1. Electrical Wiring Practices
Chapter 2
Electrical Wiring Practices
and Diagrams
PowerPoint slides by
Stf/C Harl Porter, SN
Marine Electronics
Rear Commander for Electro-Mechanical Systems is
R/C Gene Danko, SN
Left is AC boat cable
Right is DC boat cable (yellow is new color for negative)

2. Overview Safety Standards Wiring Considerations Wire Terminations
Coaxial Cable
Wiring Installations
Wiring Diagrams
Major sections in this chapter

3. Safety Lethal Current Safety Precautions
Major topics in Safety section

4. Lethal Current Fundamental policy of the USPS is SAFETY Human Body
Resistance – 4 KΩ (moist skin) to 24 KΩ (dry skin)
Safe current (through chest) – less than 20 milliamps
E = 120 VAC R = 4 KΩ I = ?
I = 30 milliamps - NOT SAFE
Don’t want current through chest cavity (may be lethal)
Good review of Ohm’s Law

5. Safety Precautions Turn circuit off If must work on live AC circuit
Disconnect service cord
Disconnect negative battery cable
If must work on live AC circuit
Need 2nd safety person
Remove metal jewelry
Know your boat and its wiring
Use outlet tester on AC outlets
Use 3-wire extension cord from GFI outlet
Read Student Text section on Personal Safety Practices

6. Standards American Boat and Yacht Council (ABYC)
AC and DC Electrical Systems is E-11
Minimum standards
Construction
Repair
Marine Dept. of Underwriters Laboratory
Test and certify commercial products
Safety, not function
(No notes)

7. Wiring Considerations
Conductors
Wire Types
Wire Size
Wire Insulation
Wire Color Code
Major topics in Wiring Considerations section

8. Conductors Connects power sources to power loads Characteristics
Safe
Dependable
Efficient (minimal voltage drop)
Boat environment
Worse than either house or car
High humidity
Vibration
Corrosive conditions
(no notes)

9. Wire Types Marine Grade Stranded copper Type 3 is recommended
Tinned is preferred
Type 3 stranded wire has more strands (than type 2)
i.e. #12 AWG
Type 2 has 19 strands
Type 3 has 65 strands
Manufacture tinned wire reduces oxidation and corrosion

10. Wire Size 3% voltage drop 10% voltage drop Minimum size AWG # 16
Critical circuits (Nav lights)
Electronic Equipment
10% voltage drop
Cabin lights
Motorized Equipment
Minimum size AWG # 16
(no notes)

11. Wire Has Resistance Inadvertent Resistors
Wire too small (min of #16 - properly size using table)
Bad connections (or corroded connections)
Clean and tighten battery connectors
Tighten lug screws and inspect wire to lug connection
Why do wires get warm / hot?
Low resistance circuits pass high current (P = I2 x R)
Wires can account for much of the overall resistance
0.1 Ώ
12 VDC
10A
What Voltage? V
0.1 Ώ
An. 10 VDC
Good review of Ohm’s law
Note that voltage drop in example exceeds 10%
Note the application of Ohm’s Law. P = I x E =I x (I x R) = I^2 x R. As resistance drops, the current goes up as the square – ½ resistance results in 4x current, which leads to heating.

12. Wire Size Comparison #16 top to #10 bottom #2 top to #10 bottom
Figure 2-1
Coin is a South Carolina quarter
Wire sizes on left (top to bottom) 16 14 12 10
Wire sizes on right (top to bottom) 2 4 6 8
#16 top to #10 bottom
#2 top to #10 bottom

13. Copper Wire Characteristics
Table 2-1
Table is a reference table – Gives max current per wire size

14. 12- VDC Wire Size Selection
Equivalent to Table 2-3 (from West Marine catalog)
Note that distance is round trip distance
Given current (side scale) and round trip distance (bottom scale) gives wire size

15. 12 VDC Wire Size Selection
Table 2-2
Same info as previous table
Given max DC current and wire length – gives wire size
Use of table will be explained in Figure 2-2

16. 120 VAC Wire Size Selection
Table 2-3
Given max AC current and wire length – gives wire size
Use of table will be explained in Figure 2-2

17. What Size Wires? Problem statement
Answers from Tables 2-1, 2-2 and 2-3

18. Step 1 What current to Load? I = 10 AmpsB
What current to Load?
I = 10 Amps
Start with determining current to load
Then given current of 10A
from Table 2-2A determine need #16 wire
Then given 10 A and #16 wire
from Table 2-3 determine maximum length of wires
P = E * I I = P / E I = 1200/120
From Table 2-1 – For 10A need #16 wire
From Table 2-3 – Maximum of 44 feet (for 10A in #16 wire)

19. Step 1 Answers AMPACITY 10 Amperes #16 AWG TW by Table 2-1
Answers for wires from Inverter to Load
for 3% voltage drop
44 feet maximum
by Table 2-3

