I am trying to identify the cause of a voltage drop. When there is a high load, it seems to affect the voltage throughout the house - dropping as low as 170v (from 230v) - clearly this isnt good.

I have a multimeter. Anywhere in the house I take the reading is showing the reduced voltage. If i take it on the consumer unit, it shows the reduced voltage. If i take it on the breaker connected to the meter, it shows the reduced voltage. When I reduce load, the voltage goes back up.

Does this sound like this is something in my house, or it it an upstream issue with the load? Is there any way I can identify where? Ive tried tripping breakers, but obviously that reduces the load from that circuit, thereby bringing the voltage back to normal levels, making it hard to isolate the problem circuit (if it is a specific circuit at all).

  • 1
    Does the voltage ever change on its own, when you are not changing your load? Any neighbors having this problem? Oct 3, 2019 at 20:28
  • How many legs/phases of service do you have coming into your house, and where are you on this planet? Oct 3, 2019 at 22:51
  • Is one load/device causing the drop? If so, details on the load? Has the service/panel been modified/upgraded? It almost sounds like an undersized service transformer to me.
    – peinal
    Oct 9, 2019 at 16:39

1 Answer 1


You may have a lose connection at the main or in the meter. Check the areas above the branch breakers. Particularly at the main breaker the main bus below the breaker and the lugs at the meter. Look for signs of overheating or burnt insulation. Also if you have an infrared thermometer look for hot spots the drop could be coming from the internal parts of a breaker. Picture attached for an example.

enter image description here

It may not look as bad but it will in time. If you find the location you need to replace that piece of equipment asap.

Good Luck

  • Thanks for your help. It turns out the problem was upstream - namely the cables coming from the substation to the property aren't sufficient to deal with the load at my property :/
    – Matt
    Feb 10, 2020 at 10:40

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