Quote Originally Posted by The Semi-Retired Electric View Post
Good advice Fencepost and would like your opinion:

I read somewhere that typical housewiring will tend to limit spikes to about 600V due to clearances in devices etc.

Also, I feel secondary surge strips located around a house will add further protection to not only the appliances plugged into them but the whole house. By their very nature their MOV's are connected L-L, L-N & L-G so wouldn't "more be better"?

Good Luck from Columbiana, Alabama
Maurice Turgeon, [URL="http://thesemi-retiredelectrician.com"]
I wonder if that "600V" figure is based on the fact that the insulation on most household wiring is rated for 600V. It seems a bit fishy; there could be effectively a spark gap between the internal prongs of a receptacle, say, but there are so many variables and variations that there's no way you can count on some 600V rule of thumb.

I am of the "more is better" opinion, but still the MOVs should be located near the protected device as voltage transients can be very localalized. For example, a laser printer can draw several amps when it is printing. When it stops printing, the current draw suddenly stops, and a surge can happen on that circuit. If your computer is on the same circuit, it can experience a small surge. Having the laser printer and the computer on a surge protector can protect both. (By the way, laser printers should NEVER be connected to a UPS. It will overload the UPS.)

When you start talking about stuff that happens in radio frequency ranges, weird things happen. For example, if you get some funky, high-voltage standing wave in the wiring and the MOV happens to be at a node and the device is at an antinode, the device blows up and the MOV doesn't know anything happened.