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Old 23-02-2019, 14:27   #1
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Arrow NMEA Backbone Questions

I recently installed a B&G Vulcan 7r chartplotter on my boat an added a a new wind anamometer, depth/speed/temp sounder and a GPS compass all connected to the plotter via the NMEA Backbone. Everything is wired and seems to be working fine but I was Looking at a schematic for the gps compass I see it shows an on/off switch for the power going to the NMEA back bone. I wired the power permanently but now Iím thinking maybe it shouldnít be hot all the time if not in use? Same goes for the chart plotter. Should it be routed through my electric panel and shut off when not operating? Iíd like to know what are the best practices to ensure Iím doing it right.

Iíd appreciate input..
Thanks!
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Old 23-02-2019, 14:38   #2
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Re: NMEA Backbone Questions

yes it needs to be shut off or it is wasting power. you should have a gps / electronics breaker or something at your main panel. they could both be on seperate breakers or same. if you only have one screen then can all be on one. each should still have it's own correct fuse after the breaker though. as the backbone is only 3a.
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Old 23-02-2019, 15:20   #3
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Re: NMEA Backbone Questions

On my distribution panel there's a breaker for navigation instruments. Opening that breaker stops power to the entire network.
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Old 23-02-2019, 15:53   #4
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Re: NMEA Backbone Questions

Some instruments get a bit shirty if other instruments aren't on in time, such as older MFDs. For this reason it's common to pull the power from the "instruments" switch, which powers up the bus and any instruments that aren't the chartplotter, and then put the chartplotter and anything more advanced on the "GPS" or other switch. Then assuming you switch on instruments first, the bus is up and powered by the time you switch on the chartplotter. Of course, as stated above make sure you have an inline fuse in the power to the backbone.
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Old 24-02-2019, 09:53   #5
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Re: NMEA Backbone Questions

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Originally Posted by Tillsbury View Post
Some instruments get a bit shirty if other instruments aren't on in time, such as older MFDs. For this reason it's common to pull the power from the "instruments" switch, which powers up the bus and any instruments that aren't the chartplotter, and then put the chartplotter and anything more advanced on the "GPS" or other switch. Then assuming you switch on instruments first, the bus is up and powered by the time you switch on the chartplotter. Of course, as stated above make sure you have an inline fuse in the power to the backbone.
So if Iím reading this correctly. Have one switch on my electric panel as the main power on/off that connects to the plotter and nmea backbone. Ensuring that each unit has its respective in line fuse?
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Old 24-02-2019, 15:36   #6
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Re: NMEA Backbone Questions

No, sorry I wasn’t clear. Most boats have an “instruments” switch. I plug all old-school instrumentation into there, and also power the bus from it. This pulls less than an amp on my boat, so fuse can be very mean here. I also have my xb8000 on this switch as it controls the interface between NMEA buses and wifi.

Most boats then have another switch for gps, on which goes the chartplotter and other more modern kit. If your chartplotter is sensitive to the bus being operational when switched on, this solves the problem by letting you put the instruments on first and chartplotter second. For me, this circuit takes more power than the instruments, and can be switched off at times of power frugality. On a long passage I’m unlikely to be using the fixed chartplotter much if at all. I then have the autopilot on a third circuit and vhf/comms on a fourth.
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Old 24-02-2019, 15:56   #7
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Re: NMEA Backbone Questions

My Vulcan 7r chartplotter has its own on/off button and it has in line fuse Iím thinking I donít need to run it though the electric panel.. as for the nmea 2000 backbone power cord, it has the wind anamometer, depth/speed/temp sensor and gps/compass all connected to it so if I run that through my panel it would turn everything on and off with one switch. The nmea power cord has its own in line fuse so if itís connected to my panel which is also fused do I need to make sure the fuse in the panel is the same amps ast the nmea fuse. Sorry if Iím confusing things Iím not an electrician and trying to avoid paying for one if possible.
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Old 24-02-2019, 15:57   #8
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Re: NMEA Backbone Questions

"Most boats have an ďinstrumentsĒ switch. I plug all old-school instrumentation into there,"
A good idea, because that also allows you to put a spike/surge protector into the "instruments" line, and protect all the sensitive stuff from any voltage spikes or regulator failure. Voltage spikes are normally given off by the starter and alternator, and the DO silently kill all kinds of things in time. (No, I don't know of any simple commercial ones for 12v systems, but the components are easily inexpensively sourced.)
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Old 24-02-2019, 16:03   #9
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Re: NMEA Backbone Questions

