low voltage incoming breaker
low voltage incoming breaker
(OP)
when the incoming breaker in a low voltage switchboard
shall be 3 pole and when it should be 4 pole?is there any
danger in using 4 pole breakers instead of 3 pole ones?
thanx.
shall be 3 pole and when it should be 4 pole?is there any
danger in using 4 pole breakers instead of 3 pole ones?
thanx.






RE: low voltage incoming breaker
Using a 4 pole device as the service disconnect is not normal and could cause problems when the neutral is disconnected but the phase circuits are not, floating neutral problems.
RE: low voltage incoming breaker
RE: low voltage incoming breaker
RE: low voltage incoming breaker
Four poles Breakers are bigger, more expensive, and normally avalable out of shelves from ABB Sace and Merlin Gerin/ Schneider. Square D is also a great source of this Breakers.
Good luck in choosing the Breaker...
RE: low voltage incoming breaker
while doing maintenace on one of the incommings why protection is lost?
RE: low voltage incoming breaker
TN, TN-S, TN-C, TN-C-S terminologies are used by european electrical codes to describe different systems of earthing(grounding in North America). Giuseppe is partially correct. But in TN-C-S(Combined Separate) system the neutral is separated from the earth only at the service entrance panel and downstream of the distribution. If you are from european region we can discuss about it in more details.
By your wordings I guess you are in the North American region.In short you do not have to worry about using a 3-pole breaker at all. But if you wish you can use 4-pole as well.
RE: low voltage incoming breaker
that was a relief .in fact I have used a 4 pole breaker and
was worried about safety concerns of breaking the neutral.
if you have any more detailed information I would be happy
to listen.
RE: low voltage incoming breaker
You have to worry about breaking the neutral while the three phases are at work(energized). That may deliver line-line voltage to a single phase load as the neutral potential is floating as electrifire explained. Therefore never break the neutral while the phases are energized. 4-pole breakers break the neutral at the same time with the phases and no worries.