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Red hot studs and melted wires, could have been worse

Ben Stein

Ben Stein

Contributing Editor of Panbo.com, passionate marine electronics enthusiast, completed the Great Loop in 2017.

10 Responses

  1. Gary Clendenin says:

    Glad you found the panel issue and shared. This should be a reminder to all of us to be more diligent. I walk past my panel twice each time I go to engine room with IR thermo to do engine checks, and never thought of checking electrical panel. Thanks for the reminder great blog.

  2. Saffy The Pook says:

    Could have very easily been a lot worse!
    This is the stuff of old boat nightmares, glad you caught it!

    • Ben SteinBen Stein says:

      It sure is. It’s the second time this season I’ve found very similar circumstances. The first time was on a friend’s boat, built in 1988. Obviously age plays a factor but vigilance regardless of age is wise.

  3. I routinely advise my clients to install smoke detectors INSIDE every compartment that contains electrical breakers or devices. Hearing an alarm from these devices early, can help avoid a full blown fire. One more thought. Consider carrying one or two Halotron fire extinguishers onboard for electrical/electronic fires. The agent in a standard ABC extinguisher is highly corrosive, and can create a real mess, if discharged inside an electrical cabinet.

  4. Glad it wasn’t more serious! It does seem that things are a bit squished and undersized, but that is not unusual in production boats from what I have seen.

    • Ben SteinBen Stein says:

      Things are definitely much more squished than I’d like, but I haven’t found things to be undersized. In fact I have to give Carver credit for being fairly conservative in the design and build of the electrical system and choosing to oversize quite a few things. Including their decision to bring 100 amps of 240v shore power onboard. It could have been done on a very fully loaded 50a circuit but instead Carver used two. It’s sometimes a pain when travelling but it also means when we’re able to get the appropriate power we don’t have to stress any parts of the system.

  5. But for some good luck where I happened to find some loose and corroded terminal connections in my yacht’s electrical distribution bus work, I would have experienced similar high resistance (temperature) electrical connector failure leading to an electrical breakdown and fire.

    My personal opinion is that the stacking order of ring lugs cited as the cause is not the actual cause. It isn’t clear from the photos whether the electrical connector failure initiated in the staked connection from ring lug terminal to the jumper conductor or from mechanical looseness at the breaker stud jamb nuts. The simplest and more likely explanation is that the staked ring lug terminal connection to jumper failed, which created a hot joint, which due to thermal cycling caused the jamb nuts to loosen, thereby creating a second problem exacerbating the electrical joint temperature under load.
    To prevent these types of failure modes on my boat I do the following:
    1) I fabricate jumpers from copper flat bar and tin the copper bus rather than use a loop of single core cable.
    2) Every electrical cable on the boat is marine grade (tinned copper strands) single core cable.
    3) Every electrical cable termination is crimped (using Amp PIDG style ratcheting crimpers and tinned ring lugs) then solder sealed. We do not allow “staked” style electrical terminations.
    4) we brush Dow Corning #4 dielectric silicone grease on the terminal stud/bolt and ring lug before tightening the mechanical fasteners.
    5) for electrical terminations that are subject to vibration, we secure the conductors with lacing tape and/or one-hole cable clamps to shunt mechanical cable forces from the electrical joint’s fasteners.
    6) we apply a removable thread locker to the fastener threads before securing the mechanical connection.
    7) in cases where the air gap space between phase/bus poles are small, we install dielectric barriers between phases or bus poles, and or we apply an electrical grade anti-tracking varnish (Glyptal) to the termination. Glyptal acts as a thread locker also.

    No boat builder I am aware of follows the proscription above, but this is for commercial reasons only. Nevertheless this is method to achieve a reliable and safe electrical system aboard a yacht.

    Electrical panel breaker/switch terminal joint tightness should be verified annually.
    Another failure mode exists at the shore power cable’s receptical in the boat cabin trunk, the run of bus cable from this receptical to the AC panel can also initiate an electrical fire from failed terminations.
    The shore power cable probably doesn’t use tinned copper stranded conductors, so the cable can initiate an electrical fire.
    IR scans are well proven maintenance technology, but you have to “shoot” the terminals when they are operating at rated load. Scanning the panel front may result in missing some compromised electrical joints.
    BR
    Marcus

    • Ben SteinBen Stein says:

      Marcus,

      I too feel quite fortunate not to have had a fire given the state of affairs. Thanks for the thorough list of steps you follow. I’d love to adopt some of the processes you follow but will also admit this would put the modified connections way ahead of the large number of existing runs. I’m not in a position to be able to redo the entire boat.

      I agree about shooting the front of the breakers not being the ideal point at which to measure. I’m curious if you have any thoughts about ways to shoot the terminals. My panel is hinged from the bottom, secured by about 12 screws and difficult to get back into position. I’m confident the benefit of being able to measure temps on the backside wouldn’t be worth the increased risk of opening and closing the panel on a highly regular basis. In this case I feel getting the front measurement is better than nothing.
      Ben

  6. Marcus Crahan says:

    Hello Ben:
    First, thank you for your ongoing efforts to manage this valuable resource for the yachting community.

    Implementing the wiring techniques I recommended will result in rewiring the yacht; speaking from experience after spending many evenings and weekends to rewire the main circuits on my sailboat (complete is the wrong term, I got most of the circuits replaced but not all). I justified the rewiring project on the fact that the boat had completed an 8 year long circumnavigation of the globe, which resulted in many “hands” working on boat’s electrical systems during this period, which resulted in a convoluted mess of an electrical system when I “blissfully” acquired the sailboat.

    The electrical panel on my boat is piano hinged at the bottom edge, and it has an acrylic plastic door to cover breaker toggles to prevent accidental switching. I use two screws to at the top right and left frame to secure the panel in its frame. These screws are well worn due to frequent removal and installation.
    IR measurement of the termination temperature requires a direct line of sight to the subject studs/poles. The only practical way to accomplish this is to swing the panel down when circuits are under load.

    Alternatively, a “keep it simple” approach (that also requires swinging the electrical panel to the maintenance position) is to wiggle each connection by hand…if there is movement of the connection lug on the stud, the connection clamping is too loose. Also any sign of corrosion on conductor strands, ring lug, terminal stud or jamb nuts indicates a problem is developing. Any sign of oxidation to breaker housing “bakelite” also indicates a problem is developing.
    Luckily these types of connection failure modes develop slowly, which gives us time to make intervention before final failure occurs.

  1. July 18, 2018

    […] while he dealt with that.  He wrote an article all about it if you’d like to read it:  https://www.panbo.com/red-hot-studs-and-melted-wires-could-have-been-worse/  The girls and I walked around and remembered where we went a few years ago when we spent a few […]

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