G90 Earthing

[ianburg]

My (one month old and working fine) G90 rack unit keeps failing a portable appliance test on the basis of poor earth continuity. I'm in Aus and many venues will require a PAT tag before they let you plug in

 

The resistance I am measuring between the earth pin on the plug and say a random screw on the case is less than 0.5 ohm. Is there something I'm missing here, is the chassis not solidly earthed? The amp and compressor in the same rack pass fine.

 

Input welcome and thanks in anticipation.

 

Ian B

[dboomer]

What is your local requirement for earthing resistance. Usually it's "less than 1 ohm" and you say you are getting better than half of that. I must be missing something here ;)

[ianburg]

I think WE are missing something here. I would expect the rack to be solidly earthed. I've separately tested the supply lead and know that's OK. An ohm meter gives me a resistance that's < 0.5 ohms.. I will have another crack at it with fresh eyes again today.PAT tester is automated to comply with ANZ standards and has passed every other piece of kit I use except a couple of Chinese-made kettle leads that have the live and neutral pins swapped, which is no big deal. Without digging out the standard, I think less than 1 ohm is the target. Anyway, I think you've confirmed the solid earth (no floating earth) so I will continue exploring. Thx.

[ianburg]

Rechecked. Finally opened up the rack unit for physical inspection. Absolutely nothing wrong, bonding is rock solid and sound. I have no doubts about the integrity of the earthing on the G90 rack. I will follow up with the PAT testing kit. BTW, I am an electrical engineer so I don't think it's total ignorance on my part. If I get to the bottom of it, I will post. Thx