1. THE ELECTRICAL SIDE OF
INSTALLING ELECTRONICS ON
BOATS
CHARLIE JOHNSON
JTB MARINE CORPORATION
cjohnson@jtbmarine.com
727.560.9065
HUDSON BEACH YACHT CLUB MEETING
SEPTEMBER 4, 2012

2. Charlie Johnson, PE
Charlie has been active in marine engineering for most of his professional career. A registered
professional mechanical engineer in two states, he is a retired Naval Officer with extensive ship
management and ship handling experience. He began his Naval career as the Chief Engineer of a
salvage vessel that saw extensive action during the Vietnam War. After his Chief Engineer’s tour, he
began a career as an Engineering Duty Officer specializing in nuclear submarine maintenance,
design and certification.
In the late 1990’s, Charlie and his wife, Lari, prepared their 53’ Gulfstar Long Range Trawler for a
three year trip to the Eastern Caribbean where they practiced retirement.
In 2001, he formed JTB Marine Corporation, a company dedicated to providing standards based,
technically strong services to the boating public, boat builders, and commercial fishermen. JTB
Marine’s work scope includes standards based designs, concise troubleshooting, and the
performance of meticulous installations of electrical and electronic systems and components on
private yachts and commercial vessels in the 35’ to 110’ range.
Charlie also performs electrical and corrosion surveys and provides forensic engineering and
accident investigation services aboard all types of vessels. His most recent forensics’ experience
includes investigations to determine the origin and cause of fires aboard two private vessels and
determining the cause of stray current damage at a municipal marina.
Recently became a partner in Clean eMarine-Americas (http://www.c-e-marineamericas.com), to
build and distribute the Danish Thoosa and Triton brand of electric propulsion systems
2

3. BORING BUT IMPORTANT STUFF
SOMEBODY INVOLVED WITH THE INSTALLATION OF
ANY ELECTRICAL EQUIPMENT ABOARD YOUR BOAT
NEEDS TO GO THROUGH THIS THOUGHT PROCESS
IF NOT YOU, THAN CERTAINLY YOUR TECHNICIAN
MUST BE KNOWLEDGEABLE
3

4. OUR SIZZLING TOPICS FOR THIS
EVENING
VOLTAGE DROP AND AMPACITY
IN-LINE FUSES
4

5. OUR SIZZLING TOPICS FOR THIS
EVENING
WOW!! FEEL THE EXCITEMENT!!!
5

6. SIZZLING TOPIC #1: VOLTAGE DROP
VOLTAGE DROP IS THE MANIFESTATION OF MR.
OHM’S LAW:
VOLTAGE = CURRENT X RESISTANCE
E=IXR
REMEMBER YOUR ALGEBRA (MATH IS FUN ☺)
INCREASING THE CURRENT ➔ INCREASES VOLTAGE
DROP
INCREASING THE RESISTANCE ➔ INCREASES VOLTAGE
DROP
6

7. VOLTAGE DROP
CONDUCTORS HAVE RESISTANCE (EXPRESSED IN
OHMS); THE “R” IN MR. OHM’S LAW
THE ELECTRICAL RESISTANCE OF CONDUCTORS
INCREASES AS THEIR LENGTH INCREASES
THE ELECTRICAL RESISTANCE OF CONDUCTORS
INCREASES AS THE CROSS SECTIONAL AREA OF THE
CONDUCTOR DECREASES
7

8. VOLTAGE DROP
FROM THE AMERICAN BOAT AND YACHT COUNCIL
STANDARDS AND TECHNICAL INFORMATION REPORTS FOR
SMALL CRAFT, 2012-2013
11.4.2.6 Voltage Drop - Conductors used for panelboard or
switchboard main feeders, bilge blowers, electronic
equipment, navigation lights, and other circuits where
voltage drop must be kept to a minimum, shall be sized for
a voltage drop not to exceed three percent.
Conductors used for lighting, other than navigation lights,
and other circuits where voltage drop is not critical, shall
be sized for a voltage drop not to exceed 10 percent.
8

