Earthing query

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

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.

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

Colin Bignell

"nightjar .uk.com>"

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

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

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

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

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

On Thu, 26 Jan 2006 13:21:50 -0000 someone who may be "Blair" wrote this:-

I assume you mean the armour.

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.

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?

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?

From: "David Hansen" Subject: Re: Earthing query Date: 26 January 2006 14:21

On Thu, 26 Jan 2006 13:21:50 -0000 someone who may be "Blair" wrote this:-

I assume you mean the armour.

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.

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?

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?

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

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.

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.

It sounds like it.

At which end?

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.

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

No this junction box is metal

At the pump end

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