NMEA-2000 Power Isolator

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jimh
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NMEA-2000 Power Isolator

Postby jimh » Tue Aug 08, 2017 10:30 am

In some configurations of NMEA-2000 network backbone wiring it becomes useful to block the power wiring between network segments. This is often done if there is a device, usually older legacy devices, which thinks that its network interface should also provide power to the network. Powering the network from a device's network port is not the recommended method, and on that basis should be avoided. To use legacy devices that try to power the network, their power circuit can be interrupted by using a power isolator wiring device and inserting the isolator into the drop cable circuit, between the device and the network T-connector's device port.

A power isolator can also be used in the network backbone circuit, to split the network into two power segments. This is usually not the best method to split network power into two segments. A better approach to creating two power segments is to use a power insertion node device that is configured for split network power, such as the MARETRON MICRO/MID POWER TAP T component. See:

https://www.maretron.com/products/pdf/M ... sheets.pdf

About the only time a power isolator might be useful in the network backbone wiring may be if the network includes a device that is providing network power on its network port AND it is useful to utilize that power for a certain segment of the network. Then the power isolator could be used to isolate that branch of the network from the remainder of the network that will be powered by another source.

For some time GARMIN has been making a power isolator component, but there is a bit of difficulty in using it. The orientation of the connectors in the plastic housing has been done at a different position than the connectors in the NAVICO branded wiring components (Lowrance, Simrad, Evinrude), and this creates a problem if the GARMIN device is used with those other brands. The GARMIN power isolator cannot be inserted into a daisy-chain of T-connectors and then be mounted against a bulkhead, as the GARMIN device won't lie in the same plane as the other components. Of course, the GARMIN component works just fine when used with other GARMIN network T-connectors, and the problem is avoided if all-GARMIN devices are used.

Just recently NAVICO has begun to make their own power isolation device, which is presumed to have the connectors in the same orientation as the rest of their components, and this should overcome the physical problems associated with the GARMIN component. The NAVICO power isolator is their part 000-12259-001 and retails for $24. If your network is wired with NAVICO wiring devices and you need a power-isolator, the NAVICO part may be preferred over the GARMIN part due to the (expected to be compatible) physical layout of the connector.

If you already have the GARMIN power isolator, the problem of mounting to a bulkhead can perhaps be overcome by using spacers to raise all the network-T components away from the bulkhead, thereby creating some room for the Garmin part to lay out of alignment with the others.