External garage wiring - above ground

[mijfife]

Hi all, I've referred to this excellent forum on many occasions and so far, have always found the answers to my questions through the search facility but I'm struggling a bit this time!
I have a garage next to my flat which had a power supply fitted to it over 15 years ago. The electrician used what I believe is some sort of fire resistant cable - orange sheathed copper with two internal copper stands set in a chalky/ceramic type substance. This runs from a second consumer unit in my first floor flat and spans the gap between flat & garage (5 1/2 ft) sitting inside a galvanised steel channel bolted to both structures at a height of about 9ft above the ground.
This weekend, the power to the garage has started tripping out constantly, I suspect the cable has degraded somewhere allowing water ingress as it does this with the c/u in the garage completely switched off. The garage side was completely rewired a couple of years ago.

Anyway, my question(s) is this - am I required to use SWA for the short run outside between the buildings with the above set up or would twin & earth be okay in a suitable conduit (what?)
If I do have to use SWA, can I joint this to twin & earth as soon as it enters both buildings as it has to run around a few corners and that ain't gonna happen with the SWA!
I have had a look using the search but most outside installations seem to be sheds & garages a good few meters away from the house and at much lower heights than mine. I should also mention, I'm in Central Scotland.

Any advice greatly appreciated

Regards, Jim

 

[Chri5]

Since there is little chance of mechanical damage SWA is a bit OTT- I'd suggest hi-tuf which is a double sheathed cable suitable for external use.

The old cable you mention is pyro.

Hi tuf is more flexible than SWA and I would suggest you run this the whole way from CU to CU, junctions should be avoided because they simply give additional points of potential failure.

http://www.tlc-direct.co.uk/Products/HT2dot5slash3.html

2.5mm 3 core should be fused at 20 amp max at the house cu.

 

[ban-all-sheds]

2.5mm 3 core should be fused at 20 amp max at the house cu.

Will that be enough for the load in the garage, and OK for volt-drop?

 

[electronicsuk]

I have a garage next to my flat which had a power supply fitted to it over 15 years ago. The electrician used what I believe is some sort of fire resistant cable - orange sheathed copper with two internal copper stands set in a chalky/ceramic type substance.

Jim; I find it odd that you don't know pyro cable when you see it, yet you seem to know a fair bit about the internal construction. If you've worked on this cable yourself in the past and haven't terminated and potted the ends correctly, then it very well could have succumbed to water damage - the magnesium oxide powder you describe is highly hygroscopic. If terminated properly, pyro should outlast almost any other PVC cable you care to name.

 

[Chri5]

2.5mm 3 core should be fused at 20 amp max at the house cu.

Will that be enough for the load in the garage, and OK for volt-drop?

The gap between garage and build is 5.5 ft, so I was working on the assumption that the total run would be 20-30 ft odd.
Certainly nothing to get concerned about any issues with distance !

I would accept that since it's a pyro cable, it may well have a longer external route (I'd gone point to point, cu central in a flat). The CU might be by the front doors at the opposite end to the garage.

So if the OP reads this, please confirm the cable end to end distance, so we can confirm the load available and the fuse requirements.

You could give me a knock for not spotting that the support height should be 3.5m high, where as the OP mentions 9ft.

 

[mijfife]

Hi guys, thanks very much for all the helpful replies

It was indeed water ingress at the end of the cable. I've managed to cut back passed the damaged bit and replace from there to the garage C/U with a longer bit of T&E in conduit. I've had to reuse the old pot on the pyro for now (I couldn't for the life of me remember what it was called earlier ) but I'll replace this asap. I've also rerouted the pyro a bit so it should be less susceptible to dampness getting into the end as well.

Thanks again, cheers Jim