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I have one of these breakers in my panel? What is its purpose (vs a pair of two-pole breakers)? There are other posts that deal with tandem breakers but not specifically dual tandem breakers.

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It is a quad breaker. The outer two are linked and the inner two are linked so that both pairs have 240 V across the connections. They are used to provide two 2-pole breakers, where a pair of ordinary 2-pole breakers would not work because the adjacent half slots are on the same leg.

If the available slots are such that the first pair of half slots are on different legs, then this quad breaker would not be used and would not fit. In that situation one would use a pair of ordinary compact 2-pole breakers.

  • So it's just a space-saver compared to two two-pole breakers? – Wynne Jul 18 '18 at 14:59
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    Yes - that's correct. It allows two 240V breakers in the space of two 120V breakers – mike65535 Jul 18 '18 at 15:02
  • Edited answer. No, it would not be a space saver compared to a pair of half-width 2-pole breakers. In a panel each full slot going down alternates between legs. An ordinary compact 2-pole breaker must be fitted astride two different full slots in order to get 240 V. If you try to fit an ordinary compact (half width) breaker in one slot it will not snap in--looks like it should fit but is designed to not fit. If you could force it in, there would be 0 V between the contacts because both are on the same leg. – Jim Stewart Jul 18 '18 at 15:05
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    But it's a space saver compared to 2 full sized 240V breaker pairs. – The Evil Greebo Jul 18 '18 at 15:06
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    @JimStewart -- you're speaking in GE a bit too much with the first pair of half slots being on different legs, as that's a situation that can only occur on Q-line, not on any other 1" breaker line.... – ThreePhaseEel Jul 18 '18 at 23:34

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