How to Use an Extension Cord With a Surge Protector

Your computer and other sensitive electronic equipment could be seriously damaged by a power spike, so it's always a good idea to plug these into a surge protector. To provide the protection they are designed for, surge protectors must be plugged directly into a grounded electrical outlet, and all protected devices must be plugged directly into the surge protector. Using an extension cord with a surge protector may compromise its protection capability and will most likely void its warranty.

Surge Protector Basics

Surge protectors are designed for sensitive electrical equipment that draws low currents of around 3 to 5 amperes. They aren't designed to handle appliances that draw more than 600 watts -- such as a room heater -- or a total load of more than 1,440 watts or 15 amperes. If you have a surge protector power strip, reserve it for your electronic equipment and plug your heaters, toaster or microwave into a grounded outlet with a sufficient amperage rating.

The heart of most surge protectors is a metal oxide varistor, which traps excess current. The MOV in each strips has three characteristics:

  • Clamping voltage -- This is the threshold voltage at which the device begins directing current to ground. There are three possible UL ratings, which are 330, 400 and 500 volts. The lower the clamping voltage, the better the protections.
  • Energy absorption -- This is the amount of energy -- in joules -- that the device can absorb. Typical values are between 200 and 600 joules; higher values signify better protection.
  • Response time -- It takes a small amount of time for the surge protector to begin diverting energy, and during this time, your equipment is exposed to the surge energy. The shorter the response time, the better the protection.