Consumer unit change

[paulthe spark]

Only qualified a year or so About to do a cu change for my neighbour, never done a cu change before in an occupied property but i thought it would be good experience for me although ive obviously fitted boards before. Anyway was just wondering if theres anything you more experienced guys think i should be aware of when doing a cu change? Ive read about a borrowed neutral on these forums, can someone please explain to me what a borrowed neutral is? also should i do an Insulation resistance test first before i start to detect any wiring problems before i become responsible? any help much appreciated
cheers lads

 

[paulthe spark]

thanks for all the replies fellas, a lot of great information which ill put to good use although steves last comment doesn't exactly fill me with confidence lol but its good to know these things. The other thing id like to ask is about the board arrangement. I know it has to confirm to 17th standards but my problem is at the company i work for we are still fitting boards the way we have always fitted them. We use a wylex split rcd, we put the two house rings and the kitchen on the rcd side, and everything else on the other non rcd side, so i don't have much experince with the new rcbo's and the new regulations. What type of board would you suggest i ask him to buy? its a 2 bed flat

 

[electricAl]

The lighting could only be on the non-protected side if it`s not buried in walls <50mm (possible) nor supplying bathroom / shower room.

As it`s reasonable to assume the flat has one or other you`ve got to RCD protect lighting circuit too. Also, take reasonable steps to offer some discrimination to avoid one RCD taking all the lights out.

From your comments, your firm is doing non-compliant work mate - unless i`ve misunderstood. Employing a little imagination does wonders. Sounds like they try to carbon copy every install, but work from the wrong copy!?!

RCBO`s aren`t anything to worry yourself about & they can get an installation out of the cart sometimes.

For this install you`ll be looking at a split board with dual RCD`s or even, possibly a `High Integrity` board with 1/2 unprotected ways (tho this would cost more if you employ RCBOs)

Hope that helps you

 

[paulthe spark]

i know a can't really understand why we havn't changed to the new regs yet. Quite a large firm doing a lot of the major housebuilders up here in Scotland would have thought we would have changed over last year but we are still fitting boards the way we have always done for years

 

[saveloy]

Paul without knowing exactly how you are doing the boards at your work It is hard to comment. But on the face of it, it sounds wrong!! For a start if the lighting circuits have cables buried in the wall less than 50mm, then they should be RCD protected, as should any circuit with buried cables (less than 50mm without earthed steel conduit). The bathroom lighting defintly should.

As for your install it depends on how many circuits there are in the flat. A dual RCD board will comply but you must divide the circuits between RCDs so that nuisance tripping and fault tripping minimises disruption.

In other words if you have two ring mains then put them on seperate rcds. If the kitchen trips it won't take out the other ring. Same with lighting. In a house (I know you are doing a flat) you would put the upstairs ring with the downstairs lights and vice versa so if a trip occurs at least you will still have lights.You can also use RCBO's to protect individual circuits within a dual board to minimise nuisance tripping of other circuits. Make sure they are seperate from the RCD's

The other option you have is to pit every circuit on its own dedicated RCBO. This will only dissconnect the affected circuit. However this can get expensive if you have a lot of circuits.

Here is a good guide from HAGER 17th Edition Consumer Unit Guide Hager
(Download the pdf)


Personally I use Wylex but the principles are the same. Hope this helps.

Blast AL beat me to it Note to self - MUST TYPE FASTER

 

[paulthe spark]

thanx saveloy ill take a look at the link

thanx again saveloy,very helpful link

 

[electricAl]

Obviously, as you`re in Scotland, our Statutory Building Regs don`t necessarily apply to work in your locale.

However, for your firm to be so blase re: Wiring Regs is surprising - seeing as tho` not Statutory, their use is as applicable North of the border as doon here.