When to use SP, DP, TP, 4P, SP+N, TP+N Circuit Breakers

  1. SP or 1P– Single Pole
  2. SP + N – Single Pole and Neutral
  3. DP or 2P – Double pole
  4. TP or 3P – Triple Pole
  5. TP + N – Triple Pole and Neutral
  6. 4P – Four Pole

1.     Single Pole (SP):

[Single Pole ABB circuit breaker: S201-C]

  • In a Single Pole CB, switching & protection happens over only one phase.
  • AC Voltage in SA is 220/230V between Phase and Neutral.
  • Application: Single Phase Supply, CB is used to break the Phase only.
  • Used for Lighting circuits, plug points, etc..

2.     Single Pole + Neutral (SP + N):[Single Pole + Neutral ABB circuit breaker: S201-C NA]

  • In a Single Pole + Neutral MCB, the switching  happens over the Phase and Neutral. However, no protection is incorporated over the Neutral Phase.
  • AC Voltage in SA is 220/230V between Phase and Neutral.
  • Application: Single Phase Supply, CB is used to break the Phase and Neutral.
  • Used for AC, Heaters, Dryers, etc..

2.     Double Pole (DP):

[Double Pole ABB circuit breaker: S202-C]

  • In a Two Pole or Double Pole MCB, the switching & protection happens over phase-phase or the phase-neutral.
  • AC Voltage in SA is 400V between Phases.
  • Application: Single Phase Supply, CB is used to break the Phase and Neutral.
  • Used for AC, Heaters, Dryers, etc..

3.     Triple Pole (TP):

[Triple Pole ABB circuit breaker: S203-C]

  • In a Three Phase or Triple Pole CB, switching & protection happens over all three phases. The neutral is not switched or protected.
  • As in the image above, the phase indications are often represented as Red-White-Blue.
  • AC Voltage in SA is 400V between Phases.
  • Application: Used in a system with a three Phase Supply.
  • Used for machinery, motors, welders, etc..

4.     Triple Pole Plus Neutral (3P+N):

[Triple Pole + Neutral ABB circuit breaker: S203-C NA]

  • In a 3P+N CB, Neutral phase switching takes place within the CB as a separate pole. However, no protection is incorporated.
  • TPN for Y (or star). The connection between ground and neutral is in many countries not allowed. Therefore the N is also switched.
  • AC Voltage in SA is 400V between Phases.
  • Application: Three Phase Supply with Neutral.

5.     Four Pole (4P):

[Triple Pole + Neutral ABB circuit breaker: S203-C NA]

  • In a 4P CB, Neutral phase switching takes place within the CB and protection is incorporated.
  • In 4-Pole MCCBs the neutral pole is also having protective release as in the phase wires.
  • AC Voltage in SA is 400V between Phases.
  • Application: Three Phase Supply with Neutral.
  • Used in application where the neutral is to be isolated from the earth in case of an earth fault, photo-voltaic installation, UPS, Generator suppler etc…

Difference between TP+N and 4P 

  • For TP+N, protection applies to the current that flows through only 3 poles (Three Phase) only; there is no protection for the current flow through the neutral pole. Neutral is just an isolating pole.
  • For the 4 pole breakers, protection applies to current flow through all poles. However when the breaker trips or is manually opened, all poles are disconnected.

Where to Use TP, TPN and 4P in a Distribution Panel:

  • An MCB is used for protection of the system if fed from a transformer. If the board is fed from a Minisub or is a sub-distribution board, the main incomer can be an Isolator, as the protection takes place up stream.
  • TP MCB: It is the most common type of breaker used in ordinary three phase supply.
  • TP+N MCB: It is generally used where there are dual incomers to the panel (utility source and emergency generator source).
  • 4P MCB: It is used where there is the possibility of high neutral current (due to unbalance loads and /or 3rd and multiple of 3rd harmonics current etc) and Neutral / Earth Protection is provided on Neutral.
  • Normally in a 3 phase + neutral system, it is common practice to use a 3 pole CB while the Neutral is connected to a common Neutral Link.  However, if the application of a 3pole will affect the operation of a protective relay then a 4 pole CB is used.

For more information contact Josh Berman or visit www.switchmanproducts.co.za

Joshb@switchman.com

0118275705