20. Step 2 What current to Inverter? Iload = 100 Amps @ 12 VB
What current to Inverter?
Iload = V
Power is power
AC current is 10 A
DC current if 100% efficiency is 100 A
I = P / E = 1200 / 12 = 100 A
But inverter is only 91% efficient
Therefore DC current is 100 / .91 = 110 A
Start with determining current to inverter
Then given current of 110A
from Table 2-1 determine need #1 wire
Then given 110 A and #1 wire
from Table 2-3 determine maximum length of wires
Iload = Iout = Iin * Iin = Iout / 0.91 = 100 / 0.91 = 110 Amps
From Table 2-1 – For 110A need #1 wire
From Table 2-3 – Maximum of 14 feet (for 110A in #1 wire)

21. Step 2 Answers AMPACITY 110 Amperes #1 AWG TW by Table 1
Note that at this load (110A), the battery must be de-rated and will not deliver 200AH. See Chapter 3.
for 3% voltage drop
14 feet maximum
by Table 2-2A

22. Wire Insulation AC cables must be type UL 1426 BC
600 volt insulation
Gasoline and Oil resistant
Won’t absorb moisture
DC wires & cables must be Marine Grade
Color coded wires
(no notes)

23. Wire Color Code Black X X1 White X Green (may have a yellow stripe) X
Color AC (Hot) AC (Neut) AC (Gnd) DC + DC -
Black X X1
White X
Green (may have a yellow stripe) X
Red X2 X
Yellow X1
Footnotes:
1 – Yellow preferred for DC negative to avoid confusion with AC Hot wire
2 – 2nd hot wire in 220 VAC is Red
(no notes)

24. Wire Color Coding
Figure 2-4

25. Wire Terminations Crimping Solder Heat-shrink Tubing Special Tool
Approved Marine Connectors
Use of Ratcheting Tool
Solder
Heat-shrink Tubing
Major topics in Wire Terminations section

26. Wire Terminals Figure 2-5
Only marine grade nylon ring terminals or nylon flanged connectors (captive spade) are approved by ABYC for wire terminals. Marine grade nylon butt connectors are used to join wires together.
Nylon insulation is color coded to indicate wire size. Red is #22 to 16, blue is #16 to 14 and yellow is #12 to 10.
Ring hole or spade opening must match the screw or stud diameter.
Waterproof connectors are adhesive lined and after crimping are heated to shrink their insulation tight against the wire insulation.
Twist-on connectors (wire nuts) are prohibited on boats.

27. YES Ratcheting Crimper NO Figure 2-4
Specified by ABYC. Will not release until correct amount of crimp is applied.
Don’t use inexpensive stripper/crimper as is almost impossible to apply the correct amount of compression. Can be used to strip insulation from wires. NO

28. Ratcheting Tool Use First select appropriate connector
Strip insulation length of stem plus 1/16”
Insert stripped end all way into terminal
End should extend 1/16”
Place terminal in same color slot
First crimp end of terminal barrel nearest ring
Then crimp wire end of terminal barrel
Check the connection with a solid tug
Makes good demonstration in class

29. Soldering Terminal connection can’t be only soldered
Must also be crimped
Soldering is normally not required
Crimped connectors are acceptable to ABYC
If solder, apply only to ring end of terminal
Solder changes stranded wire into solid
Stranded wire is flexible
Use 40% lead / 60% tin, rosin core solder
Battery lugs may be only soldered
Don’t use acid-core solder for electrical work!

30. Heat-Shrink Tubing Application Steps Bottom is Figure 2-3B
Are waterproof terminal and butt connectors.
Heat-Shrink tubing can be used to make non-waterproof terminals and connectors waterproof.
Heat is best from a hair dryer on hottest setting.

31. Coaxial Cable Antenna cable Radio coax is 50 ohm with PL-259
Radio cable is cut to length
Want attenuation under 3 db
TV cable is 75 ohm with “F” connectors
GPS cable is not cut to length
Coil excess in 1-foot loops
Major section

32. Coaxial Cable Information
Table 2-5

33. Soldering PL-259 Connector
Figure 2-6
Steps in text under Installing Coax Connectors (PL-259 male connectors)
Installing TV coaxial “F” male connectors is also covered in text. Would be a good demo in class.

34. Wiring Installation Basic Considerations Distribution Panel
Fuses / Circuit Breakers
Branch Circuits
Wire
Outlets
Switches
Grounding Systems
Bonding Systems
Major section

35. Basic Considerations Must have source and return wires
Return wires to a common point
May use feeder wire from power panel for:
engine, helm console, etc.
Wires above flood level of bilge
Waterproof if in bilge
Insulated support every 18”
Twist DC wires within 1 meter of compass
(no notes)

36. Distribution Panel Central location of Circuit Breakers / Fuses
All branch circuits from this location
AC and DC may be combined in one panel
All equipment / circuits should go to panel
Not direct to battery (except bilge pump)
Noise interference suppression covered in Section 7
(no notes)

37. DC / AC Power Panel Front View DC Side is on left
AC side is on middle and right
DC meters are switched to house, starting, or off
AC meters are switched to A service cord, B service cord or off
Note
All branches are protected by circuit breakers
Front View

