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Discussion Starter · #1 ·
Cutler hammer BR doublepole breakers appear to just be two single pole breakers rivetted together with a handle tie to make them trip simultaneously.
Am I wrong? Are they internally connected in some way to cause them to trip together even if the handle tie is removed?
 

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Just to add, don't ever remove a handle tie to get two single pole breakers on a common trip. Some brands will jam not opening an overload/short with the other pole already in the off position.
 

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Discussion Starter · #8 · (Edited)
All breakers that say internal common trip have a link where if one pole trips it will trip the other pole(s) as well.

Any pics of said breaker?
The one i was specifically referring to:



Siemens also makes similar breakers. I have some spares here at home in the panel, I might replace them with fillers then dissect them to see what's happening in there, but I really want to know about the CH ones because they're mainly what we use at work...
 

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Discussion Starter · #9 ·
Just to add, don't ever remove a handle tie to get two single pole breakers on a common trip. Some brands will jam not opening an overload/short with the other pole already in the off position.
That sounds like a serious design flaw, considering how easy it is to remove the plastic handle tie, purposely or accidentally. I can imagine them going missing over time on older installations and going unnoticed.
 

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What do the inspectors think of that?
Won't work here
14-302

(i) their handles are interlocked with a device as provided by the manufacturer so that all ungrounded conductors will be opened by the manual operation of any handle; and
 

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Discussion Starter · #13 ·
Ah good find, but reading the entire rule:
14-302 Construction of circuit breakers (see Appendix B)
Where circuit breakers are provided for the protection of apparatus or ungrounded conductors, or both, they
shall open the circuit in all ungrounded conductors by the manual operation of a single handle and by the action
of overcurrent, except
(a) where single-pole circuit breakers are permitted by Rule 14-010(b); or
(b) in branch circuits derived from a 3-wire grounded neutral system, two single-pole manually operable circuit
breakers shall be permitted to be used instead of a 2-pole circuit breaker, provided that
(i)
their handles are interlocked with a device as provided by the manufacturer so that all ungrounded
conductors will be opened by the manual operation of any handle
; and
(ii) each circuit breaker has voltage ratings not less than that of the multi-wire branch circuit.
My interpretation is that a handle tie provided by the manufacturer of the breaker (CH handle tie on two CH single pole breakers) can be used to tie together two single pole breakers.
 

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That sounds like a serious design flaw, considering how easy it is to remove the plastic handle tie, purposely or accidentally. I can imagine them going missing over time on older installations and going unnoticed.
The whole point when designing these breakers is that they would be used as listed. So what would happen if one pole was off while the other trips is never considered during testing because the breaker is not assumed that its going to be used that way. Its difficult for engineers to take into account every single bone head move someone might pull off.

The breakers that are notorious for this are older GEs made up until the early 2000s. Those will jam near 100% of the time. Some others will to but not always. As for the newer cutler hammers I don't believe they have that issue but Im not totally sure to be honest.
 

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The whole point when designing these breakers is that they would be used as listed. So what would happen if one pole was off while the other trips is never considered during testing because the breaker is not assumed that its going to be used that way. Its difficult for engineers to take into account every single bone head move someone might pull off.
While it is possible to make a device idiot-proof, it is impossible to make one that is fool-proof by virtue of that fact that it is impossible to predict just how clever a fool might be.
 

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I don't think it's required that handle-ties automatically operate both poles of a circuit breaker. UL489 just requires that it makes them manually interconnected, but it seems possible that only one pole of a handle-tied mechanism would open.

All multi-pole breakers are assumed to be common trip (mechanically connected internally) unless printed on the face.

This one specifically says it is common trip, but UL only requires labeling when they are not. They'll say something like "independent trip."

When an independent trip multi-pole breaker is tested for it's listing, each pole is tested separately of the others, so they're treated like a group of single pole breakers.
 
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