Network Surge Protection and Ground Current
Brick Wall Computer Surge Protectors Will Not Divert Surge Current to Ground
Almost all manufacturers of shunt mode surge protectors (those utilizing MOV's) design their products to divert surge current equally between the ground and neutral wires. A networked computer surge protector should not divert surge current to the ground wire.
Data Line Protection?
Our sales staff repeatedly hears this same story: It seems a company has experienced considerable surge damage to electronic equipment. The shunt mode surge protectors would appear to have done their job by protecting the loads from the front end (power line). The damage, in their estimation, resulted from surge current that traveled down the data lines. How do they know this? All the damage appears to have originated at the data ports, hence they conclude that the surge must have traveled this route. Their solution: They need data line surge protectors.
They are right in as much as the damaging current did propagate through the data lines. However, damaging surges do not originate in dataline circuits.
Their systems do not need data line surge protectors. Interconnected systems need network surge protection that does not divert surge current to the ground wire.
Interconnected Systems and Ground Loop Contamination
Interconnected (networked) systems, so prevalent in today's commercial/industrial world, have made shunt mode technology used in most surge protectors (origins 1972) inappropriate. Equipment sharing common power and data lines form circuits between themselves via the ground wire (both referenced at the load). What does current do in a closed circuit? It flows. A powerline surge diverted to the ground wire by a shunt mode surge protector will make its way to the chassis, through the motherboard (which is also grounded at the chassis), onto and through the data lines (which use the powerline ground as a voltage reference and are also connected at the motherboard) and to the data ports of the rest of the connected system. This is how most data line surges originate.
Data Line Noise
Smaller surges diverted to ground wires by a shunt mode surge protector may not immediately damage equipment (though the cumulative effect can eventually cause failures). On the other hand, low level surge current diverted to the data lines by a shunt mode surge protector (via the ground wire) can immediately scramble data, slow down data transfer and cause mis-operations or lock-ups as a consequence of its effect as system noise (unwanted current on the data lines).
Brick Wall Computer Surge Protector Series Mode Technology
Brick Wall network surge protection products are based on the current (hence voltage) limiting of a massive inductor. Residual energy that leaks through is captured by electrolytic capacitors. There it is slowly leaked back to the neutral at a harmless level. Outside of trivial amounts of parasitic capacitance our Series Mode computer surge protectors do not put any surge current on the ground of your systems. Engineers of an MOV based surge protector face the dilemma of what to do with potentially large amounts of surge current. They don't want to overload the neutral and want to prolong the life of the MOV. Using two MOV's and diverting equally between the ground and neutral wire prolongs MOV life and prevents overcurrent on the neutral. Series Mode surge protector technology presents no such dilemma.