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What is the procedure for upgrading a consumer unit from fuse type to mcb type ?

6 Answers from MyBuilder Electricians

Best Answer

the procedure of changing over a consumer unit is ,
step 1 ensure all bonding , main earth and meter tails are a satisfactory size , if not your first job is to upgrade these .
step 2 determine what size consumer unit you are going to need by counting up the amount of circuits currently being used and any circuits likely to be installed in the future.
step 3 contact a qualified electrician to have the work done this will involve having the consumer unit changed , all relevant cables upsized/upgraded , all circuits should be fully tested and a result of their condition recorded and any faults uncovered reported to the customer .
step 4 if all tests show satisfactory results then a certificate can be issued to customer .
job done


Answered 28th Feb 2011

Depending on the age of the installation.

1)Carry out periodic Inspection.This will tell you and the electrician if there are any underlying problems such as borrowed neutrals and address the need for main bonding to be checked .

2)Replace with dual RCD consumer unit (cheapest option)or install a normal consumer unit and use RCBO for each circuit(more expensive)but much better if a fault develops,you would only have one circuit trip instead of half the house.Upgrade mains tails to 25mm and main earth to 16mm.

3)Carry out FULL tests and issue Electrical Installation Certificate (assuming everything is ok)should be has its been tested already.Notify building control for Part P.


Skip option one and risk being left with a none functioning electrical system with a nice list of remedial works to be carried out.

That money you saved on the testing before change doesnt look such a good idea now ;-)


Answered 1st Mar 2011

I 100% agree with PCM, insulation resistance testing as a minimum. No point changing the board if it's not going to work once energized. I would also advice taking a light fitting down to make sure there is twin and earth cable installed.


Answered 4th Mar 2011

Asses the wiring in place via an insulation resistance test. Do any remedial work in case of faults (for example some old style metalic contact touch dimmers can really give you a nasty surprise tripping the RCD, so you need to have it replaced with suitable ones, fridges that trip the RCDs). Maybe the easier way would be RCBOs (MCB`s with RCD incorporated) and keep everyone happy, tripping just one MCB doesn`t mean that you lose more than one circuit, for example kitchen sockets (although losing the power to the kettle could be the diference between life and death...electrical joke). There is one downside, price. Usually the RCBO`s are quite expensive. Screfix is listing Crabtree RCBOs for 45 pounds each. So count the number of fuses that you have in the existing board and do the maths.


Answered 19th Mar 2011

Some old wylex boards can have mcb's fitted instead of old fuse's. However there is no way of incorperating an RCD into this type of board. The simplest way is to change the entire fuse board for a new 17th edition twin Rcd board. This should be done by a qualified electrician as new boards can sometimes throw up faults that are not currently being detected


Answered 28th Feb 2011

Remove the old fuseboard, Replace with a 17th Edition Consumer Unit, Complete a full test rectifying any faults present, Issue electrical instalation certificate, Notify local authority who will issue a Part P building compliance certificate.


Answered 28th Feb 2011

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