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"Most boats have an ďinstrumentsĒ switch. I plug all old-school instrumentation into there,"
A good idea, because that also allows you to put a spike/surge protector into the "instruments" line, and protect all the sensitive stuff from any voltage spikes or regulator failure. Voltage spikes are normally given off by the starter and alternator, and the DO silently kill all kinds of things in time. (No, I don't know of any simple commercial ones for 12v systems, but the components are easily inexpensively sourced.)
Would the inline fuse be sufficient protection from that?
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Old 24-02-2019, 23:11   #10
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Re: NMEA Backbone Questions

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Would the inline fuse be sufficient protection from that?
No. The inline fuse protects the cabling. It prevents silly numbers of amps from setting off down a small cable and burning your boat down. Thatís what boat fuses do. Every bit of cable on your boat should have an inline fuse just big enough to let whatever device itís connected to run properly, and the cable should be comfortably able to handle the fuse rated current with plenty of margin for safety.

A surge protector protects your sensitive devices from spikes that wouldnít trip a fuse. Totally different device doing a totally different job. Most fuses will let through spikes of well over their rated current Because they are very short.
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Old 25-02-2019, 01:04   #11
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Re: NMEA Backbone Questions

Gotcha! I’ll add that to the list of things I need to pick up on my next visit to west marine.. Thank you for the good advice..
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Old 25-02-2019, 01:26   #12
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Re: NMEA Backbone Questions

The best way to avoid spikes from starting loads from the engine is to isolate the starting battery and starter from the house bank with a dual circuit isolating switch and a good charging isolator.

Blue Seas Systems makes an excellent system with a dual switch that normally never combines house and starting batteries unless there is an emergency of a dead battery, or when the charging system is working and stabilized at a safe voltage. It has a starter lock-out circuit built in so the spikes and brown-down events at engine start-up never reach the house panel and the sensitive electronics on them.

https://www.bluesea.com/products/765...ery_Kit_-_120A
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Old 25-02-2019, 04:36   #13
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Re: NMEA Backbone Questions

Akafred youíll find that the units that draw power directly from the backbone consume a not insignificant amount of power. I have a B&G system similar to yours. The compass, GPS antenna, sounder, wind aenometer, rudder feedback, and two MFDs all draw power directly through the backbone. It amounts to @ 1.5 amps, almost all of which is the MFDs and sounder. So you want the backbone on its own breaker, at the very least.

My B&G Zeus is wired so it comes on when itís dedicated breaker is switched on.

I have the SI-ACR that BlueHeron linked. Itís a decent piece of kit. Not only does it isolate during starting but it also trickle charges the start battery even when the alt is not charging (although that does present a condition you need to monitor).
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Old 25-02-2019, 09:58   #14
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Re: NMEA Backbone Questions

Will-
A fuse only protects from relatively long term or large overloads. Spikes are surges can be measured in milliseconds, a fuse can't react to them unless it is something like a 5 amp "fast blow instrumentation" fuse getting hit by a thousand volts.
Surge protectors are designed to clamp surges and spikes, often without "blowing" anything, allowing the equipment to keep functioning. Totally different from fuses, although they can literally "blow" when the overload is severe enough.
Two different kinds of protection for two different reasons.
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Old 25-02-2019, 16:25   #15
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Re: NMEA Backbone Questions

Yes, when the start battery is being charged with the house bank you really need to keep an eye on the electrolyte levels.

This type of system is best used with house and starter banks being of similar chemistry. We have flooded 6v golf car batteries for our house bank and a flooded type 24 starter battery. We have tons of solar and some wind so we hit realization charge voltage just about every day, usually in the early afternoon hours before we even run out of sunshine. We don't run the engine much unless we are motoring up or down through ICW or the New York Canals.

The starter battery doesn't really need this equalization charge service often but it is "going along for the ride" anyhow being linked into the house bank charging circuit by the ACR.

I add electrolyte to the batteries every month -not a ton, but it does need to be topped off. It is a little more of a pain to insert a screwdriver into the pry-off vented plugs on the starter battery in order to check/add electrolyte than it is to remove the quick-release 3-gang speed covers on the golf-car batteries
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