4pole breakers -

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robva

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With nec 2008 adding definition for a neutral conductor as a current carrying conductor with non linear loads, we are exploring using four pole breakers in a variety of applications.

My question though, is possible unintended consequences.

Hoping folks here have some thoughts and opinions, the use of 4pole breakers for feeders to isolate the phase and nuetral conductors is somewhat non mainstream.

THANKS
Rob
 

augie47

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Location
Tennessee
Occupation
State Electrical Inspector (Retired) DINOSAUR
two questions please... where is this "addition" ? I don't see any significant change in the neutral derating rules.
Secoindly, why the 4 pole breaker ? what is the 4th pole disconnecting /protecting ?
 

brian john

Senior Member
Location
Leesburg, VA
With nec 2008 adding definition for a neutral conductor as a current carrying conductor with non linear loads, we are exploring using four pole breakers in a variety of applications.

My question though, is possible unintended consequences.

Hoping folks here have some thoughts and opinions, the use of 4pole breakers for feeders to isolate the phase and nuetral conductors is somewhat non mainstream.

THANKS
Rob

And where are you having issues with non-linear loads. In all the harmonic investigations I have completed in 25+ years I have only seen a handful of harmonic issues and all were fixed with some fairly standard distribution corrections.


Seems (and I could be wrong) someone is over thinking, looking into an issue that may not exist.


Have you completed any studies to determine if you have a legtimate issue?
Why 3/4 pole why not utilize dedicated branch circuits 2-wire in lieu of multi-wire if you REALLY have a harmonic issue?

And if you really have a major issue why not some monitoring to watch your loads? Neutral current (under normal operation) is not going to jump up overnight?
 

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
He seems to be asking about 4 pole breakers on feeders to disconnect all three phase and the neutral simultaneously.

OK Robva what you logic behind this?
 

brian john

Senior Member
Location
Leesburg, VA
He seems to be asking about 4 pole breakers on feeders to disconnect all three phase and the neutral simultaneously.

OK Robva what you logic behind this?

I was not sure.

The only positive is the circuit would open on neutral overload. You could do the same with a CT and current relay and a shunt trip CB, cost wise I would think this was cheaper.

But I still think it is someone's idea to resolve an issues that may not exist?
 
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