece of pipe coming from the T fitting
#3 Your preferred choice of a screw in flange heating element.
I personally went with a 1440 watt 120 volt element for my application, but at my local Ace they had quite a bit of selection.
I have attached some pics just for a quick reference point, to show the basic simplicity of the design. I'm taking ZERO credit for the design itself, the design is a copy of one selling on ebay for $80.00 plus shipping. The total cost of this design done yourself, shouldn't run more than $30.00 total.
(http://s29.postimg.org/nh3pnisdv/photo_1.jpg) (http://postimg.org/image/nh3pnisdv/)
(http://s29.postimg.org/mp11obo6r/photo_2.jpg) (http://postimg.org/image/mp11obo6r/)
(http://s29.postimg.org/6favlfdir/photo_3.jpg) (http://postimg.org/image/6favlfdir/)
I searched around on the forum and didn't see this exact design anywhere so I figured Id share it and hope someone finds some use for it.
I have this design in use on a small diesel engine and it is performing great. If anyone is intrested in details of the rest of my design Id be happy to share it.
Mike
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1400 watts ! At that value, I'd turn the element 90 degrees and heat the tank. Otherwise, that much heat is going to boil the oil, as your engine sips it past the element.
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Yeah after I took the picture of this new one Im building I realized uh oh lol, I picked up the wrong element.
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It's also a good idea to understand that pipe threads are tapered (USA) and water heater elements are not; hence the black rubber gasket.
I ran into this problem after I brazed a pipe coupling into a propane tank that is the foundation of my hot oil centrifugal filter project. I now have to remove the NPT coupling and replace it with an EMT coupling.
Using AC to heat WVO seems contra-intuitive as well. Most of the readings I seen want to start and stop on something like bio-diesel of petrol-diesel with the long haul being carried by WVO or a blend.
But this is all intellectual arm chair propaganda. I'm always swayed by trustworthy empirical data.
Casey
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Looks like an element selected for quick starts but needs to be controlled for continuous duty. As previously stated, is there coolant or exhaust heating planned after the engine reaches operating temperature ?
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Maybe he's heating a 55 gal drum of WVO to dry it?
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Just out of curiosity beings Ace hardware won't take this element back, does anyone know how hot this 1400 watt element would get the wvo up to?
My other one is built from a 200 watt element and gets the oil up to around 140 degrees, but as another user suggested, if I can't return this one, Im wondering about just hooking up a thermostat to this one, problem is that I'm having a issue finding something online that I can adapt to this type of setup that I'm trying to use.
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If that 120V, 1400Watt heater was connected to a 12VDC nominal electrical charging/starting system. The heat output would be approx 16.5watt.
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Just out of curiosity beings Ace hardware won't take this element back, does anyone know how hot this 1400 watt element would get the wvo up to?
This same element or it's sister is used in 25 or so gallon hot water heaters. That's why there's a thermostat in line with it that regards 140 as damn near scolding. One of the ceremonies of the 65th year is turning the water heater down to 120 (that's usually all the way down).
The water heater thermostats shouldn't know the difference between WVO and water.
I think most water heaters have a thermal / pressure relief valve as well - mine do for sure.
Casey
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A small brazed flat plate heatex should work well for pre-heat after the engine is up to temp. That 1400W element would heat the oil really fast:) Depending on where this is placed in the system and how much fuel the pipe holds, it might work well for a quick preheat of enough fuel for startup/warmup where a coolant based preheater would take over...
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Heating elements for pre-heating crankcase oil are approx 4times larger than coolant heaters of the same wattage.
If a diode was put in series with the 120V 1400watt heater. Output would be dropped to 350watts.
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If a diode was put in series with the 120V 1400watt heater. Output would be dropped to 350watts.
Interesting.
Please explain how the diode works to reduce the wattage output of the element.
and what is the math relationship to allow us to determin what the modified wattage rating will be?
For example..If I diode a 2000 watt element what is the resulting wattage?
Cheers
Veggie
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If a 120VAC 2000watt element has a 20amp or larger diode in series with the supply . Wattage will drop to 500.
Allows a simple High-Low control with 500 or 2000Watts.
A 240VAC 2000watt heater will produce 500watts on 120V. An even simpler High-Low power heater circuit.
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I have some 480volt 10kW heaters around the shop that I was wondering about using with 240volt. No diodes required? Any other losses involved?
dieselgman
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You'll need to check their schematic to make sure they aren't using 480V relays or time delayed relays requiring 480V. If so, they'll have to be modified.
