1. Came off my ring main recently to install an appliance and noticed the voltage was approximately 340v. Any idea why this is and/or should I be concerned?
  2. Hans_25

    Hans_25 Active Member

    What were you measuring exactly? Mains voltage is 230V RMS which is a peak of 320volts.
  3. Mains voltage. I was putting a volt meter across the + and - in the junction box just to see if I had removed the correct fuse (old fuse box, not labeled), and noticed the high voltage.
  4. unphased

    unphased Screwfix Select

    I think you must have misread the reading. 340 V is too high for your supply. You would damage equipment with that level. The official voltage for single phase supplies to domestic premises is 230V +10% / -6% or 216.2 V to 253.0 V. This is information provided in Appendix 2 of the wiring regulations. If you are absolutely sure you measured it correctly report it to your electricity supplier.
  5. Bazza

    Bazza Well-Known Member

    Do you have your meter on the correct range? You may get something like that if you have it set to DC instead of AC.
    What make/model of meter do you have?
  6. Bob Rathbone

    Bob Rathbone Well-Known Member

    I would check the meter on another supply in a friends house. I reckon the meter is inaccurate.
  7. nigel willson

    nigel willson Well-Known Member

    + & - on an ac supply , interesting

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