Tails and Main Earth

[imroberts]

I'm in the process of becoming registered and have been looking at existing installations and thinking through the logistics of how work would be carried out.

One example I've looked at is my mother's installation, which is an old type Wylex fuse board which she's wanted upgrading for some time. The installation is PME with 16mm meter tails and what looks like a 4mm or 6mm earth running from cutout to CU.

Obviously the tails need upgrading to 25mm with a CU change, and the main earth to 16mm.

What I'd assumed before I actually looked at the installation was that I'd get the supplier to fit an isolating switch, thus giving me the flexibility to replace the CU and tails at my convenience (probably an evening or weekend). But how do I go about upgrading the main earth?

 

[OwainDIYer]

You supply a 16mm earth cable from your main earth terminal (probably CU earth bar) which the DNO may connect into the cutout when he fixes the isolator.

On modern cutouts the earth is accessible without removing the phase cover.

 

[EFLImpudence]

Obviously the tails need upgrading to 25mm with a CU change, and the main earth to 16mm.

Not necessarily.

Study the regulations - not guides which are one size fits all without having to think.

 

[sparkybird]

And depending on your location your supplier may not be at all interested in fitting an isolating switch

 

[PrenticeBoyofDerry]

Your best bet is to call both the supplier and the DNO and ask them about upgrading the earth conductor and installing an isolator.
Some vary in what they will do or not do, charge or not charge!

 

[scousespark]

Slightly off topic, but as a newbie I suggest you change the board over one weekend. Your mum won't be too impressed if you start after tea and hit a problem.

 

[bernardgreen]

Slightly off topic, but as a newbie I suggest you change the board over one weekend. Your mum won't be too impressed if you start after tea and hit a problem.

Damn good advice..... It also means you have day light to work in.

Depending on cable lengths and location it might be possible to fit the new CU in place, feed it from a fuse / MCB in the original CU and transfer circuits one at a time from original to new. The tails from are long enough to reach the meter but go to a pair of henley blocks which are fed from the MCB in the original CU

Thus the work can be spread over several days ( or weeks ) with minimum inconvenience. Using a 32 Amp MCB to feed the new CU allows almost the entire installation to be transfered other than any heavy loads such as electric showers. (and range master cookers )