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I'm looking for an easy way to verify that the metal casing of appliances are grounded, such as a range, without needing to disconnect and pull them out.

If I use a multimeter set to continuity and place one probe on a wall plate screw (that I know for sure is grounded), and the other probe to the metal frame, is this a safe way to check that there is a complete ground connection that meets at the panel? I know this won't verify that the wiring is sufficient, but just checking for a complete connection right now.

The meter itself, on continuity mode, puts out about 0.12mA and 0.5volts.

Thanks for any comments.

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With a range or dryer in particular, you have to pull it out and look. Many ranges are groundless, and bootleg the chassis of the machine to the neutral wire. This is exactly as dangerous as you'd expect, and has a body count - but most cases are mis-reported as incorrect wiring, when in fact the wiring was correct but simply broke.

This bootlegging ground of ranges and dryers is so common because from the 1960s til 1994, it was actually legal lol.

Other than that, disconnect all other loads on the circuit, then disconnect hot and neutral from the source. Now measure resistance from the apparent ground to a known good ground. You have to disconnect hot and neutral so you can cross off any "bootlegging ground" as ranges and dryers often do.

While such a "measured ground" is fine and dandy for the 5ma needed to trip a GFCI, it is not acceptable as an honest safety ground that might need to sink 200 amps or more. For that, nothing less than physical inspection will do.

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  • This is very prudent information. Thanks very much for your answer! – rewardingyeast Apr 15 at 19:46
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Sure if the outlet or switch is grounded measuring from there to an unpainted metal point will show continuity if the range is grounded.

However use caution you can damage an ohm meter even if there is a small current flowing on the ground of the range. It would be safest to turn the power off first.

This advice can be true of the lighting circuit also. Some devices do return a small amount of current on the ground and either case can damage an ohm meter.

Note yes there are UL listed devices that do use a grounding conductor as a return.

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  • While UL listed devices using a grounding conductor as a return is a real thing, and makes a lot of sense for light switch (or similar) retrofits where there is no neutral available, I would really be suspect if there was any measurable current on ground from a range, dryer or other major appliance. – manassehkatz-Moving 2 Codidact Apr 14 at 17:10
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    The clock in a 3 wire many times is 120v especially old synchronous motors 1 RPM they draw a tiny amount and were code legal so either side could be electronic clocks on a 3 wire still a 50 50 chance return on the ground, I see this quite commonly. – Ed Beal Apr 14 at 17:18
  • Yeah, and on any grandfathered ground+neutral it gets much worse. So I suppose it is really "on any major appliance with a 4-wire connection (modern stove, dryer, etc.) or with a 3-wire connection and no 120V components (e.g., hot water heater) or with a 3-wire 120V-only connection (e.g., washer)" that metal case=ground and ground should carry no current. – manassehkatz-Moving 2 Codidact Apr 14 at 17:21
  • Very interesting, I never realized some older devices were permitted to use their ground as the return path. Thankfully in this case the range does indeed have a neutral. My biggest concern was causing trouble to the range itself. Thanks for both of your comments! – rewardingyeast Apr 14 at 18:21
  • There are devices both 240v and 120v that do this it is a small value I don’t remember the number but want to say 3 ma max. That could be total with multiple devices I will need to look it up. And I agree with it should carry no current @manasehkatz but code allows a small amount. – Ed Beal Apr 14 at 18:36

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