9. VOLTAGE DROP
A NEW AND EXCITING TERM: AMPACITY
AMPACITY IS THE MAXIMUM AMOUNT OF ELECTRICAL
CURRENT A CONDUCTOR OR DEVICE CAN CARRY BEFORE
SUSTAINING IMMEDIATE OR PROGRESSIVE DETERIORATION.
FOR CONDUCTORS, AMPACITY IS A FUNCTION OF THE THE
ABILITY OF THE CONDUCTOR’S INSULATION AND TO A
LESSER EXTENT, THE CONDUCTOR ITSELF TO REMAIN INTACT
UNDER LOAD
AMPACITY DECREASES WITH AN INCREASE IN AMBIENT
TEMPERATURE
AMPACITY DECREASES WITH THE ADDITION OF BUNDLED,
CURRENT CARRYING CONDUCTORS
9

10. VOLTAGE DROP
ABYC STANDARDS SPECIFY :
11.14.2.1.1 The construction of insulated cables and
conductors shall conform with the requirements of:
11.14.2.1.1.1 UL 1426, Cables for Boats, or
11.14.2.1.1.2 the insulating material temperature rating
requirements of:
11.14.2.1.1.3 SAE J378, Marine Engine Wiring, and
11.14.2.1.1.4 SAE J1127, Battery Cable, or SAE J1128, Low-
Tension Primary Cable
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11. VOLTAGE DROP
QUALITY BOAT CABLE; E.G., ANCOR, BELDEN, PACER, ETC.
IS RATED AS UL1426, WITH INSULATION THAT IS RATED
FOR 105℃ DRY CONDITIONS OR 75℃ WET CONDITIONS
TINNING IS NOT MANDATORY BY THE ABYC STANDARDS,
BUT IS CONSIDERED BEST PRACTICE IN THE INDUSTRY
LIKEWISE, TYPE 3 STRANDING IS NOT REQUIRED BY THE
ABYC STANDARDS BUT IS CONSIDERED BEST PRACTICE IN
THE INDUSTRY
11

12. VOLTAGE DROP
WHEN DESIGNING A CIRCUIT THERE ARE TWO
PARAMETERS THAT MUST BE CONSIDERED
VOLTAGE DROP
OPERATIONAL CONSIDERATION
AMPACITY
SAFETY CONSIDERATION
USUALLY, ADEQUATE CONDUCTOR SIZE TO PROVIDE
THE SPECIFIED ALLOWABLE VOLTAGE DROP WILL
PROVIDE ADEQUATE AMPACITY…BUT NOT ALWAYS!!
12

13. VOLTAGE DROP MATH…HOW WE
LOVE MATH!☺
FROM THE ABYC STANDARDS:
KxIxL
CM = —————
E
Where:
CM = Circular mil area of conductor
K = 10.75 (constant representing the resistivity of copper)
I = Load current in amperes
L = Length of conductor from the positive power source connection to
the electrical device and back to the negative power source connection,
measured in feet.
E = Maximum allowable voltage drop at load in volts
13

14. VOLTAGE DROP
BUT, WE DON’T HAVE TO DO THE MATH (☹) TO FIND
A CONDUCTOR SIZE FOR A KNOWN LOAD WITH A
KNOWN DISTANCE FROM THE SOURCE IN A KNOWN
ENVIRONMENT
BY SETTING E = 12VDC AND E = 24VDC AND USING
BOAT CABLE WITH 105℃ INSULATION RATING IN THE
CM FORMULA AND THEN CONVERTING FROM CM TO
AWG, THOSE NICE FOLKS AT ABYC HAVE GENERATED
A COUPLE OF TABLES TO HELP US OUT
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15. VOLTAGE DROP
THESE TABLES ARE OK, BUT THOSE REALLY NICE FOLKS
AT BLUE SEA SYSTEMS HAVE MADE THE DETERMINATION
OF CONDUCTOR SIZE EVEN EASIER, AND THERE IS EVEN
SOME MATH!!☺
LOOK AT THE VOLTAGE DROP EQUATION AGAIN:
CM = (K x I x L) / E
FOR A KNOWN VOLTAGE DROP (E) BLUE SEA DEVELOPED THE
CONCEPT OF FOOT x AMPS (I x L)
USING SYSTEM VOLTAGE AND ALLOWED VOLTAGE DROP AND
THE PRODUCT OF CIRCUIT LENGTH (L) AND THE LOAD
CURRENT(I) ENTER THE FOLLOWING TABLE TO FIND THE
PROPER WIRE SIZE
15

