Section 78
00-02-0629
08-08-07 -
8 -
Maximum Number of Devices
A maximum of 50 physical devices shall be connected to the network, and the disconnection of
any device shall not interrupt any other device on the network.
NMEA 2000 Cable
Micro cables contain five wires: One twisted pair (red and black) for 12VDC power, one twisted
pair (blue and white) for signal and a drain wire (bare).
Installing Terminators
Termination resistors are attached to each end of the trunk cable to reduce reflections of the
communication signals on the network. If you do not use termination resistors as described,
the network will not operate properly. Termination resistors are typically connected directly to
the last tee on the trunk line although they can be connected to a cordset extending from the
last tee on a trunk line.
Supplying Power
NMEA 2000 networks can use a power supply originating from a single-point connection to the
vessel’s 12 volt battery or one or more isolated power supplies distributed along the network,
but not a combination of battery and power supply connections. Over current protection
should be provided and should be sized in accordance with ABYC E-11, AC and DC
ELECTRICAL SYSTEMS ON BOATS, taking into consideration the smallest gauge of cable
being used for the backbone or drop cables. The NET-S wire is connected to the positive side
of the battery while NET-C is connected to the negative side of the battery.
Micro Power Capability
Micro cable is rated to 4 amps, however strategic placement of the power source could support
higher current. For example, 8 amps of power could be supplied to the middle of the trunk
where 4 amps is supplied to both sides of the power tap. It can handle large loads as long as
no more than 4 amps is drawn through any single segment of he trunk line. However, cable
resistance may limit your application to less than 4 amps.
