Electrical Wiring Practices Chapter 2 Electrical Wiring Practices and Diagrams PowerPoint slides by Stf/C Harl Porter, SN Marine Electronics 107Harl@sc.rr.com 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)

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

Safety Lethal Current Safety Precautions Major topics in Safety section

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

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

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)

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

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)

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

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)

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.

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

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

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

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

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

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

Step 1 What current to Load? I = 10 Amps B 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)

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

Step 2 What current to Inverter? Iload = 100 Amps @ 12 V B What current to Inverter? Iload = 100 Amps @ 12 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 *0.91 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)

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

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)

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)

Wire Color Coding Figure 2-4

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

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.

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

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

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!

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.

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

Coaxial Cable Information Table 2-5

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.

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

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)

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)

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

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

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

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

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

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

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)

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

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

Bonding Diagram Figure 2-7

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

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

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)

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