38. Inside Power Panel Buss Bars DC Side
DC side of power panel; AC side is covered by insulated cover (at right edge)
Note use of wire ties to minimize vibration at termination
Return wire buses are located directly behind the power panel
DC Side

39. Fuses and Circuit Breakers
Used to protect wiring from over current
In positive or hot wire
Newer boats use circuit breakers
Initially more expensive
Replace blown fuse with correct rating
Circuit Breakers should be Marine Grade
Trip free
Manual reset
Trip free means cannot be held closed

40. Branch Circuits - Wires
Minimum size is 16 AWG
See Wire Selection Tables
For AC normally #14 for 15A and #12 for 20A
Must terminate in closed electrical box
Of sufficient length
DC negative returned to DC Panel
May use several negative feeder terminals
AC neutrals returned to AC Panel
Bonding system never used as return wire
Of sufficient length to:
Remove stress from connections
To permit fan-out and repair
Feeder terminals for engine compartment, helm console, fused panel

41. Branch Circuits - Outlets
120 VAC outlets must be 3-wire polarized
Black (hot) to brass or copper colored terminal
Outlet wires must have crimp terminals
GFI outlets
Required on weather deck, head, galley and machinery spaces
Good practice for all AC outlets to be GFI
Trip at 5 milliamps
Different outlets for AC and DC power
White (neutral) wire to silver terminal
Green (ground) wire to green terminal

42. Outlets and Plugs 12 VDC 120 VAC 120 VAC 120 VAC DC Outlet
(Receptacle)
15 A Outlet
GFI 15 A
Outlet
20 A Outlet
AC Outlets normally installed as illustrated
Larger vertical slot (on left) in neutral
Smaller vertical slot (on right) in hot
Almost-round hole is ground
15A plug will mate with either 15 or 20 amp outlet.
20A plug will only mate with 20 amp outlet.
DC Plug
AC Plug 15 A
AC Plug 20 A

43. Branch Circuits - Switches
Modern panels use Circuit Breakers
Which also double as switches
Switches / Circuit Breakers
Must be Marine Grade
Rated for the voltage and current controlled
Interrupt the positive (DC) or hot (AC) leg
Battery Switch
Designed for high current service
Not located in engine or fuel-tank compartments
(no notes)

44. Grounding System Ground is potential of water around boat
Or potential of earth’s surface
DC – Ground Battery negative terminal(s)
Also engine block
Wire color is Yellow (or Black)
AC – Transformer center tap on shore
Also connected to ground rod at transformer
Wire color is Green and uninterrupted wire
Isolation transformers and galvanic isolators are exception and covered in Chapter 4 on AC
Engine, DC negative & AC ground connected
Ground system is very important safety feature
More in Chapter 4 on AC

45. Bonding System For lightning protection
More in Chapter 6
All metal objects should be bonded
Keeps all metal at zero potential
Engine blocks
Battery negative terminals
Non-current carrying wire
Through-hull fittings
ABYC now recommends they be bonded
Electrically isolated from metal hull
More on Bonding in Chapter 6 on Lightning

46. Bonding Diagram
Figure 2-7

47. Wiring Diagrams Elements of a Good Wiring Diagram
Documents boat’s electrical layout
Should be kept current
Used for troubleshooting
Component Identification
Physical objects to their symbol
Wires are color coded
Major section

48. Wiring Diagram Symbols
Switch, double pole, single throw (DPST)
Switch, single pole, single throw (SPST)
Switch, single pole, double throw (SPDT)
Battery (long line on top is positive)
Wires connected (at dots)
Wires crossing (but NOT connected)
Wire (insulated, metal conductor)
Incandescent Light
Alternate symbol for Light
Circuit Breaker
Fuse
Ground
Male Connector
Female Connector
Figure 2-8
Note symbols for crossing (not connected) and connected wires.
Are two options for crossing wires
Are three options for lights

49. Simple DC Wiring Diagram
Figure 2-9
Simple Series circuit
Point out Battery (top is positive), switch, fuse, light bulb, ground and cable connections
Given 12 VDC battery
What measure across open switch? An. 12 VDC
What measure across closed switch? An. 0 VDC
As drawn (switch open), what measure across light bulb? An. 0 VDC
With switch closed what measured across light bulb? An. 12 VDC
What measured from engine block to “top” of light? An. 12 VDC
(Engine block is grounded (connected to battery negative))
What color should wire be from “top” of battery to switch and fuse?
An. Either red (generic) positive or Dark Blue (cabin lights)
What color should wire be from “bottom” of battery to light?
An. Either yellow (new ABYC color for negative) or black (old ABYC color)

50. Summary Circuits should be off when working on them
Use only marine grade properly sized wires
Tables will help determine proper wire size
Minimum wire size is #16 AWG
Use wire terminations and ratcheting crimper
DC circuits are 2 dedicated wires
Waterproof wire connection in bilge
AC circuits are 3 dedicated wires
GFCI in galley, head, machine spaces & weather deck
Separate Grounding & Bonding systems required
Keep wiring diagram current