Can you tell which of the two MOVs is damaged? Neither can we.

So what is a MOV, and its effect on your business?

A MOV (Metal Oxide Varistor) is a component used to protect electrical devices from high transient voltages. A MOV is required to be connected across LINE and NEUTRAL and not LINE and GROUND, as protection against instantaneous high voltage surges

A MOV based surge protector will stop voltage spikes and surges, but not the violent, catastrophic burst of current from a close lightning strike. The size and speed of this current is simply too big for the MOV to be used as the primary electronic component inside a protection device, and that includes the protection circuit in the most common UPS units.

Varistors are sacrificial and can fail for either of two reasons.

1. A catastrophic failure-where the energy involved is greater than the varistor

2. Cumulative degradation- the varistor is not visibly damaged and appears functional, but no longer offers protection.

A MOV inside a TVSS device does not provide equipment with complete power protection as believed. In particular, a MOV device provides no protection to the connected equipment from spikes on the ground wire, sustained over-voltages or voltage sages that may result in damage to the protected equipment as well as to the protector device.

Why, because these type of spikes and surges may be lower than the threshold of the MOV product and therefore ignored by the device employed as protection.

MOVs degrade from repeated exposure to power anomalies, and now continue to function as a power strip with no protection value. So how can you put faith in this type of protection for your sensitive electronics and companies reputation.