Replacing an old CU with a new one

[John D v2.0]

But I am merely upgrading/changing a like for like CU be it more up to date with more protection. I am NOT running any new feeds/circuits!

As always, you have stated something and its contradiction in close proximity. Changing a protective device is effectively a complete new circuit using the existing wiring.

Assuming you've read and understood every aspect of the wiring regulations, think about what happens to the trip time of an MCB if the loop impedence is high? Even an old style fuse wire gives more protection in that situation.

Hopefully your over confidence/cockiness wont cause a dangerous situation. It's a shame you think any random assumptions that occur to you are definitely true.

 

[ban-all-sheds]

That you either don't know or don't care about that is yet more proof that you should not be doing this work.

Oh look - even more proof:

IF I was designing a whole new installation, then fair enough. But I am merely upgrading/changing a like for like CU be it more up to date with more protection. I am NOT running any new feeds/circuits!

 

[rules&rulers]

This thread was answered in post number 2

Why keep going ?

 

[Naz1977]

Securepsark and aptsys, Thanks for the headsup guys.

Removed the cover on the breaker and there is indeed an earth connected to it. It is hidden behind the board which is why I couldn't see it.

This sort of puts my mind at rest that the breaker is now doing what it should be doing to some extend.

I am nevertheless going to replace it with a new RCD unit. Will first speak with the northern power to see if they are prepared to install one as I don't think they install one on TT setups by default.

If they don't, I will see how much they would charge to get one installed instead of getting them to come out and isolate mains whilst I replace mine.

 

[ban-all-sheds]

This thread was answered in post number 2

Why keep going ?

Because Naz didn't think it was the right answer, so he decided to treat us to page after page of proof that it really was.

 

[aptsys]

Securepsark and aptsys, Thanks for the headsup guys.

Removed the cover on the breaker and there is indeed an earth connected to it. It is hidden behind the board which is why I couldn't see it.

This sort of puts my mind at rest that the breaker is now doing what it should be doing to some extend.

I am nevertheless going to replace it with a new RCD unit. Will first speak with the northern power to see if they are prepared to install one as I don't think they install one on TT setups by default.

If they don't, I will see how much they would charge to get one installed instead of getting them to come out and isolate mains whilst I replace mine.

I think you'd be best off to buy the 100mA time delayed RCD and enclosure and ask them to fit. They almost certainly will not provide anything other than a plain two pole isolator.

 

[EFLImpudence]

It should be 30mA.

 

[rules&rulers]

Because Naz didn't think it was the right answer, so he decided to treat us to page after page of proof that it really was.

Some people dont want to accept the truth,what is Naz hiding ?

 

[Adam_151]

This sort of puts my mind at rest that the breaker is now doing what it should be doing to some extend.

I am not 100% sure on the terminal layout of your device, but normally the E and F terminals on those are normally on the top and bottom of the device, not next to each other, so it looks like both are connected to same terminal, is this correct?

If so, it'll not be doing anything.

 

[securespark]

Looks like both what are connected to the same terminal?

EFLI, isn't a 100mA S type mounted in an insulated enclosure compliant on surface-mounted tails?

 

[EFLImpudence]

It depends why it is there.

Won't it be (not reading it all again) an up front RCD for personal protection?

 

[Naz1977]

Looks like both what are connected to the same terminal?

EFLI, isn't a 100mA S type mounted in an insulated enclosure compliant on surface-mounted tails?

There are 2 separate contacts at the bottom and not connected to the same port. I will double check.

 

[Naz1977]

It depends why it is there.

Won't it be (not reading it all again) an up front RCD for personal protection?

Yes, it will be an upfront RCD, to provide overall protection and also means of safely isolating power from the whole CU should it ever be needed in future ( like changing the main switch if it fails and ... )

 

[Naz1977]

I think you'd be best off to buy the 100mA time delayed RCD and enclosure and ask them to fit. They almost certainly will not provide anything other than a plain two pole isolator.

As the main fuse is 80A, do I go for the 80A RCD or do I get the 100A RCD as I will like to get it replaced with 100A fuse when I do extend upstairs in about 12-48 months time. If the authorities have to come and isolate mains, is it worth asking them to fit a 100A fuse?

 

[aptsys]

It depends why it is there.

Won't it be (not reading it all again) an up front RCD for personal protection?

I was (perhaps wrongly) assuming he's be installing a split or mixed RCD/RCBO consumer unit.