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Old 23-02-2012, 19:06   #1
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Shorepower Voltage Drops with Load

Alright here we go my first of probably 5 million questions!!

I have a simple 30 amp 120v system on board. Shorepower is fed into a 30 amp main breaker through a 10 gauge wire. There are two branch circuits, one feeding two outlets and one supplying a 10 amp battery charger. Both circuits are wired with 12 gauge wire and protected by 15 amp breakers.

I just purchased the boat and moved it to a new slip. The surveyor I used suggested I have the 120v system inspected by an electrician because one outlet was not grounded and there was a "melting electrical" smell. He also noted that the battery charger was getting hot to the touch after approximately 90 min. of charging. I have not been able to get the battery charger to charge the batteries since I have moved the boat to the new slip and connected to shorepower there.

So far, with the help of employees at a local boatyard and a couple good books. I have found and corrected the following problems with the system:

1. 12 ga. wire was used to make the run from the shorepower inlet plug 3/4 of the way to the 120v main panel. The wire was then spliced to 10 ga. wire to finish the remainder of the run. I removed this and used a new section of 10 ga. wire to make the entire run.

2. The circuit with the outlets correctly begins with a gfci outlet which was properly grounded at the main panel, however the ground wire from the downstream outlet was covered with electrical tape and not connected to anything. So since the wire from the downstream outlet was run to the gfci outlet which is just below the main panel, I just connected it directly to the ground bus bar in the main panel.

3. I am not sure that this was a problem but it looked strange to me and the local boatyard agreed. The incoming neutral wire was connected directly to the neutral bus bar in the main panel instead of to the "line in" side of the main breaker. There was a short wire run from the "line in" side of the neutral pole on the main breaker to the neutral bus bar in the panel. It seems to me that this arrangement would essentially bypass the neutral pole of the main breaker (it is a two pole breaker) since the incoming neutral line is wired directly to the neutral bus bar. I was under the impression that these panels come prewired however given the other other mistakes and poor craftsmanship exhibited in other parts of the boat I would not be surprised if this configuration is different from the way it came from the factory. Anyway, I may be wrong, but I connected the incoming neutral wire to the "line in" side of the neutral pole on the main breaker and ran the short wire from the load side of the neutral pole on the main breaker to the neutral bus bar. PLEASE LET ME KNOW IF THIS IS WRONG THIS IS ONE OF THE ONLY CORRECTIONS I AM NOT SURE OF!!

Ok, now that you have the background, on to my main question. Following all the above repairs, I connected to shorepower turned on the main breaker only and got a reading between 115 and 120 volts on the "line in" side of the main breaker. I also get the same reading when testing the load side of the main breaker. However when I turn on the breaker for the battery charger the incoming voltage drops drastically (reading fluctuates between 25-80 volts). I turned off the battery charger and turned on the outlets only, the voltage dropped momentarily but then returned to around 110 but then began to fluctuate between 90 and 110 volts (there is nothing plugged in to either outlet). While I was working on this, it became dark and a dock light on my shorepower pedestal came on. While still testing with the outlets circuit on, the incoming voltage dropped significantly and fluctuated between 25-50 volts. Just to be clear I am getting these voltage drop readings on the line side of the main breaker as well as the load side.

It seems to me that the problem is isolated to the incoming plug for shorepower on the boat, the shorepower cord, or the dock side of the shorepower.

Sorry for the book, anyone care to take a stab?
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Old 23-02-2012, 19:16   #2
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Re: Shorepower voltage drops with load

I guess I should also mention that the dock where the boat is kept sustained semi major damage during hurricane Irene. So the dock wiring is a little suspect.
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Old 23-02-2012, 19:36   #3
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Re: Shorepower voltage drops with load

I would hire a certified marine electrician to straighten this out. Considering the drop in voltage I would suspect there is a high resistance short to ground somewhere in the system. Remember AC is deadly and can burn you and your boat in a flash. Stop fooling with and get a professional. This sounds like someone did a DIY installation and really screwed it up.
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Old 23-02-2012, 19:53   #4
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Re: Shorepower voltage drops with load

You might try shore power from some other sure source to rule out the dock side power. Other than that, I have to agree with IKE. Based on what you noted, I would be inclined to pull the charger and have it checked away from the boat's goofy systems. If its OK and shore is OK its time to yank a mess'o wire and start over. Use marine grade stuff and over-size the wire gauge. I have wire digrams for ours and every issue is a new learning experience.
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Old 23-02-2012, 20:22   #5
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Re: Shorepower voltage drops with load

You noted that the dock lite came on and it looks like you saw voltage drops on your boat. That points to a problem with the shore power. Is there somewhere else you can take your boat and connect to shore power? If not, consider renting a small generator and use it to provide shore power, then check your voltage status.

