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I live in Germany and I have just moved into a new apartment and started to change the light fixtures, but I ran into confusion. Wires coming out of the ceiling are - two black & two white (no earth), and no grounded mounting plate - just a screw into the celling. Also, none of the wires were tied together.

The light fixture I wanted to remove had one of the black live wires attached to the live terminal of the fixture (cool), one of the white neutrals connected to the neutral terminal(cool), and then... the 2nd white neutral was connected to the light fixtures Earth!? I plan to replace it with a fixture that also requires earthing.

I believe that at the main power source (municipal), Earth and Neutral are tied together, but is this common practice? Should I connect the second neutral to the earth, or should I rather not 'ground' my light fixture?
(btw: the light is controlled by a dimmer)

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  • Does your building have a main distribution board that then serves individual distribution boards in each flat, or does power go to the meter then directly to your flat's distribution board without going through some sort of main switch anywhere? May 25, 2020 at 1:12
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    Why are they using white and black in Germany? Is this former East Germany? May 25, 2020 at 3:05
  • Bavarian: The wiring in this colours is all over the place. Livingroom: 2xwhite 2xblack Bedroom: White, Black(tested to be live), Red (tested to not be live). Bathroom: Brown Blue Green [finally something familiar;) ]. Kitchen: White & Black(tested to be live).
    – dovi
    May 25, 2020 at 7:28
  • @ThreePhaseEel - Don't know for sure, but I believe power goes to the meter then directly to your flat's distribution board.
    – dovi
    May 25, 2020 at 7:37

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This seems to be an old wiring system. What is on the other end of the white wires? Maybe one of the white wires was used as PE= Protection Earth=Ground already, but it was not marked yellow-green with shrinking tube or other reliable markings at both ends which is mandatory nowadays.

Otherwise a Neutral must not be used as PE for safety reasons. If both white wires are Neutral and none of them can be re-marked and re-used as PE, best way would be to only use lamps that are isolated and do not need PE, i.e. are having the 2 squares (small square inside 2nd square) as symbol (Schutzisolierung, Schutzklasse 2).

Yes, Neutral and PE are connected, but only very upstream close to the location where the incoming provider line is entering the building and at one and only one location. Neutral and PE must not be connected anywhere downstream, and are to be kept separated downstream.

If Neutral and PE are connected at a 2nd (or even 3rd, 4th etc.) downstream location, GFCIs (RCD, Fehlerstromschutzschalter ) could be failing, and sensible electronics may be more likely to fail, since a second connection of Neutral and PE would produce a loop which is an "antenna" resp. 1-turn secondary coil capable to catch distortions (50Hz humming) and will be more likely to catch high voltage surges (from lightning strokes nearby, switching activities at the provider's net etc.).

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  • Thank you for the very clear answer. How would I be able to test if one of the white wires was actually PE? Can I take a meter to it somehow? - Maybe trying to test continuity to a known PE or maybe checking if there is some kind of voltage differential between the the two whites? Please excuse any ignorance here as I am bit of a NOOB to troubleshooting this type of thing.
    – dovi
    May 25, 2020 at 7:46
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    No, since both Neutral and PE are galvanically connected, a continuity or voltage test could be misleading. This would only be possible if all Neutral (and/or PE) wires would be disconnected from the electric panel(s) after disconnecting all power. But there might be a way to find out via a GFCI (RCD, FI, Fehlerstromschutzschalter). Is there a GFCI in the electric panel?
    – xeeka
    May 25, 2020 at 9:47

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