How to make a "single point ground" when the ac power breaker panel is mounted away from the coax cable
entrance master ground bar.
How to apply a single-point ground protector retrofit to a site with coax entry on one wall
and ac power on the opposite wall?
The "ground" connected to the site ac power protector should be referenced to the single point (coax cable
ground bar, bulkhead or "PEEP") ground. Assuming a tower strike, the inductive peak voltage drop across the
current carrying ground leads (preferably copper strap) from the high ground bar to earth would elevate the
potential at the high ground bar compared to the (lower) earth ground connection. The high ground bar is
directly connected to the equipment cabinet(s) through the coax cable shield(s).
The important thing is -- all equipment ground connections should rise and fall in potential at the same time with
no other paths (through equipment?) to a lower ground connecting point. If there are no other paths, and the
potentials rise and fall together, there will be no current flow through the equipment = no damage.
Since the ac power protector is actually "switching" the energy through it, (shunting) around your equipment,
where the ac protector is grounded becomes very important.
If the protector and ground connection is on the opposite wall connected to a ground rod or ring, there could be
damage from current flow from the elevated coax cable shields, through the equipment, back to the ac power
ground on the opposite wall (that has not yet been elevated in potential) due to ground potential propagation
delay around the ground ring. There could be an additional danger from the energy coupled to parallel or nearby
conductors. The peak potentials could be additive and cause serious damage.
A protector mounted on the opposite wall and grounded locally would only protect from incoming energy from
the secondary ac power drop. Energy from a tower strike would elevate the equipment cabinet potential via the
coax cable shields and current could flow from elevated chassis ground returns up through power supply
circuitry on its way to the outside world via the yet to be elevated ac secondary connection. The power supply
could be destroyed.
If the protector ground was connected to the (elevated) single point ground bar and true single point connections
• The equipment protector reference ground would rise and fall with the master ground bar (Bulkhead or
• The ac power protector could protect your equipment power supplies from incoming energy on the ac
power lines AND from direct or induced energy incoming from the coax cable(s) during a tower strike.
One practical way to do a retrofit would be:
• Remove any equipment rack or active electronic equipment circuit breakers from the existing distribution
panel. Remove all wiring from the existing distribution panel to any equipment rack or active electronic
equipment. Leave the existing shunt type ac protectors at their original location.
• Run a steel conduit, grounded at both ends, from the existing main distribution panel to the new sub-panel.
Route new interconnection wiring through this conduit.
• Install a new sub panel next to the single point ground (MGB). Wire from the new sub panel, through a
properly rated circuit breaker, directly to each rack or active electronic equipment.
• Connect a second shunt type ac protector to the hot leads and neutral in the new sub panel.Strap the
protector case ground to the single point ground.For higher levels of protection and RF-EMI filtering, use
an in line filtered ac protector. This device installs in series with the wiring from the existing distribution
panel to tne new sub panel.
If you already have ac power shunt type protection installed at the main ac input, leave it there. It will provide
an extra measure of protection from an incoming strike on the secondary conductors.