Hi
Whilst checking the wiring into my garage I noticed that the feed into the garage Consumer Unit is via 3 core armoured SWA cable. The outer galvanized steel armour terminates at the plastic outer case of the CU but is not connected to the earth. The earthling conductor is connected to the earth bar in the CU as it should be. Should the outer steel armour be earthed?
Thanks
Daveo

The earthling conductor is connected to the earth bar in the CU as it
should be. Should the outer steel armour be earthed?

The armour should be earthed at the house end.

There is no need for it to be connected at the garage end, provided some
other form of earth is used, such as an earth exported as a conductor within
the SWA (which appears to be the case here) or an earth rod.

Christian.

The earthling conductor is connected to the earth bar in the CU as it
should be. Should the outer steel armour be earthed?

The armour should be earthed at the house end.

There is no need for it to be connected at the garage end, provided some
other form of earth is used, such as an earth exported as a conductor
within
the SWA (which appears to be the case here) or an earth rod.

It's unusual to see SWA with an earth wire, are you sure it's not
concentric. Consentric carries the earth and the neutral in the armouring,
with the strands that carry the neutral coated in a PVC sheath. Typicaly
concentric will have no brass glands on each end of the cable.

Regards, Blew

"David Blewitt" nospam wrote in message
...
The earthling conductor is connected to the earth bar in the CU
as it
should be. Should the outer steel armour be earthed?

The armour should be earthed at the house end.

There is no need for it to be connected at the garage end,
provided some
other form of earth is used, such as an earth exported as a
conductor
within
the SWA (which appears to be the case here) or an earth rod.

It's unusual to see SWA with an earth wire, are you sure it's not
concentric. Consentric carries the earth and the neutral in the
armouring,
with the strands that carry the neutral coated in a PVC sheath.
Typicaly
concentric will have no brass glands on each end of the cable.

Regards, Blew



Blew,

I've seen quite a few single phase runs using three phase swa and
using one of the cores as the earth and the other two as live &
neutral.

AWEM

It's unusual to see SWA with an earth wire, are you sure it's not
concentric. Consentric carries the earth and the neutral in the
armouring,
with the strands that carry the neutral coated in a PVC sheath. Typicaly
concentric will have no brass glands on each end of the cable.

TN-C earthing is not permitted within a consumer's installation. It is
permitted on the main supply line to the property, provided the earth is
separated off into TN-C-S within the supplier's cut out.

Christian.

TN-C earthing is not permitted within a consumer's installation. It is
permitted on the main supply line to the property, provided the earth is
separated off into TN-C-S within the supplier's cut out.

With concentric the earth and neutral are seperate conductors, the neutral
strands of the armouring are all seperatly earthed.

The TN-C system is called PEN when used inside an installation (protective
earth and neutral, TN-C refers to the distribution system). It is alive and
well in many of the blocks of flats in the area I work in. I belive PEN is
the main system used on the continent and that it is still ok to use in new
installations, though PME is by far the most popular sytem in the UK.

Regards, Blew


"Christian McArdle" wrote in message
. net...
It's unusual to see SWA with an earth wire, are you sure it's not
concentric. Consentric carries the earth and the neutral in the
armouring,
with the strands that carry the neutral coated in a PVC sheath. Typicaly
concentric will have no brass glands on each end of the cable.


Christian.

In article ,
says...
The earthling conductor is connected to the earth bar in the CU as it
should be. Should the outer steel armour be earthed?

The armour should be earthed at the house end.

There is no need for it to be connected at the garage end, provided some
other form of earth is used, such as an earth exported as a conductor within
the SWA (which appears to be the case here) or an earth rod.

Christian.




This is something which has long caused me some concern. If, for
example, the house is earthed by an earth rod (rural setting), and has
a phase to earth fault such that said fault is not sufficient to trip
the circuit's mcb, and is sufficient to bring the earth wiring, bonded
services and earth rod upto mains voltage - I've seen this happen -
then the swa gland at the remote building, if it's not bonded to the
remote building's "equipotential cage" will also rise to mains voltage
relative to the local earth.

Anyone touching the gland (albeit usually being sheathed) whilst
also touching a local earth, is in for a shock in more ways than one...

There are some circumstances (the one that I came across was
related to a LPG filling station) where it is required to utilise a
special type of swa gland, which incorporates an earth "break", such
that a sound mechanical joint can be made, whilst the earth continuety
is not. This means that since TT earthing is the only type allowed in
such installations, it is possible that full mains voltage could appear
across two potentially exposed conductors, very close together, which
in my book is more than hazardous...

--
Regards,

Will.

This is something which has long caused me some concern. If, for
example, the house is earthed by an earth rod (rural setting), and has
a phase to earth fault such that said fault is not sufficient to trip
the circuit's mcb, and is sufficient to bring the earth wiring, bonded
services and earth rod upto mains voltage - I've seen this happen -

I would say that the chances of electrocution in this failure mode is very
rare.

Firstly, it presumes that the house TT earth RCD has failed. Secondly, the
fault condition within the house after this failure is so severe (all metal
appliances are now live), that the minor risk of an insulated gland being
live behind its sheath in the shed is of no significance whatsoever.

Christian.