Contactor Surge Protection

[mcraddock1210]

I need some help and education on surge suppression.

Trying to select some surge protection for some Allen Bradley 100-C series contactors and the coil is 120 AC and with that I have a choice of RC Module or Varistor module?

In the product configurator it asks for coil voltage and the choices are 110-280 V 50/60 Hz RC Module or 56-136 V AC / 78-180 V DC Varistor module.

Which is better and why?

 

[jraef]

Varistors protect against more sustained over voltage spikes by "switching on" to conduct high amplitude spikes to ground, but are of limited use in protecting other equipment connected to the same circuit against inductive kickback caused by turning off the relay/contactor coil. RC snubbers are better for that because they limit the rate-of-rise of the transient, but do not really protect against sustained over voltage conditions, because eventually it gets through. So it depends on why you are installing the device. If you want to protect the COILS from spikes and surges, a varistor is what you want. If you want to PREVENT the effects of turning a coil off on other equipment in the same circuit, you want the RC snubber.