We rewired a house recently that had been subject to rodent damage,they chewed the rubber wires,which were in RMC,unusual in Australia,used 4mm 2 core romex for power ground terminal just pigtailed to the box,inspector says we should have used 3 core,pigtailing to the box at every j box or outlet,etc,i disagreed,who is right.

He is.

boora:
Please placeyour posts in the 'Non-US Electrical Systems Area".

Practice here in US is that any metal box, as well as the device be bonded to an equipment bonding conductor. That is either a bare, or green insulated conductor.

12/2 NMC(Romex) is 1-black insulated (hot); 1-white insulated (neutral); and 1-bare conductor. All are 12AWG.

Thank you guys,when I worked in the US only EMT had to have a ground wire ,Most RMC used the conduit as the ground,but I suppose will know next time.

EMT is recognized as a grounding conductor, and always has been, in the US.

No ground wire is required.

Although EMT is indeed recognized as a grounding path, I have seen many jobs where an additional ground conductor is required for the specific job.
Be sure and check what the Specifications and local amendments to the Code may say.

ONE reason that a bonding conductor is mandated is the real world experience of looking at loose set-screw fittings.

I've seen rush jobs where it became obvious that the original installer was never returning back to tighten half of the set screws! He'd slap on a coupling, tighten it, slam the bare end into the running stub, strap it, and move on. Going back ten feet to hit the other setscrew was just too tedious for this fellow.

Needless to say: the bonding to ground was terrible.

This sloppy method is NOT at all rare. You'll see a lot of it on non-union, rush-paced work. (Big box retail, grocery stores, etc.)

I just witnessed a code violating EMT job at the local auto parts house. The EC didn't EVER strap EMT running from purlin to purlin when they ran square to the purlins. Instead, they just settled for a naked, unsupported run from box to box -- all in plain view -- this was an open ceiling scheme.

In similar situations, my EC would always use back to back nineties so that the EMT could be strapped to the purlins before being sent over to the other side.

As installed, the EMT is going to separate in any earthquake -- and this is California.

The EC did do a bang-up job straping LV flex runs to the F/A system, though. So he has that going for him.

I always wonder at the difficulty some places seem to have in running EMT- and I marvel at the religious fervor of those who like seeing a green wire!

The Steel Tube Institute has a link to a UL grounding study of EMT. The amount of fault current EMT can carry is awesome. I was there for some of the tests- and, trust me, there were plenty of loose connections in the test set-up. (They didn't plan it that way, it's just that their techs are not electricians!)

Somehow Chicago seems to get along just fine without that redundant green wire. About the only time Chicago electricians like the green wire is when they can use it as a pull string

Adding a few more lines to the NEC is not going to help, when the issue is careless or incompetent installation.

I recently worked on a 20A circuit that had a #10 feeding the box, a #12 to the appliance, and a #14 ground wire - all run in EMT. One could see from afar that whoever ran the pipe was not very practiced in either running pipe, or in mounting to industrial construction.

Some folks could mess up a one-piece puzzle.

I've seen RTU EMT runs that were -- literally -- falling apart. Yep, no bonding conductor.

And, yes, set screws for outdoors, roof top HVAC installations.

With experience, I just started to insist on green for EVERY exterior run. It's a trivial expense in the over all scheme of things.

Boora
Think you'll need to consult AS3000:2007 assuming that is the current issue in Oz.
Here in the UK BS7671 still permits the use of screwed steel conduit, trunking, SWA & MI sheath to be used as a circuit protective conductor (ground wire) in final circuits subject to compliance with EFLI values. A fly-lead tail from mounting boxes to wiring accessories and light fittings is required as you describe.
However although our regs permit this use most specifications call for the installation of a separate green & yellow conductor for each circuit.
It would be pretty much unheard of to rewire an old steel conduit installation and not run an earth along with the circuit conductors. Most sparks would not trust the integrity of old steel conduit - which is typically black enamelled & prone to corrosion - especially where it is concealed within the building fabric.

No way mate.
What you should have done was tear all of that old rubber wiring out and start again from scratch.
If I had have been the inspector there, I would have failed your install and removed the supply from the building.

You don't use old metallic conduits for new wiring, especially when they are rusty inside.

What you do do though is, replace all of the old work in Medium Duty PVC conduit and run all your new circuits with it's own earth conductor, tie them together at each box with a "strip connector".
By box I don't mean junction boxes, unless you have a seperate tap off point from that box.
My idea of a box is at light fittings or switches.

Oddly enough, mate, you state you're from the US, do you hold any qualifications as an Electrician in Australia?,
reason I ask that is, if you'd been in the trade long enough to "get your trade", you would have known most of what I've posted above.