Earthing query
"David Hansen" wrote in message
...
On Thu, 26 Jan 2006 13:21:50 -0000 someone who may be "Blair"
wrote this:-
The metal junction box is at the pump end of the cable and the metal
protection
I assume you mean the armour.
is connected to the gland which is used for the cable. If I
replace the metal box with a plastic one this gland will not be in
contact
with any metal
The gland will not be in contact with any metalwork forming the box
(as the box is now plastic), though it will still be in contact with
the armour.
and therefore not earthed..
That does not follow at all, assuming that the armour is earthed at
the origin of the cable.
Is there an earth rod at the pump end? If there is then all sorts of
other considerations apply.
Is the pump Class I or Class II?
Of course there is an earth wire within the cable. Are you suggesting
that
the metal protection should be connected to this earth?
The armour should be earthed. How this is done depends on a host of
things. What sort of earthing system is in use?
Why do you want to change the box? Do you think you are skilled
enough to do so?
--
David Hansen, Edinburgh
From: "David Hansen"
Subject: Earthing query
Date: 26 January 2006 14:21
On Thu, 26 Jan 2006 13:21:50 -0000 someone who may be "Blair"
wrote this:-
The metal junction box is at the pump end of the cable and the metal
protection
I assume you mean the armour.
is connected to the gland which is used for the cable. If I
replace the metal box with a plastic one this gland will not be in contact
with any metal
The gland will not be in contact with any metalwork forming the box
(as the box is now plastic), though it will still be in contact with
the armour.
and therefore not earthed..
That does not follow at all, assuming that the armour is earthed at
the origin of the cable.
Is there an earth rod at the pump end? If there is then all sorts of
other considerations apply.
Is the pump Class I or Class II?
Of course there is an earth wire within the cable. Are you suggesting that
the metal protection should be connected to this earth?
The armour should be earthed. How this is done depends on a host of
things. What sort of earthing system is in use?
Why do you want to change the box? Do you think you are skilled
enough to do so?
--
David Hansen, Edinburgh
From: "David Hansen"
Subject: Earthing query
Date: 26 January 2006 14:21
On Thu, 26 Jan 2006 13:21:50 -0000 someone who may be "Blair"
wrote this:-
The metal junction box is at the pump end of the cable and the metal
protection
I assume you mean the armour.
is connected to the gland which is used for the cable. If I
replace the metal box with a plastic one this gland will not be in contact
with any metal
The gland will not be in contact with any metalwork forming the box
(as the box is now plastic), though it will still be in contact with
the armour.
and therefore not earthed..
That does not follow at all, assuming that the armour is earthed at
the origin of the cable.
Is there an earth rod at the pump end? If there is then all sorts of
other considerations apply.
Is the pump Class I or Class II?
Of course there is an earth wire within the cable. Are you suggesting that
the metal protection should be connected to this earth?
The armour should be earthed. How this is done depends on a host of
things. What sort of earthing system is in use?
Why do you want to change the box? Do you think you are skilled
enough to do so?
David Hansen, Edinburgh
I have a junction box in the garage which is fed from a spur in the garage
ring main and is protected by an RCD. The supply is a three core cable
I have used a correctly sized armoured gland with a brass earth tag which is
connected to the earth from the supply cable
At the other end next to the pump a similar brass tag is used which earths
the armour to the
box.There is no earth rod at the pump
So I believe the system is at present earthed correctly.
If I did use a plastic box I assume that the brass earth tag should be
connected to the supply earth wire for full protection
Incidentally I installed the whole system about 12 years ago which consists
of a pump previously submersible but now surface mounted. pressures vessel
and a pressure switch.Water is pumped up about 50 feet from source.
I probably should leave it alone and forget the plastic box?
Blair
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