The "B20" marking on a circuit breaker indicates two important things:

1. Type of Tripping

Characteristic (B):

The letter "B" refers to the type of tripping characteristic of the circuit breaker. In this case, a "B" type breaker is designed to trip when the current exceeds 3 to 5 times the rated current. This type of breaker is generally used for residential or light commercial applications where the connected equipment has low inrush currents, such as lighting and general outlets.

2.Rated Current (20A):

The number "20" represents the rated current of the circuit breaker, which in this case is 20 amperes (A). This means the breaker is designed to carry a current of up to 20 amps under normal conditions, and it will trip if the current exceeds this rating to protect the circuit from overloads.

In summary, "B20" on the circuit breaker specifies that it is a type B circuit breaker with a 20-ampere current rating.

Or

"B20" on a circuit breaker indicates two things:

1. Type B:

The "B" denotes the trip curve or the type of the breaker. A Type B breaker trips when the current is between 3 to 5 times the rated current. These breakers are typically used in residential or light commercial applications where the electrical load is more predictable and less prone to surges.

2. 20 Amps:

The "20" refers to the breaker’s rated current capacity in amperes. This means the breaker is designed to handle up to 20 amps of current continuously. If the current exceeds this rating, the breaker will trip to prevent overheating and potential damage to the circuit.

So, a "B20" circuit breaker is a Type B breaker with a 20-ampere rating, typically used in residential or light commercial settings to protect circuits from overloads and short circuits.