A metal-oxide varistor is Great
I use the MOV type that just shorts out when they reach a certain voltage, then the fuse or breaker opens.
Originally Posted by jadnashua
Never seen one smoke, but the MOV will stay shorted if it gets a big surge, and most good protectors have a led if the MOV has any leakage, or the device is not working.
The MOVs work good, but you have to have a fuse to open the circuit just in case they short.
I like to use the lower voltage MOVs because it don't do much good to Clamp at 220V if you are protecting a 120V device, Many clamp at near 200-220 V. They must be made for people that connect a 120V appliance to 240. Even tho the plug don't fit it can happen by incorrect wiring.
140 Volt MOVs seem to be the best for protection at 120 Volt normal use.
The good protectors come with a warranty for what you have plugged in , but I have never had the need to see if the warranty really pays out.
A lot of the filtering is to keep computers and switching supplies from sending RF or Harmonics back into the AC power, and eliminates RF from coming in. X10 devices will not work very well when plugged into a good filtered strip.