Not if the GFCI breaker is supplying the circuit you are wanting to put the GFCI receptacle into.
Your question is a bit vague, but let's try a two part answer. If you have a GFCI breaker in an electric panel you should only have one connection at the breaker, but the breaker will protect all devices on the circuit. If you are talking about a GFCI outlet, they are equipped to extend the GFCI protection to other non-GFCI outlets by using the proper "output" connection on the GFCI.
Deoends on code you are governed by. In USA, a GFCI outlet or a circuit controlled by a GFCI circuit breaker would be required.
There are tow places to put a Ground Fault Circuit Interrupter. There is a GFCI breaker which would be installed in a breaker box and a GFCI outlet that can be installed anywhere. Most GFCI outlets allow you to connect regular outlets to the GFCI and those outlets will also be protected.
You need a GFCI outlet at any location that is within 6' of a water source. You also need a GFCI outlet in a room with a concrete floor, any garage, and any location outside the home or under the home in the crawl space. A GFCI outlet protects you from electrical shock near water or moisture. You can protect more than one outlet with 1 GFCI outlet. Connect the incoming power to the LINE side of the GFCI outlet and all the other outlets getting power from that outlet to the LOAD side of the GFCI outlet. That way they will all be protected by 1 GFCI. A GFCI breaker is used to protect an entire circuit and not just individual receptacles. It is often cheaper to use GFCI receptacles than a breaker, especially if "piggy-backed" such as described above. It is also more convenient to reset a GFCI receptacle than to reset a breaker. But your question is "why." From this I suspect you may be misunderstanding the difference between a breaker and GFCI protection. To keep things simple let me say that a GFCI does not work on the same principles as a standard breaker. It provides a much safer protection than a standard breaker. Even with a ground you need GFCI protection as listed above.
Not if the GFCI breaker is supplying the circuit you are wanting to put the GFCI receptacle into.
A GFCI device in a breaker is intended to trip the breaker open when a ground fault is sensed in the circuit that the breaker is protecting.
No, you could use a GFCI circuit breaker instead.
Your question is a bit vague, but let's try a two part answer. If you have a GFCI breaker in an electric panel you should only have one connection at the breaker, but the breaker will protect all devices on the circuit. If you are talking about a GFCI outlet, they are equipped to extend the GFCI protection to other non-GFCI outlets by using the proper "output" connection on the GFCI.
Deoends on code you are governed by. In USA, a GFCI outlet or a circuit controlled by a GFCI circuit breaker would be required.
In North America they are known as a GFCI. Ground Fault Circuit Interrupter breaker.
No they must be seperated.
Yes but it's redundant and may cause unnecessary "tripping" of the circuit. The GFCI circuit breaker is intended to protect an entire receptacle circuit whereas a GFCI receptacle is designed to protect only that receptacle and any which are provided power from its load side. (downstream)
A GFCI breaker monitors the imbalance of current between the ungrounded (hot) and grounded (neutral) conductor of a given circuit. With the exception of small amounts of leak-age, the current returning to the power supply in a typical 2-wire circuit will be equal to the current leaving the power supply. If the difference between the current leaving and returning through the current transformer of the GFCI exceeds 5 mA (61 mA), the solid-state circuitry opens the switching contacts and de-energizes the circuit. Touch the neutral or hot and you change this current which will trip the breaker.
GFCI = Ground Fault Circuit Interrupter.
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The pool light is usually on a 15 amp circuit. The breaker feeding this circuit must have a GFCI rating.