122 electrical systems troubleshooting
together via the grounding circuit inside the
boat, or make up the entire grounding system
connection to the seawater.
All of the tie-ins must use—as a minimum—
6 AWG (13 mm^2 ) cabling. This in itself creates
a problem on some boats that already have a
bonding system in place, because the standards
for that system dictate the use of either copper
strapping or minimum 8 AWG (8 mm^2 ) wire.
Consequently, if you choose to install an LPS,
you would have to upgrade the bonding system
wiring. Many people find this to be a tough
decision, as it is almost impossible to perform
any kind of reliable cost/benefit analysis for
installing the system. My view is that if you are
going to spend any time offshore, or live in an
area of the world that is statistically prone to
lightning activity, the scale gets tipped in favor
of installing an LPS.
Although more exposed metal surface area
is always better, the electrical conductivity of
the various underwater metal components
might be a concern in some cases. Lead, for
example, is roughly a tenth as conductive as
copper, so even a good-sized lead ballast keel
may not provide sufficient conductivity. Iron,
in contrast, is approximately a fifth as conduc-
tive as copper, and even bronze alloys that
contain copper are only about a third as con-
ductive as pure annealed or hard-drawn copper.
The best ground plate for an LPS is clearly a
pure copper plate. But even with a copper
ground plate in place, it can be worthwhile to
increase the total exposed surface area by con-
necting all available through-hulls (typically of
a bronze alloy), stainless rudders, and even
lead keel ballasts.
Most of these metal components installed
on or through the hull often have a coat of
antifouling paint on them. In theory, this
insulates the metals from the seawater, but in
practice it’s not enough to make much of a dif-
ference. When we consider the potentialsinvolved with lightning current, it’s going to
take a better insulator than a coat of paint to
hold it back!
Finally, tie in all large metal objects in
proximity to any of the cabling included in the
LPS, using 6 AWG cabling. (ABYC TE-4
states that any large metal object within 6 feet
of a conductor must be connected to the sys-
tem.) On a typical recreational boat, this
almost always means that all metal objects
must be tied in, including fuel tanks, engines,
and generators. The objective is to minimize
the risk of side flashing, in which lightning
jumps out of the conductor to the metal
object in search of a better path to ground
(even if there isn’t one).
Lightning Protection for Electronic
Equipment
What, if anything, does an LPS do to protect
sensitive electronic equipment? This is a com-
mon question among boatowners who are
thinking about installing or upgrading an
LPS. The simple answer is, nothing. The only
way to really ensure that electronic equipment
remains unaffected by a lightning strike is to
completely isolate it from the entire boat’s
electrical system. Since this is generally
impractical, it’s safe to say that you should sus-
pect the integrity of all electronic equipment
after a lightning strike, and carefully check all
of its operational characteristics. It’s important
to note that LPS standards focus on personal
safety and protection of a vessel’s hull below
the waterline, nothing more.Grounding to Minimize RFI Effects
Electrical noise, which is essentially synony-
mous with RFI, is interesting stuff in that it
can be transferred (radiated) through the air or
through the wiring on board a boat. As discussed