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Electrical Issues - Shocking!

Nov 25, 2015
49
Catalina 30 Hoodsport
The boat: 1989 Catalina 30 MKII

The issue: Shore power circuit breaker tripping

Hi All,

My boat is in a slip, with 120VAC shore power. The dock-mounted shore power receptacle is on a 30-amp circuit breaker. After more than three years of no issues since I’ve been in this particular slip, I arrived at my boat and noticed that the shore power circuit breaker was tripped. I unplugged the shore power, and opened all of the AC circuit breakers on my boat’s electrical panel. The panel is 120VAC, 30-amp, 60HZ. There are three (3) 120VAC circuit breakers on the electrical panel. They are labeled ‘OUTLETS’ (15amp) ‘WATER HEATER’ (20 amp) and ACCESSORY’ (no amperage placarded). With the WATER HEATER breaker tripped (pulled) the shore power breaker does not trip, but it accepts limited load. The example being that if I turn on the microwave, the shore power breaker trips, or if I plug in a computer charger, the breaker trips. So, I am able to load to a low-draw (amperage). This low-draw includes the successful operation of my battery charger, and cellphone charger. Also, all of my DC lights are operable. Even after a few days of this low-draw load, the shore power breaker still trips.

Troubleshooting:

My slip AC power shares a common outlet box with my adjacent slip. I swapped my cord to the adjacent slip’s outlet, and that breaker also tripped under load, so that leaves the problem from the shore power outlet box on the dock, to the boat.

So, do shore power cord go bad? Could this be the culprit? What components could be the culprit from there? The shore power receptacle on the boat? Any, or all of the 120VAC circuit breakers? Wiring? Battery Charger? Batteries?

Thanks in advance for you input.
 
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Feb 20, 2011
7,004
Island Packet 35 Tucson, AZ/San Carlos, MX
I'd take a good look at the blades on the plugs/receptacles for any corrosion or deformation.
 
Oct 22, 2014
9,919
CAL 35 Cruiser Portland OR, moored EVERETT WA
I would look at the connection where you plug the shore power in to the boat first. The plug and the socket. Check the wires behind the socket.

If you have an IR Temp sensor it might help to find a hot spot. A short or failing connection will get hot.
 
May 20, 2016
2,791
Catalina 36 MK1 Everett, WA
Once a breaker starts tripping. The amperage it takes to trip keeps going down. My recommendations
1) get an amp meter on the AC in
2) If you trip at less than 98% of breaker rating - get a new breaker ( if you don’t buy the meter get a new breaker) they are cheap in boat terms.
3) now check you voltage while running microwave- if it drops from 120 to <100 then look at cables and connectors.

Les
 
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Jan 22, 2008
7,028
Beneteau 323 Annapolis MD
Strikes me as a hot/neutral reversal somewhere-anywhere.. Applied power, it goes right to ground. POP goes the weasel.
 
Jan 22, 2008
1,110
Hunter 37-cutter Richmond CA
The boat: 1989 Catalina 30 MKII
I swapped my cord to the adjacent slip’s outlet, and that breaker also tripped under load, so that leaves the problem from the shore power outlet box on the dock, to the boat..
You do mean you have concluded that the problem is not at the dock?

Can you clarify whether the dock supply has ground fault protection?

If the answer to the first question is yes then I would start a process of elimination by connecting one service at a time If the answer to the second question is question is yes that could be much more tricky. I use a 1 mA resolution clamp on meter to trace leakage to ground.

If you are in any doubts as to whether you can do it safely consider getting help
 
Jan 24, 2017
371
Hunter 34 Red Bank NJ
Corrosion on any connections either on the land side or boat side can cause this issue. Mine had corrosion on the ground and caused the circuit breaker to trip on high or low load. Cleaned it up
And worked fine sense.
 
Nov 25, 2015
49
Catalina 30 Hoodsport
Thanks for the responses.

