We had lightning strike our house a few years back. The surge protectors (which really aren't intended to protect against lightning) protected our PC but "fried" the modem and the built-in ethernet of my iMac. ... The lightning also took out the phone answering machine, one out three TV's, and the garage door opener.
No protector - not even the effective 'whole house' protector - stops or absorbs surges. That myth is quite apparent in some posted examples. Why was the modem and ethernet port damaged? Because that adjacent protector made damage easier. It violated what all protectors must do.
Cable TV needs no protector. The best protection is a wire from the cable and low impedance (ie 'less than 10 feet') to single point earth ground. Nobody could ask for better protection.
Unfortunately other wires cannot be earthed directly. So we connect AC electric wires just as short to earth via a 'whole house' protector. If every wire inside every incoming cable connects to single point earth ground, then all computers are used without fear during every thunderstorm.
Learn what your telco has been doing for over 100 years. Their $multi-million switching computer connects to overhead wires all over town. It is threatened, on average, by 100 surges during each thunderstorm. So your telco turns off all phone service with each approaching storm. Please read that sentence again.
Your telco's computer is threatened by 100 surges and can never be damaged. They also do not waste money on magic box (plug-in) protectors. For over 100 years, telcos connect every incoming wire to earth. No exceptions can exist. Each protector must connect as close as possible to earth. So that a protector does not make damage easier, telcos want that protector up to 50 meters (150 feet) distant from electronics. Distance between protector and an appliance increases protection.
'Whole house' protectors mean protection even from direct lightning strikes. You do same so that one potentially destructive surge every seven years also does no damage. Protection was always and is always about how short that protector connects to earth. No protector does protection. Not one. Protection is always about connecting surges to the only item that does protection - earth ground.
Many protection systems have no protector. But every protection system always has one item - earth ground. Protectors either connect to what does protection. Or the protector has a history of even making damage easier - ie that modem and ethernet port.
The Square D protector is an example of what more responsible companies provide. Other more responsible companies include ABB, General Electric, Intermatic, Siemens, and Leviton. A Cutler-Hammer solution sells in Lowes and Home Depot for less than $50.
A minimal 'whole house' protector starts at 50,000 amps. A typical lightning strike is 20,000 amps. The protector connects direct lightning strikes short (ie 'less than 10 feet') to earth. And remains functional. Only ineffective profit center protectors fail during a surge. Effective protection means nobody even knew a surge existed. That is why informed homeowners only earth one 'whole house' protector. And divert money otherwise wasted on plug-in protectors into upgrading the only item that does all protection - earth ground.
Anything that might work on an appliances power cord is already inside all electronics. For example, a superior isolation transformer is already inside. Some of the best protection inside a house is already inside appliances. Protection in that Mac may have been compromised due to an adjacent protector. Destructive surges are typically once every seven years. We earth a 'whole house' protector so that the rare surge will not overwhelm superior protection already inside every appliance.
Protection is always about where those hundreds of thousands of joules dissipate. Energy that will increase voltage as necessary to blow thought anything that might stop a surge (ie a magic box protector). Protection is about hundreds of thousands of joules harmlessly absorbed outside the building in earth ground. A protector is only as effective as its connection to earth. That is science well proven and repeatedly demonstrated for over 100 years.
