PME head , builder forgot earth cable , 100amp 3phase supply , 10 bedroom house , 10 bedroom house

[andysparkfree]

goes from supplyers main head via meter to 100amp 3 phase switch fuse (this is where im to gland into )

 

[The Ghost]

Ok so what do you do with the armour of the cable at the suppliers end? Just truncate it there?

 

[westward10]

The easiest thing is to create a TT system at the house. Use the PME earth for the swa cable supply then at the house end gland it off in an all insulated enclosure to separate the PME earth from true earth. Fit rcbos to each circuit.

 

[westward10]

Ok so what do you do with the armour of the cable at the suppliers end? Just truncate it there?

Fit a switch fuse disconnector.

 

[Wilko]

As far as I know, since the installation earth is taken at source (before your swa) then you can't take it again further down the supply.

I think this comes from Reg 543.4.1

 

[The Ghost]

Fit a switch fuse disconnector.

Yeh that makes sense, OP did say that.

 

[Des 56]

You best have that main Rcd as S type
100A 4 Pole 300mA Time Delay RCD | CEF - http://www.cef.co.uk/catalogue/products/142693-100a-4p-300ma-time-delay-rcd

 

[The Ghost]

Don't suppose they put it in ducting by any chance?

 

[KEV 1 N]

I think this comes from Reg 543.4.1

Well if it's in the regs, then it's in black and white....just seems maddnes having a good earth at the DNO cutout, then at the DB end ditching it and then put in earth rod. Again , the University has several of its own substations with massive section boards that feed other large buildings (so technically the substation is the DNO supply) so then there'll be say 3 or 4 300mm2 SWA cables go out to feed other buildings, no separate cpc, then when they enter the building, an earth conductor is took off the armour to an earth bar and then from that you'll have a main protective conductor to the buildings section board, and protective earthing conductors to other services.

 

[westward10]

You could always just use two of the phases and use the other core as the cpc.

 

[westward10]

Well if it's in the regs, then it's in black and white....just seems maddnes having a good earth at the DNO cutout, then at the DB end ditching it and then put in earth rod. Again , the University has several of its own substations with massive section boards that feed other large buildings (so technically the substation is the DNO supply) so then there'll be say 3 or 4 300mm2 SWA cables go out to feed other buildings, no separate cpc, then when they enter the building, an earth conductor is took off the armour to an earth bar and then from that you'll have a main protective conductor to the buildings section board, and protective earthing conductors to other services.

The armour of those cables may be adequate to support bonding.

 

[andysparkfree]

thanks for comments guys , i need all phases as massive house with a lift and various kitchens with big appliances etc , but i guess the main switch being 300ma rcd then me using 30ma rcbo units is the way , there is a 6 inch duct howeve its not a straight route and they didnt pull in a draw wire just the cable (bless them )

 

[KEV 1 N]

The armour of those cables may be adequate to support bonding.

Ah so smaller SWA cables may not be suitable for that. Funnily the cables I've seen used in this way were much bigger that 35mm2, 50mm upwards if I remember correctly.

 

[KEV 1 N]

thanks for comments guys , i need all phases as massive house with a lift and various kitchens with big appliances etc , but i guess the main switch being 300ma rcd then me using 30ma rcbo units is the way , there is a 6 inch duct howeve its not a straight route and they didnt pull in a draw wire just the cable (bless them )

Well I suggest you get a pet rat and train it to run through drain pipes with string tied to it, put it through your duct, then tie a rope to the string, then use rope to pull in earth cable.....job done

 

[andysparkfree]

haha KEV 1 N has solved it haha thanks lol ill go to pet shop 1st thing !!