Using conduit as earth.

[aaelectric]

Went to carry out condition report on a flat. There is no earth cables from fuseboard to first point . The installation is over 30 years old and other contractors have just added twin and earth under floors/walls. R1+r2 values seem to be high aswel. Zs is not so bad and is within allowed time.main bonding to gas is 2.5 single earth and main earth from pyro cable is 6mm. The tenant and i could not find the main water supply to see if it was earthed. No isolators for equiptment in kitchen. Socket wired from cooker circuit in 2.5mm t&e on 32amp breaker. Cooker is wired in 6mmt&e.earths not connected at light switches and they are using metal plate switches.
i was goin to advise arewire wat are your thoughts?
Is the conduit allowed to be used as an earth or do you need a earth cable installed?

 

[Engineer54]

Of course Metal conduit is allowed to be the CPC for whatever circuits are enclosed in the system. The only time you should need to include a separate CPC conductor in a well installed conduit system, is if and when the conduit is breaking down due to corrosion...

You obviously need to upgrade the bonding conductors to the service pipes!! Maybe also upgrade the flying lead off the MICC supply cable to a 10mm...

As for rewiring the system, that depends on the condition of the installed wiring?? The T&E wiring was probably installed for placement of extra/additional socket outlets etc, that the original conduit system didn't cover!!

 

[Guest123]

A steel containment system is one of the permitted methids of providing a CPC, 543.2.1 (vi) refers.

 

[aaelectric]

As stated the r1&r2 value is very high and the conduit is behind walls cupboards etc. this leads me to think there is some corrosion on conduit.
what about isolators for appliances in kitchen, bathroom fan etc do they have to have isolators. Also the 2.5 comin off 6mm on a 32amp breaker
cheers for the advise