ring main earth

[c.boy]

hi

Done a ring main test,its wired in 2.5 singles and 1mm earth, its a very old install.

continuity readings were 0.35 live 0.35 neutral all good.but the earth is 0.34. does this sound ok to yous??? a know in twin and earth its 1.67 x higher than the conductors.

 

[Darkwood]

Possible got a parallel path when testing the earth, like a steel conduit or metalclad sockets on steel girders either way the lower the resistance the better if it is a confirmed ring.

The 1.67x is applicable when the earth ratio is correct to the phase conductor but in your case it seems the earth is alot smaller and the expected reading should be 2.5x but as i said it seems you have a parallel path somewhere which if a recognised earth then the undersized earth might not be an issue, not sure if 1mm earth is acceptable with 2.5 ring?
Will leave this open for someone else.

 

[Spudnik]

1mm cpc is no longer permitted on 2.5 RFC.

 

[Darkwood]

1mm cpc is no longer permitted on 2.5 RFC.

Thanks jason dont often use it now so lose track of some things thanks for the update save me looking

 

[roonbergz]

rewire ;-)

 

[c.boy]

rewire ;-)

well this is the council i work for!!!! so we will wait and see all is on my test sheet so ave covered my butt!!! will they?????

 

[zupos40]

hi

Done a ring main test,its wired in 2.5 singles and 1mm earth, its a very old install.

continuity readings were 0.35 live 0.35 neutral all good.but the earth is 0.34. does this sound ok to yous??? a know in twin and earth its 1.67 x higher than the conductors.

what were the singles installed in plastic or metal conduit, mini trunking etc

 

[c.boy]

hi
they were in metal conduit,got to be a prrallel path

 

[zupos40]

hi
they were in metal conduit,got to be a prrallel path

Possibly to late now, but the next time, remove the 1mm or 1.5mm single CPCs and check the continuity of the metal conduit first, then preform the ring contiuity test on the CPCs, just because you do not get the reading as specified by GN.3 OSG etc it does not mean it unsafe.

If the insulation test result were satisfactory and Zs complied, inspection satisfactory I see no need for rewiring circuit.

I would test continuity of the conduit usinfg long lead method working from CCU to wards furthest outlet