Are tee's ok on NEMA 2000 drop cables?

[s/v Jedi]

Originally Posted by Paul L

So is this spec compliant or not?

Yes, approved by nmea and iec as shown in the specs:

[Paul L]

Originally Posted by s/v Jedi

Yes, approved by nmea and iec as shown in the specs:

It maybe in the marketing brochure but it isn't listed in the NMEA certified devices site
https://www.nmea.org/content/STANDAR...=&PageNumber=1

[s/v Jedi]

Originally Posted by Paul L

It maybe in the marketing brochure but it isn't listed in the NMEA certified devices site
https://www.nmea.org/content/STANDAR...=&PageNumber=1

You think it’s a fraudulent claim from Maretron?

[s/v Jedi]

Originally Posted by Paul L

It maybe in the marketing brochure but it isn't listed in the NMEA certified devices site
https://www.nmea.org/content/STANDAR...=&PageNumber=1

I checked that but it only lists devices like displays, gps etc., no cabling items there at all.

Also, I think Maretron’s reputation is good enough to assume they don’t put fraudulent claims in their spec sheets

[Paul L]

Originally Posted by s/v Jedi

You think it’s a fraudulent claim from Maretron?

I don't know. I assume the Nmea certified site is a pretty up to date list. I do not understand how you can have multiple devices on a single drop and still be compliant. That said, I don't have access to the current spec to look for exceptions. That's why I adked the question. Plus I've had multiple instruments on a single drop for years and it works fine, even though I believe it is a spec violation.

[Dsanduril]

This is straight from the NMEA website in a presentation on proper NMEA 2000 installation and multi-drop taps. Seems they do allow, within the restrictions shown (and their example is the Maretron device).



Which then means the Maretron, while inert, isn't really 4 tees, as it is not intended to continue the backbone.

[goboatingnow]

It’s means what the OP wants to do is fully compliant ie a T from a T once all the cabling is less then 6 metres which given his situation is more then likely

[Paul L]

Originally Posted by Dsanduril

This is straight from the NMEA website in a presentation on proper NMEA 2000 installation and multi-drop taps. Seems they do allow, within the restrictions shown (and their example is the Maretron device).

Attachment 245696

Which then means the Maretron, while inert, isn't really 4 tees, as it is not intended to continue the backbone.

Which makes sense. Do you know if this is a change from the orginal spec?

[PerfectPirate]

In my previous boat, I installed a B&G Triton system with 3 display heads. The Triton heads each had in "IN" NMEA 2000 port and an "OUT" port. They were literally designed to be daisy-chained off of a single drop cable/T-Connector. I had three displays chained off of a single drop cable and everything functioned flawlessly. The backbone also hosted two transducers and a Garmin GPSMap unit and was designed to terminate one end at the masthead transducer. Interestingly, even when the cable to the masthead transducer, with its terminator, was disconnected the rest of the network continued to function flawlessly.

I loved the B&G systems so much that for my new boat I went out and bought a Triton II system. I was surprised to find that the daisy-chaining capability is not built into the Triton II display heads and that the masthead transducer no longer acts as a backbone terminator, which means that the drop cable running up the mast to the transducer will exceed the NMEA-spec maximum length for a drop cable. When I inquired of B&G if I could in fact daisy-chain my two display heads by putting a T-Connector on the back of one, I was told that this is not supported in the NMEA spec and that I should use two drop cables. However, given what has been discussed in this set of posts, when I install the display heads I will try daisy-chaining them off of a single drop cable, to see if it works. If not, I will then simply re-orient the network cabling to make them the end units on the backbone. I too have space/accessibility problems with running multiple cables.

Incidentally, I love the field-connectable Maretron NMEA 2000 plugs, as they allow me to fish network wires through spaces and openings too tight for cables with pre-made plugs attached. I made great use of them in my old system and found that if you are careful and meticulous in prepping your wires and fastening them then the plugs are completely reliable. It ain't easy, but then what part of boat maintenance is?

