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Strange AC voltage issues

Discussion in 'Newport' started by MitchK, Feb 3, 2018. Add this thread to a FAQ

  1. MitchK

    MitchK

    Joined Sep 22, 2017
    51 posts, 8 likes
    Capital Yachts Newport 28
    US Burbank, Wa Burbank, WA
    All, Sorry in advance for the long post. I had a rather strange experience today. I have been in the process of upgrading the shore power system on our N28-2. So I get the old panel such as it was removed, enlarge the opening for the new Paneltronics panel, run a new 10ga wire from the shore power plug to the panel, and hook it all up. I temporarily hooked the old outlet wiring to the new panel for testing. Everything was looking good. Plugged in one of my power tools, and turned it on. The circuit breaker immediately tripped, as well as the main 30A breaker. As the breaker tripped, the reverse polarity LED lit. So , back to the shore power plug. Verified it was wired correctly. Checked the wiring at the panel, which was also correct, restored power, and tried again. Same result. Both the circuit and Main breakers tripped and the reverse polarity LED was lit. Got out the DVM., Thinking that the marinas power was faulty. Started checking voltages. Checked the voltage at the panel, saw 120 from hot to common, and also to ground. That looked good. Checked the voltage between common and ground, and saw about 60v. Now that should not be. So I scratched my head a bit, trying to figure out what was wrong. Checked the voltages at the end of the shore power cable, and got the same voltages. Ok, so I think to myself, that the marinas power has a problem. Check the voltages at the marinas plug in, and found 120v from hot to common, and to ground, just as it is supposed to be. Checked the voltage between common and ground, an it was 0v. Again just as it should be. I had brought a new shore power cable to replace the old cable that came with the boat. There was nothing visually wrong with it, but I had a new cable I had purchased for the CM26 I rebuilt last year that I wanted to use. Plugged the new cable in, and everything worked perfectly. Able to plug in power tools and run them without the breakers tripping. So with all of that said, there appears to be a high resistance short between the hot and either common or ground in the old shore power cable. The resistance is high enough that it does not trip the marinas shore power breaker, but it lets enough voltage pass to trip the voltage actuated breaker in the new AC panel. Anyway, I figured that you guys might want to know about what I discovered today. I will take the cable ends off in future and see if I can see what is causing the voltage issue.
     


  2. jssailem

    jssailem

    Joined Oct 22, 2014
    4,136 posts, 1,076 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    Mitch. Glad for you that you identified the problem. That might not have turned out well if you had tried to force the issue. Fortunately the breakers all performed as advertised.

    Look along the cable. You might find a spot where the cable looks damaged Like it got between a boat and the dock, A slice in the insulation, or just a collapsed spot. The type of event that damages the inner cable but leaves the outer shield in tack.

    Good luck and thanks for sharing your experience.
     


  3. Will Gilmore

    Will Gilmore

    Joined Oct 19, 2017
    1,353 posts, 450 likes
    O'Day 19
    US Littleton, NH Littleton, NH
    JS is probably right, as I'm sure you were already thinking. I have just a fanciful thought though.
    If, supposing there is no damage, per say, to the cable. Is it old and well used or is it new? What I'm getting at, and I've never heard of this happening, but I can imagine it being possible, if the cable had been twisted alot over the years, there may be an induction charge from one wire to the other. After all, transformers and inductors work on the principle of coiling two wires together so the magnetic force of moving electrons induce movement into other electrons with a perpendicular vector. The voltages would be dependent upon the ratio of twist in each wire.
    It would be fascinating if it turned out to be the case.

    - Will (Dragonfly)
     


  4. MitchK

    MitchK

    Joined Sep 22, 2017
    51 posts, 8 likes
    Capital Yachts Newport 28
    US Burbank, Wa Burbank, WA
    Here is a picture of some of the wiring I am replacing. This is piece was the run from the shore power plug to the original AC panel. It looks to be 12ga, but there is no markings on it that I could read. Also attached is a picture of the new panel in place. I will be filling the holes in the bulkhead with some colored epoxy in the near future.
     

    Attached Files:



  5. jssailem

    jssailem

    Joined Oct 22, 2014
    4,136 posts, 1,076 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    Positive work Mitch. Looking at your wire, I have replaced some wires like that.
     


