External Electrics, cable

[Mary1234]

Hi all, I'm after a second opinion before I allow somebody to do the work on my garden in Yorkshire.
I got a few quotes from qualified electricians to run electrics from the house to a garden room (approximately 6m away). Each electrician (including the one I instructed) made mention of the need for an armoured cable for the run from the house to the garden room. It will be buried under the lawn.
However, when the electrician started the work we noticed that he was not using armoured cable. We queried this and he said that it isn't necessary, providing the right cable size is used, has an isolation fused spur inside the house and is protected by the RCD of the consumer unit. Is this correct?

 

[Cid]

If he quoted for an armoured cable then that is what should be used!

However armoured cable is not necessary provided it's adequately protected, ie in conduit

 

[Lucien Nunes]

The cable must be suitable for the purpose to which it is put. Do you know what type of cable it is, and how it is being protected? A picture would help...

 

[ruston]

What kind of cable has he supplied , this may have an influence between the quotes and given him an advantage.
I agree with @Cid , he should supply what he has quoted for or better.

 

[Strima]

As above, we need pictures of the cable.

 

[Midwest]

If he quoted for an armoured cable then that is what should be used!

However armoured cable is not necessary provided it's adequately protected, ie in conduit

I'd use swa cable as well, but I would also install in some twin walled ducting, as its being buried under ground.

 

[Pete999]

I'd use swa cable as well, but I would also install in some twin walled ducting, as its being buried under ground.

What is twin walled ducting?

 

[Mary1234]

Thanks all, I check on the cable when I get home tonight. He was planning on burying it in some flexi hose, so that wouldn't protect it in any way. My concern was about somebody putting a spade through it or something in the future.
I'll check and get back to you
[automerge]1575392018[/automerge]

Thanks all, I check on the cable when I get home tonight. He was planning on burying it in some plastic flexi hose, so that wouldn't protect it in any way. My concern was about somebody putting a spade through it or something in the future.
I'll check and get back to you

 

[Midwest]

What is twin walled ducting?

This stuff;

50mm Twin Walled Cable Duct - Black | Univolt (FXKVR 50)

Edit: I've even used some large diameter water pipe, but this stuff is more easer to manhandle.

 

[Pete999]

This stuff;

50mm Twin Walled Cable Duct - Black | Univolt (FXKVR 50)

Ah right never heard it called that before

 

[davesparks]

However, when the electrician started the work we noticed that he was not using armoured cable. We queried this and he said that it isn't necessary, providing the right cable size is used, has an isolation fused spur inside the house and is protected by the RCD of the consumer unit. Is this correct?

Cable size, type of isolator and RCD protection have nothing to do with what can, or cannot be buried underground.

Any directly buried cable must be approved by the manufacturer for such use and the regulations require that the cable have an earthed metallic screen or armour (which must be capable of handling the maximum fault current)
Alternatively the regulations allow underground cables to be in a suitable duct (the duct must comply with the British standards mentioned in tbe regulations) and the cable would need to be approved for this use by the manufacturer.

Steel Wire Armoured (SWA) cable satisfies the requirements for direct burial and is the most commonly used cable for this purpose.
There are other types of cable which comply but you won't normally find them used on a domestic installation or commonly available.

 

[Midwest]

Steel Wire Armoured (SWA) cable satisfies the requirements for direct burial and is the most commonly used cable for this purpose.
There are other types of cable which comply but you won't normally find them used on a domestic installation or commonly available.

I know your picky about being picky, but some cable manufacturers don’t recommend installing their swa cables direct in ground with high water content, e.g. under a lawn. Hence the recommendation to use ducting.

 

[davesparks]

I know your picky about being picky, but some cable manufacturers don’t recommend installing their swa cables direct in ground with high water content, e.g. under a lawn. Hence the recommendation to use ducting.

I've never come across that before, do you have any examples?
SWA is not suitable for long term immersion in water and most state this, but I've not yet seen reference made to wet ground or lawns.

It does make some sense, but it's hard to know how wet is too wet.

 

[Megawatt]

Hi all, I'm after a second opinion before I allow somebody to do the work on my garden in Yorkshire.
I got a few quotes from qualified electricians to run electrics from the house to a garden room (approximately 6m away). Each electrician (including the one I instructed) made mention of the need for an armoured cable for the run from the house to the garden room. It will be buried under the lawn.
However, when the electrician started the work we noticed that he was not using armoured cable. We queried this and he said that it isn't necessary, providing the right cable size is used, has an isolation fused spur inside the house and is protected by the RCD of the consumer unit. Is this correct?

No he quoted you a higher price cable and used a cheaper one

 

[Midwest]

I've never come across that before, do you have any examples?
SWA is not suitable for long term immersion in water and most state this, but I've not yet seen reference made to wet ground or lawns.

It does make some sense, but it's hard to know how wet is too wet.

Here’s one such piece I read on the subject;

Electric Cables in Water?

Electric Cables in Water?

www.whyprysmian.co.uk

You’ll note it suggests MDPE Sheathed Cable as more suitable for water logged soil.

 

[richy3333]

It does make some sense, but it's hard to know how wet is too wet.

You've never had a Scottish lass have ya

 

[suffolkspark]

@Mary1234 I'd get this nipped in the bud hes doing it wrong....

 

[davesparks]

Here’s one such piece I read on the subject;

Electric Cables in Water?

Electric Cables in Water?

www.whyprysmian.co.uk

You’ll note it suggests MDPE Sheathed Cable as more suitable for water logged soil.

Interesting, MDPE seems like a logical choice as it's used for water and gas pipes, though I'm sure it comes with it's own set of problems.

Yellow MDPE gas pipes aren't allowed to be exposed to sunlight due to UV degradation, so I wonder how much better a black cable would be?

Maybe it's time to bring back lead sheathed cables for direct burial

 

[Mary1234]

Thanks all, it’s a H6242Y cable in a black hose. Photo attached...
Mary

 

[richy3333]

Rough as! And its not an armoured cable you were priced for