QM-13d: Electricity Course Outline

1. QM-13d Quartermaster Electricity Elective Instructors: George Crowl

2. Course Outline • b. Electricity: • i) Know and demonstrate the correct method of rescuing a person in contact with a live wire. • ii) Understand the construction of simple battery cells. Demonstrate the proper care of storage batteries. • iii) Explain the difference between direct current and alternating current and the best uses for each. • iv) Demonstrate that you know how to replace fuses, reset circuit breakers, and properly splice shipboard electric cable. • v) Submit a diagram of the electrical system aboard the vessel used by your ship. • vi) Explain wire tables, the current-carrying capacity of circuits, and the hazards and prevention of electrical overloading. • vii) Explain electrolysis as applied to the deterioration of a boat’s underwater fittings by galvanic action and its prevention.

3. QM-13d i) Know and demonstrate the correct method of rescuing a person in contact with a live wire.

4. Rescuing a Person • DO NOT TOUCH THEM! • You will get the same shock they have, and be disabled • Call 911. They will likely guide you. • Cut off the power at circuit breaker • If a line is down, DO NOT TOUCH • Call power company, ask them to cut power

5. Still in Contact with Live Wire • Stay 100 ft away from downed high wires! Do not attempt rescue. • Household current – • Find wood or plastic pole (non-conducting) • Dry rope is also non-conducting • Pull wire free of person, or person from wire

6. After Freed from Contact • Move away from danger • Call 911 if not already done • Lay person on back • Check breathing and heartbeat • Start rescue breathing or CPR if needed • Treat for shock, cover above and below • Treat burns with cold water, no oil / grease • Bad burns – cut away clothing, sterile dressing

7. QM-13d ii) Understand the construction of simple battery cells. Demonstrate the proper care of storage batteries.

8. Battery Construction • Lead-acid battery. Ea cell = 2V, need 6 for 12V. • Dilute sulpheric acid conducts electricity • Positive = lead dioxide, negative = pure lead • Positive = +, red; negative = -, black

9. Care of Storage Batteries • Clean terminals regularly (baking soda) • Insure cells of conventional batteries are full with distilled water • Put a “boot” on the positive (red) terminal • Light dielectric grease on terminals • Insure tied down tight • Eliminate wing nuts, they come loose • Charge fully, 13V or more

10. QM-13d iii) Explain the difference between direct current and alternating current and the best uses for each.

11. AC vs. DC • Direct Current (DC) flows in one direction at a level voltage (below left), usually from a battery • Alternating Current (AC) flows back and forth at varying voltage (below right), usually from an alternator or commerical power source

12. AC vs. DC (2) • Shore power is AC, powers lights, TV, microwave, electrical sockets for tools, etc. • Shore power is normally 110V, 60 cycle • Commercial vessels may use self-generated AC at 240/480V to run motors, etc. • Boat power is DC, powers nav lights, engine and navigation instruments, cabin lights, etc. • Boat power is 12V, does not cycle, generator • Provided by 1-4 batteries, controlled by battery switch. Special starting batteries sometimes.

13. AC vs. DC (3) • AC is needed to transmit electricity a long way over power lines. • High voltage can be transformed down to house-hold 110V by transformers relatively easily • Universally used for household and manufacturing purposes • DC is best for many electronic applications • DC cannot travel far, so within a black box is OK

14. QM-13d iv) Demonstrate that you know how to replace fuses, reset circuit breakers, and properly splice shipboard electric cable.

15. QM-13d iv) Demonstrate that you know how to replace fuses, reset circuit breakers, and properly splice shipboard electric cable.

16. Replace Fuses • Demonstrate, don't talk • Fuses may actually be hard to find, check your car fuses if you don't have fuses on your boat • Check fuse box list. If you don't have a list, experiment (BUT start the list!) • Turn off master switch if possible • Remove fuse cover

17. Replace Fuses (2) • Remove (pull out or unscrew) fuse • Inspect to see that it is blown (broken) • Confirm proper fuse rating (in amps) • Install fuse of equal or lower rating, then cover • Common ratings – 10A, 15A, 30A • If fuse blows quickly, solve the underlying problem first! Then reinstallanother fuse. • Overloaded circuits can lead to fires

18. Reset Circuit Breakers • Look like small light switches • Button forced out of alignment • Run your hand along to find one “popped” • Push to “OFF”, then back “ON” • If it pops again, fix the problem,don't keep resetting C/B

19. Shipboard Cable Splicing • Meet ABYC standards (see NOTES for article) • Use marine racheting crimp connectors • Nylon-jacketed butt connectors (nylon tube) • If exposed to water, use and melt heat-sensitive adhesive to waterproof the connection

20. QM-13d v) Submit a diagram of the electrical system aboard the vessel used by your ship.

21. Electrical System • Includes AC and DC • Shows batteries, motor, instruments, etc • Uses conventional electrical diagram symbols • Good starting source should be the motor electrical diagram for your engine • Most Sea Scout boats have been modified – show reality, not the way it was built • Probably will require you to use a circuit tester to find out what reality is

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23. QM-13d vi) Explain wire tables, the current-carrying capacity of circuits, and the hazards and prevention of electrical overloading.

24. Wire Tables • Two kinds – AWG and Metric (mostly AWG) • Standardizes wire selection • Provides conservative general guidance to the public about how much current a wire can carry • Design engineers will do a more precise job • Sizes #0000 (0.46”) to #32 (0.008”), large to small • For solid wire, stranded wire is based on total cross-sectional area to carry same current

25. Typical Wire Table • #16 wire • Diameter – 0.0508” • Diameter – 1.29032mm • Ohms/1000' – 4.016 • Ohms/km – 13.17248 • Max amps for chassis wiring – 22 • Max amps for power xmsn – 3.7 • Max freq – 11,000 Hz • Breaking strength – 75 pounds

26. Current-Carrying Capacity • Also Current Rating or Ampacity • Depends on: insulation temperature rating, conductor resistance, AC frequency, ambient temperature, heat dissipation • Insulation is often the driving factor • Cables (several wires) have lower capacity because of heat buildup, or conduit • Figures are for continuous current, short overloads will not usually affect • Circuit breakers are sized to fit capacity

27. Electrical Overload Hazards • Fire and electrical arcing are main issues • Overheated wire or arcing wire can start a fire • Electrical arc could set off gasoline explosion

28. Overload Prevention • Size your circuit breakers and/or fuses to the current capacity • Loose or corroded wires increase resistance and current. Means more current, possible arcing. • Troubleshoot popped circuit breakers • Unplug high current appliances (microwave, toaster, waffle iron, etc.)

29. QM-13d vii) Explain electrolysis as applied to the deterioration of a boat’s underwater fittings by galvanic action and its prevention.

30. Electrolysis, Galvanic Action • Electrolysis – “Chemical decomposition produced by passing an electrict current through a liquid or solution containing ions.” • Galvanic corrosion – Two different metals will cause corrosion if in contact, or if in water that can pass ions from one metal to the other

31. Prevention • Install one or more zinc sacrificial anodes on the prop shaft and/or other other equipment • Check your berth for stray electrical currents • Check your through-hulls at every quick haul

32. Questions?