POWERBOATER’S GUIDE TO ELECTRICAL SYSTEMS could well be the pigtail on the back of the fixture, not the feed wire. 6. Check the total load on the distribution panel, and if the wire and circuit protection on the panel are not large enough, change them to a larger size before doing anything else. 7. Once wire gauge and circuit protection ratings are determined, string the wire from the distribution panel to the location of your new cabin light. Don’t forget to support your new wiring at least every 18 inches, and preferably more frequently than that. If the wire must go through an area where chafe protection is needed, provide it as shown in figure 4-20 on page 59.
Figure 9-1 provides a wiring diagram showing what your new light circuit might look like in a typical installation. (Individual switches are not illustrated at the light fixtures.)
Installing a New Bilge Pump
To install a new bilge pump, first establish the gph (gallons per hour) rating of the pump you’ll need based on the volume of the area the pump will service, the height from the base of the pump to the point of discharge, and other factors. With bilge pumps, depending upon several variables, the actual amount of bilge water the thing will move overboard will vary considerably from the rat8. Connect the ground wire from your new light to ing embossed on the pump. Aside from mechanical the negative bus bar on the back of the distribu- variations in pumps, you’ll need a circuit with a 3 tion panel and the positive wire to the switch or percent maximum voltage drop if you’re going to get circuit breaker output terminal. You might need a anything close to the rated output of the pump. Extwo-to-one connector to tie into a breaker or fuse cess voltage drop here will affect pump motor speed on the panel. and the volume of water it will move. 9. At the fixture end of the wire, use crimp-type According to the ABYC and the chart in figure butt connectors to attach the new light to the 2-5 on page 16, a bilge-pump circuit should have a feeder wires. If the wire on light-fixture pigtails is brown positive wire, and either a black or a yellow more than two AWG sizes apart, use one of the ground-return wire is acceptable. new-style step-down butt connectors available Because this load is a 12-volt motor, the bilge through West Marine or any good electrical sup- pump must be protected with a fuse rated at no ply house. higher than the manufacturer’s recommendation. In 10. Finally, flip on the switch. Is there light? If so, my own tests, I have experimented with fuses as lityour new circuit is a success. Mount your new fix- tle as 1.5 amps over the rating recommended by the pump manufacturer. In these tests I locked the ture in position and enjoy. pump’s impeller to simulate an actual installation and let the pump run. Figure 9-2 on page 141 is a photograph of the result of DC DC one test. As you can clearly see, the body of the pump is melted away and badly deformed. The wires feeding the pump, on the other hand, are unscathed. Why does this happen? Why is the pump itself destroyed, generating enough heat to torch the boat while the wires remain intact? Cabin Light Cabin Light Cabin Light When a motor seizes, it works Fig. 9-1. Simplified wiring diagram of a cabin light circuit.
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