Alternating Current and AC Equipment To test a GFCI, simply depress the test button on the assembly faceplate. This trips the internal breaker and actually exercises the outlet’s inner workings to ensure that it’s functioning as it should. If the test and reset buttons feel spongy and seem to have lost their crisp snap action, odds are good that the GFCI mechanism is corroded, and the outlet should be replaced. Another point worth mentioning here is that just because the dock box that your boat is connected to at the marina is protected by GFCI (and it always should be), you shouldn’t think that you’re protected from shock hazard on your boat. These dockside GFCIs are likely to be forgotten by the maintenance crew and never tested until it’s too late. To be safe, always test the dockside outlets before you plug in your shore-power cord, and to eliminate any worry, upgrade your boat with this important protection as soon as you can.
these problems usually originate at the dock, not on the boat, and it’s easy to check for them yourself. Figure 11-10 demonstrates using the inductive AC tester to see if there is voltage present at an outlet. If the tester’s LED flashes and it emits a steady beeping noise, AC is present in the circuit. The only remaining question is how much voltage. To determine that, you’ll need your multimeter.
Checking Voltage, Continuity, and Polarity on AC Circuits Sooner or later, problems will crop up with the AC circuits on your boat, and you’ll need to do basic multimeter tests for voltage, polarity, and continuity. There is no need to be afraid of doing these tests on AC circuits, even for the novice, but following some basic rules, in addition to the safety rules listed above, will ensure that you won’t damage your meter or end up having a shocking experience. Besides your multimeter, several small, inexpensive testers can be extremely useful when working around AC systems. Figure 11-9 shows an LED outlet tester with a built-in GFCI test function, and figure 11-10 shows an inductive voltage sensor used for verifying the presence of AC voltage, even behind panels and through insulation. The LED outlet tester is useful in determining whether reverse polarity exists and whether or not there is an open circuit in any of the three conductors. It is not at all uncommon for low voltage to be a problem in an AC circuit, or reverse polarity for that matter. A disconnected green grounding conductor is quite common and can go unnoticed until someone gets a shocking jolt. The good news here is that
Fig. 11-9. An LED outlet tester.
Fig. 11-10. Using the inductive AC tester to check voltage at an outlet.
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