FAQ
TL;DR: Field tests show up to 40 % of budget RCDs are out-of-tolerance [Elektroda, Anonymous, post #16843824] “If the TEST button stays dead, swap the device” [Elektroda, Łukasz-O, #16847982]. Faulty or miswired three-phase RCDs rarely self-heal; replacement restores protection 100 % in this case [Elektroda, ralfi76, post #16863046]
Why it matters: A silent RCD can leave every circuit unprotected from lethal leakage.
Quick Facts
• Typical residential RCD trip current: 30 mA, 0.03 A, IEC 61008-1, Table 1 [IEC 61008].
• IEC 60364 advises pressing the TEST button monthly [IEC 60364-6].
• 40 A/4-pole RCD price range: €25–€60, EU retail 2023 [Mouser Catalog, 2023].
• Polish safety law mandates full inspection every 5 years [Elektroda, kortyleski, post #16843863]
1. Why can an RCD TEST button stop working after wiring changes?
The built-in resistor needs live and neutral on specific poles. Moving sockets can leave one phase or neutral disconnected, so the TEST circuit never energises [Elektroda, Anonymous, post #16848032]
2. Could swapping neutral (N) and protective earth (PE) disable the TEST?
No. The TEST loop flows between one phase and N inside the device; PE is not part of that path, so reversing N / PE will not silence the button [Elektroda, Krzysztof Kamienski, #16843781].
3. How can I confirm a dead RCD in three quick steps?
- Kill main power. 2. Disconnect load wires from the suspect RCD. 3. Re-energise and press TEST; if it still ignores you, replace it [Elektroda, Akrzy74, post #16843967]
4. At what current should a 30 mA RCD trip?
Standards accept 0.5–1 × In, so 15–30 mA. Values near 30 mA already warrant replacement [Elektroda, Anonymous, post #16863089]
5. Can a mechanical jam be fixed by toggling the lever?
Sometimes. Switching off and on can free stiff contacts; if TEST then works, only the mechanism was stuck [Elektroda, CYRUS2, post #16845467]
6. What’s different about testing a 4-pole RCD on a single-phase supply?
If only one phase is powered, the internal TEST resistor may sit on an unenergised pole, so the button appears dead even when the RCD is healthy [Elektroda, kSmuk, post #16847995]
7. How long do RCDs last?
Manufacturers quote 10–15 years or 20,000 operations, yet parameters can drift sooner; routine tests catch early failure [ABB Specs, 2022].
8. How much will replacing a 40 A, 4-pole unit cost?
European retail runs €25–€60 depending on brand and sensitivity [Mouser Catalog, 2023].
9. Are budget brands reliable?
Less so. Forum data shows 40 % of cheap units ship outside tolerance, versus under 5 % for premium lines [Elektroda, Anonymous, post #16843824]
10. What edge-case keeps TEST silent even on a good RCD?
A lost incoming phase deprives the TEST resistor of voltage; the installation still works via the remaining phases, masking the problem [Elektroda, Anonymous, post #16848159]
11. Who should perform formal RCD measurements?
A licensed electrician with an RCD test meter must verify trip time and current during scheduled inspections [Elektroda, Akrzy74, post #16843967]
12. How often should I press TEST?
Press monthly and after any wiring work, per IEC 60364 Clause 6.4.3 [IEC 60364-6].
13. Can an RCD fail yet still power the installation?
Yes. Contacts may weld closed, allowing current flow while safety protection is lost—exactly what happened before replacement in the thread [Elektroda, ralfi76, post #16847972]
14. Which standards define RCD performance?
Key documents are IEC 61008-1 (residual current circuit-breakers without integral over-current protection) and IEC 61009-1 (with over-current), both referenced in EU harmonised norms [IEC 61008].
