Main Earth to Sub Main

[swifters]

Hi all, regards the csa of the earth to a sub main in a flat, does it need to me 6mm or 10mm or larger still? There is a flat with PME and they have asked for an EICR. However, the sub main is fed via 10mm t&e and the earth is only 6mm with a 10mm supplementary bonding and 10mm to gas reliant on this. The 10mm to water goes directly to the MET at the incoming main. Would this be a C2 or C3? Got a Ze of 0.21. I would have thought with the Adiabatic equation that it would suffice but not with selection based on the tables.

It states a C2 on the electrical safety council best practice guide [FONT=&quot]"Cross-sectional area of the earthing conductor does not satisfy adiabatic requirments (that is does not comply with regulation 543.1.1)[/FONT]

Yet, regulation 543.1.1 seems to say it can either be calculated or selected?? There is a 60amp BS 1361 at isolator. Gona be a pig to run a new earth cable if required as in a communual area and a fair way.

Many thanks

 

[telectrix]

it the earthing conductor satisfies adiabatic, but not the min. stated for pme, then maybe a code C3.

 

[Guest55]

it the earthing conductor satisfies adiabatic, but not the min. stated for pme, then maybe a code C3.

I agree ^^^
If connections are good and no sign of heat damage , C3.

 

[swifters]

Sorry Ze was actually 0.2 So 230/0.2=1150amps, therefore for the adiabatic equation is it the square root of (1150 x 1150x0.2) divided by 143? = 3.6mm. Not sure if I am using correct time and K values???

 

[telectrix]

at that fault current , fuse should go in<0.1 sec. as the earthing conductor is enclosed within the T/E cable, you might be better off using 115 for k. even so, the 6mm is well in. code C3 IMO.

 

[Engineer54]

You also need to bond the incoming water supply pipe to the the flat/apartment's MET, if it's of metallic construction!! Each Flats/Apartment should be treated as an individual dwelling unit and therefore should comply with all normal bonding arrangements and requirements...

Telectrix has answered your other question...

 

[Guest123]

The CPC within a 10mm T&E is 4mm.

 

[londonlec]

I usually find these to be 16mm T + E with a 6mm CPC.

 

[swifters]

Sorry yes, I think it is 16mm. Once again thank you all.

 

[swifters]

You also need to bond the incoming water supply pipe to the the flat/apartment's MET, if it's of metallic construction!! Each Flats/Apartment should be treated as an individual dwelling unit and therefore should comply with all normal bonding arrangements and requirements...

Telectrix has answered your other question...

Water main is bonded to MET at the main incomer. Gas is bonded to consumer unit earth in Flat.

 

[rich.250]

Water main is bonded to MET at the main incomer. Gas is bonded to consumer unit earth in Flat.

Then surely you need 10mm cpc to comply with PME conditions between felt CU and Mains position.
Otherwise 10mm bonding is pointless.....

- - - Updated - - -

flat* lol

 

[swifters]

Felt??? I do see what you mean though. Why bother running a 10mm to the Gas when the main earth is only 6mm. Waste of copper! It even has 10mm to the bath and taps too.

 

[rich.250]

Might as well bond all those knives and forks......... there metal!!! LOL

 

[Engineer54]

Water main is bonded to MET at the main incomer. Gas is bonded to consumer unit earth in Flat.

Wherever the main water supply enters the flat/apartment then you must bond that pipe to your CU's MET regardless of whether is has been bonded elsewhere in a multi dwelling building.

Bonding arrangements have nothing to do with sizes of main earthing cables. The two systems are there to satisfy two completely different purposes...