16. VOLTAGE DROP
16

17. VOLTAGE DROP
AN EXAMPLE
12 VOLT SYSTEM
NEW READING LIGHT TO BE INSTALLED 20’ AWAY
FROM THE CONNECTION TO THE CIRCUIT BREAKER
PANEL
ACTUAL TO/FROM CIRCUIT LENGTH IS 45’
ELECTRICAL LOAD IS 2A
OUTSIDE THE MACHINERY SPACE
F-AMPS = 45’ x 2A = 90 F-AMPS
17

18. VOLTAGE DROP
ENTER THE BLUE SEA TABLE WITH 90 F-AMPS, NON
MACHINERY SPACES, 12VDC AND 10% VOLTAGE DROP
TO FIND THE A NUMBER ≥ 90 F-AMPS
18

19. VOLTAGE DROP
☟
19

20. VOLTAGE DROP
ONE MORE EXAMPLE (WE ♡ MATH!)
12 VOLT SYSTEM
ANCHOR WINDLASS TO BE INSTALLED WITH AN
ACTUAL TO/FROM CIRCUIT LENGTH OF 52’ FROM THE
LOAD SIDE OF THE CIRCUIT BREAKER ADJACENT TO
THE STARTING BATTERY
ELECTRICAL LOAD IS 90A
INSIDE THE MACHINERY SPACE
F-AMPS = 52’ x 90A = =4,680 F-AMPS
20

21. VOLTAGE DROP
ENTER THE BLUE SEA TABLE WITH 4,680 F-AMPS,
MACHINERY SPACES, 12VDC AND 10% VOLTAGE DROP
TO FIND THE A NUMBER ≥ 4,680 F-AMPS
21

22. VOLTAGE DROP
☟
22

23. VOLTAGE DROP
WHY DO WE CARE ABOUT VOLTAGE DROP?
ALL ELECTRICAL LOADS HAVE A VOLTAGE AND A
CURRENT SPECIFICATION
EXAMPLE: THE POPULAR ICOM MARINE SSB/HAM
M802 SPECS
30A MAXIMUM
13.6VDC ±10%
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24. VOLTAGE DROP
ICOM 802
LET’S HAVE MORE FUN WITH MATH!! ☺
13.6VDC + 10% = 13.6VDC + 1.36VDC = 14.96VDC
REASSURING: THE MAGIC SMOKE WON’T COME OUT OF
THE BOX WHEN CHARGING WITH THE ALTERNATOR OR
THE CHARGER. THIS IS GOOD.
13.6VDC – 10% = 13.6VDC -1.36VDC = 12.24VDC
REASSURING: MAYBE. WE’LL HAVE TO COME BACK TO
THIS.
24

25. VOLTAGE DROP
ICOM 802
OH BOY, MORE MATH AND ELECTRICAL FORMULAE
(DON’T YOU JUST LOVE THIS STUFF?♡)
SPEC IS FOR 30A MAX CURRENT DRAW @ 13.6VDC
POWER = CURRENT X VOLTAGE
P = I X V (POWER IN WATTS; I IN AMPS; V IN VOLTS)
FROM THE SPEC’S A NOMINAL 13.6VDC AND 30A ON
MAX OUTPUT RF POWER WOULD YIELD AN INPUT
POWER REQUIREMENT OF :
P = 30A X 13.6VDC = 408W
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26. VOLTAGE DROP
ICOM 802
SO THE POWER REQUIREMENT FOR MAX RF OUTPUT
IS 408W
MORE MATH!!☺
12.24VDC IS THE BOTTOM OF THE ALLOWABLE
VOLTAGE RANGE AND WE NEED 408W FOR MAX RF
OUTPUT
P=IXV➯I=P/V
PLUGGING AND CHUGGING THE NUMBERS:
I = 408 / 12.24 = 33.33A
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27. VOLTAGE DROP
ICOM 802
THE ICOM 802 MAIN UNIT IS GOING TO BE LOCATED
SUCH THAT THE CIRCUIT LENGTH FROM THE HOUSE
BANK CIRCUIT BREAKER IS 30’, THE HOUSE BANK IS
IN THE ENGINE COMPARTMENT, THE SYSTEM IS
12VDC AND ALLOWING FOR MAXIMUM RF OUTPUT
AT MINIMUM BATTERY VOLTAGE, LOAD CURRENT IS
33.3A
WHAT SIZE CONDUCTOR IS REQUIRED?
F-AMPS = 30’ x 33.3A = 999 F-AMPS
27

