Lights out! The fuse box quiz

The questions

1. Question 1 of 6An RCD, a FI-Schalter and a GFCI: what are they?

   • Three different fuses
   • The same kind of safety switch, with UK, German and US names
   • Types of light bulb
   • Smart meters

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   Answer: The same kind of safety switch, with UK, German and US names

   It is the same idea in three countries: a switch that cuts the power within milliseconds when current leaks away, for example through a faulty appliance or a person (ADAC). In the US it is usually an outlet with TEST and RESET buttons.

   Source: ADAC: FI-Schalter fliegt raus, was jetzt zu tun ist (German, 2 Sep 2026); Leviton: What to do when your GFCI trips (PDF)

   How to reset a tripped RCD

2. Question 2 of 6How do you spot the tripped switch in the fuse box?

   

   • It is the one that is warm
   • It is usually wider, has a test button, and its lever is down
   • It flashes red
   • It beeps

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   Answer: It is usually wider, has a test button, and its lever is down

   The RCD is usually wider than the other switches and has a test button; if its lever is down, it has tripped (RBH). ADAC adds that some stop half-way and look on from a distance.

   Source: RBH: How to reset a Residual Current Device (RCD); ADAC: FI-Schalter fliegt raus, was jetzt zu tun ist (German, 2 Sep 2026)

   How to reset a tripped RCD

3. Question 3 of 6Before you push it back up, what should you do?

   

   • Nothing, just push it
   • Unplug everything on that circuit: switching off at the socket isn't enough
   • Turn off the water
   • Call the energy company

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   Answer: Unplug everything on that circuit: switching off at the socket isn't enough

   Pull the plugs out, because the RCD can still detect a faulty appliance that is only switched off at the socket (RBH). Don't forget extension leads and rarely used things like a cellar freezer (ADAC).

   Source: RBH: How to reset a Residual Current Device (RCD); ADAC: FI-Schalter fliegt raus, was jetzt zu tun ist (German, 2 Sep 2026)

   How to reset a tripped RCD

4. Question 4 of 6The lever is stuck half-way. What do RBH and ADAC say?

   • Leave it there
   • Push it all the way down first, then back up
   • Tape it up
   • Wiggle it gently until it stays

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   Answer: Push it all the way down first, then back up

   If the lever is stuck half-way, push it fully down first, then firmly back up (RBH, ADAC).

   Source: RBH: How to reset a Residual Current Device (RCD); ADAC: FI-Schalter fliegt raus, was jetzt zu tun ist (German, 2 Sep 2026)

   How to reset a tripped RCD

5. Question 5 of 6How do you find the faulty appliance?

   • Guess the oldest one
   • Plug things back in one at a time; the one that trips it is the culprit
   • Smell each plug
   • Check the electricity bill

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   Answer: Plug things back in one at a time; the one that trips it is the culprit

   Plug things back in one at a time, waiting a few seconds after each. When the RCD trips again you have found it: leave it unplugged and don't use it until it is repaired or replaced (ADAC, RBH).

   Source: ADAC: FI-Schalter fliegt raus, was jetzt zu tun ist (German, 2 Sep 2026); RBH: How to reset a Residual Current Device (RCD)

   How to reset a tripped RCD

6. Question 6 of 6Fact or fiction: if it keeps tripping, holding the lever up will keep the power on.

   • Fact
   • Fiction: it is built to trip while a fault exists. Never bypass it

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   Answer: Fiction: it is built to trip while a fault exists. Never bypass it

   ADAC says holding the lever up won't work, because the switch is built to trip again while a fault exists. If it trips with everything unplugged, the fault may be in something wired in or the wiring itself: call an electrician.

   Source: ADAC: FI-Schalter fliegt raus, was jetzt zu tun ist (German, 2 Sep 2026)

   How to reset a tripped RCD