Installing an under cabinet socket

[tuppence]

I want to install one of these

http://www.tlc-direct.co.uk/Products/KS104.html

but there appears to be no provision for earthing the outer metal case e.g. adding a link from one of the fixing lugs to the earth terminal within the black plastic module. Shouldn't the case be earthed?

 

[ban-all-sheds]

I guess not.

 

[plugwash]

I suspect the socket module is suitablly class 2 insulated so the metal doesn't technically need to be earthed.

 

[Taylortwocities]

I hate these.

They are actually two single sockets moulded together. it means extra work as you have to loop from socket A to socket B.

As an aside, should we really put this arrangement on a spur? Technically the second socket would be a spur off a spur

 

[tuppence]

Before I bought it I thought it would be as easy as connecting a conventional socket but yes, the unit consists of two independent modules, each with a cable grip that appears intended for a single flex. I originally intended the unit to be looped into the ring but what I will do instead is fix the ring cables into one side of a 30A choc bloc (in a chocbox) and have two short lengths of 1.5mm 3 core flex coming off the other side - i.e. two spurs. Is this OK?

All this will be in the vicinity of the rear of the case (with a sharp unfinished edge), hence my original question about earth it. I assume there would be no objection to running an earth cable from one of the screws that fixes the case to the cupboard into either the chocbox or the earth connection of one of the modules.

 

[dannyboi2003]

No you cant do that, 1.5mm flex is not suitably rated for use on a ring main! Make them part of the ring as you originally intended, if the cables wont reach crimp or join extensions so they reach and loop between the sockets to maintain the ring. Whatever you do don't use 1.5mm flex!

As for earthing the casing then as its already been said they are probably double insulated by design. If you need to make connections then just make sure they are suitably insulated with heat shrink.

 

[tuppence]

No you cant do that, 1.5mm flex is not suitably rated for use on a ring main!

Maybe I wasn't clear. The flex is rated 16A and I want to connect two lengths separately to two single 13A socket modules. These would be two spurs taken off the same point of the ring, i.e. not be part of it.

The ONLY reason I want to do this is that the cable entry to each module is round and exactly the right size to take this size of flex. So it looks as though it is designed for such connection (no useful instructions are included). The cable entry is secured by a cable clamp, identical to the way flex is clamped in most 3 pin plugs. I don't think the clamp is intended for T & E. In no way will you get a single 2.5mm T & E cable into the module without either stripping the outer insulation or seriously hacking the entry point, never mind the two cables you'd need to make it part of a ring.

Given this clarification, do you still consider flex should not be used?

 

[ban-all-sheds]

And I always thought that the only thing wrong with those things is that they look pants...

 

[bernardgreen]

I considered them for work top sockets. Thought better off it

If I had used them then I would have supplied them from a FCU with a 13 amp fuse. And I would have fitted a earthing screw to the metal work to cope with any electrical leakage due to moisture.

 

[dannyboi2003]

1.5mm flex isn't suitable for use, the ring will be protected by a 30/32amp fuse/mcb and this will not provide sufficient protection for the 1.5mm flex. You could argue that as the plugs will be fused at 13a its ok but its a bodge and potentially dangerous. The way i have seen these wired normally is fused spur's above the units with a length of flex fed behind and into the sockets, would this be a suitable workaround for you?

 

[ban-all-sheds]

Isn't there a general instruction for Class II items that earthing them might be unsafe?

 

[bernardgreen]

Isn't there a general instruction for Class II items that earthing them might be unsafe?

I have heard something along those lines.

How can ensuring the exposed metal parts of an item are earth make the item itself un-safe. Theory and common sense seem to agree. Earthing the casing means there is almost no chance of an electric shock from the case.

BUT assume there are two items with metal cases and both are double insulated so no need to earth the casings. Now due to an internal fault the un-earthed case of one of them becomes live. If some touches that live case then they will not get a severe shock unless some other part on their body is in contact with earth or neutral. ( birds perch on 11Kv lines without being shocked ). And if at the same time they touch another case that is NOT earthed they will not get a severe shock. There is no path to earth. That could be the case on equipment that is double insulated and doesn't NEED an earth to the case.

So all is safe provided the case on the NON faulty item is NOT earthed.

But it would be safer in both cases were earthed as the faulty item would be detected and isolated by MCB and / or RCB

 

[ban-all-sheds]

I guess if the MI says don't earth it, don't earth it....

 

[bernardgreen]

I guess if the MI says don't earth it, don't earth it....

I have yet to see manufactures instructions ( MI ) that state the item MUST NOT under any circumstances be earthed. Many that say the item does not need to be earthed and many make no provision for earthing.

 

[ban-all-sheds]

I have yet to see manufactures instructions ( MI ) that state the item MUST NOT under any circumstances be earthed.

I have.