FAQ
TL;DR: Up to 70 % of nuisance trips in small flats are caused by surge-bar or cord faults [Schneider, 2021]. “Selectivity fails when identical B-curve breakers sit in series” [Elektroda, Darrieus, post #6580584] Check strips first, then breaker curve mix.
Why it matters: Quick checks can stop double-fuse blowouts, protect appliances, and avoid paid call-outs.
Quick Facts
• B-curve MCBs trip at 3-5× In; C-curve at 5-10× In [IEC 60898].
• 2100 W iron ≈ 9.1 A at 230 V; within a 10 A fuse’s continuous rating.
• Pre-meter reseal fee: PLN 30 ± 10 [Elektroda, Darrieus, post #6581086]
• Recommended SPD cable size: ≥ link conductors, typically 4 mm² Cu [Moeller SPD Guide].
• Contracted power in thread: 4 kW, protected by C20 breaker [Elektroda, 6583880]
Why does my apartment blow both the room breaker and the pre-meter fuse when I press the RCD test?
All loads restart simultaneously after the RCD resets, creating an inrush that exceeds the identical B-curve trip levels of both breakers; without curve selectivity they open together [Elektroda, 130880, post #6580611][Elektroda, Darrieus, post #6580620]
Can a single 2100 W iron legitimately trip a 16 A socket breaker?
A hot iron draws about 9 A; that is only 56 % of a 16 A breaker’s rating. If it trips, the cause is usually cumulative inrush from other devices or a weak/faulty breaker [Elektroda, 130880, post #6580573]
Do I need type C breakers on socket circuits?
Use C-curve only when inductive or high-inrush loads (compressors, vacuum cleaners) share the line. For mixed electronics, B-curve remains standard; pre-meter protection should then be C for selectivity [IEC 60898][Elektroda, Darrieus, post #6580584]
What’s the fastest way to locate the real culprit?
- Unplug all surge strips and multi-plugs. 2. Re-energise circuit. 3. Add devices one by one until the breaker trips. In the thread, removing one power strip stopped all trips [Elektroda, 130880, post #6590995]
Could a buzzing breaker or fuse be the problem?
A mild ‘zzz’ often stems from the electromagnet vibrating inside low-quality MCBs; it’s annoying but not automatically faulty [Elektroda, Darrieus, post #6580692] Persistent buzz plus heat means replace the unit.
How do I wire a single-phase Moeller surge arrester correctly?
Connect phase to the L terminal (top), neutral to N (top or second slot), and PE to earth bar; keep leads as short as possible (<30 cm). The user’s final photo shows correct layout [Elektroda, 6581011]
What happens if the SPD fails short?
The SPD’s varistor turns into a near short; the closest upstream breaker—often the C-curve pre-meter device—opens within milliseconds, isolating the fault [Elektroda, michcio, post #6599082]
Is it safe to daisy-chain two surge strips?
No. Chain increases contact resistance and cumulative inrush. In the thread, two chained strips tripped breakers even under light load [Elektroda, Darrieus, post #6585125]
How much does it cost to legally replace a sealed pre-meter breaker in Poland?
Energy utility unsealing and resealing averages PLN 30; labour varies widely (PLN 50 – 150 typical) and no extra measurements are required for a straight swap [Elektroda, Darrieus, post #6581086]
Edge case: can a neutral-only fault trip the RCD without blowing fuses?
Yes. An N-PE fault induces 30 mA residual current needed for an RCD trip while line current stays below fuse limits. Always secure the N conductor when adding SPDs [Elektroda, michcio, post #6585859]
