Voltage Protection Device Questions


I recently installed Voltage Protection devices for my 2 x aircon circuits… and I have noticed that 1 of them is displaying a much higher voltage.

Circuit 1 = ± 231v
Circuit 2 = ± 247v to over 250v

When device 2 goes over 250v it cuts off and then switches back on. I have a few questions

  1. What could be causing this higher voltage on Circuit 2?
  2. Is it safe to run at over 250v to 260v? I see I can configure the voltage protection device up to 280v

Are they on different phases?

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First step is to take a multimeter and check the measurements.

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No they are on the same phase - I used to have 3 phase but I moved everything to a single phase… still need to log with eskom to remove the other 2 phases.

I have 1 of those but don"t know how to use it lol… will try and figure it out

Then you need to use the multimeter to check the voltage at the point of connection to the voltage protection device.

If they are both properly connected and tight and at the same voltage on the input side of the device then you possibly have a faulty reading from one of the devices.

It’s pretty simple to find a YouTube video on how to read voltage with a multimeter.

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Thanks - managed to learn how to use the multimeter!

So the input side from Eskom to the device is showing as ±233v (similar to other working device reading) so its possibly a faulty device?

Could it be a wiring issue causing this? I’ll need to double check that its all tightly connected

Very likely. A bad connection will tend to make it read lower rather than higher.

The only time a bad connection causes a higher reading is when the device is MAKING power. Then the additional impedance pushes the voltage up on the generation side.

Something else you can do is to swap the two devices and see if the problem moves with the device. I mean, I probably wouldn’t do that (mess with the perfectly good one) if the multimeter already tells me that the device is likely not properly calibrated… but it is something you could do if you had to diagnose without a multimeter.


Thanks @plonkster - will be replacing the device. Hopefully ACDC play nice around this.

Beware of meters (displays) showing volts and amps etc. on cheaper products. I had an Amp-hour meter that displayed the measured current which was hopelessly inaccurate!

Sorry forgot to post back to say this is solved. I took it back to ACDC and apparently it wasn’t configured correctly (not sure how/why) but I connected it back and it’s working fine.

Thanks all for the help/advice!