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I'm trying to learn what the following means in relation to wiring a 240V Euro appliance in the US.

With European 240 V mains, one side of the circuit might be neutral, i.e., about ground potential. US split-phase always have neutral in the middle, with 120 VAC either side. If there is any connection between chassis and one of the two power lines, it would not work.

The Neutral wire is currently capped off at the appliance. Does it need to be disconnected from the circuit breaker in the box? I have a 4-wires (2 leads, 1 white, 1 green/ground)

Can somebody explain what it means to be 'connected to the chassis'? is the chassis the neutral bar in the panel?

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    Neutral should not be connected to the chassis for US 120V devices. That is what real ground is for.
    – Jon Custer
    Commented Jul 8 at 15:05
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    Nema 10 type circuits use neutral to ground the chassis. They were ban in 96 because they killed people. If neutral is not used, then capping it off at the panel is good. Code allows the use of white to be changed to hot/live if marked, so you can save a bit by using /2 instead of /3 cable.
    – crip659
    Commented Jul 8 at 15:20
  • @terryward that question belongs in the post ... it does not belong in a comment ... please edit your post and delete the comment ... this site is not a forum where you ask questions as you go along
    – jsotola
    Commented Jul 8 at 17:14
  • The white wire used for neutral is usually connected to a bar/bus on the side of panel and not the breakers. If the white is on a 240v circuit and in a black/white only(plus ground) cable then it can be marked black or red as a second hot and connected to the breaker.
    – crip659
    Commented Jul 8 at 17:28

2 Answers 2

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"Chassis" is the metal housing of the appliance. "Connected to chassis" literally means one of the incoming wires is electrically connected to the metal housing, and usually is implemented by one of the wires ending in a ring terminal which is screwed to a sheet metal panel somewhere.

As noted in your question, in the USA-style scheme, we regard earth ground and "neutral" as the "zero volts" reference. We have 120 volts between either of the mains lines and that neutral/ground reference, and 240 volts between the two mains lines.

You can see what would happen if a Euro appliance has one of its mains wires connected to the chassis (metal cabinet) and this were wired to one of the USA mains lines. Whereas made-for-USA appliances do have their metal cabinet connected to earth ground, if this Euro appliance has its metal cabinet connected to one of the mains lines, then we'll have 120 volt potential between the metal cabinets of the two appliances. A person touching the metal cabinet of the Euro appliance while also touching another appliance, or a sink, etc, will receive a shock.

On the other hand, if the Euro appliance is isolated so that neither of its mains wires connects to the chassis, then for use in the USA the chassis could be connected to earth ground and the appliance could be operated safely.

There's no need to disconnect the neutral at the breaker box. Unused conductors can be capped in any junction box where it's convenient to do so.

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  • Your hypothetical would trip the circuit :P Commented Jul 8 at 23:46
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    @ThreePhaseEel I see I should have clarified the hypothetical better: If one of the mains wires (the Euro neutral) were connected to the appliance chassis, but ground were not, then the chassis would be live and dangerous. With connection to both line and ground you're correct, we'd have a bolted fault and a quick-tripping breaker.
    – Greg Hill
    Commented Jul 9 at 17:45
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European and American wiring does not differ in the area of neutrals and grounds.

Neutral is not ground. They are never connected together (except, America: in the service equipment i.e. main panel not subpanels).

Neutral is the name of the hot wire which is "best effort" kept near ground. That doesn't always work out, which is why the neutral wire wears insulation.

Neutral is the normal return wire when current needs a near-ground wire to return on for voltage reasons.

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