Greenhouse electrics

Joined
27 Mar 2009
Messages
418
Reaction score
20
Location
Yorkshire
Country
United Kingdom
Whats the best way to proceed with wanting to install a power socket in my greenhouse?

I already have an SWA armoured cable going from my house consumer unit to my greenhouse. The cable is terminated in a junction box in the greenhouse, and turned off at the consumer unit.

I now want to install an outdoor plug socket in the greenhouse. Can the cable go straight into an outdoor plug socket (with CW gland) if I remove the junction box? Should it first go into a switch so the socket can be isolated whilst I'm in the greenhouse if needed?

I can't get a local sparky to come and look as the job is too small, and perhaps they don't like that it's an existing cable?
 
Sponsored Links
Can the cable go straight into an outdoor plug socket (with CW gland) if I remove the junction box?
Yes, if you use a back box which will accept the gland.

Should it first go into a switch so the socket can be isolated whilst I'm in the greenhouse if needed?
No, not necessary, you can take out the plug to isolate it.

The circuit should, of course be tested first.
 
It's always going to more watertight if the cable and gland enter the BOTTOM of the weatherproof socket.

Also, be sure that the armour/gland is connected to earth.
 
It's always going to more watertight if the cable and gland enter the BOTTOM of the weatherproof socket.
Whilst that's true (and probably what we all would usually do), a potential downside is that if water does get into the enclosure then, if the gland is at the bottom, water may well get into the SWA and potentially (eventually) result in destruction of the armour by corrosion.

Kind Regards, John
 
Sponsored Links
Very good point - a big discussion due here, as that problem could effect all cables, and even a drainage hole in the box wouldn't necessarily prevent it.

I HATE outdoor electrics, you just can't get them 100% waterproof, what with rain, condensation and the like.
 
Whilst that's true (and probably what we all would usually do), a potential downside is that if water does get into the enclosure then, if the gland is at the bottom, water may well get into the SWA and potentially (eventually) result in destruction of the armour by corrosion.

Kind Regards, John
We had a Fusebox blow out once in a pub and appeared to have water dripping into it, one of the Swa cables went some distance up to the roof and glanded into the bottom of an isolater, on opening that too was somehow half full of water, it appeared the water had eventually run down inside the swa all the way too the other end.
 
Very good point - a big discussion due here, as that problem could effect all cables, and even a drainage hole in the box wouldn't necessarily prevent it. I HATE outdoor electrics, you just can't get them 100% waterproof, what with rain, condensation and the like.
Indeed - and I personally think the best approach is probably to concentrate more on 'drainage holes' than on (pretty futile) attempts at total 'waterproofing'.

For the reason i mentioned, I knew one electrician who always put SWA glands on the side of an outdoor box whenever he could (plus drainage holes at the bottom), because he regarded that as the best compromise between the 'swings and roundabouts' problems of 'top' and 'bottom'. Maybe he was right!

Kind Regards, John
 
We had a Fusebox blow out once in a pub and appeared to have water dripping into it, one of the Swa cables went some distance up to the roof and glanded into the bottom of an isolater, on opening that too was somehow half full of water, it appeared the water had eventually run down inside the swa all the way too the other end.
I can believe it. Maybe what I've just written about 'glanding into the side' (plus drainage holes) IS 'the best compromise'?

Kind Regards, John
 
It's always going to more watertight if the cable and gland enter the BOTTOM of the weatherproof socket.

Also, be sure that the armour/gland is connected to earth.

I'll be connecting the SWA cable to a plastic outdoor socket so i'll just take the SWA's earth cable straight to the socket earth terminal.
 
I'll be connecting the SWA cable to a plastic outdoor socket so i'll just take the SWA's earth cable straight to the socket earth terminal.

Using the core of the cable does not necessarily mean that the Armour and gland is also earthed
 
So what's the best way of earthing the SWA cable?

The armour of the SWA should be connected to the Earth at the supply end. In your case that will be the Earth in the consumer unit.

Is the greenhouse frame wood or metal ? If metal you may need to Bond the metal frame to the Earth core in the SWA. The core and not the armour. Damage to the sheath of the SWA may allow moisture into the cable and this may result in corrosion of the armour to the point it goes open circuit.
 
The armour of the SWA should be connected to the Earth at the supply end. In your case that will be the Earth in the consumer unit.

Is the greenhouse frame wood or metal ? If metal you may need to Bond the metal frame to the Earth core in the SWA. The core and not the armour. Damage to the sheath of the SWA may allow moisture into the cable and this may result in corrosion of the armour to the point it goes open circuit.

Yes it is connected to earth at the consumer unit. Is that sufficient so I don't need to earth at the gland end of the SWA cable?

It's an aluminium greenhouse and the outdoor socket will be fitted to a piece of timber board, this board will be fitted to the greenhouse frame. Is that sufficient with no requirement for further earthing?

I'd normally earth any socket fascia to its back box, though with this back box being plastic is this needed?
 
Last edited:

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top