You Asked:

Does turning off the power switch on a surge protector offer better protection than when the power is left on? — Jordan, Denver, Colo.

Marshall Brain Answers:

A typical surge protector uses metal oxide varistors, or MOVs, to absorb surges. MOVs don’t do anything unless they detect a voltage that is too high. When they detect it, they shunt the excess voltage to ground.

But MOVs have their limits (if a surge is too big, the MOVs won’t be able to shunt it – hence the maximum joule ratings on the package), and MOVs also wear out from repeated surges.

If you physically switch off the power strip, then you disconnect the hot wire in the power strip from the grid. There is no voltage at all in the strip, meaning that there are no surges for the MOVs to worry about. So yes, turning the strip off gives better protection.

Unplugging the strip would be even better. If lightning strikes the house, chances are that it will jump through the open switch if the strip is plugged in. Lightning is the ultimate surge. If the strip is unplugged, that won’t happen.

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