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Old 24-03-2015, 08:18   #61
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Re: Running 220v water heater on 110v supply

Wow this subject is very interesting.

So I did a bit of experiment. Each morning I heat up the 240v small electric kettle. Usually I let it boil until the auto switch cut off the power.

Exp 1: Supply 240V, Water temperature 26.2 C Vol = 0.8 liter Time = 2 min 21 sec

Exp 2: Supply 120V, Water temperature 28.7 C Vol = 0.8 liter Time = 10 min 01 sec

In my case, half the voltage the time took more than 4 times longer. Mains is 240v 50 hz and step down transformer is giving 120v 50 hz.

note: I am sure there is a lot variables in my simple set up in the galley.

Good info from CF members. thanks.
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Old 24-03-2015, 08:22   #62
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Running 220v water heater on 110v supply

Thanks ericoh! Well done. Interesting to see the water temperature 10% hotter. I wonder why.

Edit, oh wait, I see that's the starting temp? I wonder what the finished temps were. Probably above your thermometer range?
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Old 24-03-2015, 08:45   #63
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Re: Running 220v water heater on 110v supply

Quote:
Originally Posted by monte View Post
Thanks ericoh! Well done. Interesting to see the water temperature 10% hotter. I wonder why.

Edit, oh wait, I see that's the starting temp? I wonder what the finished temps were. Probably above your thermometer range?
100 C, boiling point of water. One thing that can cause errors is determining what time it is boiling.
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Old 24-03-2015, 08:48   #64
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Re: Running 220v water heater on 110v supply

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Originally Posted by monte View Post
.............. Btw, some people would suggest having an expert diagnose systems and wiring etc, but from my experience the information found on CF is usually a lot more professional and accurate than the many technicians and experts we have come across in our travels. So short of being located somewhere where I would have absolute faith in the technician, such as mainsail or goatboatingnow amount others, CF is the best I can do...
Yep, go with that thought. Keep a fire extinguisher handy and don't touch any metal on your boat without rubber gloves.
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Old 24-03-2015, 08:57   #65
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Re: Running 220v water heater on 110v supply

What do you mean by that rw? Sounds a little sarcastic but I'm not getting the point...
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Old 24-03-2015, 09:34   #66
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Re: Running 220v water heater on 110v supply

I smile as I read this thread

I am reminded of this ditty

"Lord Finchley tried to mend the Electric Light/Himself. It struck him dead: And serve him right!/It is the business of the wealthy man/To give employment to the artisan."

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Old 25-03-2015, 02:21   #67
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Re: Running 220v water heater on 110v supply

Because it is a heating element, it is a simple resister, therefore applying 220 volts results in the 1200 watts of heat/energy. Cutting the voltage in half cuts the current and wattage.
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Old 25-03-2015, 02:59   #68
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Re: Running 220v water heater on 110v supply

Quote:
Originally Posted by ericoh88 View Post
Wow this subject is very interesting.

So I did a bit of experiment. Each morning I heat up the 240v small electric kettle. Usually I let it boil until the auto switch cut off the power.

Exp 1: Supply 240V, Water temperature 26.2 C Vol = 0.8 liter Time = 2 min 21 sec

Exp 2: Supply 120V, Water temperature 28.7 C Vol = 0.8 liter Time = 10 min 01 sec

In my case, half the voltage the time took more than 4 times longer. Mains is 240v 50 hz and step down transformer is giving 120v 50 hz.

note: I am sure there is a lot variables in my simple set up in the galley.

Good info from CF members. thanks.
I think the increase in time over and above the factor of 4 in your experiment is probably due to using the cutoff thermostat to determine the end point. The cutoff themostat ususally cuts out well after the water reaches 100 C. I thinking this may skew the expected theoretical time.
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Old 25-03-2015, 03:31   #69
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Re: Running 220v water heater on 110v supply

Monte,

I did not check the cut out temp but I can do that the next time I get back to boat as the temp laser gun can go up to hundreds c. The starting temp is diff maybe the water tank got warmer in the day. Presently in Portugal to do a bit of sailing in Lagos.
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Old 25-03-2015, 03:38   #70
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Re: Running 220v water heater on 110v supply

