In their basic form, they have an On/Off Switch, and a few, or more, receptacles. You plug them into the wall, and various things into them.
Something on my mind is Surge Suppressing Power Strips. I read a story, not many years ago, of a man that entered his office, early in the morning, and his computer was gone, kind of. There was a mess there, it melted, as did the power strip next to it, but somehow didn’t catch the remainder of his office on fire.
The Power Strip, next to the computer, caught fire, because it had a surge suppressor. The Surge Suppressor was a Metal Oxide Varistor (MOV):
“A MOV contains a ceramic mass of zinc oxide grains, in a matrix of other metal oxides (such as small amounts of bismuth, cobalt, manganese) sandwiched between two metal plates (the electrodes).”
The Surge Suppressor routes voltage spikes, or surges, from the Hot to Neutral Line, preventing the surge from reaching sensitive equipment. If I’d connect a light bulb from Hot to Neutral, it lights. If I’d connect a Switch across Hot and Neutral, and closed the Switch, it would certainly spark, and in theory the Circuit Breaker would Trip on Over Current. Not a smart thing to do.
But, in an MOV, eventually, the material between the plates deteriorates, and current starts to routinely conduct between the two plates, it heats it, worsening, and eventually gets too hot, and the overheating either combusts nearby material in the Power Strip, or it self destructs, and directly combusts the wiring and shell of power strip if plastic.
At one time, they made Power Strips with On/Off Switches and Surge Suppressors, but the On/Off Switch won’t interrupt fault current once the switch is on, it was just there for convenience. The solution to self destructing MOVs catching the Power Strip on fire, and the Power Strip catching the home or business on fire, was to require a Fuse, or Circuit Breaker in the Power Strip.
The Circuit Breaker may be incorporated into the On/Off Switch, or it might be a Separate Device, often a cylindrical shaped switch that has to be depressed to reset. See the attached drawing for examples of Power Strips burned up, or damaged, by MOV Failures or Overloading and resultant generated heat damage.
The attached drawing also shows Circuit Breaker and Fuse Protection of a Power Strip to help protect against MOV Failure and Overload Fires.
Christmas is nearly upon us, many of us decorate, and Power Strips that sat dormant for a year might be pressed back into service.
Some points that stand out.
#1. Inspect them, do not use defective ones. Look for signs of overheating, this can occur from overloading, or from operating devices that should be OK to use, but the Power Strip has loose contacts in its receptacles. Also inspect plugs being used in those receptacles for damage, and signs of overheating. Inspect the Power Strip Cord, and Cords Plugged into the Power Strip, for signs of insulation tears, exposed or frayed wires.
#2. Check for Recalls on the Power Strips. Stop using if a Recall is in force for your model and manufacturing lot.
#3. Do Not Daisy-Chain Power Strips together.
#4. If the Power Strip has Surge Protection, it must have a Circuit Breaker or the Surge Protector must otherwise be fused.
#5. Do not use High Current Devices on Surge Protected Power Strips.
Power Strips are available without Surge Protection, for many uses, Surge Protectors are not needed, be selective when buying, don’t automatically choose Surge Suppressing models if they’re not needed, but use Surge Suppressing Power Strips on Electronic Equipment.
Inspect your surge protectors for fire danger
How to Keep Your Power Strips From Catching Fire
Varistor Tutorial
Phone Chargers, Wall Warts, etc., have periodically caught fire spontaneously. To reduce that likelihood, we use a few Power Strips that we shut-off before going to bed. That way, the Chargers and Wall Warts plugged into them can’t get into mischief during the night. We walk around and make sure the Power Strips are Shut-off every night.
Meanderings 