Varistor Values

Hi, I have a question about varistors.

I fix stuff for a living, I don’t design it ... and I’ve never really understood how the values are chosen because the datasheets show so many different values for each device.

I have a basic 240V – 24V switched mode power supply that got hooked up to 440V apparently.

Seems to have blown a fuse, NTC resistor and a varistor.

What I am surprised about is that the varistor is a 470V varistor ... TVR14471-D.

Does that sound right for a supply operating on 240V?

Thanks.

With the numbers on the right it seems correct, you don´t want it to activate for minor overvoltage. You can have 264Vac in the 240V system all the time, so rating it for 300Vac (thats 424V peak) sounds reasonable.

Thanks kubeek, I don't look at varistor datasheets that often ... and I got myself confused in the way some of the parameters are listed ... between the original ... and the ones I keep in stock.