Replacing an old CU with a new one

[Naz1977]

Wrong way - testing (and any required repairs) first, replacement CU afterwards.

Before that, as an absolute minimum the old VOELCB should be removed and a 100mA RCD installed in it's place. That isn't technically compliant but will ensure that power is disconnected in the event of a fault.

Testing was done last year and the only item picked on it was the fact that no RCD protection was provided on the Ring main and lighting circuits. The rest were tested ok. And since the sockets were plastic, this was forgotten about. The only place with metal equipment, Fridge/Dishwasher/Wasing Machine/Kettle and ... was the kitchen which had RCBO fitted.

Testing this year: Still waiting for the EICR from the leccy but won't be holding my breath as he said it was a failure due to incorrect size of the earth spike cable! Needed 10mm even though it is not buried and protected! Gonna wait and see if he sends me his report and then if thats the only item on it, politely send him a note to refer him to OSG for the size of the conductor.

The only 100mA RCDs I can see are designed for DIN rail mounting. As the contacts won't be covered by protection, it will be a safety issue to have that fitted outside the CU. Do you have any links to ones that can be installed outside the CU? Unless I get a single Unit enclosure and mount it inside it?

 

[aptsys]

You can get small enclosures exactly for that purpose.

https://www.tlc-direct.co.uk/Products/WYESE2.html

 

[securespark]

This is a bit easier to fit, as regards the tails:
https://www.tlc-direct.co.uk/Produc...Xgi_S0grv0yZx3gECWg8TBJFv68YINee5YhoCXWvw_wcB

 

[flameport]

Testing was done last year and the only item picked on it was the fact that no RCD protection was provided on the Ring main and lighting circuits.

What does that report say about the earthing type and the earth loop impedance?

 

[Naz1977]

This is a bit easier to fit, as regards the tails:
https://www.tlc-direct.co.uk/Produc...Xgi_S0grv0yZx3gECWg8TBJFv68YINee5YhoCXWvw_wcB

That look good. Thanks mate. Shame SF don't sell these as a lot easier for me to go collect from them!

 

[securespark]

Where else is near you?

Any wholesalers?

 

[Naz1977]

Looking at the regs again last night,

3.5.3 : Says as it is a TT circuit, the disconnection time can only be achieved by means of RCD on the required circuits, which is again mentioned in Reg 3.6.1 (i)
3.6.2 (b) TT Installations says that 30mA RCD needs to protect the shower, socket outlets not exceeding 20A and outdoor equipment. The rest need a 100mA RCD. However 3.6.2(d) allows the use od double 30mA RCDs which is what I will be using.

9.3.1 (iv): For TT system Fault loop impedance doesn't need to be measured and instead it is the Earth Electrode Resistance.

R1+R2 will be measured using test1.

According to the initial EICR, The system is TT which is correct.
The Nominal Voltage 247
Fre 50
Fault Current: 0.87kA
External Loop Impedance ( Ze): 1.87Ohms ( Doesn't say if it is measured or declared from supplier)
Electrode resitance to earth : Not measured
Earthing Conductor: 6mm
Main Bonding Conductor: 10mm

 

[Naz1977]

Where else is near you?

Any wholesalers?

I have CEF or YESS electrical

I am in York

 

[John D v2.0]

That nominal voltage is wrong and the ze is basically impossible for TT. Plus he appears to have failed to spot a potentially dangerous defect ie no disconnection of sockets circuits causing exposed live parts on a fault.

 

[securespark]

He seems to have filled it in as if it were a TN- supply...

 

[securespark]

I have CEF or YESS electrical

I am in York

Can't find that product on either website.

 

[ban-all-sheds]

Well he turned out to be a bit of d1ck.

But you have got a replacement, surely?

 

[ban-all-sheds]

I will just go ahead and replace it myself

You do not know enough to be doing that.

If they take too much f**** around, I will just break the seal and remove the fuse

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

That anybody here is saying anything to you except "get an electrician" is shamefully irresponsible.

 

[flameport]

The Nominal Voltage 247

Wrong, it's 230.

Fre 50

Correct

Fault Current: 0.87kA

If measured at the origin, that is rather low.

External Loop Impedance ( Ze): 1.87Ohms ( Doesn't say if it is measured or declared from supplier)

Not impossible but exceptionally unlikely in a domestic property. Perhaps tested with main bonding in place and one or more of your neighbours has a TNCS/TNS supply.

Electrode resitance to earth : Not measured

The most important item for a TT supply was not measured.

The book you are incorrectly quoting from isn't the regulations either, it's an out of date version of the on site guide or some other unionised equivalent.

 

[securespark]

That's me. Shamefully irresponsible.