  6. MitchK

    MitchK

    Joined Sep 22, 2017
    51 posts, 8 likes
    Capital Yachts Newport 28
    US Burbank, Wa Burbank, WA
    All,
    Here is an update on the wiring issues I am encountering with my 1982 N-28-2. I apologize in advance for the long post, but I think it is important.
    Well, it was a very interesting day working on the N28-2 AC wiring, and I had posted earlier that I was re-wiring the AC circuits. I have installed a new wire run from the shore power plug to the new breaker panel. Last weekend, I got the wiring run from the panel to the first outlet which is a GFCI that is wired so that it protects all the other outlets downstream. Anyway, today I was continuing with the wiring runs and outlet replacement. I got the wires run from the GFCI to the starboard outlet. Now on this outlet I had to re-use the existing wire as it appeared it was glassed in during construction, and I was not able to get it out. So, no problem, its a good grade of wire so I just ran the end of it to the junction box and made the splices. Ran the next segment of wire across the V berth to the second junction box where the wire will run up between the liner and hull. Got all that in place, and the port junction box installed. I was pretty much done with the wiring for the day, so I separated the hot wire from the rest at the end of the run and temporarily installed a wire nut to make it safe. I still had a few things to do, so I plugged a work light into the starboard V berth outlet, and it did not work. Took the light to the GFCI, and plugged it in, and it worked fine. So I unplugged the shore power from the boat and started trouble shooting the wiring. result of the investigation showed 120v between the hot wire and ground, but 0v between the hot wire and common. After a bit more investigating, the old wire from the starboard junction box to the outlet that I had not been able to remove was bad. No continuity between the two ends of the common (white) wire. So I started trying to figure out how I could get the wire out as it was stuck solidly. As I was following the wire with my hand to where it get covered over by a piece of fiberglass, I felt something odd. Stuck my head down in the storage compartment to try and see what I was feeling. There was a 1/4-20 bolt sticking out of the fiberglass and it appears it was sticking right through the wire. Turns out this bolt is one of the three bolts that holds the hanging locker on the starboard side to the rear of the V berth liner. After a bit of studying, I was able to get the bolt out. And guess what, the wire could now be moved. I attached a new piece of wire to the old so it would feed in as the old was removed. Got the wire out, and it was indeed bad. Best I can tell, this outlet never worked from day one. When they drilled the hole from inside the locker, they drilled right through the wire, completely severing the white wire, severely damaging the ground wire, and damaging the insulation on the hot wire. It looks and is really bad! I have attached some pictures showing the wiring damage. IF you have a N28-2, you may want to check the location of the bolt and wiring located under the starboard V-berth where the locker meets the V berth. You have to stick your arm down in and feel up until you locate the wire, then follow it up to where it gets covered by a thin layer of fiberglass. If you feel a bolt sticking out of the fiberglass cover, check the location of the wire and the bolt. A mirror would help in making this inspection. There are three bolts that are drilled through the locker wall and protrude into the v-berth storage compartment. The upper most one is the one you need to check. Anyway, here are the pictures. They speak for themselves.
     

    Attached Files:



    Will Gilmore and justsomeguy like this.
  7. jssailem

    jssailem

    Joined Oct 22, 2014
    4,136 posts, 1,076 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    Mitch. Welcome to the fun of old boat maintenance. If it is not the original boat manufacturer, or the marina yard install, or the previous owners “this would be cool project”, it is self inflicted current owner stuff. One good idea sometimes creates unexpected consequences.
     


  8. MitchK

    MitchK

    Joined Sep 22, 2017
    51 posts, 8 likes
    Capital Yachts Newport 28
    US Burbank, Wa Burbank, WA
    Jssailem, you are so correct. Unfortunately, this appears to be a factory issue. I, and previous owners are fortunate the wiring did not catch fire. If I was not so determined to ensure everything is installed and working correctly, I probably wold not have undertaken the rewire, and could have easily caught the boat on fire. As it is, the middle of the stainless bolt is black from heat, and there is a nice blob of copper welded to the bolt. So it got plenty hot! Anyway, only a few more junction boxes and outlet replacements to go,and I will be able to call this repair/upgrade complete. Then on to lowering the mast to service the masthead sheaves, light and vhf antenna. I'll be glad when the wiring is done. Hopefully then the various cuts and scratches on my hands will heal. Rough fiberglass edges are tough on the hands.
     


    jssailem likes this.
  9. jssailem

    jssailem

    Joined Oct 22, 2014
    4,136 posts, 1,076 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    Feel your pain. I am fortunate not to have too many plugs with most of them easily accessible. I am considering locating a refrig. This will entail a wiring change. Oh Boy... Keep up the fight.
     


  10. CharlzO

    CharlzO

    Joined Jan 14, 2014
    178 posts, 4 likes
    Newport Newport 28
    US Upstate NY Fair Haven, NY
    Part of the reason that I'm planning on ditching the AC side of my N28 altogether, and just using DC and a small inverter for the rare chance I need one. If I'm at the dock, I can always use an extension cord through the hatch. But things like this are good reminders, and why I'm going through all my wiring too. I can't wait to see how your progress continues, and interested in your masthead work - mine was jigged up for halyards instead of having the sheaves fixed, and since it's in storage where the masthead isn't reachable, I'm hoping to get ideas of what I'm looking at before the season gets here.
     


  11. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    1,156 posts, 293 likes
    Catalina 36 MK1
    US Sammamish, WA Everett, WA
    Please buy a cord with a built in GFCI. don’t want you to fry trying to be safe!!!

    Mahalo
     


    jssailem likes this.
  12. CharlzO

    CharlzO

    Joined Jan 14, 2014
    178 posts, 4 likes
    Newport Newport 28
    US Upstate NY Fair Haven, NY
    Oh certainly! I really don't even see myself coming to that point, but it'll definitely be as safe as I can make it.
     



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