Plug Socket Earth

[Wes]

So this may seem like a stupid question but I thought I'd put it out to the hivemind. 

We have bought some 240v plug sockets for our fit out and they have a secondary earth, so live, neutral and earth for the 2.5mm 3 core wire and then a secondary "earth port" to go to a functional earth. We are having an electrician install everything and test the whole system but I just need to know if anyone has come across this before and if there is a resolution that I need to find or swap these out? 

 

Thanks,

 

Wes

[Scholar Gypsy]

Do you mean a second earth connection in the backbox? 

Are you installing a galvanic isolator, a transformer, or neither?

[Wes]

1 minute ago, Scholar Gypsy said:

Do you mean a second earth connection in the backbox? 

Are you installing a galvanic isolator, a transformer, or neither?

Hey, 

We will have a galvanic Isolator installed yes. 

Left is earth, above it is Live then Neutral and below the nuetral the "earth to functional earth". Now we were thinking of using the clip in plastic back boxes so there is nothing to earth it to essentially? Usually the secondary earth is to the metal backbox? 

 

Again I am not doing the install just trying to get to grips with the logistics of it all before our install is done. 

 

Thanks again,

 

Wes

[Scholar Gypsy]

11 minutes ago, Wes said:

Hey, 

We will have a galvanic Isolator installed yes. 

Left is earth, above it is Live then Neutral and below the nuetral the "earth to functional earth". Now we were thinking of using the clip in plastic back boxes so there is nothing to earth it to essentially? Usually the secondary earth is to the metal backbox? 

 

Again I am not doing the install just trying to get to grips with the logistics of it all before our install is done. 

 

Thanks again,

 

Wes

It looks to me as though the two earth terminals are connected (by the metal strip), so your electrician  can use either or both as convenient. For example you might use one to connect the cables and the other to bond to the metal back box (which you won't need).

[Wes]

1 minute ago, Scholar Gypsy said:

It looks to me as though the two earth terminals are connected (by the metal strip), so your electrician  can use either or both as convenient. For example you might use one to connect the cables and the other to bond to the metal back box (which you won't need).

Right so when plastic back boxes are used you would need to find an alternative earthing point? 

[Scholar Gypsy]

1 minute ago, Wes said:

Right so when plastic back boxes are used you would need to find an alternative earthing point? 

 It's the other way around. Being plastic it doesn't need to be earthed.  A metal back box needs to be earthed so that if, for example, the live cable became detached and touched the metal then the fuse/circuit breaker would trip immediately. (This is belt and braces, really, as the backbox is connected to the unit via the bolts, and the latter are earthed as well, as you can see in that photo).

[Wes]

Lovely stuff, that has cleared it up and I now understand better. Much appreciated. 

[Alan de Enfield]

10 minutes ago, Wes said:

Lovely stuff, that has cleared it up and I now understand better. Much appreciated. 

 

Just asking - is your electrician a 'boat' electrician ?

If he is used to 'doing houses' then he will be doing it incorrectly for a boat. Boat wiring regulations are very different to house wiring regulations - even to the type of cable used.

 

Example : The domestic 3-core Twin & Earth with solid conductors does not comply with the boat standards, it must be multi-stranded cable (a minimum number of strands are required for each size of cable.

 

Ask him is he wiring the boat to comply with :

(There are similar specifications for the 12v DC wiring)

 

 

 

 

 

 

 

[Wes]

1 minute ago, Alan de Enfield said:

 

Just asking - is your electrician a 'boat' electrician ?

If he is used to 'doing houses' then he will be doing it incorrectly for a boat. Boat wiring regulations are very different to house wiring regulations - even to the type of cable used.

 

Example : The domestic 3-core Twin & Earth with solid conductors does not comply with the boat standards, it must be multi-stranded cable (a minimum number of strands are required for each size of cable.

 

Ask him is he wiring the boat to comply with :

(There are similar specifications for the 12v DC wiring)

 

 

 

 

 

 

 

Hey Alan, 

 

Yeah he is a certified boat electrician and works solely on boats and vans. We are not using solid core wires, we are using 2.5mm multi strand and will all be terminated with bootlace ferules.

Obviously I am just researching for my own knowledge and understanding. The electrician will be doing all the install and follow the relevant code along with sign off of the system. 

[Alan de Enfield]

Just now, Wes said:

Hey Alan, 

 

Yeah he is a certified boat electrician and works solely on boats and vans. We are not using solid core wires, we are using 2.5mm multi strand and will all be terminated with bootlace ferules.

Obviously I am just researching for my own knowledge and understanding. The electrician will be doing all the install and follow the relevant code along with sign off of the system. 

 

Great - well done.

You'd be surprised how many 'fitter outers' just call someone in 'Yellow Pages' and the lowest price quote gets the job.

No thought in getting it done properly.

 

Enjoy.

[Wes]

Just now, Alan de Enfield said:

 

Great - well done.

You'd be surprised how many 'fitter outers' just call someone in 'Yellow Pages' and the lowest price quote gets the job.

No thought in getting it done properly.

 

Enjoy.

Yeah, I'd rather spend the money (small fortune) on getting someone to do iut properly along with the sign off. I'll be running all the cables etc but he will be doing the connecting and full install and testing of all components. 

It aint cheap but it means we only have to do it once and then its done. 

[Alan de Enfield]

2 minutes ago, Wes said:

Yeah, I'd rather spend the money (small fortune) on getting someone to do iut properly along with the sign off. I'll be running all the cables etc but he will be doing the connecting and full install and testing of all components. 

It aint cheap but it means we only have to do it once and then its done. 

 

 

 

[cuthound]

A functional earth is an earth connection for a specific purpose, such a a "silent" or noise free earth and used as a reference point for sensitive electronic equipment rather than the protective earth, which has all sorts of electrical noise imposed on it.

They are commonly found in telephone exchanges and data centres.

 

Functional earths are deliberately kept seperate from the protective earth as far as possible, only being commoned at the main building earth connection.

 

In the OP's case it can be safely ignored or connected to the boats ac earth point, viathe existing boat earth wiring.

Edited July 5, 2022 by cuthound
Clarification