NMEA 2000 - Micro or Mini?

[carlylelk]

On my 53' sailboat, I'm looking at putting a N2K backbone and system in.

The references I've found provide formulas to calculate the voltage drop from the backbone and the gear attached. It references the load from the gear as "Length Equivalent Number" or LEN. I can't seem to find that information in the data for the gear I'm buying: B&G Zeus 3, 4G Radar, and Simrad Precision 9 Rate Compass. I also plan to eventually add depth, boatspeed, and wind instruments to the N2K system.

The Micro backbone is smaller cable, which would be good, but the documents note that it shouldn't be used "...for larger systems". I'm not sure what they think of as large!

Can anyone give me a reference for the LEN for equipment?

Thanks,
Duane

[Paul L]

The tech specs in the install manuals list the load equivalent mumble, LEN. The radars main data path is Ethernet not n2k.

[smac999]

that is a tiny network. big ones are like 50 items.

you shouldn't have any issue with micro. I have only used mini a couple times. on 100'+ multi story boats.

Len data should be in specs. generaly anything already powered will be 1. IE the screen and RI10 box likly are.

a compass and nmea 2000 depth sounder probably len 2-3 since they are powered from n2k

[SailRedemption]

We use micro on our 47' and have the same thing you are asking about. When buying the cables buy the "Mid" cords for you backbone and buy "Micro" for your drops. The Mid cords have 16ga power wires and 20ga for the data. The Micro cable is 4x 22ga for data and power. They are the same size cords and both use the micro connectors. So for instance, we have a 6m Mid cord from our central network hub area at the nav desk to the cockpit for the backbone. And the Maretron 25m Mid single ended cord from the WSO100 wind transducer down the mast to a field attachable micro connector to the central hub. We also have the Maretron multiport boxes instead of a bunch of tees to keep things more tidy.

[bobmcd625]

I installed a similar "small" system last year and used Maretron's Network Builder software https://maretron.com/products/N2KBuilder.php to lay it out. Worth the effort. I went with mid cables for the backbone and mini for the drops.
Good luck.

[northwestsailor]

I went all micro for my B&G system. It does not go up the mast since I used wireless for that. All works fine.

[carlylelk]

Thanks everyone.

I still can't find the LEN for the B&G unit, I've looked in Installation and Operation Manual. Thanks to smac999 for the suggestion that all non-n2k powered units are a LEN=1.

I did a layout with everything I could think of that I might add in the future in the Maretron software and Micro works, so why not use it? Still, I will probably pull the Mini for the backbone and up the mast.

Thanks to all,
Duane

[indimini]

You can use this NMEA link to look up LEN information.

Looks like the plotter is LEN 1.

[Skip A]

The LEN for the B&G Zeus 3 is 3 per the users manual. Good luck on the install, I'm about to start my network installation.

[indimini]

Based on Skip A's note, and a look at my Zeus 2 docs, it is certainly not LEN 1.

I guess the data on the NMEA site isn't fully vetted, so it may be a good start, but not an authoritative source.

[carlylelk]

24v?

One other question:

The house system is 24 volt. I do have three Thrane & Thrane Sailor 24V to 12V regulators that provide up to 8amps each. One powers the VHF, one is marked for the AM/FM radio to maintain the preset channels, the other is marked "Navigation".

The Zeus 3 has a power feed that accepts 12/24V. Is there any issue with powering the Zeus with 24V but powering the N2K with 12V from one of the Sailor Regulators?

Thanks,
Duane

[northwestsailor]

Our boat is also wired for 24v, I have a large 24/12v converter which supplies the B&G VHF and N2K system with 12v whilst all other B&G components that will accept 24v are wired in with the native voltage. Does not seem to be an issue at all.

[continuouswave]

Originally Posted by carlylelk

...It references the load from the gear as "Length Equivalent Number" or LEN...

LEN stands for Load Equivalent Number. It is not related to a length dimension.

[continuouswave]

Originally Posted by carlylelk

...The Micro backbone is smaller cable, which would be good, but the documents note that it shouldn't be used "...for larger systems"...

The term "MICO" describes the size of the connector, not the cable. The alternative and larger connector is described as "MINI."

In NMEA-2000 wiring, the cable is described as "light" or "mid" or "heavy."

A good reference to understand these terms and to calculate the necessary cable size is found at

https://www.nmea.org/Assets/2012%20i...stallation.pdf

This reference will explain how to use LOAD EQUIVALENT NUMBER or LEN to calculate cable size needed based on total network loads and distances.

The MICRO connector will be found on most recreational grade electronics. Use of the MICRO connector is generally the standard for device interfaces.

If there is unusual length and power needed for the network backbone, you can use cable of MID size; otherwise the normal backbone will be cable of LIGHT size. Cable are made with MID cable and MICRO connectors by MARETRON.

Note that with LIGHT cable and MICRO connectors, you can split a network power wiring into two 3-Ampere segments, giving a total of 6-Amperes. Since a LEN = 0.05-Ampere, a network of 6-Amperes would power loads totaling (6/0.05) or 120 LEN. To have devices whose network load exceeded 120 LEN would be quite unusual.