RCCB: the switch that trips on a leak
How an RCCB compares phase and neutral current and cuts the power by itself when 30 mA leaks to earth.
One tiny leak and the power goes OFF by itself? That's your RCCB saving a life ⚡🛡️
1️⃣ INSIDE: the phase AND the neutral both pass through one iron ring. Normally the current going out (phase) = the current coming back (neutral). Their magnetic fields cancel, so the ring feels nothing.
2️⃣ A LEAK: a damaged heater in a geyser leaks 30 mA to earth through the metal body. Now 1.03 A goes out but only 1.00 A comes back. The 30 mA difference magnetises the ring → sense coil → trip coil → both contacts open (shown slowed down; the standard says within 0.3 s, usually much faster). Same if the leak goes through a PERSON — that's why it's 30 mA.
3️⃣ TEST BUTTON: it makes a small fake leak around the ring. Press it every month. If it doesn't trip, call an electrician.
An RCCB guards PEOPLE, not wires: it does not trip on overload or a short. That's the MCB's job (next part!).
⚠️ Mains work = electrician only, with the main switch OFF. AC shown slowed down.
Read the voiceover (transcript)
- One tiny leak... and the power's gone?!
- Inside, phase and neutral pass through one ring. Out equals back, so the ring feels nothing.
- A leak to earth! Thirty milliamps goes missing. Out and back don't match, so it trips. Even if the leak is through you!
- Press test every month. No trip? Call an electrician!
- It guards people, not wires!
- Next: why your MCB trips! Follow for part four!
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