28. VOLTAGE DROP
DON’T FORGET…
FROM THE AMERICAN BOAT AND YACHT COUNCIL
STANDARDS AND TECHNICAL INFORMATION REPORTS FOR
SMALL CRAFT, 2012-2013
11.4.2.6 Voltage Drop - Conductors used for panelboard or
switchboard main feeders, bilge blowers, electronic
equipment, navigation lights, and other circuits where
voltage drop must be kept to a minimum, shall be sized for
a voltage drop not to exceed three percent.
28

29. VOLTAGE DROP
☟
29

30. THAT’S IT FOR VOLTAGE DROP
(THANK YOU, SIGHS THE AUDIENCE!)
ANY QUESTIONS BEFORE MOVING ON TO THE
NEXT, EDGE OF YOUR SEAT, TOPIC?
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31. SIZZLING TOPIC #2: THOSE IRRITATING,
BUT OH SO NECESSARY, IN-LINE FUSES
ATO/ATC FUSE HOLDER
(BLADE TYPE)
AGC FUSE HOLDER-DRIP PROOF
(GLASS TYPE)
31

32. IN-LINE FUSES
WE HAVE TWO ISSUES:
PROTECTING THE CONDUCTORS FROM A SHORT CIRCUIT
SITUATION
REMEMBER AMPACITY?
PROTECTING THE EQUIPMENT
HOWEVER, MANY ELECTRONIC DEVICES REQUIRE CIRCUIT
PROTECTION AS LOW AS 1A.
ELECTRONICS’ MANUFACTURES GENERALLY PROVIDE A
FACTORY INSTALLED IN-LINE FUSE HOLDER IN THE B+
CONDUCTOR TO THE PIECE OF ELECTRONIC EQUIPMENT
THIS FUSE HOLDER IS OFTEN OF POOR QUALITY AND PRONE TO
WATER INTRUSION
32

33. IN-LINE FUSES
RECENTLY ON A 44’ CALIFORNIAN MOTOR YACHT
THE “WIGGLE IN” FLYING BRIDGE ACCESS SPORTED NO
FEWER THAN SIX FACTORY INSTALLED AGC IN-LINE FUSES
UNDER THE DASH
THE TILT BACK LOWER STEERING STATION HAS THREE
FACTORY INSTALLED AGC IN-LINE FUSES
ESSENTIALLY IMPOSSIBLE, OR AT LEAST VERY DIFFICULT,
TO QUICKLY CHECK TO SEE IF A FUSE IS BLOWN IF THE
ELECTRONIC EQUIPMENT DOES NOT POWER UP
33

34. IN-LINE FUSES
A SOLUTION THAT SOMETIMES WORKS.
34

35. IN-LINE FUSES-A BETTER WAY
THOSE NICE FOLKS AT BLUE SEA SYSTEMS HAVE
JUST COME OUT WITH ANOTHER OPTION…MY
OPINION IS THAT IT IS JUST ABOUT IDEAL!
35

36. IN-LINE FUSES-A BETTER WAY
Independent Sourced Circuit ST Blade Fuse Block
36

37. IN-LINE FUSES-A BETTER WAY
B+ OUT TO
B+ IN FROM
INDIVIDUAL
SOURCES
LOADS
Independent Sourced Circuit ST Blade Fuse Block
37

38. SUMMARY
VOLTAGE DROP AND ITS IMPORTANCE
AMPACITY AND ITS IMPORTANCE
CONDUCTOR SIZING, THE EASY WAY
HOW TO PROTECT YOUR EXPENSIVE ELECTRONICS
WITHOUT USING CONVENTIONAL IN-LINE FUSES
BURIED BEHIND THE JOINERY
38

39. QUESTIONS
PLEASE BE KIND!
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