So, here's an update. The recommendations from some of you to check the shore power cord connection to the boat presented a clue. The power inlet on the boat is stainless stell, and has a threaded outer flange which a threaded collar on the shore power cord couples to. I went to test the connection of the cord/inlet by grasping the cord, and the breaker instantly tripped. Unfortunately, I was called away by work, so I had to leave the marina. This gives me a starting point.
 
Nov 25, 2015
49
Catalina 30 Hoodsport
Okay. Today I replaced the shore power inlet on my boat, and decided that it was time to replace the shore power cord as well.

The good news is that the outlet replacement went well, and the breaker on the dock does not trip when I handle the shore power cord at the boat's inlet. The bad news is that I am still not able to put much of a load on the 120AC power system (computer charger, microwave oven). Not sure what direction to go in from here. Could possible suspects be the boat's AC Master breaker (120 VAC, 30 amp, 60 hz)? One, or more of the 120 VAC Service breakers?

Again, thanks in advance for your input.
 
Oct 22, 2014
9,919
CAL 35 Cruiser Portland OR, moored EVERETT WA
EJ this link might help you with you search to solve the problem.
https://www.inchcalculator.com/watts-to-amps-calculator/

Are you running the battery charger in the background while trying to run the microwave and a computer charger? What is the amp draw of the computer charger?

How old are the circuit breakers? Your boat is 30 years old. If original installation breakers and the previous owner allowed some abuse it is reasonable to guess that they need to be replaced.
 
Jun 3, 2012
544
Hunter 33 Bay Pointe, Quincy
When a circuit breaker takes time to trip under load you have an overload situation and not a short circuit. Is your battery charger hot?
 
Apr 3, 2019
269
Macgregor 26M P Cub Boo Mobile AL
The loads you describe, coupled with the fact you have run this setup for years with no problems, leads me to think you may have corrosion and/or ground fault issues.

Someone above asked you if your shore power was ground-fault protected. You need to answer that before anyone can get a good picture of your situation. Also, Leslie asked you if you had a meter and could watch the load current up to trip condition. I don't see a reply to this. This is another key piece of the puzzle.

You have stated that your battery charger and D.C. Lighting is running, and that you try adding the microwave, computer charger, and water heater to that - causing a trip. Will any of the three items do it? Have you tried one at a time?

Without measurements, and over long distance, this will be a fun puzzle to unravel. But, based on the level of most of the questions above, with enough time and patience, someone will likely figure it out. Keep the clues coming.

The fact that the breaker trips, even under your "base" load of battery charger and D.C. Lighting, leads me to think you may be ground fault protected, and have a ground fault issue aboard. The fact that it's intermittent, makes me think it could be corrosion at a connection. Also, the age of the boat and the fact that it's slipped is suggestive of corrosion... You may want to go through your distribution panel and each load, tightening/checking each connection. A loose connection can drive you nuts as well.

You changed the most likely corrosion issues, shore power cord and boat connection, and eliminated one trip point (based on what I read above). That probably only leaves about 100 more to check. Good Luck, and Keep us up to date.
 
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Nov 25, 2015
49
Catalina 30 Hoodsport
When a circuit breaker takes time to trip under load you have an overload situation and not a short circuit. Is your battery charger hot?

The battery charger is war to the touch - not hot in the sense that I pull my hand away because the case is uncomfortable.
 
Nov 25, 2015
49
Catalina 30 Hoodsport
The loads you describe, coupled with the fact you have run this setup for years with no problems, leads me to think you may have corrosion and/or ground fault issues.
I am way out of step with today's culture. I do not live my life with a cellphone in my hand, and it takes me time to answer folk's email. I do sincerely appreciate the input from those that seek to help others on this forum.

There is one GFCI 120VAC outlet mounted on the electrical panel. It does not trip.

Yes, I have operated the microwave while charging the computer (85 watt charger). For the last three years - no problem.
 
Jun 3, 2012
544
Hunter 33 Bay Pointe, Quincy
Most large draw electrical items produce heat. Water heaters, toasters, microwaves and the like consume significant power. You only have 30 Amps at 120 Volts available. Do you leave your water heater on? What is your battery charger output rating? Are your batteries warm?