Where should earth-neutral bond be

[recre8]

Hi Guys

Our small complex recently changed over from three phase coming in (and being reticulated from our kiosk to each property) to being supplied single-phase directly by the municipality. Our private contractor for some reason joined all the neutrals together on the old 3-phase neutral bus bar which definitely seems wrong... but my question is this:

In each of the houses, the inspection/junction box on the outer garage wall where the house's mains cable is joined... there is a earth bar which bond neutral and earth again. From my understanding, the neutral-earth bond should only be done ONCE at the point of supply (meaning the kiosk outside the complex, or at the minisub?) and nowhere from there up to the house where there should be a separate neutral and earth? The area is relatively new and from what I remember there is definitely an earth-neutral bond in the supplier's kiosk. Why would the electrician have bonded the earth and neutral again at each house? I've attached a photo

Note: I had two CoC's done in recent years and both passed. The one ticks the earthing arrangement as TN-C-S and the other CoC has it as TN-S?

[Isetech]

Hi Guys

Our small complex recently changed over from three phase coming in (and being reticulated from our kiosk to each property) to being supplied single-phase directly by the municipality. Our private contractor for some reason joined all the neutrals together on the old 3-phase neutral bus bar which definitely seems wrong... but my question is this:

In each of the houses, the inspection/junction box on the outer garage wall where the house's mains cable is joined... there is a earth bar which bond neutral and earth again. From my understanding, the neutral-earth bond should only be done ONCE at the point of supply (meaning the kiosk outside the complex, or at the minisub?) and nowhere from there up to the house where there should be a separate neutral and earth? The area is relatively new and from what I remember there is definitely an earth-neutral bond in the supplier's kiosk. Why would the electrician have bonded the earth and neutral again at each house? I've attached a photo

Note: I had two CoC's done in recent years and both passed. The one ticks the earthing arrangement as TN-C-S and the other CoC has it as TN-S?

I would say it is incorrect, however it seems that this is the new way to fix high loop impedance readings.

[recre8]

I would say it is incorrect, however it seems that this is the new way to fix high loop impedance readings.

Ah ok... so it helps with the CoC. But is it compliant though?

My cursory search of the SANS gets me:

6.1.6 The neutral conductor shall not be connected direct to earth or to the
earth continuity conductor on the load side of the point of control except as
allowed in 7.16.4.

7.16.4.2 From the point of supply to each user or part of a communal
installation, the neutral and earth conductors shall be separate conductors.

[GCE]

Hi

It is very dependent on how the installation is done from a supplier point - The definition of " Point of Supply" will determine the outcome

Is your municipality feeding power to the meter box ? if they are then they are allowed to bridge neutral and earth

If your complex has bulk metering and each individual unit is being metered privately the the neutral shall not be bonded to earth.



3.58
point of supply
point at which a supplier supplies electricity to any premises

3.56
point of control
point at which a consumer can, on or in any premises, switch off the electrical
installation from the electricity supplied from the point of supply

3.61
premises
place such as a site, building or structure, whether stationary or mobile, that
can be electrically wired

[recre8]

Hi

It is very dependent on how the installation is done from a supplier point - The definition of " Point of Supply" will determine the outcome

Is your municipality feeding power to the meter box ? if they are then they are allowed to bridge neutral and earth

If your complex has bulk metering and each individual unit is being metered privately the the neutral shall not be bonded to earth.



3.58
point of supply
point at which a supplier supplies electricity to any premises

3.56
point of control
point at which a consumer can, on or in any premises, switch off the electrical
installation from the electricity supplied from the point of supply

3.61
premises
place such as a site, building or structure, whether stationary or mobile, that
can be electrically wired

The installation is now so that there is a split prepaid meter in the municipal kiosk on the public street outside the kiosk. From each DIN meter, the SWA cable is run to the respective house. And then I noticed that at each house in the junction box on the garage wall where the 16mm house wire is joined to the SWA conductors, there is a earth-neutral bond as per the photo. Surely this isn't right? The houses don't have earth spikes, they rely on the earthing from the minisub.

[GCE]

Without knowing the full scenario of how the changes came about and what is existing network and the reason behind the change it is difficult to condemn or condone what has happened.

7.16.4.1 allows the backbone to be TN-C but 7.16.4.6 does not allow a TN-S system to be changed back to TN-C and then back again to TN-S

It all depends on the start point , supply point and size of installation.

7.16.4.1 Whereas TN-C systems may be implemented along the distribution
system backbone, the individual service connections at every distribution
kiosk shall be TN-S.

7.16.4.6 A TN-S system shall not be converted to a TN-C system.