Earthing query
 

I have an underground cable controlling a water pump which supplies my house
, The cable is armoured. Is it necessary to earth the metal armour
protection?
Blair

Earthing query
 

On Tue, 24 Jan 2006 05:45:30 -0000 someone who may be "Blair"
wrote this:-

I have an underground cable controlling a water pump which supplies my house
, The cable is armoured. Is it necessary to earth the metal armour
protection?

Yes.

Whether you make such a connection at both ends depends on how you
are earthing the pump and any building it is in. There have been
several threads on this recently to do with garages.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Earthing query
 

"Blair" wrote in message
...
I have an underground cable controlling a water pump which supplies my
house
, The cable is armoured. Is it necessary to earth the metal armour
protection?

Definitely. There should be a brass tag for that purpose in the cable gland
set.

Colin Bignell

Earthing query
 

"nightjar .uk.com" nightjar@insert my surname here wrote in message
...

"Blair" wrote in message
...
I have an underground cable controlling a water pump which supplies my
house
, The cable is armoured. Is it necessary to earth the metal armour
protection?

Definitely. There should be a brass tag for that purpose in the cable
gland
set.

Colin Bignell

Thanks for your reply.
I should have said that I have a metal junction box where the cable armour
is earthed as you say but I am proposing to change this to a plastic
junction box, and there will be no earth available.
Can I safely do this?
Blair

Earthing query
 

On Wed, 25 Jan 2006 05:06:12 -0000 someone who may be "Blair"
wrote this:-

I should have said that I have a metal junction box where the cable armour
is earthed as you say but I am proposing to change this to a plastic
junction box, and there will be no earth available.

Why will there suddenly be no earth available because you change the
box?

Can I safely do this?

Assuming the junction box is at the other end of the cable to the
pump. No.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Earthing query
 

"David Hansen" wrote in message
...
On Wed, 25 Jan 2006 05:06:12 -0000 someone who may be "Blair"
wrote this:-

I should have said that I have a metal junction box where the cable
armour
is earthed as you say but I am proposing to change this to a plastic
junction box, and there will be no earth available.

Why will there suddenly be no earth available because you change the
box?

Can I safely do this?

Assuming the junction box is at the other end of the cable to the
pump. No.


--
David Hansen, Edinburgh
The metal junction box is at the pump end of the cable and the metal
protection 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 and therefore not earthed..
Of course there is an earth wire within the cable. Are you suggesting that
the metal protection should be connected to this earth?
Blair

Earthing query
 

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 will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

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

Earthing query
 

On Fri, 27 Jan 2006 14:57:54 -0000 someone who may be "Blair"
wrote this:-

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

This junction box is presumably plastic? If not then provided the
metal of the box is earthed in some way everything sounds like it is
in order.

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

If you replace this with a plastic box then, assuming the pump is
Class I equipment, you need a similar arrangement to that which you
described inside the garage, with the earth tag connected to the
earth conductor in the lead to the pump.

So I believe the system is at present earthed correctly.

It sounds like it.

If I did use a plastic box

At which end?

I assume that the brass earth tag should be
connected to the supply earth wire for full protection

If you are talking about the one in the garage then yes.

If you are talking about the one by the pump then I can only imagine
you are using one of the cores as an earth, in addition to the
armour. It is good practice to connect both together at this end as
well.

I probably should leave it alone and forget the plastic box?

Out of interest, why do you want to replace the metal box?



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Earthing query
 

"David Hansen" wrote in message
...
On Fri, 27 Jan 2006 14:57:54 -0000 someone who may be "Blair"
wrote this:-

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

This junction box is presumably plastic? If not then provided the
metal of the box is earthed in some way everything sounds like it is
in order.
No this junction box is metal



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

If you replace this with a plastic box then, assuming the pump is
Class I equipment, you need a similar arrangement to that which you
described inside the garage, with the earth tag connected to the
earth conductor in the lead to the pump.

So I believe the system is at present earthed correctly.

It sounds like it.

If I did use a plastic box

At which end?

At the pump end

I assume that the brass earth tag should be
connected to the supply earth wire for full protection

If you are talking about the one in the garage then yes.

If you are talking about the one by the pump then I can only imagine
you are using one of the cores as an earth, in addition to the
armour. It is good practice to connect both together at this end as
well.

I probably should leave it alone and forget the plastic box?

Out of interest, why do you want to replace the metal box?

I am struggling to give a sensible answer. In the past I had the pressure
switch adjacent to the pump in a wooden box with insulation for frost
protection. Mice got in and chewed the plastic insulation and generally
caused a mess including the junction box. Since installing the new pump I
have built a brick housing to make it mouse proof and I wanted to tidy up
the wiring and fit a new junction box. Why plastic.? probably because it
looks better!! Not a good reason!
Blair