Conduit used as earth

[m4tty]

Hi,

Just a quick one. My house has all wiring in conduit sunk into concrete Walls using the conduit as the cpc and my cu is metal. I'm gonna put a split load cu

in for assessment and wondered if the new cu had to be metal?

Cheers

 

[m4tty]

Just checked at the consumer unit and the conduit has bs951 clamps with 4mm earth cable going to the met. Is this ok being just 4mm ?

Thanks

 

[sellers]

are your back boxes metal and bushed onto the conduit? Same with ceiling roses are they conduit boxes behind? If not you may have problems with no earths at class 1 accessories.

I've been to a few house which have a proper full conduit install, MOD houses especially.

 

[wozz]

do u mean dual split? i take it the conduits terminate into the CU?

 

[m4tty]

are your back boxes metal and bushed onto the conduit? Same with ceiling roses bare they conduit boxes behind? If not you may have problems with no earths at class 1 accessories.I've been to a few house which have a proper full conduit install, MOD houses especially.

All backboxes and ceiling roses bushed onto conduit. All class 2 fittings anyway mate. The whole house was wired like it in 1974 it's ex council. Cheers

 

[m4tty]

do u mean dual split? i take it the conduits terminate into the CU?

I'm gonna put a dual split loader in and the conduit is not glanded into cu it's got bs 951 clamps on Them with 4mm earth going to met

 

[m4tty]

Pictures attached. May not be too clear but im no good at explaining things.

Cheers for any help.

ut the kettle on

 

[batty]

Can you attach new consumer unit to conduits?

 

[Lee321]

i'd want to be testing the conduit with a high current tester not seen one for a long time tho

 

[sparkytim]

Yes you can but it looks like whoever put the last one in made a bit of a bodge of it.

Are the conduits just ends in the wall, or into a back box enclosure of some sort?

Looks like just ends with earth clamps on.

 

[m4tty]

Can you attach new consumer unit to conduits?

No as they are behind the consumer unit metal back box (drip tray?) theres an immersion heater above it in the same cupboard. I will have to fit the new consumer unit where the old one is as its inside this metal cabinet but have cables coming in from top bottom back from sides. All singles are from conduit with T&E coming from everywhere else (upgrades)

GuinnessThanks again

 

[m4tty]

Yes you can but it looks like whoever put the last one in made a bit of a bodge of it.Are the conduits just ends in the wall, or into a back box enclosure of some sort?

Looks like just ends with earth clamps on.

Yeah mate your right. Its just ends in the wall with bs951s clamped on with 4mm going to met.

Is this gonna be ok?.

ThanksGuinness

 

[batty]

No reason you cannot use clamps on conduit but i would use 10mm cable to be on safe side although that probably is over the top.

 

[Evans Electric]

Presuming your conduit is wired in X grade cable , how does it get from the conduit to the consumer ?

 

[m4tty]

It just comes out conduit and the singles go through back of cu loose if you get me. Cheers

 

[Evans Electric]

Thats not strictly kosher M4 , singles should be sheathed, when you fit new C/U (which can be plastic) does it seal the space between the C/U and the conduits.

Can you screw earth terminal couplers on to the tubes ,then loop them together with earth wire?

 

[m4tty]

Excuse my ignorance but what are earth terminal couplers and i was going to put a backboard behind the cu which will hide all the cabling. Is that what you meant ? Thanks again

 

[ProDave]

Those pictures are not clear to me. It looks more like a photo of the DNO's incommer than your conduits you are talking about.

Last CU change I did on a house like this (ex council), all the conduits terminated into a large metal box in the wall behind the CU, but you won't know that for sure until you remove the old CU.

In my case a poxy 4mm (or imperial equivalent) earth wire came from an earth stud on said back box to the MET. I just upgraded that to 16mm and all tested well (though as others have said I don't have a high current earth tester which may have given a different reading)

However in a case like this, I satisfy myself that even if not perfect, I am leaving the installation safer than when I found it (in my case new CU with MCB's and RCD in place of old fuse box with rewirable fuses)

 

[m4tty]

Thanks everyone for your comments. Them pictures were the best I could manage as the light was shining off the metal tag on the clamp blinding the photo so sorry but it's the best I can do. Cheers

 

[Evans Electric]

M4tty, Earth couplers are steel, have a terminal as part of the casting with a brass screw. You could connect all the tubes together with cable. Screw 'em on and tighten with grips. Bit of 6mm back to the board.

You can't really have X grade cables floating around without outer sheathing, or they are within an enclosure.

I presume all your back boxes have earth jumpers fitted to the earth terminals. You are supposed to carry out a conduit/trunking test but TBH I would think the Zs is good enough.