Main Breaker Popping

[Lance Jones]

Ok, I'm not at the boat to diagnose. However, my wife reported that while in the shower, the main breaker popped. She checked the connection at the plug in and also at the junction box on the dock. She also unplugged and replugged in the shore power cable. Any idea as to what is going on?

[Exodus]

A little more information would be helpful.  Is your dockside connection 30 amp?  What was on at the time?  Air conditioner, battery charger, coffee maker??  Maybe your wife overloaded the circuit.

[Lance Jones]

It is the standard 30amp receptacle. The only items on were: Battery Charger, Fans (2) and Engel Fridge. Never overloaded before to include an air conditioner running.

She reset the breaker and it doesn't stay. She also said a red light came on the panel....

[Exodus]

Have her turn everything off and then try resetting the breaker.  If that works then turn on one appliance at a time until it trips again.  If it trips immediately without anything on the breaker probably needs to be replaced.

Also, is that red light the reverse polarity indicator light?

I highly recommend owning a copy of "Sailboat Electrics Simplified" by Don Casey.  That book has helped me out on numerous occasions. 

[Stu Jackson]

If it's electrical, the first thing you need to do is to check ALL of the connections.  Rip the stuff out of the port locker and check the back of the shorepower connector.  Open the electrical panel and check the wiring and connections.  Check the connections at the terminal strip that's glued to the hull behind the electrical panel.

While each of the dozens of connections might LOOK good, loosen each and every one and spray with Boeshield T-9.

Buy another breaker in case you need one.

Check the incoming shorepower blades and the ones on the dock.  Spray T-9 into both ends of the shorepower connectors.

[Roc]

Lance,
Was there a recent thunder storm?  Here is what I've experienced with the main breaker.  A thunderstorm came through the area one night.  The next morning, noticed that my main breaker was tripped.  Breaker at the dock pedestal was still on.  Turned the main breaker on and all seemed ok.  12 volt systems worked fine.  Then I turned the air conditioner on and that caused the main breaker to trip.  I thought my AC unit had a issue, had it diagnosed and was told the compressor was bad.  But after further investigation by another mechanic, the compressor was ok.  Installed a new breaker, and for two years now, everything is back to normal.  I would guess that the electrical storm did something to compromise the breaker, in that under normal loads, it worked.  But that quick surge from the AC when it starts was enough to cause it to trip.

[Ken Juul]

Shower at the dock...would assume the hotwater heater was used.  Could be a simple overload, the HW heater draws alot.  It also takes several minutes for the CB to cool down after it pops.  If she was trying to reset immediately that may be part of the problem. 

Hot summer days.....it's hot in VA, you must be melting in GA.  Sometimes the power company (or dock wiring) can't keep up with the demand.  Low voltage will cause an increase in current for the same load, that can lead to an overheat/over current condition.

[Stu Jackson]

Good points, Ken.  Lance, don't know if you know this, but it bears repeating:  the hot water heater does NOT have to be ON all the time.  Shorepower will heat it up in about 20-30 minutes.  Then turn it off until you need it again.  There's no reason to have to keep the element hot all the time once the water is heated up.

[Ron Hill]

Lance : Exodus & Ken have given you some sound advice. 
The red light that you mention is the Reverse Polarity Light!  I'm sure you are plugged in correctly, but check and cycle that breaker.  A one time trip is usually OK, but if it keeps happening, you'll need to do some real electrical trouble shooting.     

[Lance Jones]

  Thanks for the great advice all of you..... When I was able to get to the boat, I started from the shore power box on the dock and worked my way aboard from there. Everything was sound as a pound until I got on the boat. I cycled the breaker (Which had been off for several hours) and it failed to stay in the on position.

Taking y'all's advice, I pulled the panel. All connections were checked, loosened, checked and then tightened. No joy. I then went and emptied the port locker. Hummmm either y'all are skinny or I'm fat. Ok, I'm fat. So, I unscrewed the shore power receptacle and removed it. I then removed the plastic, protective cover on the backside.

What I found was indeed the problem. The center (White) wire had corroded through and then shorted out. I removed all of the wires from the receptacle and cleaned them. I then spliced in a length for the center wire and re-installed. BEFORE YOU START SCREAMING.....this is a temporary fix until this weekend when I replace the entire length from receptacle to panel.

Now for the big question... What is the proper gauge wire for that circuit?

Thanks again for all of your wonderful insight!!!

[Stu Jackson]

Lance, good detective work.  Wire size:  why not just bring in the piece you removed and match it?  It wouldn't hurt to go up one size either.

I recommend you do a wiring diagram of the incoming AC power behind the panel before you take anything apart.  It's a bit confusing as the terminal blocks take the green and white if you have only a single pole breaker.  Watch the jumpers on the terminal blocks carefully, too.  One of the first things I did when we bought the boat was to start making wiring diagrams.  Then I studied them and figured out what was going on back there.  Label the wires as you work.

[Craig Illman]

Lance - I just know you want to spend more money, but while you're re-wiring that path, consider adding a galvanic isolator. My opinion on wire size? 30A = 10 gauge, even though my C34 came from the factory with 12 gauge. One of the many upgrades I never got around to addressing, at least from the Galvanic Isolator to the AC panel.

I'm sure there are forum discussions about the benefits of G.I., both from a corrosion and safety perspective.

Craig

[Lance Jones]

OK Craig, I'll bite! What's a Galvanic Isolator? Does it keep the people of Galvan apart from other people for some reason? Do they have infectious illnesses?

Mine came with 12 gauge as well and I'd like to move up to 10 gauge too. Great minds...

[Stu Jackson]

There are varying opinions about galvanic isolators.  Calder's basic conclusions is they aren't very helpful, and that if you're looking for isolation, you really need an isolation transformer.

Lance, if you don't have any corrosion issues underwater with your prop in your fresh water, don't bother because the galvanic isolator and the isolation transformer are primarily for salt water use.

When and if you move your boat to the coast, then you'll have time to think and learn about them.

[Lance Jones]

Thanks Stu. No issues with corrosion. That's one of the things I love about being in fresh water!!!! Thanks all!