[s/v Jedi]

Originally Posted by PerfectPirate

In my previous boat, I installed a B&G Triton system with 3 display heads. The Triton heads each had in "IN" NMEA 2000 port and an "OUT" port. They were literally designed to be daisy-chained off of a single drop cable/T-Connector. I had three displays chained off of a single drop cable and everything functioned flawlessly. The backbone also hosted two transducers and a Garmin GPSMap unit and was designed to terminate one end at the masthead transducer. Interestingly, even when the cable to the masthead transducer, with its terminator, was disconnected the rest of the network continued to function flawlessly.

I loved the B&G systems so much that for my new boat I went out and bought a Triton II system. I was surprised to find that the daisy-chaining capability is not built into the Triton II display heads and that the masthead transducer no longer acts as a backbone terminator, which means that the drop cable running up the mast to the transducer will exceed the NMEA-spec maximum length for a drop cable. When I inquired of B&G if I could in fact daisy-chain my two display heads by putting a T-Connector on the back of one, I was told that this is not supported in the NMEA spec and that I should use two drop cables. However, given what has been discussed in this set of posts, when I install the display heads I will try daisy-chaining them off of a single drop cable, to see if it works. If not, I will then simply re-orient the network cabling to make them the end units on the backbone. I too have space/accessibility problems with running multiple cables.

Incidentally, I love the field-connectable Maretron NMEA 2000 plugs, as they allow me to fish network wires through spaces and openings too tight for cables with pre-made plugs attached. I made great use of them in my old system and found that if you are careful and meticulous in prepping your wires and fastening them then the plugs are completely reliable. It ain't easy, but then what part of boat maintenance is?

The displays were daisy chained into the backbone, not in a drop cable. This reduces network reliability because the backbone is interrupted by active devices.

Maretron and others sell in-line terminators that install between the masthead instrument and the backbone cable running up the mast, eliminating the T connector and normal terminator.
See: https://www.amazon.com/Maretron-IT-c...%2C235&sr=8-15

[goboatingnow]

Originally Posted by s/v Jedi

The displays were daisy chained into the backbone, not in a drop cable. This reduces network reliability because the backbone is interrupted by active devices.



Maretron and others sell in-line terminators that install between the masthead instrument and the backbone cable running up the mast, eliminating the T connector and normal terminator.

See: https://www.amazon.com/Maretron-IT-c...%2C235&sr=8-15

It doesn’t really. It just means the T is inside the device rather then external. In both cases the backbone is unchanged.

[PerfectPirate]

Originally Posted by s/v Jedi

The displays were daisy chained into the backbone, not in a drop cable. This reduces network reliability because the backbone is interrupted by active devices.

This implies that my backbone was split into two, since the primary network backbone continued on in both directions past the T-connector which fed into the three Triton displays. Also, there was no terminator at the end of the line which fed the displays, unless there was some sort of terminator inherent in the display units themselves. So I will stick by my impression that there were simply 3 displays daisy-chained off of a single drop cable.

[Kelkara]

Originally Posted by PerfectPirate

This implies that my backbone was split into two, since the primary network backbone continued on in both directions past the T-connector which fed into the three Triton displays. Also, there was no terminator at the end of the line which fed the displays, unless there was some sort of terminator inherent in the display units themselves. So I will stick by my impression that there were simply 3 displays daisy-chained off of a single drop cable.

Raymarine also used to make their displays with 2 seatalkng ports so that they could be daisy chained like this, some of their installation diagrams still show it, although I don't think they still put 2 ports on them ... probably because it isn't compliant.

[goboatingnow]

Originally Posted by Kelkara

Raymarine also used to make their displays with 2 seatalkng ports so that they could be daisy chained like this, some of their installation diagrams still show it, although I don't think they still put 2 ports on them ... probably because it isn't compliant.

Does nmea demand external tees , seems strange

[Bycrick]

Putting a multiport connector in a drop cable will work just fine. I’ve got 5 instruments at the helm that have been connected that way for years. Remember that you used to be able to daisy-chain multiple devices on a drop cable? It was never officially compliant to the spec, but was used by all of the manufacturers to solve just exactly the problem that you are addressing. I’d think that the multiport connector would be smaller, cheaper and easier to do than using multiple T connectors.