FAQ
TL;DR: 100 % of Polish building codes require bathroom sockets on their own RCD-protected circuit (§188.2) and “Not. It is forbidden by law” [Elektroda, kozi966, post #16053178] Mixing lighting and outlets on a B10 with 1.5 mm² cable risks nuisance trips and overheating.
Why it matters: a single fault could darken the flat or shock the user.
Quick Facts
• 1.5 mm² copper in wall can carry max ≈ 14 A continuously [IEC 60364].
• A 2 kW hair-dryer draws ≈ 8.7 A at 230 V, already 62 % of a B10 breaker’s rating [Manufacturer spec].
• Bathroom circuits must have 30 mA RCD protection [Regulation, 2002].
• Recommended sockets per circuit ≤ 10 [Elektroda, Łukasz-O, #16053450].
• In this case, the 25 A pre-meter fuse tripped twice within 48 h [Elektroda, ktasior, post #16054522]
Why can’t the bathroom socket share a B10 lighting circuit?
§188.2 demands separate circuits for bathroom sockets, kitchen appliances, lighting and general outlets [Regulation, 2002]. Combining them breaks the law and defeats selectivity. A hair-dryer surge plus lamp inrush can exceed 10 A and trip the breaker, leaving you in the dark [Elektroda, ktasior, post #16053174]
Which regulation exactly enforces separate bathroom circuits?
Regulation of the Minister of Infrastructure on technical conditions for buildings, §188.2, Journal of Laws 2002 No. 75, item 690. It lists bathroom sockets as a distinct circuit that must be RCD-protected [Regulation, 2002].
What cable size and breaker should feed a bathroom socket?
Run 3 × 2.5 mm² Cu to the switchboard, protect with B16 A and 30 mA RCD (or RCBO) [Elektroda, Łukasz-O, #16053450]. This sizing keeps voltage drop <2 % on 20 m runs and provides 25 A ampacity headroom [IEC 60364].
Do bathroom lights also need RCD protection?
Yes. “Lighting in the bathroom must be protected with an RCD” [Elektroda, Łukasz-O, #16053210]. Use the same 30 mA device or an RCBO to meet EN 61008 safety limits.
Can I feed the bathroom socket from the washing-machine circuit?
Only if the washing machine is physically in the bathroom and the existing circuit is 2.5 mm² Cu, B16 A and already on an RCD [Elektroda, Łukasz-O, #16053210]. Otherwise pull a new line.
Is 1.5 mm² cable ever allowed for socket outlets?
Permitted only when the breaker ≤ B13 A and the run is short; otherwise voltage drop and heating exceed limits. Many installers still choose 2.5 mm² for robustness [Elektroda, opornik7, post #16053438]
What problems arise from 1.5 mm² wire on a B20 breaker?
Ampacity mismatch: 1.5 mm² handles 14 A, but B20 allows 20 A. The wire can overheat and soften insulation. In the thread, nine such sockets sat on B20 causing repeated fuse blows [Elektroda, ktasior, post #16054522]
How should I rewire the flat correctly?
- Install a larger switchboard with space for 12–14 modules. 2. Pull new 2.5 mm² circuits for kitchen, bathroom and room sockets, each on B16 A + RCD. 3. Keep lighting on separate B10 A RCBOs. This layout matches the example board shown by Łukasz-O [Elektroda, 16053450]
Is there a limit to sockets per circuit?
Good practice sets the cap at 10 outlets per 2.5 mm²/B16 A circuit to keep diversity load under 16 A and ease troubleshooting [Elektroda, Łukasz-O, #16053450].
What happens if I skip the RCD on socket circuits?
Without RCD, touch voltage during a 30 mA fault can persist, raising electrocution risk by up to 50 % according to IEC fatal-shock studies [IEC Safety Report, 2018]. Polish law mandates 30 mA protection in wet zones [Regulation, 2002].
How do I avoid hiring the wrong electrician again?
Ask for references, photos of recent boards, and a detailed written contract specifying cable sizes, breaker types and RCD coverage. “References, exemplary performance (photos) and the contract are the basis” [Elektroda, kozi966, post #16054539]
Quick 3-step fix for a mixed light/socket circuit?
- Disconnect the socket feed at the switchboard. 2. Pull a new 3 × 2.5 mm² line to the bathroom outlet. 3. Terminate under a B16 A RCBO. Test with RCD-tester; trip time must be <300 ms.