Send me the schematic or post it and I'll take a look.
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When you cut the voltage in half, then the amperage will also be one half (assuming a linear device). Thus the 1/4 wattage.
What a single diode will do in AC feeding a heating element is only allow 1/2 of the AC cycle to pass thru, effectively giving 1/2 the voltage. But that only works once (you can't stack multiple diodes to keep cutting it in 1/2), it only works for AC (not DC), and it assumes that the generator doesn't mind you're only using 1/2 of the AC cycle, etc. It also assumes you didn't use a full wave bridge, but just a single diode.
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I have some 480volt 10kW heaters around the shop that I was wondering about using with 240volt. No diodes required? Any other losses involved?
dieselgman
2.5Kw on 240volt AC
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Thanks guys, I will experiment a bit to see what the current actually reads on the lower voltage. I have to get some single-phase blower motors to make this work.
dieselgman
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Thanks guys, I will experiment a bit to see what the current actually reads on the lower voltage. I have to get some single-phase blower motors to make this work.
dieselgman
Oh yea of little faith....................
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Diode only allows current flow in one direction, so a 120V AC sine wave will have half of it's wave cutoff resulting in a 60V waveform. That part of the waveform that is cutoff also occupies time, so the 120V sinewave becomes a 60V pulsed waveform with a 50% duty cycle. SO half the voltage with only half the on time/energy density leaves you with 25% energy being delivered. SO the 2KW heater becomes 500W give or take:)
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I mentioned the relays as it is common that there is some sort of sequencing of elements; the full load surge current into a cold resistive load like that would be impressive.
+1 for Thob's wattage approximation on 240V, +1 for Ronmar's diode wattage approximation. Both will vary slightly for resistive heating elements operating at cooler temperatures, you may get slightly more than 1/4 the rated wattage.
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Thanks fellas for explaining the diode/AC element operation.
What type of diode is required to do this?
Obviously not your everyday circuit board diode.
I a guessing it may be purchased from an electrical supply shop rather than an electronics component place?
Cheers
veggie
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Right, Vege, at 0.75V drop time times the current through the diode being dissipated as heat, these are going to be big through bolt type diodes, (several in parallel) mounted on a big aluminum heat sink when you get to higher currents. At high currents, the diode noise (EMI) will also be impressive without RC snubber suppression. Forget AM radio reception near the heater.
Diodes are sometimes used in portable, 1500 watt or less resistance heaters. You're not likely to see them being used in high wattage devices because the cost and heat sinking required. Most higher wattage devices, like electric boilers, will have multiple elements and sequencing on start up and/or selection of elements for variable ouput levels.
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Diode only allows current flow in one direction, so a 120V AC sine wave will have half of it's wave cutoff resulting in a 60V waveform. That part of the waveform that is cutoff also occupies time, so the 120V sinewave becomes a 60V pulsed waveform with a 50% duty cycle. SO half the voltage with only half the on time/energy density leaves you with 25% energy being delivered. SO the 2KW heater becomes 500W give or take:)
It's 120VAC half wave, not 60V half wave.
P=I squared x R
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You take a 120VAC(pk-pk voltage) sine wave, half of the sine wave goes positive and half of the sine wave goes negative. If you run it thru a diode, you block say the negative going half of the signal. This leaves you with a positive going 60V half wave with spaces between where the negative going half cycles used to be(50% duty cycle).
Now if you are starting with a 240VAC signal, then you would be left with 120V half cycles with spaces between where the missing cycles should be(50% duty cycle). Still about 25% of the power delivered by the full 240VAC waveform.
But I thought we were discussing a 1400W 120V heating element...
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You take a 120VAC(pk-pk voltage) sine wave, half of the sine wave goes positive and half of the sine wave goes negative. If you run it thru a diode, you block say the negative going half of the signal. This leaves you with a positive going 60V half wave with spaces between where the negative going half cycles used to be(50% duty cycle).
Now if you are starting with a 240VAC signal, then you would be left with 120V half cycles with spaces between where the missing cycles should be(50% duty cycle). Still about 25% of the power delivered by the full 240VAC waveform.
But I thought we were discussing a 1400W 120V heating element...
Don't know where you went to school for electrical theory?
With a diode the applied power is now with one half of the entire sine wave. Measuring either and only the positive or negative portion of the complete sine wave.
With 120V rms AC power through a diode. Between 0 and 180 degrees there will be for example a positive half of the sine wave. With a 170 volt peak. Then virtually nothing from 180 to 360 degrees.