Now, having said all that, I also recommend that you have a professional electrician check out your issues. The 12 to 10 gauge splice on the incoming line is just plain wrong.
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Old 23-02-2012, 20:36   #6
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Re: Shorepower voltage drops with load

I believe Quioxotic said there was nothing plugged in to the load side of this circuit. this leads me to think it is a problem with the supply.
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Old 23-02-2012, 20:52   #7
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Re: Shorepower voltage drops with load

The battery charger sure looks suspect. I assume that this is a 10 amp 12v battery charger (120 plus a little watts) . This should not be putting a substantial load on anything. It's getting hot but not charging. Almost certainly dead and a likely fire hazard. Leave it turned off. If there turns out to be a different problem fix that and then try the battery charger again.

I'd plug a standard incandescent lamp into one of the outlets. Say a 100 watt bulb. If the voltage stays up then the problem was with the battery charger.

The next most frequent problem is a bad shore power cable or corrosion in the dock pedestal outlet or your outlet. Plug into a different pedestal. Borrow someone else's shore power cord. Clean the prongs on the boat end outlet. Make sure that you twist the cord when connecting to lock the prongs. Without that twist the prongs are not correctly engaged and you can have arcing.

After this, it's likely to be problem in the dock wiring. Very common. Talk to the marina.

And yes - in any event you should have someone look at some of the mystery wiring on this boat.

Carl
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Old 24-02-2012, 04:32   #8
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Re: Shorepower voltage drops with load

I forgot to mention that I did pull the charger and take it to a local boat yard that has been helping me (they have been helping for free so far since my girlfriend's dad owns the yard ). We bench tested the charger there and it seemed to work fine. However we did not leave it connected long enough to test for the heating up problem.

I can take the boat over to the boat yard which is almost within sight of the entrance to the channel leading to the marina and connect to their shorepower with my shorepower cord. If I still have the same problem then I can try a different cord then have them review the wiring.

From the looks of things the previous owner did several DIY projects on the boat and unfortunately his craftsmanship, or that of whoever helped him, is piss poor at best. Some people should just put the tools down.
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Old 24-02-2012, 04:42   #9
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Re: Shorepower voltage drops with load

If you're reading 115V then voltage drops when you apply a load you have a bad neutral somewhere. But the best advice is to get a pro out there to be sure.
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Old 26-02-2012, 06:16   #10
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Re: Shorepower Voltage Drops with Load

whenever i have a problem like that i always take the shore power outlet on the boat apart. 9 out of 10 times the neutral wire connection has melted the connection on the 30 amp outlet . i change at least one a month on boats. the other times it's the outlet on the pedestal at the marina or the cord. it only takes minute to pull your 30 amp outlet out and look to see the condition of the wires.
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Old 26-02-2012, 09:06   #11
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Re: Shorepower Voltage Drops with Load

Thank you for all the replies. The dock owner came over and checked out the situation. He decided to look inside the dockside outlet box and replaced the outlet after seeing the corrosion on the inside. I also took apart my shorepower inlet on the boat and made sure all the terminals were clean and the wires were all well connected. I did the same in the main panel. When I plugged in to shorepower and turned on the breakers everything is working as it should. Not sure exactly where the problem was but as was previously suggested it was probably a poor neutral contact.

On a side note, I looked on the paneltronics website and found the detailed wiring diagram for the main panel. After confirming with paneltronics that the panel should absolutely be wired according to the diagram I can confirm that whoever did the installation changed the wiring for some god awful reason. Lucky for them (and now for me) the boat never caught fire. Looking forward to many more surprises as I go through the boat.
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Old 26-02-2012, 12:58   #12
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Re: Shorepower Voltage Drops with Load

Nice job! Despite all the recommendations to "hire a pro", it sounds like you found and fixed all the screwed up wiring problems and got the boat sorted out correctly. Unfortunately, in my experience a randomly hired "pro" is only slightly less likely to make a mess of your electrical system than an a amateur. Like in any discipline, "pros" range widely from very good to very bad.
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Old 26-02-2012, 13:11   #13
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Re: Shorepower Voltage Drops with Load

Satisfaction (and wallet) are both improved when you figure it out yourself. Also, its better to know what is going on inside your panels.
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Old 26-02-2012, 13:38   #14
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Re: Shorepower Voltage Drops with Load

Whenever you see a voltage drop on shore-power, first place to look is the external connections that are exposed to weather (corrosion). Most often the shore-power cord, deck connector or dock. If you see green (ambergris) on your connection prongs you have spotted the resistance point right there. Your copper/brass conductors should be gold or brown at-worst, but never green or white.
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Old 26-02-2012, 14:32   #15
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Re: Shorepower Voltage Drops with Load

Great call on the poor connections. The results would have been similar if any large load was applied. The battery charger was simply big enough to expose the bad connection. It can be the ground or any of the legs. Keep this in mind and next time plug in a space heater.
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