No earth... Zs and rcd

[james king]

Hello,

Just a quick q....

Went to change a cu and carried out a few test and visual inspections. Found a problam, I think the cable was micc but couldn't tell as none of ends were made off. All cables for all circuits where 2 core NO earth. Zs test on sockets came out with >99kohms....

No I am have a argument with another spark... I think there is no point in installing a rcd cu yet as it wouldn't make any differnce...

What do u all think?

 

[Engineer54]

Hello,

Just a quick q....

Went to change a cu and carried out a few test and visual inspections. Found a problam, I think the cable was micc but couldn't tell as none of ends were made off. All cables for all circuits where 2 core NO earth. Zs test on sockets came out with >99kohms....

No I am have a argument with another spark... I think there is no point in installing a rcd cu yet as it wouldn't make any differnce...

What do u all think?

I think you need a bit more explaining to do here?? lol!!

 

[james king]

No cct have an earth... But they are protected by mcb.

It's tncs supply.

It's a very old installation. The rcd will not work properly if there is no earth present correct?

At the sockets it's just 2 black cables coming through in to the back box..

Same as it enters the cu.

 

[Engineer54]

I was talking about the maybe MICC cable and the ends not being made of?? What about bonding conductors, are they in place??

 

[james king]

Yes 4mm to water. 6mm main earth.... 16mm tails.

No gas in property

 

[Geoffsd]

RCDs don't need a CPC to operate.

You can be the earth.

 

[rmdes]

Socket outlets must be earthed, tell them they have to be rewired if there not interested then don't touch it, it will come back to haunt you when something goes wrong and you've altered a potentially dangerous installation

 

[Deleted member 9648]

Hello,

Just a quick q....

Went to change a cu and carried out a few test and visual inspections. Found a problam, I think the cable was micc but couldn't tell as none of ends were made off. All cables for all circuits where 2 core NO earth. Zs test on sockets came out with >99kohms....

No I am have a argument with another spark... I think there is no point in installing a rcd cu yet as it wouldn't make any differnce...

What do u all think?

How can you not tell an MICC FFS?


If nothing at all is earthed.....either sort it and then change the cu, or dont touch it at all.

 

[tigerpaul]

If its MICC, then the sheath is the earth.
RCD's will make a difference!

 

[Sintra]

Think there is a bigger problem than just bunging an RCD on it. This installation needs to be checked properly.

 

[kingeri]

Are the sheaths terminated/connected to the earthing terminals in the CU/accessories?

 

[Clive P]

Hi,

Don't quite understand the 'ends not made off'. If all of the circuits are wired in micc with the glands earthed to the backbox, then you have your earthing and the two black wires are the line and neutral sleeved as they should be ' black' with an indication as to which is live and which is neutral. A lot of older installations would of been done like this, before the 'earthed pot' arrived on the scene. I would retest and check for your continuity, could be a loose gland on one of the backboxes, I can't see that they wouldn't have been glanded.

Regards.

 

[MDJ]

I expect the DB end of the system has just the phase conductors into the board and the gland not earthed at that point, if an earth was connected to that gland I bet it would all be fine, I love micc, wish my house had it, it would last for 70 years haha

 

[GLENNSPARK]

How can you not tell an MICC FFS?


If nothing at all is earthed.....either sort it and then change the cu, or dont touch it at all.

aye and upgrade that bondin n all....caus as it stands its an instant (2)...

 

[Engineer54]

I expect the DB end of the system has just the phase conductors into the board and the gland not earthed at that point, if an earth was connected to that gland I bet it would all be fine, I love micc, wish my house had it, it would last for 70 years haha

And then some!! lol!!

 

[james king]

lol, cables are not earthed to the back box. as in the there is no continuity from the MET to the back box. the micc end are not connected to the CU.

 

[HandySparks]

lol, cables are not earthed to the back box. as in the there is no continuity from the MET to the back box. the micc end are not connected to the CU.

Any chance of a photo or two so we all know what we're discussing?

 

[gdr7671]

rcds don't need a cpc to operate.

You can be the earth.

you are wrong !!

 

[Baker1988]

you are wrong !!

how is that wrong obviously a earth would always be better but a rcd only measures any imbalance between live and neutral and if you touch something you shouldn't there will be a imbalance between live and neutral as what is going through you will not be be returned and the rcd will notice the imbalance and operate, you dont connect a earth to a rcd

 

[diditrain]

I would say that the whole of the install would be worthy of a thorough inspection and test before any proposed works proceed as you will just end up inheriting the existing problems. If the MICC has not been correctly terminated then chances are that the magnesiun oxide within the cable could be damp as it is hygroscopic

 

[Octopus]

you are wrong !!

I fixed a problemm recently on a circuit without an earth and the "broken" cable was tripping the RCD

Back to the OP, wouldn't an urgent thorough inspection be required?? I certainly wouldn't touch this install without this first, and probably remedial workk before considering the CU.

 

[Geoffsd]

you are wrong !!

No I'm not.

How/why do you think I am?

 

[gdr7671]

I would say that the whole of the install would be worthy of a thorough inspection and test before any proposed works proceed as you will just end up inheriting the existing problems. If the MICC has not been correctly terminated then chances are that the magnesiun oxide within the cable could be damp as it is hygroscopic

i agree. by the way, it's hydroscopic

 

[JulianC]

by the way, it's hydroscopic

No it's not. Not doing too well here are we? :wink_smile:

 

[shagbite]

i agree. by the way, it's hydroscopic

it's absorbing moisture from the air, so it's hygroscopic.

 

[Engineer54]

If the MICC has not been correctly terminated then chances are that the magnesiun oxide within the cable could be damp as it is hygroscopic

If MICC, this wouldn't cause the loss of earthing etc, but would cause far bigger problems to this installation!! lol!!​

 

[Kem]

Seriously Micky mouse thread. Are you even qualified?

 

[tony mc]

you are wrong !!

Lots of misleading information on this post.

IMO the above should explain why they think you need a CPC for the device to work !

I am with geoffsd on this !

So every class 2 bit of equipment that is used with RCD protection will not work !

 

[trev]

wouldn't an urgent thorough inspection be required

By someone who knows what they're doing.
Sorry op mate but I don't think you've got the right stuff for this one.

 

[Eggster71]

By someone who knows what they're doing.
Sorry op mate but I don't think you've got the right stuff for this one.

Agreed! Old pyro can be a royal pain in the butt and that's with tools and experience.

OP should walk away from this one.

 

[Engineer54]

Agreed! Old pyro can be a royal pain in the butt and that's with tools and experience.

OP should walk away from this one.

Only when it was installed by muppets or has been interfered with by other muppets... lol!!
Otherwise it will outlast the original installer...