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seen it 3-4 times now, last time it had taken out the flexy hoses under the kitchen sink, when they turned the shower on! scarry stuff. but hey they had a good Ze :)

As snowhead says wonder why they dont fit a 100A 500ma RCD before the NE join.
 
Speak to the DNO ask them if you can fit an Earth Rod as a back up they will probably say no but do it anyway lol
J


That is the way it is done in some countries an external electrode is connected to the N / E juncture within the service head.
 
That is the way it is done in some countries an external electrode is connected to the N / E juncture within the service head.

As the N/E are shared at the head can you see any problem with taking a rod from MET ? I am struggling to find a reason how this wouldn't improve the safety of the installation if you lost the Neutral
J
 
I don't quite get where he's saying it should be positioned in relation to it's effectiveness ? My CU has a 30mA non delayed RCD as a main switch will it trip out if the N drops out ? it's the same as his diagram isn't it ?
J
 
I don't quite get where he's saying it should be positioned in relation to it's effectiveness ? My CU has a 30mA non delayed RCD as a main switch will it trip out if the N drops out ? it's the same as his diagram isn't it ?
J

This is looking at loosing the incoming neutral, before the Neutral / Earth connection, the normal C.U RCD can't detect that.
Current flow thro' the C.U rcd won't be any different.
The Green / Yellow ("Earth") now becomes a return waiting for someone to complete the path.
 
Doesn't the white wire on the RCD help with this?

The old MEM RCD did have a functional earth but that was years back. the only time Ive seen the functional earth now is on RCBO's. With any normal front end RCD if the neutral is lost before its split then the RCD wont become unballenced.
Supply comes down the live through all your equipment, back up the neutral/earth and as theres no neutral back to the substation then its only return path is your bonding conductors, or what ever the lowest resistance it can find to earth!
 
Afternoon Snowhead , interesting thread you introduced. One of the contributors mentions this "pre" rcd as unsuitable for UK'S tncs system.This must be due to DNO's
not wanting sparks fitting an rcd to the(concentric) supply cable.
 
Found an interesting PDF on this now I am thinking if 10 houses are on the same phase as me and the N drops off will I get all their fault load as well because my nice shiny new earth rod will provide a lower path of resistance than all their bonded extraneous water and gas ?
J
<snip> It is not a simple matter to retrofit TN-C-S distribution systems with such a facility. This is true for
TN-C-S systems (such as those in South Africa) that do not require the installation of a foundation
earth at the service entrance. Unless every consumer each have their own service entrance
foundation earth facilities, in the event of a break in the PEN conductor, the load current of all
other consumers may find a return path through those foundation earth connections that happen
to be present.
An extreme example would be the case of only one consumer having a foundation earth. In such
a situation, all the load currents of all consumers connected to that distribution system would try
to flow through the single foundation earth present. The consequential overheating together with
the related possibilities of incendiary ignition will be obvious.

View attachment Loss of Neutral.pdf
 
It happened to my house years back.

Happened to mine last year. Broken neutral in the joint box under pavement at end of drive. Guy who fixed it reckons there's loads of them happening. Daz
 
I am thinking if 10 houses are on the same phase as me and the N drops off will I get all their fault load as well because my nice shiny new earth rod will provide a lower path of resistance than all their bonded extraneous water and gas ?

This is the problem I had years back. I had 40A+ going down to the rod.
Will have a read of the PDF later
Thanks
 

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