Hi guys, I have what looks like 2 red thermistor that blew up. They are located between both of my 240v line and my neutral. Can anybody confirm thermistor could be located there and does anybody have a idea why the blew up. How do I know what replacement part to get now that they blew up and that the number is gone.

by Spike009
May 18, 2020

Can you provide more context? Is this part of some electrical appliance? You can also add a photo.

by mrobbins
May 18, 2020

Thank you for your answers. After further research, found out that those component are probably MOV varistor. I think that there must be a short some where in my card that increased my neutral voltage causing my mov to blow. I will look into it tomorow.

by Spike009
May 18, 2020

A MOV, or metal oxide varistor is like a very non linear resistor; high resistance when the voltage across it is low and low resistance when the voltage across it is high. They have a number of uses but are commonly connected across a voltage supply to protect downstream equipment from a transient voltage spike and from your description this is why they were used in you case. If they exploded it's either because you are getting high voltage spikes from a low impedance source in your supply or because they are too low a voltage rating. The voltage rating of a replacement should be greater than the maximum voltage of the supply and keep in mind that for ac supply the maximum is 1.414 times the ac rms voltage. For a varistor I would add an ignorance factor of 15% or 20% over this. These things fail with quite a bang so keep your fingers away when you first energize it.

by Foxx
May 19, 2020

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