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37
TECH
tip
by BLUE SEA SYSTEMS
BEST PRACTICES AND ABYC STANDARDS RECOMMEND
EVERY WIRE ON THE BOAT, EXCEPT THE ENGINE STARTING
CIRCUIT, HAVE CIRCUIT PROTECTION.
When excessive current flows in an electrical circuit, wire insulation
can melt and possibly start a fire. Circuit breakers and fuses protect
the wire in electrical circuits. Blue Sea Systems extensive selection
of circuit breakers, fuses, fuse holders, and fuse blocks offers a
range of choices for main and branch circuit protection.
To help in the selection process, Blue Sea Systems has developed
several tools to determine the correct size wire and fuse or circuit
breaker for the application. This information is outlined on page 38.
All of these guides are to help in the selection process but are not
a substitute for calculations based directly on industry tables, the
Blue Sea Systems Circuit Wizard, or as recommended by an ABYC
certified Electrician.
Most circuit protection is installed to protect the wire.
Determine wire size and circuit protection options.
Considerations of Circuit Protection
The DC Main circuit protection system uses circuit breakers
or fuses to protect the wires of the DC main distribution
system. The American Boat and Yacht Council (ABYC) publishes
voluntary standards for the type and placement of the fuse or
circuit breaker to be used as a DC main circuit
protection device.
The diagram below shows the required placement of main
circuit protection devices. Note that wire intended to carry
engine starting currents between the batteries, the switch and
the starter, is not required to have main circuit protection
devices installed.
ABYC Rules for distance of a circuit breaker or fuse from
power source:
7" ABYC Rule:
If the conductor is not housed in a sheath or
enclosure in addition to the wire insulation.
40" ABYC Rule:
If the conductor is housed in a sheath or
enclosure in addition to the wire insulation.
72" ABYC Rule:
If the conductor is connected directly to the
battery and housed in a sheath or enclosure in addition to the
wire insulation
.
Mounting Placement of a Fuse or Circuit Breaker
- distance from power source
C
I R C U I T
P
R O T E C T I O N A N D
S
W I T C H E S
7" Max.
ABYC Rule
Fuse or
Circuit Breaker
Bilge Pump
Single Conductor running directly
from the source of power to the load
Start
Start
Bilge Pump
72" Max.
ABYC Rule
Fuse or
Circuit Breaker
Sheathed Conductor running directly
from the source of power to the load
Single Conductor
Sheathed Conductor
40" Max.
ABYC Rule
Fuse or
Circuit Breaker
Sheathed Conductor running from the
source of power to a battery switch
then to the load
House
Start
Scan to
use the
Circuit
Wizard
Use the Blue Sea Systems Circuit Wizard
to select the correct wire size, circuit
protection, and fuse holder
20008
You Can Do it, Protect
Your Boat with the
Correct Size Wire,
Fuse, and Fuse Holder
· 20 guides per pack
20010
20" x 17" Deskmat
Blue Sea Systems provides free tools to select the correct
size wire, fuse, circuit breaker, and fuse holder.
The Circuit Wizard App for iPhone and Android devices
is the latest addition to the company’s available
resources. Other tools include the online
Circuit Wizard, Counter Mat, and brochure
version of the Circuit Wizard.
Resources
Online Circuit Wizard