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Australian 240v power supply.

Worked fine without incident for 5 years. One day I plugged washing machine into a plug adapter with no ground connection between the washing machine plug and the power outlet. (so it just has live and neutral connections). I received what felt like a 100 to 240v shock from the metal drum of the washing machine.

Putting my proximity voltage detector within 40cm of the unit resulted in it beeping (it usually needs to be within 1cm to detect anything.)

My question is: does this mean that the washing machine drum was always energized, and the only thing saving me from being shocked was that the ground wire was safely attracting the current away from me when I touched the machine? Does this mean that the only possibility is that somewhere inside the machine a live wire is touching the metal exterior of the machine? or could it be another possibility?

My multimeter results: From ground on plug to washing machine drum is infinite to 120,000 ohms resistance (changes when drum rotates). To other parts of the metal chassis it shows 83 ohms resistance. These parts still cause the proximity detector to light up. The live, neutral on plug to drum and chassis show infinite resistance.

The live, neutral and ground prongs on the plug all show infinite resistance to each other.

My voltage testing screwdriver lights up when touched to the drum, chassis and internal ground wiring.

All other readings are infinite/blank, including voltage and current readings from drum and chassis while they are energized.

I don't understand how I can get shocks from the drum and chassis and they can set my proximity voltage alarm off, but no readings come through the multimeter. Is it because I can only rest the probes on the metal drum and the resistance is too high in my multimeter and the current is happier to flow through the chassis?

Note: the machine does not have to be turned on for the proximity meter to detect voltage in the drum.

Thanks

  • You can have induced electricity, this will transmit voltage but a (DC) multimeter will show infinite resistance. Note: I am not saying this is happening to you. – Ariel Jan 13 '15 at 19:30
  • Could this happen with the way the washing machine motor works? I am interested in this theory because touching the chassis on the outside does not result in a shock, only the steel drum inside. – skybreaker Jan 14 '15 at 1:41
  • The ground pin to chassis should show nearly zero ohms (or infinite ohms but nothing in between), the 83 ohms suggests that it's not really bonded to the chassis. If you were in the USA, I'd suggest that it's using split-phase 240VAC power and was using the ground connection as the 'neutral' to get 120VAC. However, I believe in Australia 240VAC is your 'base' powerline voltage, so split-phase 120VAC doesn't exist. Did the washer work normally aside from the (potentially dangerous) shock? – Johnny Jan 14 '15 at 2:15
  • Yes, you are correct about Australian power. I tested it again on various spots and it varied from 4omhs to infinite. Yes, it worked normally whilst being plugged into a grounded plug, without shocking and whilst being plugged into an ungrounded plug, with shocking. – skybreaker Jan 14 '15 at 3:02
  • The washing machine drum is likely coated with something, screwing with your measurements. If you probe between two separate spots on the drum what resistance(s) do you get? If its not near 0, your measurements arent working properly. It may be insulated well enough to stop the tiny voltage from an ohm meter from being detected, but not stop 240V. – Grant Jan 14 '15 at 4:33
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Putting my proximity voltage detector within 40cm of the unit resulted in it beeping (it usually needs to be within 1cm to detect anything.)

This usually means hot/neutral is reversed. There might be nothing wrong with the washer. Call an electrician first. And ground that outlet! Your machine's electronics will thank you.

(FWIW I use a non-contact voltage detector daily for diagnosing home appliances.)

  • Is it common for Neutral to be bonded to the chassis in Australia? If not, then I don't see how a swapped hot/neutral can cause this problem. – Johnny Jan 16 '15 at 23:15

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