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The electrical installation in my house is old and have no earth wire, with the outlets having only two holes. However, the new equipment come with three pins plugs, so I installed some new three hole outlets without any earth wire connected.

The problem is that if I measure the voltage between neutral and the chassi of a device that has a three pins plug, I get almost 60V. I think this voltage is being induced by the nearby live wire inside the power cord.

In such a situation, would it be better to disconnect the earth wire inside the equipment, so the induced voltage coming from the earth wire doesn't energize the chassi?

I know this is all far from ideal, but I'm just trying to figure out what would cause less harm.

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  • \$\begingroup\$ Frankly I don't think there is a difference. A long unconnected lead may pickup some more interference than a short unconnected lead, but for practical purposes is the same thing. I'll let someone more qualified answer though. \$\endgroup\$ – Passerby Aug 21 '16 at 1:58
  • \$\begingroup\$ What country are you in? Each country will have its own regulations, standards and 'normal' wiring expectations. Here in the UK most houses now are part of 'protective multiple earth' wiring type system. Historically 'wire' was in short supply, having any electricity was valuable, and danger was all around. Now wire is plentiful electricity is expected and safety expected. So a safety ('earth') wire is brought to the home as the optimum way of ensuring that fuses blow and circuits trip when faults occur. Get a good electrician to help provide you with the best of safety! Don't let it be luck. \$\endgroup\$ – Philip Oakley Aug 21 '16 at 7:11
  • \$\begingroup\$ Your 60V is not, in itself, indicative of a problem. As mentioned in other comments, the typical RFI filtering will result in a high impedance path from both power lines to the protective earth - it is probably that this path can't provide enough current to be a significant risk. (until there is a fault or ageing of some components, or a mains transient - so in reality, it is not safe since this equipment is required to connect chassis to the ground pin). Certainly the length of earth wire in the cable is irrelevant. \$\endgroup\$ – Sean Houlihane Aug 21 '16 at 8:46
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Yes, it's worse, in the sense that it is quite illegal in most jurisdictions.

A 3-hole outlet installed in a wall is a promise that the third pin is grounded. Suppose someone who doesn't know the truth plugs in a faulty piece of equipment and gets shocked because the ground is not there to protect them. You would be held liable for creating an installation that doesn't meet the building code.

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    \$\begingroup\$ It would be legal & provide some protection if the OP installed a 3-hole GFCI outlet and labeled it "No Equipment Ground". \$\endgroup\$ – brhans Aug 21 '16 at 2:25
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    \$\begingroup\$ @brhans So, basically, a labeled GFCI outlet would be the legal alternative. But it would not solve my 60V chassi to neutral problem. \$\endgroup\$ – Monfico Aug 21 '16 at 2:41
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Electrically, it doesn't matter. While it is illegal to do what you have done, it is not more physically dangerous (as long as everyone using the outlet KNOWS that it was modified) than using a 3 to 2 adapter.

What you absolutely should not do, is connect neutral to ground inside the outlet. While it may fool a building inspector, it creates a dangerous situation if there is a fault/break in the neutral line.

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    \$\begingroup\$ It is legal to do this downstream of a GFCI (at least under the NEC) -- you need a "No Equipment Ground" label though to satisfy your parenthetical, even with GFCI protection in play \$\endgroup\$ – ThreePhaseEel Aug 21 '16 at 2:32
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    \$\begingroup\$ Electrically it does matter. It matters because the equipment that has a 3 pin plug expects, as part of it's safe working, to have that third pin connected to a true independent power return. Importantly almost all equipments now have EMI/RF filters which pass voltage/current into pin (upto international standard / legal limits). It could be worse, they could have only one supply wire... (which needs two connections to the 'soil' - one as power return, and one as safety return) \$\endgroup\$ – Philip Oakley Aug 21 '16 at 7:17
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Yes, it's worse.

If a leakage current passes to the chassis of any electrical device by fault, and someone touches that device, he will be shocked if it is not grounded.

About the voltage you get when you measure between chassis and neutral, the chassis is not grounded so it has not to be any voltage in this case. So I would like you to check the voltage between phase and chassis, and to check if there is a continuity between phase/neutral and chassis to have a clear situation.

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The REASON that it is illegal is because it IMPLIES that the ground pin is actually grounded (else it wouldn't be there).

Your problem with seeing 60V (1/2 the mains voltage) on the chassis is because the device was designed with the assumption that the ground pin would be properly grounded. And since you did not actually ground the safety ground pin, you are probably seeing low-current leakage of some kind of filtering circuit on the device. This is just one example of WHY it is wrong (AND illegal) to leave the ground pin floating. DON'T DO IT!

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Time to take a chance. For this you need a length of green/yellow cable, so that everybody can see that it is earth, and rated 13 Amps or higher so that if ever there is a fault it will blow the fuse before this wire. Also probably a drill to get from the earth 3rd pin in your indoor wall to a copper water pipe such as under the sink, some sandpaper to scrape the copper to shiny, and a bit of metal often called a "jubilee clip". Even if the earth 3rd pin wiring in your house is incomplete, it is best that it really is earthed to your water pipes.

If you have a multimeter you can also check for earth leakage current from faulty or old or incorrectly wired appliances BEFORE you make this connection, mA from 3rd pin to earthed pipes. If you get anything more than 0.01mA then you have a faulty appliance somewhere in the house to find and disconnect. If you get less than 0.001 mA then adding this earth wire will fix your fault. If not then you have a faulty appliance.

For example I have a HP980 Deskjet printer whose earth leakage current crept up as its power converter board aged. Eventually I took out the mains to 31V DC power converter and run it direct DC (only two wires) off solar panels or batteries and a "boost" DC-DC converter-regulator. I make sure that the chassis of that appliance converted to two wire direct DC is crocodile clipped to a green and yellow wire which goes to the same earth as mains earth.

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What would cause less harm is wiring in the EARTH to all the sockets.

the appliance is "requesting" an earth connection for a reason

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