Split load CU required for loft conversion?

[bendavies]

We're in the process of converting our loft to a bedroom with en-suite.

I've been informed that any electrics installed as part of this will not pass a test/ regulations unless the house is upgraded to a split load CU.

I've already run a new seperate ring main, lighting circuit, and fire alarm circuit through the house up to the new floor in preparation for the work.

The current CU is a recent installation (Wylex 16way), and has had the main switch replaced with a 100A 30mA RCD (also Wylex, designed for the board).

As an RCD is already protecting all circuits, why would I need to replace the CU for a split load one? Am I being fed false info about regulations?

The RCD was put in at the outset, when we moved into the house, partly due to the apalling state of the wiring at the time... All of this is now repaired, but I would still prefer to keep it over the whole board.

Many thanks for any replies!

Ben

 

[Adam_151]

I don't really think there is anything to force you to change it, unless you find yourself neededing extra ways and with 16, well.... anyway ... let me explain in more detail

There is nothing that says you have to bring existing stuff upto scratch, however if you add anymore, that new should be to standard and it should be checked that the existing can support any extra load and that earthing and bonding is reasonably upto scratch

one you may fall fowl of is: there is a regulation which requires circuits to be arranged to minimise inconvenience, it is the view of the NICEIC that whole board RCDs where the lights are on it as well, don't comply with this, whether or not you share that same view varies between electricians...

So, its possible that you might not need a new board [depending on interpretations of the light thing*] , it might be sensible while you are having work done to change over to a split arrrangement, the cost in your case should be minimal, if you can buy a wylex split load without RCD (I'm not sure, but they are only about £60 with 30ma, 80A RCD) and reuse your RCD, and of course as long as its the latest range your MCBs will be re-useable

Though if you have a TT (earth from electrode bashed into the ground in the garden) supply, you would also need a 100ma 100A time delay RCD


* Do consider carefully the possible danger of tripping down stairs etc if it nuisense trips (remember that as quite a lot of suff these days has a leakage to earth when working correcting, a house of the size to need a 16way board might not be best served by an overall 30ma from a nuisense tripping POV)

 

[JohnD]

Rather than go to the trouble and expense of buying and installing a new CU, I would be more in favour of fitting RCBOs to the circuits that need RCD protection - presumably the downstairs sockets and the electric shower if you have one.

If you like, you could put an RCBO on the upstairs sockets as well.

Like Adam says, it will be very inconvenient if you have a minor fault on one circuit (or an accumulation of small leakages from the outside lamp, the immersion heater, the cooker and the washing machine) that trips the whole house and means you lose all power on all circuits. It will be especially tiresome if you have a N/E fault that you cannot isolate by turning off the MCBs.

Do you have any outside circuits (apart from lighting) or outbuildings?



RCBOs are great

 

[bendavies]

Thanks very much for the condsidered replies, guys! This is certainly a great forum - I'm sorry I haven't joined up sooner!

I think the advice I'd been given must have been an interpretation of the "arange to minimize inconvenience" rule that you mention, Adam.

Thinking more about both your responses, it may well be in my interests to change things around again, particularly now that the rest of the wiring in the house is up to scratch! (Errant halves of ring mains are now re-united, no thanks to the previous owners!!!)

It is a small house (will be 3 bedroom!) - the main reason for the large CU was the addition of 2 DIN mounting X10 dimmers for the living room lights, which take up a large amount of space!

As you say, I can do it fairly cheaply re-using all the expensive bits!

 

[dingbat]

And another thing - you should not put fire/smoke alarms on a whole house 30mA RCD.

Adam said.

there is a regulation which requires circuits to be arranged to minimise inconvenience, it is the view of the NICEIC that whole board RCDs where the lights are on it as well, don't comply with this, whether or not you share that same view varies between electricians...

It's not just a NIC view; it's frowned on by everybody - electricians who don't agree probably think that Part P introduces new wiring regulations or that suddenly they can't rewire their own house or that kitchen sinks must be bonded... in 6 sq mm... etc