# Thread: Regarding the Cuicuit Breaker (MCB)

1. Junior Member
Join Date
Oct 2009
Posts
1

## Regarding the Cuicuit Breaker (MCB)

Dear all, i am really a new bee in the electrical industry, and i need to learn about the basic conponents of the cuicuit to do the design

is there anyone can kindly advice me about the MCB, especially the difference between the 1p 1p+n and 2p MCB & 3p 3p+n and 4p MCB?

as well as the usage (where & when) of the above MCBs. Thanks very much in advance

2. Moderator
Join Date
Jun 2003
Posts
6,888
I assume 1p means a single pole breaker, 2p is a two pole breaker, and 3p is a three pole breaker.

Are you familiar with three phase systems? If not, you need to find some reading material on this.

1p+n, 2p+n and 3p+n probably means a "1 pole plus neutral", "2 pole plus neutral", and "3 pole plus neutral". That doesn't make much sense for circuit breakers because the neutral wire is never ran through a breaker, it is tied on to the neutral bus. But it does make sense for describing a load, or the wiring to the load.

3. Moderator
Join Date
Feb 2003
Location
Wisconsin
Posts
9,860
Originally Posted by Yuyu_XX
Dear all, i am really a new bee in the electrical industry, and i need to learn about the basic conponents of the cuicuit to do the design

is there anyone can kindly advice me about the MCB, especially the difference between the 1p 1p+n and 2p MCB & 3p 3p+n and 4p MCB?

as well as the usage (where & when) of the above MCBs. Thanks very much in advance
The terminology you are using is not common in North America.

1P - is a single set of contacts which have overcurrent protection

1P +N - is two sets of contacts, one has overcurrent protection and the other is simply a switch. In the US we call this type of breaker a 2-wire Switched Neutral

2P - is two sets of contacts, both with overcurrent protection

3P - is three sets of contacts, all with overcurrent protection

3P + N - is four sets of contacts, three with overcurrent protection and the fourth is simply a switch

4P - is four sets of contacts, all with overcurrent protection

You can find more information by looking at literature from manufacturers that make both European and North American equipment. Try someone like Schneider Electric and their Merlin Gerin breakers.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•