Hello all - my first post here and only a few months in the job so, be gentle ... I qualified last year after a lifetime of doing my own electrics and electronics, and am getting used to the correct way of doing things as per the wiring regs. A job I have just done is to replace an old fuse board with an 18th edition RCD consumer unit. This is a secondary unit to the main CU (an older MCB based unit with an external RCD) presumably fitted when the property was extended some time ago. The new CU has 4 circuits, 1 lighting ring final, 1 socket wing final and 2 socket finals. All is fine and dandy - but what certificate do I complete? No new circuits have been added BUT the CU has been changed, so the way I read the regs (644.1) a EIC is required. Is this correct? And if so, does this cover just the new CU and it's circuits or the WHOLE installation (please God, no!)? I'm fast discovering that certification is the worst part of the job Thanks in advance all for your time and trouble.