MCB (Miniature Circuit Breaker)
Basics
- The MCB disconnects the circuit in case of a short or an overload. It protects the devices and the infrastructure from damage.
Details
- In case of a short one consumer in the circuit isn’t creating a resistance. (“bad” faulty device)
R ≈ 0 Ohm, I = U/R, U ≈ 230V, I → ∞
- In case of an overload are too many consumers in the circuit. (They are parallel.)
1/R = 1/R1 + ... + 1/Rn, R → 0 Ohm, I = U/R, U ≈ 230V, I → ∞
Setup
- The MCB gets passed just by the required phase conductors of that circuit.
RCD (Residual-Current Device)
Basics
- The RCD disconnects the circuit in case the current between the input and output differs. It protects living beings from damage.
Details
- This current differs if it flows either through the protective conductor (“good” faulty device) or through a resistance (living being) to ground.
Setup
- The RCD gets passed by the required phase conductors and the neutral conductor.
- The RCD is in front of the MSBs.
Example (with one RCD and two MCBs)
PE N L1 L2 L3 | | | | | | | X--|--|---| |--X-------------X--| L1 | | | X--|---|--- RCD ---|---X---------------| L2 | | | | X---| | | |----X--------------| L3 | X--|--|--|--------| | ||| | | | | | | | MCB MCB | | | | | | ||| |---|---| | | | | | | ||| | | | | | | | | Cooking Wall Ceiling | | | | | | plate socket lamp | | | | | | || || || | | | | | |--------||------||------|| | | | | | | | | X--|--|--|--|--------------------|-------|-------| | | | | |