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Monte,

I did not check the cut out temp but I can do that the next time I get back to boat as the temp laser gun can go up to hundreds c. The starting temp is diff maybe the water tank got warmer in the day. Presently in Portugal to do a bit of sailing in Lagos.
If the water is at a rolling boil, the temperature will be so close to 100C that it doesn't matter and it will never be higher than100C. What might matter is the time period between the water reaching 100C and when the cutout operates!
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Old 25-03-2015, 04:04   #71
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Re: Running 220v water heater on 110v supply

I am reading some troubling things here. For those who really know their stuff, feel free to step off the reservation. For the rest, it is very unwise to be messing around with mains AC power. As has been pointed out it is possible to use resistive loads intended for 220VAC with 110VAC (with degradation) and also some electronics designed to work with both voltages, but a lot of devices/motors may be damaged. And of course the other way around would drive 4X the power into the circuits - you don't want to see what that looks like. The proper way to do this involves a step-down transformer. Also, it is a very good idea to have an isolation transformer just after the power input connection and dual-pole breaker. Fortunately you can do both with a single transformer. I have a Charles IsoG2 3.8kVA transformer that can be used 1:1, 2:1, and 1:2 so it is easy to adapt to any nation's power supply and boat requirement.

BTW please do not think that 220-240VAC is the same everywhere. The 220V in the US is made up of two 110V legs, out of phase. Each leg (Line, or "hot") is 110VAC from Neutral (ground potential), while the 220V (actually 234VAC) is between the two Line connections (but still referenced to Neutral by 110V). In Europe the 220V is usually between a Line and Neutral (at ground potential) or two floating Lines. It can be dangerous to mix the schemes if one doesn't know the difference, or particularly if using a non-isolation type transformer. Since the iso xfmr will also eliminate electrolysis from off-boat sources it is a good idea to buy one. They run about $600-700, which could be a bargain, but are heavy at 60+lbs.

As for explaining the reduction of power by 1/4, consider that the proper name for "Voltage" is actually "ElectroMotive Force" or EMF, shown as "E" in physics. Cutting E in half means cutting the driving force in half as well as reducing the current (electrons/second) due to resistance. Think of it as water, which has less pressure (force/area) and hence can do less work (in a layman's sense, not the physics sense of work).

Greg
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Old 25-03-2015, 04:40   #72
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Re: Running 220v water heater on 110v supply

Quote:
Originally Posted by monte View Post
What do you mean by that rw? Sounds a little sarcastic but I'm not getting the point...
Don't worry...it means the same as goboatingnow's ditty, but nowhere near as clever.
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Old 25-03-2015, 05:40   #73
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Re: Running 220v water heater on 110v supply

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Because it is a heating element, it is a simple resister, therefore applying 220 volts results in the 1200 watts of heat/energy. Cutting the voltage in half cuts the current and wattage.
I've been meaning to post this just to stir up some sh*t:

It's not a simple resistor. Heating elements typically increase in resistance as they heat. So that "Xohm" heating element may be "X+50%"ohms when powered by the expected voltage. You can't measure it with an ohm meter, you have to calculate it.

Why does this matter? Well, at half the expected voltage the element won't heat as much and the resistance increase will not be linear, therefore the current decrease will not be linear.

Does this matter to the OP? Nope. None of this matters except that the water heater won't work like it should. And he stands a good chance or damaging something on his boat connecting it to the wrong voltage. Plugging it in to see what happens is not a good idea.
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Old 25-03-2015, 05:54   #74
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Re: Running 220v water heater on 110v supply

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Originally Posted by rwidman View Post
I've been meaning to post this just to stir up some sh*t:

It's not a simple resistor. Heating elements typically increase in resistance as they heat. So that "Xohm" heating element may be "X+50%"ohms when powered by the expected voltage. You can't measure it with an ohm meter, you have to calculate it.

Why does this matter? Well, at half the expected voltage the element won't heat as much and the resistance increase will not be linear, therefore the current decrease will not be linear.

Does this matter to the OP? Nope. None of this matters except that the water heater won't work like it should. And he stands a good chance or damaging something on his boat connecting it to the wrong voltage. Plugging it in to see what happens is not a good idea.
Oh dear...
The water heater will still reach the thermostat set temperature so the resistance of the element will remain the same; will take longer of course

Best way to check is plug it in and try it
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Old 25-03-2015, 08:23   #75
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Re: Running 220v water heater on 110v supply

I hope this thread doesn't get as long as the LiFePo4's for a House Bank.
I posted about the non linear properties of a heating element many posts ago.
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