Power off does not cause hardware damage.
A utility power failure can also result in surges. They are not real likely when power is restored.
The best information on surges and surge protection I have seen is at:
http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf
- "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" published by the IEEE in 2005 (the IEEE is a major organization of electrical and electronic engineers).
And also:
http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf
- "NIST recommended practice guide: Surges Happen!: how to protect the appliances in your home" published by the US National Institute of Standards and Technology in 2001
The IEEE surge guide is aimed at people with some technical background.
If you had a surge or surges, then you are constantly replacing less robust devices including dimmer switches, digital clocks, bathroom GFCI, smoke detectors, etc.
The NIST surge guide suggests that most failures are caused by high voltage between power and phone/cable/... wires.
What does a protector do without an always short connection to earth ground? It must earth energy somewhere.
The IEEE surge guide explains (starting page 30) that plug-in protectors work primarily by limiting the voltage from each wire (power and signal) to the ground at the protector. The voltage between the wires going to the protected equipment is safe for the protected equipment.
When using a plug-in protector all interconnected equipment needs to be connected to the same protector. External connections, like cable, also must go through the protector. Connecting all wiring through the protector prevents damaging voltages between power and signal wires.
Any protector that does not protect from typically destructive surges - ie lightning - is best called a scam.
Westom's believes plug-in protectors are a scam.
Both the IEEE and NIST surge guides say they are effective.
More responsible manufacturers provide effective solutons including General Electric, Intermatic, Square D, ABB, Siemens, Polyphaser, and Leviton.
All these manufacturers except SquareD and Polyphaser make plug-in protectors and say they are "effective solutions".
SquareD says for their "best" service panel suppressor "electronic equipment may need additional protection by installing plug-in [protectors] at the point of use."
A Cutler-Hammer solution to make direct lightning strikes irrelevant sells in Lowes and Home Depot for less than $50.
If westom is talking about service panel protectors, provide a link to a Lowes or Home Depot protector for less than $50 that has westom's rating of 50,00 amps.
Lightning is typically 20,000 amps. So a minimally sized 'whole house' protector is rated 50,000 amps.
The author of the NIST surge guide looked at the surge current that could come in on residential power wires. The maximum with any reasonable probability of occurring was 10,000A per wire. That is based on a 100,000A lighting strike to a utility pole adjacent to the house in typical urban overhead distribution.
Recommended ratings for service panel protectors is in the IEEE surge guide on page 18. Ratings far higher than 10,000A per wire mean the protector will have a long life.
