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Im in the EU. In my room i have 3 outlets. One by the door, one at the balcony door and one in the middle.

I used an air space heater (not for the first time) in the same outlet where my PC is connected (the one at the balcony door). I went outside of the room for two minutes and came back to a shut down computer and the heater not running any more. At that time the heater was already running for around 20minutes and my PC didnt do a lot so shouldnt have drawn a lot of current. The light in my room was still running. I checked the breaker box but everything is good there.

Then I checked the voltage of the outlet and noticed that two of my three outlets in my room are outputting 130V instead of the usual 230V. The one outlet by my door outputs 230V and works fine.

I unplugged everything in that room and the two outlets still show 130V on the multimeter. When plugging in an extension cord with a light, it is on but very dimmed. No applications designed for 240V work in these outlets.

What could be the reasons for this? Is it possible that the use of the heater on the same outlet as my PC has damaged the mains line? And should I be concerned about a immediate fire risk due to broken wires in the wall or anything?

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    I would first turn off the breaker and after checking for no power at the outlets, pull each one out and check for loose connections. Do this for the good outlet also. Not sure of the regulations in EU, but if multi family building/rental, might need an electrician to do the work. So no touch until you know the regulations.
    – crip659
    Commented Dec 4, 2023 at 23:19
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    @crip659 it is getting late and I will do this tomorrow after checking my local regulations and if they allow me to do it. thanks for letting me know and for the suggestion :) Commented Dec 4, 2023 at 23:39
  • This makes me think your power is three-phase delta (three-phase is much more common in the EU than the US, due to apartment buildings) and one phase is broken. Maybe there's another circuit with 100V. Commented Dec 5, 2023 at 0:21
  • FWIW, in the US an electric heater (on full power) plus a desktop PC would be quite likely to overload an outlet. I don't know what's typical in EU though. Commented Dec 5, 2023 at 4:15

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Almost certainly have a serial arcing condition at wire connection to an outlet. Either on the still good outlet, or the first in line with low voltage. Normally the issue is quite evident from visual inspection, melted plastic/black marks/ashes, at the bad connection. If no burning is noticed, tighten all the screws and retest voltage

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  • What is "serial arcing"?
    – FreeMan
    Commented Dec 5, 2023 at 13:09
  • Serial arcing is from a loose connection. The wires / screws are not in solid contact with each other causing a small spark to "jump" the gap. This creates a lot of heat (same concept as a welder) which damaged outlets, melt wire nuts, even cause a fire. The USA has started requiring arc-fault circuit interrupters on most residential circuits to prevent this.
    – Keith
    Commented Dec 6, 2023 at 15:53
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    The series or serial is used to differentiate between short to ground, short circuit, and arcing occurring in the correct path of current flow. Short circuits are generally high enough current to trip the circuit breaker, mitigating the risk off fire. Series arcs will draw little more than the normal current of attached loads, so overcurrent protection does not come into play.
    – Keith
    Commented Dec 7, 2023 at 1:26
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    Exactly... Can also occur in wire nuts that were not installed correctly. Hope you get feeling better.
    – Keith
    Commented Dec 8, 2023 at 2:26
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    Hello thanks a lot you were right, there was a tiny damage on the neutral pin. Replaced the socket and got 230V in all outlets again. :) Commented Dec 8, 2023 at 8:18

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