Ring main

[Geffers]

Hi Guys (& Gals) came across a ring done out in 1.5mm cable at the CU. Customer says it was put in 15yrs ago. Customer says no to upgrade due to carpets flooring etc. My problem is do i put it on the EIC as a deviation? There are only 3 x double sockets on the ring & only standard lamps fed from it. Tests show everything is ok. Any answers appreciated.

 

[sparky b]

Put a smaller mcb?

 

[ADS]

Agree - 16A MCB should do it.

What's the EIC for?

 

[Evans Electric]

Fit a 16A MCB, if they don't want to pay for it , walk away.

 

[Revved Up Sparky]

With a combined csa of 3mm (1.5+1.5) I think a 20A MCB/ RCBO would still be OK, although 16A is fine.

 

[Geffers]

EIC is for CU change. Thanks for all the answers a smaller mcb is going in. But should i still mention it on the EIC?

 

[Manator]

Looks like it could have been an old 5amp circuit for standard lamps, now utilised for power by adding double socket outlets. A 16 amp like others have suggested would be ok.

 

[ianmacd]

16A assumes nothing is derating the cable. Could end up being a 10A. Sorry Revved but its not a ring as defined in 433.1.5 so your suggestion of 20A may not comply with 433.1.1 (ii).

---------- Post Auto-Merged at 12:57 ---------- Previous post was made at 12:56 ----------

Looks like it could have been an old 5amp circuit for standard lamps, now utilised for power by adding double socket outlets. A 16 amp like others have suggested would be ok.

Unlikely if its only 15 years old. more like diy bodge.

---------- Post Auto-Merged at 12:58 ---------- Previous post was made at 12:57 ----------

EIC is for CU change. Thanks for all the answers a smaller mcb is going in. But should i still mention it on the EIC?

You could mention it on the last page but you will have listed it on the schedule of test results page anyway.

 

[Nicky Tesla]

Ok so a 32A mcb requires cable to be rated at 20A or above for a ring cct, so what is the formula. Is it 2/3 of the MCB rating?

Therefore a 16A MCB will require that the cable needs to be rated to at least 10A

 

[PC Electrics]

A 20A ring will require cable rated at 14A. All the other usual rules for a ring apply (continuity end to end, load spread, derating etc etc). Don't forget to check your voltage drop (you don't say how large this ring is).

If there's no derating, 1.5 cable is only 1A short of being compliant on a conventional 32A ring !! So I believe it'll be perfectly safe as a 20A ring.

 

[revjames]

are you 100% sure its 1.5? some older cables have a smaller earth and thinner overall insulation. Worth checking thats all.

 

[PC Electrics]

are you 100% sure its 1.5? some older cables have a smaller earth and thinner overall insulation. Worth checking thats all.

The Rev makes a valid point. Check the wire diameter with your vernier. 1.5mm csa has a dia of 1.38mm

 

[Evans Electric]

Have some posts disappeared from this thread ? :C

 

[revjames]

Found them here

 

[ianmacd]

A 20A ring will require cable rated at 14A. All the other usual rules for a ring apply (continuity end to end, load spread, derating etc etc). Don't forget to check your voltage drop (you don't say how large this ring is).If there's no derating, 1.5 cable is only 1A short of being compliant on a conventional 32A ring !! So I believe it'll be perfectly safe as a 20A ring.

Have you got a reg to back that up so its complies?

---------- Post Auto-Merged at 08:59 ---------- Previous post was made at 08:56 ----------

Ok so a 32A mcb requires cable to be rated at 20A or above for a ring cct, so what is the formula. Is it 2/3 of the MCB rating?Therefore a 16A MCB will require that the cable needs to be rated to at least 10A

There is only one option for a compliant ring 32A MCB, =<2.5mm T&E installed such that max load >=20A. There is no provision for 1.5mm T&E therefore it has to be treated as a radial.

 

[Geffers]

Its definitley 1.5 twin & earth - old colours the length is about 28mtrs back to the CU i doubt if anything near 10A will ever be on it. A 16A mcb is looking as the best option. Checking OSG table 6A no derating needed.