I have the very annoying problem of not having grounded wall sockets in an old house. Because of this, e.g. my large SMPS has a voltage potential of 115V AC to a ground wire I pull to a radiator. Hardly best practice, I just use it to ground myself before handling ESD sensitive stuff. Now I bought a 'ground spear', and need to know a few things:

  • What things absolutely must be grounded?

  • How can I best ensure a long life with regards to weather, contact between the ground spear and wires.

  • What type of wire should I use? I expect copper will oxidize rapidly once exposed.

  • How deep should I bury it?

  • Can I use a system of diodes to prevent voltage from the grounding wire killing my electrical devices? I don't expect this, but I would rather not explain to an insurance agent that my ground wire was played with. Note that I have both DC and AC to ditch from various devices.

  • And last, but not least stupidly, I want to be certain ground is ground, and that from A (my apartment) to B (the earth), I have continuity. I want to trip a relay instantly if GND is not on the line, so to speak, and alert me with a buzzer. My janitors are morons, and may interfere with my ground wire. It's no use explaining it to them. I'm adept enough to build a sensor - but what should I sense for? And how should I go about filtering out transients and a bit of AC on the wire being sensed upon?

Thanks, you boys are the best. Cluebats at the ready!

  • \$\begingroup\$ You must learn about the difference between Protective earth and ground, and if you own the house, you need to rewire, because no ground socket is just asking for troubles. \$\endgroup\$
    – Sclrx
    Sep 5, 2017 at 11:59
  • \$\begingroup\$ @Sclrx I know the difference. I need to ditch this 115V AC signal somewhere, and it's not going to be into my radiator. My janitors are in charge of electrical installations, and they don't even speak my language. They refuse to do it. Should I then take it up with city hall utility department? \$\endgroup\$
    – user2497
    Sep 5, 2017 at 12:17
  • 2
    \$\begingroup\$ i would at least check if your building is up to safety standards for your area. \$\endgroup\$
    – Sclrx
    Sep 5, 2017 at 13:27
  • \$\begingroup\$ @Sclrx It is not up to code. \$\endgroup\$
    – user2497
    Sep 5, 2017 at 14:02
  • \$\begingroup\$ @Sclrx While he says the wiring is "not up to code" and while I agree that lack of an earth at mains sockets is problematic, this is allowed in some administrations in some contexts. Unfortunately. \$\endgroup\$
    – Russell McMahon
    Mar 1, 2019 at 5:25

1 Answer 1


It really should be fixed properly, not just bodged, but...

  • Anything that's not double-insulated. Especially anything that heats water, or which has a switched-mode power supply.
  • Get a proper kit from an electrical supplier, designed for the purpose.
  • A fat copper wire.
  • As far as it will go.
  • No. If your appliances are "killed", they were faulty already.
  • I'll leave that up to you. It's not going to be easy without another ground reference, and you don't want to introduce dangerous voltages into the system as part of the testing.
  • \$\begingroup\$ Very good, thank you. And let's just say I won't be connecting this ground electrode to the GND pin of every wall socket - because there isn't one ;) \$\endgroup\$
    – user2497
    Sep 5, 2017 at 12:44
  • \$\begingroup\$ Some people seem to recommend a 1Mohm resistor between a SMPS and protective earth. Surely this isn't necessary? I tried adding one, but there's still an uncomfortably high AC potential present. I'm glad I found out about this problem, it's likely the cause that some chips have died for no apparent reason. \$\endgroup\$
    – user2497
    Sep 9, 2017 at 17:38
  • 1
    \$\begingroup\$ 1M will do nothing to protect you in the case of a fault - it's way too high. it may not even be low enough to let through the natural leakage of the filter capacitors in a power supply. The ground pin on an appliance is meant to be solidly grounded. \$\endgroup\$
    – Simon B
    Sep 9, 2017 at 18:32
  • \$\begingroup\$ 115V AC at 0.5mA. I use direct grounding now though. \$\endgroup\$
    – user2497
    Mar 6, 2019 at 16:05

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