Nema 2000 Backbone Switched (Y/N)?

rlynch03

rlynch03

Well-Known Member
GOLD Sponsor
May 16, 2019
1,035
Annapolis, MD
Boat Info
07 52 Sedan Bridge, 2019 Brig Falcon 360HT-30HP Honda, 2003 16' Dauntless
Engines
Cummins QSM 11 660 HP w/ ZF 325-1A
Most literature I read recommends switching your Nema 2000 backbone On/Off to reduce the risk of running your battery down.

What do you folks do?

Dash mounted switch?
 
I switched both the NMEA Backbone and my AIS. I had an empty "Accessory" spot on the dash.
 
Mine comes on with main house battery switch. Only goes off when batteries solenoids are shut off.
 
I think the answer is maybe; it depends.
I have three zones which are the engine room/solon, helm, and bridge roof; it's a rather large system. The engine room/solon is not switched and has a circuit breaker in the master distribution panel (unswitched starboard section, the old SR Monitor circuit breaker location) but the other two zones are from a double pole switch on the helm that is fed from two independent fuses under the helm.
I have safety systems, audible alarms (the things that were on the SR Monitor) and others that display in the solon (fresh and black water tank levels, generator, etc) on the network and didn't want those switched.
As it ends up I never turn off any of the NMEA 2000 network.
 
Pretty sure mine is on all the time until I turn the battery switches off. Small system though, not really sure if there would be any significant drain. Heading sensor, simrad, and the radar interface plugs into NMEA 2000, GPS is using older 183 interface.
 
I agree it depends. I run mine off the elect. Switch at the bridge. My reasoning is I only use the N2k for VHF, MFD, And GPS. My sonar and radar are direct connect to MFD. so I guess it really is about what you need to keep on while away from the boat.
 
rlynch03 said:
Most literature I read recommends switching your Nema 2000 backbone On/Off to reduce the risk of running your battery down.

What do you folks do?

Dash mounted switch?
Click to expand...

I guess that would depend on the intended use of the NEMA2000 network. It if is only for navigation communication then it would be fine to power down after turning off the engines. However, more and more components are becoming N2K friendly. So if you want to control your stereo from your MFD you will need power to that network. If you are monitoring sensors (ie tank sensors) or controlling systems (ie lighting controls) then you will need power to the network.

-Kevin
 
Once I power the helm down the only thing I need the N2K for is GPS antenna for location info to the VHF. Now, when we are on the hook I leave the MFD running and can monitor our position and anchor alarm via the TV in the salon.

I was thinking about all the down time when no systems are needed.

I don’t have bilge alarms or sensors tied to my N2K system.
 
Last edited:
My radar has a clock running I didn’t notice when installed but was told to switch it so I have switches for the radar/FLIR/ AP so as to keep the running time down.
 
@ttmott is on the mark as usual... It depends

The buss power is very limited the maximum any powered segment can provide is 3 amp for typical 22AWG wiring.
(there is a heavy duty specification for 16AWG backbone @ 8 amp but it would be rare to see this on a recreational vessel)

This is for sensors and remote displays to make it easier to wire, no dedicated power needed.
Devices such as the MFD, VHF, Sonar black boxes will have direct DC power of there own, they need to much power.

So as stated if you use monitoring of sensors 24x7 you want that sensor segment powered all the time.
Every segment should always be fused, but switching is optional.
 
I have my network segregated into five segments, but not to save on power or my batteries. Like @Havana Shamrock I don't shut my batteries off ever, for any length of time that is.

A couple of things on NMEA 2000 power. Some network devices publish the power being used. The N2K power is referred to as "LEN" short for "Load Equivalence Number". Each LEN equals 50ma and most devices only use a few LEN to operate and there are 20 LEN to 1 amp of current. So there isn't much current being used at all, but if you turn your batteries off and the N2K bus is still powered you would run them down fairly quickly.

EDIT: Just to clarify, any device on the N2K bus will always be rated at a minimum of 1 LEN or more. Also most devices require the N2K portion of that device to be powered by the N2K bus. That is by design and proper use of the NMEA 2000 network, otherwise you would need power blocking tees for every device.
 
Last edited:
Just a note on why powering different sections of the network might be wanted or not. First, if you don't have remote monitoring of any system then why leave the electronics on, that's just opening up potential problems IMO. Also if systems are not not needed I like to shut them down as a precaution and protection issue(s) that may arise.

That said, I have remote monitoring so I have a section of the bus that is switched by it's own 12v breaker at the panel, which is always on and is rarely shut down. Then other systems are turned on/off as needed, like the engine and generator N2K converters, which turn on with each engine along with the N2K displays that are for each engine. Then the "Electronics" segment is for the MFD's etc. which are all powered by it's own breaker as well.
 
Same switch as controls my MFDs.

It bears mentioning that you should really turn off your buss when adding or removing devices, and sometimes, during troubleshooting, you need the ability to cycle the bus power.

All that is to say, yes, you should absolutely have the buss wired through a switch.
 
Last edited:
I'm similar to Skybolt. I have mine segmented off. Engine sensors come on when the engine starts, other things run full time, others are switched on/off as needed. All independantly fused.

They make power isolator T's. The data can pass, but power can not. You will need additional Power Tee's. Actisense make a good one that powers the Left and Right branches separately, and is a good fit if you power is coming into the network about midpoint.

upload_2021-2-16_21-55-35.png
 
Last edited:
You must log in or register to reply here.

Forum statistics

Threads
113,120
Messages
1,426,604
Members
61,037
Latest member
wojozobl
Back
Top