Earthing Galvanised conduit boxs in garden

[PhilipKS]

Hi All,

I continue to find curious quirks in my new-ish (2004) install (NICEIC certified installer...).

Garden lighting is installed, off a garage style consumer unit fed from the main cu box. It is protected by a 30mA RCD, and external wiring is 3-core SWA. One of the cores has been used as the earth...fair enough so far.

But the armour is not connected to earth at the consumer unit, consequently the galvanised conduit boxes through the garden where the SWA connects to the low voltage transformers are also not earthed - should they be?

My thought is yes...but...I'm about to have a PME connection provided by EON (no proper earth connection...see earlier posts!!!) and its crossed my mind that if they were earthed would it not be equally potentially dangerous in the event of a neutral supplier fault?

(similar to say bonding a metal outside tap...in prep for which I've just installed a section of 15mm plastic pipe in the copper run to the outside tap to insulate it from the rest of the bonded pipework)

Thoughts?

cheers

 

[holmslaw]

..

 

[ban-all-sheds]

I've just installed a section of 15mm plastic pipe in the copper run to the outside tap to insulate it from the rest of the bonded pipework

How long a section?

 

[securespark]

Holms. I think the SWA is glanded at its destination, but not at the CU.

What was this guy doing, doing this work when the earthing was not tip-top to start with??

And I hope he used CW glands not BW...

 

[jason1958]

Did the the NICEIC himself do the work or subby it and act as QA?

- SWA armour should be earthed correctly via a gland at supply-end
- Glands outside must be CW, inside you can use BW (saves little TBH)

If any other work was done, it might be worth checking further.
For example whether the certificate figures are correct.

 

[Taylortwocities]

Did the the NICEIC himself do the work or subby it and act as QA?

- SWA armour should be earthed correctly via a gland at supply-end
- Glands outside must be CW, inside you can use BW (saves little TBH)

If any other work was done, it might be worth checking further.
For example whether the certificate figures are correct.

Aye, and what colour certificate did you get?

 

[PhilipKS]

Right - thanks for the replies so far!

I've checked the system again, some more info

Holmslaw

cu the gland should be fastened through a banjo ring that is also bolted to the cu and has a separate earth wire

The main house cu is plastic, the gland is bolted to the case but no earth wire... This then goes outside (above ground fixed to house wall) and back inside to a small garage unit. This is a metal box and has the banjo ring...but no earth wire. The metal case is fixed to the earth block, so there is 'some earth' there .

Another SWA goes out from there to a socket in a workshop, again gland bolted to the box (no earth cable)

Untitled

• PhilipKS
• 27 Apr 2009
• 1

But the garden lighting circuits go to wall switch, with switch live going up to a plastic junction box in the loft in T&E, where is connects back to the SWA

Untitled

• PhilipKS
• 27 Apr 2009
• 2

I've pulled the plastic back to show the connection which appears ok (except no earth again)

From there its into the garden where the SWA terminates in various conduit boxes eg

Untitled

• PhilipKS
• 27 Apr 2009
• 1

Appear to be connected up correctly.

So...I'm pretty sure the conduits aren't earthed. What should be done at the cu's to improve the earth?

Ban-all-sheds

How long a section?

About 7" (plus a speedfit straight connector) - is that enough to isolate?

Jason 1958

Did the the NICEIC himself do the work or subby it and act as QA?

Don't know sorry, all done by the previous owners, perhaps he got his mate 'blind bob' to do it...

Taylortwocities

Aye, and what colour certificate did you get?

Black & white (a.k.a a photocopy!) one of the docs supplied with the house sale, my wife did speak to the sparks though and he does exist!

Hey ho the plot thickens!
Thanks all
Philip

 

[plugwash]

Personally I would say the best thing to do is make sure the outside lighting system is RCD protected then earth it with a seperate rod kept away from any metal that connects to the PME earth.

If you go down this road make sure you clearly label that there are two deliberately seperate earthing systems and test the rod gives an adequate earth.

 

[ban-all-sheds]

About 7" (plus a speedfit straight connector) - is that enough to isolate?

Hmmm...

About 3kΩ.

I wouldn't fancy it.

 

[holmslaw]

..

 

[londonboy]

Sorry for me stating the obvious but had the op checked the flyleads aren't inside the cu? He might be expecting to see them on the outside.
As for the blue being used as a line, at least its sleeved!
Should the 12v transformer be installed outside though? I thought these usually have 'indoor use only' written on them.

 

[RF Lighting]

That hager CU is metal clad, and the banjo is bolted to it.

You only have to earth SWA at one end providing there is an earth running within the cable.

 

[londonboy]

That hager CU is metal clad, and the banjo is bolted to it.

Will open my eyes in future!

 

[Taylortwocities]

He has used the wrong type of gland externally because they are not weatherproof (type CW). .

Those boxes are in the loft

he said

a plastic junction box in the loft in T&E, where is connects back to the SWA

So use of BW glands is fine.

 

[holmslaw]

..