earthing fcu

[rich22]

Hello i am just wiring an fcu for a dishwasher .
On the faceplate the earth connection is very small i need to put 4 earth cables into it.
One from the unswitched socket under the worktop then two which are the ring main and one as the flying earth to the back box.
Only three will fit i have read in a book that if the back box has a fixed lug that the flying earth isn't used.
Is this wright the faceplate has a screwless cover in white pvc and the switch is the same.

 

[RF Lighting]

Is there not two earth terminals on the FCU? Normally in this situation you would put two wires into each earth terminal.

 

[rich22]

No just one they are made by varilight.

 

[RF Lighting]

Odd. Yes, providing there is a fixed lug on the back box it is permissable to omit the wire link to the back box, but still preferable to leave it in place if possible.

 

[JohnD]

throw it away and buy a better-quality one by MK, Mem or Crabtree.

 

[rich22]

Any way i can get round this.

 

[JohnD]

have you already fixed the back-box? Any chance you could take it out? What sort of earth connector does it have - a brass stud or a steel clamp? how deep is it?

 

[conny]

Would it be permissible to put the two ring main earths and a fly-lead earth to the back box, the unswitched socket earth and the other end of the fly-lead to the faceplate?

Can any sparks confirm if this is allowed?

 

[rich22]

The back box is 47mm deep and it has a metal clamp.
Yes its fitted and carnt get it out.

 

[industryspark]

conny wrote

Would it be permissible to put the two ring main earths and a fly-lead earth to the back box, the unswitched socket earth and the other end of the fly-lead to the faceplate?

Ive come across plenty of sockets and switches that have had the cpc (circuit protective conductor) terminated into the backbox and then the fly lead earth to the accsesory. I dont like it however, i was always taught to take the cpc's to the accessory and then a 'supplementary' earth fly lead to the backbox-this is how it should be done imo.

If the backbox has at least one fixed lug then just omit the fly lead - always best to put it in if you can but preferable in this case to make sure you get the three 'important' cpc's terminated nice and secure rather than try forcing 4 into the terminal and have them all poorly connected.

Regards.

 

[JohnD]

the metal clamps tend to be quite roomy so I would probably go that route.

The fly-lead is important, though in the past I have seen accessories relying on the fixing screws this is unsatisfactory as the connection through the threads can go high-resistance if there is corrosion of the galvanised lugs or they are loose (quite apart from the fact that it is lost when you take the screws out).

Make the flylead long enough that it is not under tension when you tug the faceplate out against the wires (it should be slacker than the others)

 

[conny]

i was always taught to take the cpc's to the accessory and then a 'supplementary' earth fly lead to the backbox-this is how it should be done imo.

Thats the way I was taught in college many many years ago but wondered what modern day practices were. Always best to do it the correct way.

 

[ebee]

I'm surprised the earth terminal won't take all 4.

Make one cpc (earthwire) extra long (eg twice length of the others), double it over and connect the doubled bit to the backbox and the single end into the FCU along with the other two.

Did anyone mention Part P applying ?

 

[GaryMo]

Did anyone mention Part P applying ?

Part P applies to all electrical installations that are intended to operate at low or extra-low voltage and are:

(a) in or attached to a dwelling;

(b) in the common parts of a building serving one or more dwellings, but excluding power supplies to lifts;

(c) in a building that receives its electricity from a source located within or shared with a dwelling; and

(d) in a garden or in or on land associated with a building where the electricity is from a source located within or shared with a dwelling.