I'm going to ask a power raise. I'm moving from 3kW + 30% (15A) to 4,5kW + 30% (25A).

I'd know if my main feed (3m, 2,5mm2) is enough to hold the new max rate.

EDIT: I've checked my main feed and it's actually 4 mm^2, not 2,5.

  • Where are you? UK, US (unlikely, given metric measurements), somewhere else? – Martin Bonner supports Monica Aug 20 '19 at 17:15
  • I'm in Italy. Thank you Stack Exchange for having me to write unuseful stuff! "comments should be at least 15 characters". – DDS Aug 21 '19 at 14:39
  • The right way to have answered my question would have been to edit your original question to include the info - not to write a comment at all. – Martin Bonner supports Monica Aug 21 '19 at 16:18

2.5 mm2 is equivalent to #14 for us Americans, which is required for use on 15 A circuits (or a larger wire). On a 20 A circuit, you need (at least) #12 [4 mm2], and for a 30 A circuit (the next step up for your 25 A needs), you need #10 [6 mm2].

So, given your current wire size of #14 [2.5 mm2], you cannot increase the capacity of the circuit at all.

  • Thanks, Actually I'm on a 4mm^2 (I checked the wire mark) that I taught it was 2,5mm^2. So I'll go for 4 kW+30% (20A) instead of 4,5+30% (25A) and I'll be safe. – DDS May 3 '18 at 13:09
  • Keep in mind American wire ampacity ratings are quite conservative compared to EU ratings. Look at an old copy of NEC table 310.16, and remember those too are conservative. – Harper - Reinstate Monica May 3 '18 at 14:11
  • To reiterate Harper's point, in the UK a 30A fitting only needs 4mm². See tlc-direct.co.uk/Book/6.3.3.htm – Martin Bonner supports Monica Aug 20 '19 at 17:16
  • @MartinBonner UK-style ring circuit or normal "radial" circuits? – DDS Aug 21 '19 at 14:41
  • The link is to a section titled "The radial circuit". You can use 2.5mm² on a ring circuit - but the (not particularly convincing) justification is that the socket is fed with two wires. – Martin Bonner supports Monica Aug 21 '19 at 16:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.