Experience with bus based power systems?

Discussion in 'Electrical Systems' started by Nordic Cat, Oct 11, 2008.

  1. goboatingnow
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    goboatingnow Junior Member

    despite Nigel Calder writing about it everywhere, I cannot see the advantages of distributed power systems for yachts say under 80 feet. Its full of single point failures, completely impossible to repair at sea, requires a technical sophistication that most users don't have, Its one thing to loose a radio or an instrument, its another to have a whole electrical system go down

    I come from a background in industrial electronics, and I cannot see the advantage say in the capi system of having the switching nodes near the load. IN practice there isn't a "huge" amount of wiring in a boat and its mostly star based anyway. The requirement to run a fairly heavy duty power bus means lots of expensive cable running around the boat.


    IF somebody wants to go this way, then conventional wiring with smart circuit breakers is the way to go. This are replacements for conventional breakers but allow current monitoring and hence programmable trips and PWM operation etc. This gives all the software advantages that calder rabbits on about but allows the units to be substituted with conventional circuit breakers in the event of system wide malfunctions. ( with some loss of functionality of course).

    I just cant see any advantages to these fully distributed systems , none that are safe anyhow
     
  2. BigCat
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    BigCat Junior Member

    I'm a KISS (keep it simple, stupid!) fan

    Nigel Calder is very smart, no doubt much smarter than I am. I'm not smart enough to use this system. Even Nigel Calder had 4 man days of consultation when installing this system. There are a couple of thousand USD spent right there. Rewriting software because you put in another lighting fixture? No thanks. IMHO, if there is a simple way to do something, that's the way to do it, especially on a boat.
    Simple is low tech, reliable, cheap, and easy to trouble shoot and repair. Who needs tech problems while fighting off a lee shore in a gale? Not me.
     
  3. Nordic Cat
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    Nordic Cat Senior Member

    Please keep your comments coming. I plan to go and have a look at this stuff sometime soon, so your comments give me good questions.

    As I work with bus based sensor systems, I'm not too intimidated by the programming part, if the interface isn't too geeky to use. Being able to rewire to a traditional breaker/fuse in case of problems is a must.

    Alan
     
  4. goboatingnow
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    goboatingnow Junior Member

    I think that using electronic circuit breakers/relays like http://www.e-t-a.com/uk_ssrpcs M59d7f67440d.html for example can provide all the advantages of a computer controlled power system with the ability to go back to simple circuit breakers if required. ( or just back up each unit with a parallel manual breaker and remove the electronic one in the case of major failure. This gives all the advantages of calders system ( short and open detection , PWM operation , current sensing etc) without the requirments and failure modes of a bus based system
     
  5. Landlubber
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    Landlubber Senior Member

    Nordic Cat,

    I am currently doing my homework on building a 120 foot displacement boat for a local fella, he is into Bling Bling etc, and i just know he will want me to be using Can Bus systems to let him play with his toys, but i plan on doing so with a redundancy system attached locally somehow. Possibly a simply single pole switch to allow acces to the bus from the relayed unit, and when the system fails computer wise, i can switch the switch and the unit in question will be supplied from the bus directly, removal of the relay (nodes) is possible required too, but I will have to see what develops as the game goes.

    I am very concerned with computer comtrolled display switchboards as lightning or even RFI influences could send the whole kit and caboodle haywire....I seem to believe that I have to still somehow allow an alternative manual system into the whole picture too.

    I will follow this thread with interest.
     
  6. CDK
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    CDK retired engineer

    That's no real alternative because you need a set of control wires for each device. That means lots of terminals behind the central console, color coding, cable numbering etc. Adding a device that has not been foreseen means drawing a new cable.
    The bus concept has been developed to avoid just that: one power cable, one control wire and an unlimited number of devices.
     
  7. goboatingnow
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    goboatingnow Junior Member

    Dont agree, the whole system can be PCB mounted, with a local CPU to program the switches, The next advantage is that you dont need to place it anywhere near the nav station or console. its actually crasy that companies do that, because you have remote monitoring you dont need physical access to teh board. If fact on most boats theres no need to get to the breakers on a regular basis anyway. Far better to put a couple of switches for common functions ( nav lights etc) on the console. monitoring of the electronic circuit board can be done by a simple CPU and display.

    The reason why its an alternative is

    (a) point to point traditional wiring, simple to debug and understand
    (b) fallback to manual circuit breakers , with (a) above the standard system
    (c) you get the benefits of current monitoring, open.short circuit detection, life cycle monitoring etc
    (d) allows the circuit break board to be mounted out of sight ( though accessible).

    The one power cable method is a very poor fit for small to medium yachts, (a) you have to thread a fairly big cable throughout the boat, (b) any device that draws alot of current will put a lot of noise and voltage drop on teh cable and (c) I suspect that real installations run several such power cable system to provide some redundancy and to isolate high current sources. and this removes some of the advantages anyway.

    I have direct experience of distributed power sytems in industrial applications and I think bringing them into yachts is madness

    Major failure modes on central power cables are big problems, A direct short takes out all the nodes and also leaves a fault finding mess, particular if the control side of the nodes are powered from the power bus, rather then via the control buss, as all the nodes fail. Then you have the physical access, the nodes are scattered all over the boat in inaccessible places., thirdly while adding a device is theorectically simple, you can bet in the real world the power cable still will not be anyway near where you want it and you'll still have to run extensions. Given that in a 50' foot boat most central panels are within 30 feet of the power consumer the wire runs are small anyway., then forthly you have the issue of people adding on additional nodes outside the total power delivery ability of the cable , resulting in the need to replace the whole power cable

    The fact is that bus systems are not the most suitable systems for a environment where (a) the tech level of the user is low (b) uncontrolled expansion may take place and (c) high and low current consumers are mixed.

