Consumer Unit Replacement

TerryH · Jun 17, 2011

Hi All -
Regarding our present domestic electrical installation, I haven’t touched our consumer unit for 47 years - yes it is correctly fused. So today I checked out the CU, and find to my horror I have only three fuses in the unit, two 30 amp one wired for the cooker with 7/044 T&E, one ring main with two lots of 7/029 T&E and one 5 amp fused with Twin no earth 3/029. I worked for an electrician when I left school at 15 until 17 and I still remember the oldcable sizes even now, although I am a retired service engineer ( best job I’ve ever had boys – retired that is).

My chalet style semi detached house and was built in 1960and consists of a ground floor and first floor. I would like to have installed a PV system comprising Sanyo HIT-H250E01’s with the Enecsys micro inverters into a FITsystem. There are no spare ways in my CU, fishing on the internet for information, leads me to believe that I will need amodern CU with split domestic wiring, and dual RCBs with an MCB to each circuit to conform to edition 17 regs.
Is there anyway within the over solicitous and bureaucratic electrical safety and building regs that you lot have to put up with now - that would allow a qualified and certificated electrician, to just fit an additional CU for connection to a properly installed MCS FIT system?

Your advice will be greatly appreciated. Regards Terry

truckster · Jun 17, 2011

It's notifiable work so you will need to be Part P registered to self certificate or involve the LABC before starting any work so they can charge an extiornate fee to inspect the work. As the installation is 50 odd years old it could probably do with an inspection anyway so why not get a sparky in to give you a quote

PC Electrics · Jun 17, 2011

An RCD is the electrical equivalent of an airbag in your car. One day such a device could save your life (or that of one of your grandchildren).
Have a new CU fitted and the installation inspected.

If you can afford PV you can afford a CU.
General Public : Electrical Safety Council

nickblake · Jun 17, 2011

Hi terry i agree with truckstar here , being a spark yourself you can understand the complications the old systems can give shared neutrals etc , you ll be aware of the fact you have no cpc so no metal clad light fittings or switches can be used , as truck has said get in a reegestered spark or several to give you a quote ,could well need a partial rewire and if you speak to the spark you may well be able to assist and reduce your costs too

TerryH · Jun 18, 2011

Thanks to Nickblake and Truckster for the constructive advice, and PC Electrics for his observations.
I’m not concerned with costs, but the general up heaval that will be caused installing new cable runs all around the house, removing fitted carpets, furniture etc. just to conform to the split CU regulations.

I do take on board the necessity to have the wiring properly tested for all the previously mentioned reasons. I am just trying to get a handle on the probable discussions, problems and alternative remedial actions I may be discussing with electricians applying for the work, forewarned is for forearmed they say.....

Can the installation conform to present day regs, by replacing the existing CU with a new 4 or 6 ways CU, incorporating RCBO’s rather than RCD’sto each of the existing circuits, for lighting, and ring mains on the two floors. At the moment one 5amp fuse supplies the lighting circuit on both floors and one 30 amp fuse supplies ring main circuit on both floors. A separate RCBO for the cooker circuit is envisaged, also incorporate spare ways for example, a PV FIT installation?

Your observations again greatly appreciated – Thanks – Regards Terry

telectrix · Jun 18, 2011

if the wiring is pvc, then there's a good chance that most of it is sound. the main problem is the lack of cpc on the lighting. without seeing the job, just going by your posts, i think a rewire of the lighting, splitting it into 2 circuits and a full test/inspection of the installation, together with a new CU and upgrade to earthing and bonding, could be a winner.

truckster · Jun 18, 2011

Hi Terry

By using RCBO's you will be bringing the installation more into line with current standards however in order to do this there is going to be upheaval. For instance, to split the ring into seperate ones for up/down and same for lighting is going to involve running new cabling. The main bonds will almost certainly be undersized and need upgrading. Having no cpc's in the lighting ccts is non compliant and whilst it is possible to get round this it is not really satisfactory.

Putting up a new RCBO is a minimum measure but it is, as my old man used to say, putting lipstick on the pig

malcolmsanford · Jun 18, 2011

Terry if I was sitting down in the local with you the first thing I would be saying is stop being a tight wad and get a pint in..........

Seriously as your saying the existing installation is 50 yr old near enough, and to be honest I bet you have had new bathrooms fitted, new CH systems and all, so really that old installation as done you proud. Time ot move on. I understand the point about the upheaval, so can I recommend this.

Get a local lad in and let him do you an PIR on the system, as it is just a few circuits I bet the cost will be less than 200 pounds for the work, he will tell you what condition it is in and what you really need to do. You never know he may find that the installation is in good condition.

If he fails it then yes go ahead and do the CU change, and the RCBO's IMO are the best way to go. He will do it for you mate if he is a scheme member of Part P for as little as 400 pound most likely, it will cost you double that yourself to do it with notification, tools, material, and the biggie use of a multifunction Test Meter.

If he passes the installation then, If I were him I would suggest henley block the tails and fit a small sub board just for the PV install. Cheap and cheeful ....now mines a pint

telectrix · Jun 18, 2011

if you post your approx. location, terry, a forum member may be close enough to you to come round and have a look. most of the lads / lasses on here would be happy to give a free estimate.