On my ceiling there's this connector where you attach your lamp's wires but it has no indication which side is hot and which is neutral. Is there a simple way to figure it out or does it not really matter?

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  • 1
    It's hard to tell what's going on with all that plaster coating everything. That looks like a ground wire on the left, completely coated. The terminal on the right .... does it have a cable attached at the back, buried in plaster? Or is it just a terminal block where the supply and lamp wires can be attached? If the former ... you need to dig it all out and clean it up. Then hopefully it will be obvious which one's hot. If the latter .. then it doesn't matter but then you have bigger problems. You might have a box with a cover that can be removed. Scrape off the plaster.
    – jay613
    May 23, 2021 at 18:13
  • This must be in the UK. Don't need to scrape off. You need to get a non-contact voltage tester. Some lights might be polarized so you should find out which is hot and which is neutral. May 23, 2021 at 19:14
  • Yes indeed, that's the ground wire. Apparently when the house was painted they spray painted everything so now it's all coated. There is a cap, all the wires are underneath it and I assume there are 2 screws (also currently coated) to hold it in place. I believe my situation is the latter. Could you elaborate on the bigger problems? Edit: This is in the Netherlands. Considering I am a complete noob, is there any danger while handling this voltage tester?
    – John
    May 23, 2021 at 19:34

1 Answer 1


Looks like they just covered the connector and textured everything.

Using a volt meter put one side to the cover plate then one side of the receptacle should show line voltage the other much less or nothing,

there is a possibility of a voltage being measured on the neutral with no connection to a load (called phantom voltage) in that case the lower voltage is neutral.

It matters for safety if wired wrong a metallic fixture may be energized on conductive surfaces but since there is a ground this should trip the breaker.

  • Thank you for the answer. As for the safety part, if a light's wired wrong and its fixture is plastic nothing can happen?
    – John
    May 23, 2021 at 20:14
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    With the an Edison socket the shell is required by code to be neutral if the shell is live it creates a greater hazard even if the housing is plastic. I have seen fixtures that both the neutral and ground were connected that would not be code or UL and would trip the circuit breaker. Note the code issue is nfpa or underwriters labs,
    – Ed Beal
    May 23, 2021 at 22:13
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    @john: almost nothing: the exception being while carelessly changing the bulb (touching the ring) without turning off the switch, and being referenced to ground somehow. It's happened to me a few times in the US, and would be worse in the UK.
    – dandavis
    May 23, 2021 at 22:24
  • I agree with Dan, 230/240 to ground bites hard compared to 120v.
    – Ed Beal
    May 24, 2021 at 15:17

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