Adding a further TT Earth Rod to garage

[securespark]

It's actually not what I would call conduit. It's something I believe they used in times gone by. It is a fairly thin copper tube (~5mm) which I believe has an inner sort of ceramic insulator. This goes to a metal junction box with a metal gland and the box is earthed so the pipe will be. From there it goes with a short cable to the consumer box. But this is probably my biggest area of concern in that the concrete above it is cracked (not sure how deep the pipe is) but the earth wire in that is all that carries it to the garage, so if that alone broke (it's very old) there would be no earth. I'd assumed that if I put in another earth spike any short would take the path of least resistance to ground which would be either to that one or the existing depending, but if the single earth wire were to be damaged the external circuit would have a backup from the new spike and the external consumer unit. In the long run I will probably get the electrician to put a new external supply to it as I noticed there are spare connections on a Henley block in the Consumer unit but thought this might be a simple interim measure.

OK.
Sounds like you have a length of MICC cable. A copper sheath filled with a hygroscopic compound (Magnesium Oxide) compressed around the conductors.
To have a fusebox with 32A and 6A CPD's on the end of a spur off a ring final is pointless. And you can't really have MICC cable buried direct in the ground. It is fragile and once damaged, moisture will easily penetrate the Magnesium Oxide and cause a short circuit.

 

[ban-all-sheds]

Scenario

It is late, dark and you need lights in the garage but there is a reason to switch of power to the sockets without losing the electic lights

OK, go on then.

Propose a remotely feasible set of circumstances which would create that scenario, and try to estimate their probability, citing evidence if possible.

 

[ban-all-sheds]

no doubt before the 2003 regs as some wires are red and black.

2006.

(I'm more concerned about disruption than cost, to be honest, as it has a concrete floor)

There's a good chance that all the cables drop down the walls from the 1st floor.

I am in a belt of very heavy clay which is good (except for gardening!).

It's hard work, but AIUI, clay soil is pretty good for growing.

 

[fairplay]

Yes, I think it is MICC cable. I didn't put it here hence my concern although it's clearly survived for some time. Sorry, yes 2006. That will be the cables dropping down the newly plastered walls in the refurbished lounge then and so I meant no way of getting new cables in from below. And yes , not good for gardening in the sense of waterlogged and heavy but good in the sense things grow well with a lot of work. Gardening I'm ok with.

 

[ban-all-sheds]

That will be the cables dropping down the newly plastered walls in the refurbished lounge then and so I meant no way of getting new cables in from below.

That can often be a problem if refurbishing and plastering etc are done before any electrical work is considered

And yes , not good for gardening in the sense of waterlogged and heavy

I could grow rice in my garden in the rainy season.

but good in the sense things grow well with a lot of work. Gardening I'm ok with.

I believe the solution is years of digging well-rotted manure, compost, and similar materials into the soil.

 

[securespark]

I could grow rice in my garden in the rainy season.

You mean from January to December?

 

[ban-all-sheds]

I live in west London, and I have known rain alone (i.e. no overflowing of rivers) to flood my entire garden to a depth of several inches.

 

[fairplay]

That can often be a problem if refurbishing and plastering etc are done before any electrical work is considered

It was considered and what was needed for the lights was done. I'm confident that the ring main cables themselves are in good condition so if the testing shows any faults there are ways round it hopefully.

 

[securespark]

That can often be a problem if refurbishing and plastering etc are done before any electrical work is considered

It was considered and what was needed for the lights was done. I'm confident that the ring main cables themselves are in good condition so if the testing shows any faults there are ways round it hopefully.