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11-20-2012, 09:42 PM   #1
Frige
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 Element wiring question

On my HLT I have 2 120 volt 1500 watt elements. I am going to power them using 1 230 volt circuit and connect them in series. The math works out for this and it looks like they will pull about 13 amps on each leg. Any reason this would not work?

11-21-2012, 12:26 AM   #2
SirJoshuaIV
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What type of wire is run, what gauge? Does it have a 2 hot legs, a neutral and a ground? If so, then I would imagine this would work. But wouldn't it be easier to just switch out the breaker to a 30amp single pole breaker? Each element draws 12.5 amps, so you would be fine on amperage and the existing wire should work (if the wire is rated to 30 amps) regardless of it is 3 wire or 4 wire.

I am no electrician, so take what I say with a grain of salt.

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11-21-2012, 04:14 AM   #3
whoaru99
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Quote:
 Originally Posted by Frige On my HLT I have 2 120 volt 1500 watt elements. I am going to power them using 1 230 volt circuit and connect them in series. The math works out for this and it looks like they will pull about 13 amps on each leg. Any reason this would not work?
No reason it wouldn't work. But, for the 230V circuit, total draw is ~13A, it's not really considered ~13A per leg, per se.
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11-21-2012, 05:45 AM   #4
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Yes, it will work but there is a very minor consideration here which suggests that the common point be connected to the 230V circuit neutral. The two elements won't have exactly the same resistance. Suppose R1>R2. If the interconnection between R1 and R2 floats (not connected to anything else) the voltage across R1 will be bigger than the voltage across R1 so that this element will get a bit hotter than the other and its resistance will go up even more causing it to get still hotter and so on. Conversely, if the common point is connected to the neutral the voltage across each element will be the same and the higher resistance one will be a little cooler than the other bringing the resistances closer to one another. This suggests that thermal runaway is possible in the series connection without neutral but it is extremely doubtful that this would happen with the elements immersed in liquid as even if one of the elements dissipates a few more watts than the other it's temperature is isn't going to be much different from the other.

Based on this if the neutral wire were available I'd connect them

H htr N htr H

rather than

H htr htr H

but I wouldn't stay awake nights worrying if they were connected in the latter configuration.

11-21-2012, 12:57 PM   #5
Frige
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I considered using a neutral but I only have a 3 wire 230 circuit so I would have to run a new 4 wire outlet with special plugs etc. I dont want to use the ground wire for a neutral for fear of being zapped.
Thanks

11-21-2012, 01:10 PM   #6
ajdelange
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Don't worry about it. The idea just popped into my fevered brain late at night. You should not use the ground wire for this purpose as you note.

11-21-2012, 02:01 PM   #7
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Quote:
 Originally Posted by Frige I considered using a neutral but I only have a 3 wire 230 circuit so I would have to run a new 4 wire outlet with special plugs etc. I dont want to use the ground wire for a neutral for fear of being zapped. Thanks

So it's a true 230V 2 wire w/ground circuit, not the rather common 3 wire 120/240V (or perhaps in your case 115/230V) dryer type circuit using neutral/ground in common?
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11-21-2012, 03:31 PM   #8
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All 3 wire 230 volt circuits are the same, however you look at it. I work in commercial refrigeration and there are some ice machines that require a dedicated neutral for the computer board. If you do not have a 4 wire 230 volt circuit you risk losing the board and voiding the warranty.
http://www.hoshizakiamerica.com/tech...ll/tips153.pdf

11-21-2012, 06:15 PM   #9
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I guess I'm not sure what you mean by "all 3 wire 230 volt circuits are the same, however you look at it".

It sound in your descriptions though that you have neutral and grounding terms reversed.
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11-21-2012, 06:55 PM   #10
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Ok you got me confused. How is your set up different from 2 120 volt legs and one ground?