    BTW ligthening damage to these systems is not really a concern, in that generally while ligthening will take on the electronic switching, it also takes out the equipment, hence replacing the switching module may be one thing , finding a new radar or VHf or autopilot is quite another. Ligthening is not a reason to not have distributed swicthing its more a reason not to have anything electrical on board at all.!!

    Its interesting to read Calders blog as to what has happened, They had a lot of problems debugging the system that resulted in crasy things happening due to looses connections, they also stripped out delays timers because users didnt understand what was happening ( poor system feedback) etc. I suspect hes reports on this system will be interesting to read. I also understand he has removed the diesel electric propolsuion system as well

    The fact is that on large yachts these distributed power systems have been used to power lots of fairly small and mostly identical consumers. ie fire detection, systems monitoring, securtity etc. They have not been used to repalce the whole electricall distribution system as per Calder.
     
  8. tanjera
    Joined: Jul 2009
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    tanjera Hennie

    Please take a look at www.yachtwiring.com

    I have personally experienced this system and it is great. Biggest advantage imo is ease of installation, troubleshooting, weight saving and the 'if all else fails' option.

    Imo also cheaper (once installed) than conventional system.

    Hennie
     
  9. apex1

    apex1 Guest

    Go for "Empirbus" Sweden and forget about wiring.
     
  10. mark775

    mark775 Guest

    I'm not an electrical engineer and won't pretend. I was sceptical and behind the eightball on wiring, including gages, of my D-9 Volvo. Three sizes of hole saws, a drill motor, a handful of wire ties, four screws, and in 115 minutes it was running. There was one non-critical glitch from using a 12 volt starter and alternator on a system designed for 24 and it was fixed with a coded message in ten minutes another day. Two years later, three lightning storms, not one hiccup. Fuel flow added later, shaft RPM sensor, trolling mode (clutch plate slippage - you want 50 shaft RPM... or 55?), diagnostics, all perfect. I would go with one of these bus systems in a heartbeat and feel that the real advantage comes down the line when you want to add or change something. I have come to trust electrical devices more than mechanical - Simple, clean.
     
  11. tanjera
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    tanjera Hennie

    I am not sure how one can forget about wires with empirbus, unless they came up with something new since I last looked at their system. In fact because of the large number of controllers in one unit you will need more wires than for yachtwiring systems.
    Hennie
     
  12. Frosty

    Frosty Previous Member

    I totally and utterly agree that wiring can be simple, but hey who will pay 50 dollars an hour then.

    I run small wires to small supplies from bus of bigger wires. it means that I can put in another circuit easily and have a supply without going over load.

    I always fit twice as many switches as I need and double the size of conduit. I always needed it.

    Do a circuit at a time and write it down as line diagram.
     
  13. apex1

    apex1 Guest

    Ja for sure you´re not sure. Wiring in boatbuilders nomenklature is the classical way. A bus system is just installed. And if you need more wires in a bus system (no matter which) you do something completely wrong!
     
  14. Stumble
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    Stumble Senior Member

    Earlier this year Professional Boatbuilder did a pretty long spread on the Capi2 system, while I haven't seen it or used a distributed power buss system yet I see a lot of major advantages over traditional wiring systems, and am not willing to dismiss it as an alternative to traditional wiring systems without further investigation.

    Advantages:
    -Vastly easier installation process than traditional wiring
    -Significantly less copper put on the boat
    -Easier to trace wiring problems
    -Few or no long runs other than the main trunk line, helping to reduce chaff issues, wire routing problems, and simplifying bilge layout
    -Much easier to add a new circuit or fixture
    -Ability to control groups of points acording to any scheme you can dream up (all lights, all interior lights, all exterior lights, ect) and the ability to quickly change the points in each group
    -Wire runs from the trunk to the points can be much smaller since the distance is much less
    -Losses due to wiring can be minimized cheaply and overall efficiency gains can be achieved
    -Multiple control head can be placed almost anywhere on the boat with minimal wiring (just a data cable run, instead of running load bearing wires)
    -Ability to data log each point to determin cycle rates, usage activity, and early warning of failure
    -Ability to bypass the computer controllers in the event of a failure (though this would leave multiple circuit breakers scattered throughout the boat instead of one large panel)
    -Easier and faster troubleshooting of non-functional points
    -Cheaper initial installation
    -Cheaper re-wiring job when it becomes necessary
    -Remote/internet login and control capability, including the ability of factory technicians to remotly diagnose problems



    Disadvantages:
    -Like any new technology there is a lack of long term reliability studies
    -Must be incorperated from the ground up of a new build or a re-wiring job
    -More complexed operation due to advanced features
    -Concern over proper shielding
    -Lack of qualified technicians who understand the system
    -Lack of robust equipment designs to meet varying needs.



    Most of this list is from Nigel Calder's article in Professional Boatbuilding june/july 2009. There should be followups to this article which I will be watching closely, but from what I can see now the system seems to be makeing a very good argument that this will become the new way to wire boats in the future.
     

  15. apex1

    apex1 Guest

    Stumble
    >>>-Like any new technology there is a lack of long term reliability studies<<<

    CAN-Bus (Controller Area Network) is the system most of todays installations are based on. That was developed in 1983 by BOSCH Germany and first installed 1987.
    It is in use since and installed in the 100 million numbers by so far. Todays Car electronics, Avionics, Med. technique, space exploration, satellites, flight simulators and so on rely on CAN bus. I would say that is truly proven.
    NMEA 2000 btw is a further developed sort of CAN.
     
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