63A sub mains board off a 32A MCB?

Hello peter , The situation you have could be worse than you anticipate . To determine what size cable you need to supply your sub-main is determined by the amount of current drawn when potentially all circuits are being used ( add to this given diversity factors ) at the same time , This would give you maximum current rating . Your sub-main supply cable would need to be able capable at carrying this as a minimum requirement , ideally carry more . Add to this calculation the enivonment that the cable is to be run ( clipped direct to surface , layed in conduit / trunking , buried in the wall , covered by loft insulation , etc ) again each different environment changes the cable current rating . Once the cable rating has been determined then you can establish the breaking capacity of the fuse required to cover this sub-main ( This figure can not exceed to maximum carrying capacity of the supply cable ) . The main fuse to the property would also need to be checked to ensure it can cover the additional loading . The main tails and earthing conductor would also need to be checked . There are various other things that should be looked at to ensure that everything is satisfactory within this altered installation . Please get an approved electrician to give you a complete peace of mind explanation as to exactly what can be done and the options you have to achieve a safe and compliant installation . wayne soppitt (WPS Electrical Services ) .

"Best get an NICEIC electrician round to sort it out asap and ensure that the work is fully tested and notified to building control" The electrician dose not have to be NICEIC registered any electrician who is partp registered will be fine!

Hi Report him to his body ie Niceic ? Anyway the 10mm cable could be supplied with a 50 a mcb ? Just need to check a few things such as length of run and total load supply Hope this helps If you need any further work,post on here and get an approved electricain like me to quote on the works Thank you

Hi He should have used a double pole Henley block and installed a separate 63A switch fuse to create a proper sub main. Always check main fuse as is could only be a 60A. Why are people still getting away with this. Cheers Rob.

Do you mean that the main switch in the new consumer unit is rated at 63amp? only its unclear what the 63amp relates to? If the SWA 10mm cable runs back to the meter position then the best way of doing this is to have a 100amp main switch and 50amp MCB installed and connect 16mm tails from this unit in with your existing meter tails using Henley blocks. This will be a much better arrangement and still leaves you a spare way on your old existing fuseboard. Sounds like you were not using a registered electrician! - you need to be careful as if the local authority get wind of unregistered part P notifiable work, then they could fine you for breaching the regulations. ( up to £5000!) Best get an NICEIC electrician round to sort it out asap and ensure that the work is fully tested and notified to building control.