Installing a tandem breaker question

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Old 10-24-14, 01:37 PM
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Installing a tandem breaker question

I plan on installing a tandem circuit breaker. I have installed breakers before. But my question with the tandem, is there a certain way it needs wired? I read on one site that you must make sure to alternate the phases and to make sure it is not on the same phase. Could anyone elaborate on what that means please. Thank you in advance.
 
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Old 10-24-14, 02:06 PM
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Welcome to the forums! Since single phase residential only has one phase, we refer to them as "legs", or other terms. If you are referring to a double breaker (for a 240 volt circuit, or multiwire setup), it will automatically derive power from the two legs since the busses alternate going down the panel. If you are talking about a piggyback breaker, one behind the other, then it will be on the same leg.
 
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Old 10-24-14, 05:13 PM
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Also, not all panels can accept a tandem.

IIRC GE tandems can span both hots.
 
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Old 10-25-14, 08:44 AM
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Thank you for the reply. I am referring to the piggy back breaker. Do you wire the ground a special way? Do you wire it any differently then a single pole breaker?
 
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Old 10-25-14, 08:58 AM
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I am referring to the piggy back breaker. Do you wire the ground a special way? Do you wire it any differently then a single pole breaker?
That would be commonly referred to as a tandem breaker; two separate single pole breakers within a single molded 1 inch or 3/4 inch thick case (depending on the manufacturer). These are used for two separate 120 volt circuits where each circuit has it's own dedicated neutral conductor. Both circuits are fed from the same leg of power feeding the panel. If you are installing a multiwire branch circuit which has one shared neutral conductor, this is the wrong breaker to use.

Do you wire the ground a special way?
If the circuit originates from the main service panel with the main OCPD, the bare ground (from a NM cable) goes to the neutral bus or ground bar if there is one. The neutral always goes to the neutral bus.

Do you wire it any differently then a single pole breaker?
Not much differently at all. There are two handles and two termination lugs, one for each circuit. The tandem breaker attaches to one bus stab and therefore feeds both circuits from the same leg.

IIRC GE tandems can span both hots.
Actually, GE doesn't make a tandem breaker. They make thin style (1/2" thick) Type THQP breakers. Two THQP 1-pole breakers fit in the space of one full sized (1" thick) Type THQL 1-pole breaker, if the GE panel is designed to accept Type THQP breakers. GE also makes Type THQP 2-pole breakers for 240 volt circuits.
 
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Old 10-25-14, 09:41 AM
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GE also makes Type THQP 2-pole breakers for 240 volt circuits.
And they can be installed wrong just as easily as right. (I'll take the 5th on how I know.)
 
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Old 10-25-14, 02:47 PM
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Just for clarification. Tandem

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Piggy back

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Old 10-26-14, 05:59 AM
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Ok, I see what you mean by piggyback design with the old Square D tandem. I really don't know why they changed their tandem design to have the switches side-by-side like they do today, must have been a cost reduction in there somewhere. Schneider Electric is noted for their cost reductions since the bought Square D.
 
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