One Phase - 240V Wiring question

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Old 08-08-07, 04:40 AM
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One Phase - 240V Wiring question

We have a 4.5KW (4500W) 240V Single Phase immersion heater. This heater has three wires that go to it.

White
Black
Green

With that being said, Please tell me:

1) What type of breaker should be used (pole #)
2) Where does each of the 3 wires go in the panel.

The theory behind it.

I need to prove a point here.

Thanks!

(My understanding is that white and black each go to a pole on a double pole breaker -- green goes to the usual "bare" (neutral) -- please the theory as to why the lack of anything going to the white (ground))
 
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Old 08-08-07, 04:47 AM
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You are confused.

A straight 240 volt device needs two wires for current. Both are hot wires, the white and black in this case. They get connected to the two terminals on a 240 volt breaker.

The green wire is the ground. It gets connected to the ground buss in the panel. The ground wire is for safety. it does not carry current under normal operation.

There is no neutral in a straight 240 volt system.
 
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Old 08-08-07, 05:39 AM
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Thanks for confirming!
 
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Old 08-08-07, 06:39 AM
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How sure are you it is 240v? if the black and white wire are factory installed on the heater I would wonder. Normally a factory installed black and whit indicate 120v. Or can it be used on either 120v or 240v. If it was intended only for use on 240v I'd expect to see two black or a black and red.
 
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Old 08-08-07, 07:49 AM
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The unit reads:

240V - 4.5KW - 1 Ph

You tell me.
 
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Old 08-08-07, 08:45 AM
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Smile

TWO CENTS from a guy who likes to read these posts_______Is the C/B your planning on installing going into a MAIN PANEL or a Sub-Panel? If if it's in a Main Panel then your ground (green wire) will go to the location of the rest of the ground wires which will be the NEUTRAL bus bar, where you will also find attached the grounded conductor wires (the white wires from your branch circuits. If your C/B is to be installed in an existing "sub-panel "with a 4 wire feeder (2 hots, a Neutral and a Ground, then your Ground wire would not be attached to the NEUTRAL bus bar in "said" Sub-Panel, but would be attached to a seperate ground bar bonded to the "box" and isolated from the Neutral. If you are indeed installing your C/B in a Sub-Panel, and it indeed has four wires feeding it and you find the white wires (the neutral conductors) attached to the same bus bar as the bare or green ground wires, THen check back here with the Pro's. If your heater is rated for 120 V then you would install a single pole breaker (matched with correct wire size of course) The black wire would be attached to the C/B The white wire would be attached to the NEUTRAL bus bar , and the GROUND wire would be attached as explained . If the Heater is indeed 240v rated then hook up like the Moderator described. Keeping in mind if you are installing your C/B in a MAIN PANEL or a SUB-PANEL.(with concerns for where to place the ground wire) Please verify eveything I've said here with the Pro's. Maybe the Moderator will read this and give me a grade.
 
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Old 08-08-07, 10:30 AM
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You need a double pole 240 volt breaker as well. Make sure you don't try and use a twin or tandem breaker that only takes up one slot.
If you are in Canada you can buy cable that only has bare, black and red wires. it is made just for this purpose.
 
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Old 08-08-07, 02:13 PM
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Originally Posted by joed View Post
You need a double pole 240 volt breaker as well. Make sure you don't try and use a twin or tandem breaker that only takes up one slot.
If you are in Canada you can buy cable that only has bare, black and red wires. it is made just for this purpose.
They make a 2 spot, 4 tandem breaker, where the top breaker is a 20 the middle two are 30/30 and the bottom is a 20. This way you split the load between two different poles, yet get the benefit of the space saving in the box. Naturally the 30/30 are linked.

Didn't think they made such a beast, but they do.

 
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