FAQ
TL;DR: In Polish flats, 2.5 mm² copper can carry ~24 A continuously [PN-IEC 60364] yet “swap-out becomes near impossible after three bends” [harlejowiec, 4999405]. Use rigid 18 mm conduit plus 3×2.5 YDY to future-proof sockets.
Why it matters: Repairing a buried run later can cost 3× more than installing conduit now.
Quick Facts
• 3×2.5 mm² YDY flat: ≈24 A long-term current capacity in concrete [PN-IEC 60364-5-523].
• 18 mm rigid PVC conduit (RKGL 20 × 14.5): crush strength 320 N; floor-rated [jarecki 86, 5009250].
• Retail price: YDYp 3×2.5 flat ≈2.50 PLN/m; round ≈5 PLN/m [gintur, 5003489][saimon79, 5009887].
• PN-IEC 60364-5-52 minimum socket conductor: 1.5 mm² Cu; many inspectors enforce 2.5 mm² [HeSz, 5006718].
• Practical pull limit in corrugated conduit: <10 m with 3 bends for 3×2.5 mm² [Wakmen, 5002562].
What cable size should I run for apartment socket circuits?
Most Polish electricians specify 3×2.5 mm² Cu for general-purpose sockets because it supports ≈24 A and 2.5 kW heaters safely [Anonymous, 5009746]. Smaller wires risk overload when multiple appliances share one circuit.
Is 1.5 mm² ever allowed for sockets under Polish standards?
PN-IEC 60364-5-52 sets 1.5 mm² as the minimum for fixed power circuits, but only if load, voltage drop, and protective devices keep current below 16 A [HeSz, 5006718]. Many site inspectors still reject it outright, so confirm before installation [Anonymous, 5003637].
Flat YDYp vs round cable—does shape matter under a screed?
Only mechanically. Flat YDYp needs a shallower chase and costs less; round fits more easily in trays and pipes but doubles price per metre [gintur, 5003489]. Electrical ratings are identical when conductor size matches.
Do I need conduit if I lay cables in the floor screed?
Conduit isn’t mandatory, but it protects against cracked screed and lets you pull extra wires later. Without it, repairs mean breaking concrete [harlejowiec, 4999405]. Risk rises on ground floors where moisture and settlement occur.
Which conduit type works best under concrete floors?
Rigid PVC pipe (e.g., RKGL 20 × 14.5) stays straight and has 320 N crush strength, so cables pull easily even years later [jarecki 86, 5009250]. Corrugated flex conduits can kink and trap cables during bends [Madrik, 5003554].
How wide a chase do I need for 3×2.5 YDYp without conduit?
A 10–12 mm deep by 18–20 mm wide groove usually suffices, leaving ≥5 mm cover to meet mechanical-protection rules [PN-EN 50086-1].
Can I fill the conduit or cable run with expanding foam?
Foam around, not inside, the pipe is fine. Filling the tube blocks future pulls and traps moisture; use cement grout instead at entry points [Anonymous, 5006396].
What’s the risk if the neutral conductor burns out?
A lost neutral can put 400 V across single-phase devices, destroying electronics; one case caused ≥30 000 PLN damage [Anonymous, 5006396]. Loose terminations, not small cross-sections, are the usual culprit [Łukasz-O, 5007793].
How much current can a 16 mm² copper earthing conductor handle?
In air it carries ~76 A continuously, giving a 6 kA short-circuit limit for 0.2 s faults [PN-IEC 60364-5-523].
How do I pull a replacement cable through rigid pipe?
- Push a nylon fish tape or 2 mm shepherd’s wire through the empty pipe.
- Tie on the new 3×2.5 YDY with insulating tape.
- Lubricate lightly and pull steadily from the far end. One person pushes, one pulls for runs >8 m [Madrik, 5003554].
What’s the cheapest place to buy 3×2.5 cable in Poland?
Forum users report electrical wholesalers selling YDYp 3×2.5 for about 2.50 PLN/m—half the DIY-store price [saimon79, 5009887].
How to deal with inspectors who demand 2.5 mm² everywhere?
Show load calculations proving compliance, then request written refusal if they object. You can appeal to the Voivode to review their licence [HeSz, 5009856]. One installer replaced 1.5 mm² with 2.5 mm² rather than fight, adding one day and <200 PLN cost.
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