On Thursday, September 6, 2012 8:36:49 AM UTC-4, The Natural Philosopher wr= ote: And MOVS are not applied between phase and earth. That would result in ins= tant RCD operation.
Discussion is confused by two completely different devices that, unfortun= ately, share a same name. An effective protector is from each phase to ear= th. It never tips an RCD (or GFCI) because the protector looks like an ope= n circuit (disconnected) when a surge does not exist. =20
Effective protectors are for lightning strikes (and other lesser surges).= Effective protectors even have numbers that say it is for protection from= lightning - ie 50,000 amps.
Undersized 'profit center' protectors are for tiny surges that typically = cause no appliance damage. As others have noted, protection already inside= appliances makes that tiny surge (and that tiny protector) irrelevant. Th= ose tiny protectors are rated maybe in hundreds of joules. The surge that = can overwhelm protection already inside appliances is something like hundre= ds of thousands of joules.
A protector for appliance protection is for surges that are hundreds of t= housands of joules. Is provided by other and more responsible companies in= cluding Keison, ABB, Siemens, General Electric and others. That undersized= protector for tiny (irrelevant ) surges is often promoted with brand names= such as Belkin and Tripplite.=20 =20 An effective protector must remains functional even after direct lightning= strikes. Protectors that are catastrophically destroyed (a potential hous= e fire) or that degrade significantly are ineffective. Are profit centers = sold because it happens to have a same name even though it is a completely = different device.
An effective protector means surges, such as direct lightning strikes, do= not overwhelm protection already inside appliances. Do not even harm the p= rotector. These superior devices, that cost less money, make the 'always re= quired' connection from phase to earth. Only when a surge exists. And too= quickly to trip an RCD.