Murray MP3030 duplex breaker states it's 120/240v

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  #1  
Old 10-09-15, 02:32 PM
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Murray MP3030 duplex breaker states it's 120/240v

...but I've always been told that you can't get 240v from a single bus, that you need two.

Am I missing something? Would it be possible to use a connector to attach the two breaker handles and use this to power a hot water heater?
 
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Old 10-09-15, 02:46 PM
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but I've always been told that you can't get 240v from a single bus, that you need two.
That is correct.
Would it be possible to use a connector to attach the two breaker handles
True 2-pole breakers usually have a common internal trip. Just looked on Google and it is definitely a single pole breaker.
 
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Old 10-09-15, 02:46 PM
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Welcome to the forums.

That is correct. That breaker will only fit on one leg which means you can only get 120v from it.
I'm not sure why it's rated for 240v.

That breaker is called a tandem breaker and cannot be used for a 240v application like a water heater. You would need a two pole breaker.

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Old 10-09-15, 02:56 PM
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Bummer, it looks like my only good solution would be to pick up a triplex unit that spans 2 legs, like the MP23020 but noone keeps them in stock locally.
 
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Old 10-09-15, 03:07 PM
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Interesting.... it looks like that triplex breaker occupies three breaker locations. It looks to have three stabs on the back.

Actually on second look.... what looks like a center stab must be a divider slot.
 
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Old 10-09-15, 07:02 PM
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The MP3030 is rated for 240 volts because it COULD be used in a 240 volt, 3-phase delta panel. The MP23020 is two single pole 20 ampere circuit breakers along with a 30 ampere, 2-pole circuit breaker all in a two-pole frame. The two 30 ampere CBs have a common internal trip as well as the external handle tie.
 
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Old 10-10-15, 08:54 AM
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Ah, so if the whole panel was at 240, meaning that a single bus provided 240, it would work? That makes sense.
 
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Old 10-10-15, 12:31 PM
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The circuit breaker is rated for operation up to the rated voltage, plus a safety factor, maybe five or ten percent over the rated voltage. Use at lower voltages is always acceptable.
 
  #9  
Old 10-10-15, 10:26 PM
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The MP3030 is not rated for 240 volts. It is "slash" rated for 120/240. This means it is OK for standard single phase (120 to ground, 240 phase-to-phase) but not OK for 240 to ground.

The MP230 is their standard 2 pole common trip also rated at 120/240V AC
The MPH230 is a 2 pole common trip rated at 240V AC - specs say UL Listed for use on 3 phase grounded "B" systems
 
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