outside power

[rodhalls]

I am installing outside lights and pond pump using a separately fused existing supply from the internal, modern distribution board. The armoured cable was put in years ago - at least 20 - to supply power to the greenhouse. I has an old metal junction box half way along which simply joins the cable from the house to the one which goes underground to the greenhouse. I have replaced that box with a new one from where I am taking the other feeds. However the cable from the house is three core but the one which goes to the green house is only two core, tho' it is armoured. I am worried about the need for very good earthing given proximity of water, metal green house etc and am now wondering if this is safe/good enough; and if it isn't what can I do short of running another cable to the green house which is obviously a big job I want to avoid.

Appreciate advice
Thanks
Rod Halls

 

[Steve]

what sort of box did you use? is it a plastic one?

i suspect this box was once used to supply a light or a pond pump, supplied seperately from the greenhouse, so that 3 core might have 2 lives and a neutral, with earthed armour. Check where the cores go at the origin before making assumptions though!!

Using armour as the earth is ok, but after 20 years, it would be a good idea to get an electrician to test the earth fault loop impedance from the greenhouse, because if the outer plastic gets cut, water gets in and corrodes the steel armour. 20 years of rust will see the protective value of the steel practically zero! But it should be fine anyway!