Troubleshooting RCD: Step-by-Step Guide When the Power Goes Out

A tripping residual-current device (RCD or Jordfelsbrytare in Swedish) is a good sign — it has done exactly what it should: detected an electrical leakage and protected you. But being without electricity in parts of the house is frustrating. Here is our complete troubleshooting guide that you can follow step by step — without risking your safety.

Why does the RCD trip?

An RCD compares the current going out in the phase with the current coming back via the neutral wire. If the difference exceeds 30 mA (milliamperes) — a sign that the current is taking another path, e.g., via water or a person to ground — it breaks the circuit in under 40 milliseconds.

Most common causes:

• Moisture or water in outdoor lighting, facade outlets, or cables
• A broken coffee maker, vacuum cleaner, or other appliance with broken insulation
• Underfloor heating with a damaged heating cable
• An old outlet with a cracked interior

Step-by-step troubleshooting — isolate the fault

Follow this method in order. You don't need any tools.

Step 1 — Turn off ALL circuit breakers Go to the electrical panel and flip down all the miniature circuit breakers (if you have old plug fuses — unscrew them). Now all circuits in the house should be de-energized.

Step 2 — Reset the RCD Flip up the RCD switch.

• If it stays up: The fault is in a specific appliance or circuit — proceed to Step 3.
• If it trips immediately again (with all breakers down): The fault is in the electrical panel or the cable before the RCD. Call an electrician immediately — this is not a DIY job.

Step 3 — Turn the breakers back on one by one Flip up one circuit breaker at a time and wait 5 seconds.

• If the RCD holds → that group is probably okay, move to the next one.
• If the RCD trips → you have found the faulty group! Leave that breaker down.

Step 4 — Unplug everything on the faulty group With the faulty group identified — turn that breaker OFF again and pull out all plugs belonging to the group (check all outlets in the affected rooms).

Step 5 — Turn on the RCD and the faulty group Now the RCD should stay up. Plug in the appliances one by one until the RCD trips — the appliance that was just plugged in is broken. Discard it.

Step 6 — If nothing is found If you unplugged everything but the RCD still trips on that group, the fault is likely in a fixed outlet, in the cable inside the wall, or in a fixed lighting fixture. Call an electrician.

Quick decision guide

Frequently Asked Questions about RCDs

How often should you test the RCD? The Swedish National Electrical Safety Board recommends testing the RCD every three months. Press the test button (the T button) on the RCD — the power should cut immediately. If nothing happens, the RCD is defective and must be replaced.

Can you bypass the RCD temporarily? No. It is directly life-threatening and violates the Electrical Safety Board's regulations (ELSÄK-FS). Never do it.

What does it cost to replace an RCD? Materials: 300–800 SEK depending on type (AC, A, B). Labor: 1–2 hours electrician. Total approx. 2,000–4,000 SEK, of which the ROT deduction applies to the labor cost.

What is the difference between RCD type AC, A, and B?

• Type AC: Standard, detects sinusoidal AC residual currents. Sufficient for most normal homes.
• Type A: Also detects pulsating DC residual currents. Required for EV chargers and heat pumps.
• Type B: Detects all types of residual currents including smooth DC. Required in certain EV charger installations.

Can't find the fault?

Smista El troubleshoots electrical installations throughout Greater Stockholm. We use a megger (insulation tester) to find leakage currents and cable faults that are not visible during manual troubleshooting. Contact us for a quick and safe diagnosis.