family argument about SWA

[SparkyTris]

when did it become "the law" to run cables across gardens in SWA?

The reason I ask is, many years ago, a detached garage electric supply was allegedly repaired by a trusted local electrician. (after the original 1930s probably rubber or textile cable + steel conduit broke)

About 10 years ago, I discovered that this supply was in fact 4mm PVC/aluminium singles run in a shallow ditch in plastic conduit.

I have now replaced this with SWA but my contention was that it would never have been done like that by a proper electrician, so somebody else must have done it - unless it was acceptable at the time (mid 1980s) to run non-armoured cable around underground.

My replacing the cable with SWA resulted in another argument about the depth of burial requirement. Is there a depth of burial for SWA across private property specified in the regs?

 

[ban-all-sheds]

when did it become "the law" to run cables across gardens in SWA?

Never.

my contention was that it would never have been done like that by a proper electrician

Sounds reasonable.

unless it was acceptable at the time (mid 1980s) to run non-armoured cable around underground.

Not really.

Is there a depth of burial for SWA across private property specified in the regs?

Yes.

Have you looked?

 

[securespark]

Aluminium suggests 1970's, not 80's...

 

[securespark]

According to the 14th Edition (1966-1981), cables (whether rubber or pvc) laid in non-metallic conduit have to be insulated and sheathed. Singles do not comply.

Cables must have been installed at a depth of at least 18 inches. Cable covers conforming to BS2484 or equivalent mechanical protection was desirable.

 

[sparkwright]

I seem to recall it was not unusual to encase a twin and earth cable in loose bricks, topped with bricks or paving slabs, underground.

 

[JohnW2]

I seem to recall it was not unusual to encase a twin and earth cable in loose bricks, topped with bricks or paving slabs, underground.

If I recall correctly, at least some DIY books back then (I must still have some of them, so may try to have a look!) advised burying T+E in hosepipe.

I also recall that, even then, I thought that a bit silly, in as much as the hose pipe would provide minimal 'mechanical protection' but was also unnecessary in terms of insulation (since the T+E was already adequately insulated) - so achieved very little.

Kind Regards, John

 

[John D v2.0]

so achieved very little.

Not true, actually it's disguised a dangerous cable to look like a benign bit of hose pipe.
I saw a recent safety alert about cable colours because someone had used blue cable underground and it looked just like 25mm mdpe. Electric cable was supposed to be red or back underground.

 

[SparkyTris]

Yes.

Have you looked?

Mea Culpa, I have not looked, my book is 700 miles away, but I have an internet here so I thought I'd ask the helpful people on DIYnot electrical forum. Many "thanks" for your "help".

 

[JohnW2]

Not true, actually it's disguised a dangerous cable to look like a benign bit of hose pipe.

As I would have thought was evident from my words and context, when I wrote that it "... achieved very little', I meant that it "...achieved very little that was beneficial". One does not often try to 'achieve' something detrimental

Kind Regards, John

 

[SparkyTris]

According to the 14th Edition (1966-1981), cables (whether rubber or pvc) laid in non-metallic conduit have to be insulated and sheathed. Singles do not comply.

Cables must have been installed at a depth of at least 18 inches. Cable covers conforming to BS2484 or equivalent mechanical protection was desirable.

Interesting, and thanks for this. This implies that it was indeed permissible to lay unarmoured cable underground?

 

[JohnW2]

This implies that it was indeed permissible to lay unarmoured cable underground?

It still is, if it is adequately protected against mechanical damage.

In fact, even SWA does not afford much protection against determined attacks with, say, a spade (let alone 'machines'). The main value is that anything metallic penetrating it should touch the earthed armour as well as live conductors, and therefore should cause a protective device (e.g. MCB or fuse) to operate.

Kind Regards, John

 

[SparkyTris]

Very interesting. That... seems curious.
Yes, I totally get that the wire armour's main value is in providing a reliable earth path leading to disconnect in the event of tool penetration. I guess I thought that particular aspect of it might have been a regulation

 

[JohnW2]

Very interesting. That... seems curious. ... Yes, I totally get that the wire armour's main value is in providing a reliable earth path leading to disconnect in the event of tool penetration. I guess I thought that particular aspect of it might have been a regulation

Even today, the requirement is essentially that a buried cable should have either adequate protection against mechanical damage or have an earthed outer sheath/armour.

Kind Regards, John

 

[EFLImpudence]

Yes, I totally get that the wire armour's main value is in providing a reliable earth path leading to disconnect in the event of tool penetration.

A CPC has a reliable earth path.

It's more that live conductors cannot be contacted without first contacting the earthed covering.

The armour is in my opinion a misnomer.

 

[Mottie]

If I recall correctly, at least some DIY books back then (I must still have some of them, so may try to have a look!) advised burying T+E in hosepipe.

The supply to my garage is run in hosepipe. Been there since before we moved in in 1990 and it was the stranded T&E cable, so well old. My mate accidentally just slightly nicked it with a kango drill when digging out a concrete fence post a year or so ago and it started sparking away before I switched it off at the consumer unit. Would have been a major job to dig about 8m of concrete ground up and do it properly so we just pulled it all out and dragged a fresh length of 2.5 cable through. Only runs a light and a single socket in the garage - not ideal but better than an extension lead and the old one had lasted at least thirty years so good enough for what I need.