1. What is the efficiency comparison between quality type plug-in units compared to a panel mount?
Not sure how you would measure "efficiency" here, but a unit at the service entrance is FAR superior to ANYTHING installed at the point of use.
A TVSS relies on a short, heavy, low-impedance path to earth ground. The only reasonable place to get this is at the main service panel. A plug-in unit relies on the ground path back through the branch circuit wiring, which presents too much impedance to be of any value with fast-risetime events like a lightning strike.
2. Which is better? A higher, or lower "clamping Voltage" rating.
Lower, as long as the clamping voltage is higher than the peak voltage seen under any normal condition. In an area subject to high line voltage, a unit with a very low clamping voltage may be destroyed by firing continuously on mormal line voltage.
3. From the data that I have read, (supplied by the manufacture's ), is it really adviseable to combine panel mount TVSS with Plug-in strip type tVSS?
It certainly wont hurt anything, but the point of use units are pretty useless by themselves. They do often contain RFI filtering components, which may help in an interference situation.
