Advanced Marine Electrics and Electronics Troubleshooting A Manual for Boatowners and Marine Technicians

to the source and a circuit breaker will trip,
shutting off the circuit. Remember that the
green ground wire is attached to the case of
AC equipment, which is key to the success of
this configuration.
So here’s the rub, but in the case of boats
it’s actually a useful one. The SureTest will
identify these “false” grounds within about 15
to 20 feet of the occurrence of a neutral-to-
ground link, including a distribution panel,
onboard generator, inverter, or isolation
transformer. So in a nutshell, “false” may be
exactly what you are looking for at these
devices. It’s at AC appliances that you don’t
want this link. A good example of where a
false ground may appear is at a 240 V electric

testing ac and grounding systems 49

range or clothes dryer that is wired for older

residential applications, which are often installed

on older boats (see photo page 50).

These neutral-to-ground links must be dis-

connected when installed on a boat (see photo

page 51). Otherwise, every time you turn on

the appliance, you run the risk of AC power

(which would normally be returned down the

neutral conductor) being pushed down the

grounding conductor, and possibly entering

the water via the DC bonding system. Remem-

ber that on ABYC-compliant boats, the AC

and DC grounding systems should be linked

either at the engine’s negative terminal or, occa-

sionally, at the grounding buses behind the

boat’s main AC and DC distribution panels.

Proper neutral-to-ground bonding of an inverter, according to Standard E-11. (Courtesy ABYC).