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

testing ac and grounding systems 57

Testing ASCC. The SureTest shows 0.08 kA (80 amps).
This result won’t cause problems for the circuit breaker, but
it does indicate that undersized wiring may have been
used to construct the circuit. (The smaller the wire, the less
current it can carry.)

Other Options

The SureTest comes equipped with enough
probes for testing receptacles, while the
optional 61-183 alligator clip adapter is a use-
ful option for checking power supplies that
are hard-wired to AC equipment. You will
also need to make an adapter (see the sidebar
on page 58) for the shore-power connection,

like the one shown above, and possibly sev-

eral adapters if you plan to test various ser-

vices (30 amps, 50 amps, etc.).

For 50 amp, 240 V service, I usually check

L1 and L2 as two separate entities using two

50 amp plug sets that key into the L1 hot and

L2 hot terminals. Keep in mind that in North

America, a 240 V system is similar to two

Measuring the actual (as opposed to the rated) trip rate

for a GFCI device. The 7.3 mA value is perfectly normal

for a 5 mA rated device.

Measuring the trip rate for a GFP. The SureTest shows
30.6 mA, which is close to the 30 mA trip rate required
for whole-boat protection (outside the United States).

plug SureTest

into 15 A

plug 30 A into

shore-power pedestal

A homemade 30 to 15 amp adapter for checking dock

wiring.

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