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