TT and Earth rods

[PEM]

Just replaced old CU on TT with 7 way Crabtree RCBO board.

Original Ze was 230 on a copper tooth pick. Got Ze down to 6.5 ohms using 3 x 4ft 5/8th rods.

Just interested to know how low you guys have got a Ze down on TT and when you'd stop hammering down to Australia?

Cheers

 

[jamie-spark]

MCBs don't detect neutral - earth faults, they detect over currents and break the fault.

SP RCBOs detect a neutral - earth fault and then break the live! Where is the sense in a protective device which detects a fault and then effectively masks it?

I think he is getting at the fact there are undetected N-E faults

Interesting post though

 

[Knobhead]

With the correct protection N→E faults won’t go undetected, will they?

 

[jamie-spark]

Tony you are correct

I think he is getting at, that in an tns or tnc-s installation. say industrial where there is no requirement for a circuit to be rcd protected. Either sp or spsn or DP. That the fault would go undetected until there was further testing done

 

[davesparks]

Unlikely to go undetected in industrial, somewhere up the chain there will be earth fault protection in the system. Or failing that the resultant fire from the neutral currents going astray will soon help it be detected!

 

[Engineer54]

MCBs don't detect neutral - earth faults,

But MCB's do detect faults to neutral and to earth .... if they didn't, we'd be in some serious trouble!! Just like the SP RCBO the faulted neutral or earth, will still be in place too, only the phase will be broken ...lol!!

 

[davesparks]

You know what I mean!