Gremlins! AC short?

I think that the Gremlins have invaded my boat. First it was the engine (still haven't solved that one so I am going to have to call a mechanic). Now it is a problem with one of my AC circuits.

I went down to the boat today and noticed that the power was off in the boat. The breakers had tripped. Trial and error led me to the AC circuit in the saloon. The system seems to be fine until I flip that breaker on, then the boats main breaker disconnects.

So, somehow magically between the time we left the boat on Monday evening until I got to the boat today, a fault developed. I already checked the GFI on that circuit and it is fine. I didn't have any more time to chase it down today and I won't until next weekend. In the mean time, since I know nothing about electricity, what would be the most likely things to check first?

The yellow pages or the Internet for a good marine electrician.

Ted

O C Diver said:

The yellow pages or the Internet for a good marine electrician.

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Good point Ted.

what would be the most likely things to check first?

AC Things you have plugged into outlets.

Dave: what about that new oil pan heater you just installed? I'd start there. It might be on that saloon circuit.

JDCAVE said:

Dave: what about that new oil pan heater you just installed? I'd start there. It might be on that saloon circuit.

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Different circuit entirely.

FF said:

what would be the most likely things to check first?

AC Things you have plugged into outlets.

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That was the first thing I did was to unplug everything on that circuit. Second thing was to eliminate the gfi outlet on that circuit. The next step will be to remove and check every outlet on that circuit.

I recently had an ac go out. The compressor shorted. It would cause the circuit breaker on my smaller 6 kw generator to torn off. I was sure I had a generator problem, until an electrician found the bad ac.

Gordon

Had a weak breaker on the post at the pier that caused a problem for me last year. Caused a lot of looking on my part.

Electrical issues can be difficult to hunt down. Also had a switch to my depth sounder fail which caused a significant amount of hunting. It was an easy fix, but still caused a lot of time in chasing things down.

What is connected to your saloon breaker? Sometime just a light bulb can short your circuit. Do a list of what is connected this part of the circuit than fheck one by one.

Dave. Have you checked the plug in receptacles, inside the cabinet on the stbd side. The tv goodies are usually plugged in there. I have 3 receptacles on that side, 2 in the cabinet and 1 outside the cabinet. Dan

Rebel112r said:

Dave. Have you checked the plug in receptacles, inside the cabinet on the stbd side. The tv goodies are usually plugged in there. I have 3 receptacles on that side, 2 in the cabinet and 1 outside the cabinet. Dan

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Thanks Dan, I haven't yet. I ran short on time last weekend as I needed to do some work on my sailboat. Checking all those will be on the work schedule this weekend.

dhays said:

.................. Trial and error led me to the AC circuit in the saloon. The system seems to be fine until I flip that breaker on, then the boats main breaker disconnects. ...............

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OK, you are switching on the saloon breaker (which is probably a 20 amp breaker) and when you switch it on, the main breaker (which is either 30 amp or 50 amp) trips.

It's possible, of course that the other circuits are drawing 29 amps (in the case of a 30 amp main breaker) and the saloon circuit (which would have to be powering some sort of load) brings the total draw to over 30 amps and the breaker trips, but this is unlikely and a slightly overloaded breaker takes some time to trip.

If the breaker is tripping immediately, you probably have a direct short somewhere or the breaker is defective.

If you don't have a thorough knowledge of electrical circuits and the necessary test equipment, your best bet is to bite the bullet and call in a marine electrician. He (or she) will likely find the problem in a few minutes while you could spend hours or days trying to track it down and possibly create additional problems.

Put a clamp on ammeter on the black shore power lead at the tripping breaker. Duplicate the condition that makes the breaker trip while watching the meter. Do the amps actually spike?

WesK, it is an immediate trip, so my feeling was it is a direct short. While it is possible that it is a faulty breaker, that wouldn't be my first assumption. One of my very few complaint about the North Pacific is the quality of the AC wiring installation. My guess is there is a problem at one of the outlets. If all of those check out OK, then I will bight the bullet and call in a professional. The extent of my electrical knowledge is pretty much how to turn on a switch, and even that can be questionable at times.

dhays said:

WesK, it is an immediate trip, so my feeling was it is a direct short. While it is possible that it is a faulty breaker, that wouldn't be my first assumption. One of my very few complaint about the North Pacific is the quality of the AC wiring installation. My guess is there is a problem at one of the outlets. If all of those check out OK, then I will bight the bullet and call in a professional. The extent of my electrical knowledge is pretty much how to turn on a switch, and even that can be questionable at times.

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It is possible that the ground wire at one of your receptacles is touching the hot terminal of the receptacle. It's not hard to create this when stuffing the receptacle back into the box. It could have been close all along and a slight movement caused it to touch. Many electricians routinely wrap tape around the receptacle to avoid this possibility.

Of course, this is just one of many possibilities.

If you disconnect the load side of the breaker you can determine if it is the breaker or further down stream.

Thanks for the ideas. I spent last Saturday chasing it. Using the multimeter I found there was a short at the breaker, but it wasn't the breaker causing it.
The saloon circuit is 30 amp with 8 outlets connected to it. The short was evident at each outlet. Some of the outlets were daisy chained, but none of the outlets had any internal shorts.

Down in the ER there is an AC panel. There I found a bunch of hot leads for the saloon circuit. These were all bridged together and when the bridges were removed I found that one of those leads had a dead short.

I disconnected the disconnected the shorted hot lead, bridged the rest together again and the saloon circuit now works with the exception of one outlet.

Here is the odd part, that outlet is fine. However, that outlet has wires leading from it as if another outlet is daisy-chained to it. The problem is that I have no idea where they go. They disappear into the out wall of the saloon and head up towards the boat deck. There are outlets up there but I believe they are on a different circuit. At this point I had been working on this for 10 hours straight. I was tired and sore from crawling around with my bad back and knees, I was shaky from lack of calories, and it was too dark to see anything up on the boat deck anyway. So I went home.

So the good news is that all but one of my saloon outlets are now working. I also have a better understanding of how the AC system on the boat is wired. The bad news is that there is still a problem somewhere in the system that I haven't found yet.

Yesterday was spent working on plumbing problems at the house so next weekend I will try and tackle the electrical gremlins again.

sounds like you did well. The next thing I would do is pull the outlet on the boat deck to look for water intrusion and corrosion

bayview said:

sounds like you did well. The next thing I would do is pull the outlet on the boat deck to look for water intrusion and corrosion

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You get the prize.

It quit raining long enough for me to check today. There was an outlet on the boat deck that was Daisy chained to the outlet in the saloon that was showing the short.

When I took it apart this is what I found.


The seals had failed with time and water was getting into the electrical box. It was pooling at the bottom of the box and rusted-out the base of the outlet.

I removed the outlet take off the wires and sealed up the opening for now. I need to get another waterproof cover and outlet for that box.

Islanddreamer said:

Had a weak breaker on the post at the pier that caused a problem for me last year. Caused a lot of looking on my part............. .

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I had that problem a few weeks ago. I moved my shorepower cord to a different pedestal and that breaker didn't trip.

That was enough evidence to convince the marina manager to replace the breaker. Everything is fine now.

dhays said:

...................water was getting into the electrical box. It was pooling at the bottom of the box and rusted-out the base of the outlet..

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Leave the bottom plug out of the box (or drill a few holes in it) and water will drain out the bottom.

WesK said:

Leave the bottom plug out of the box (or drill a few holes in it) and water will drain out the bottom.

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Good idea.
Somehow a couple other photos didn't upload.

Wow, there is a good example of the value in circuit breakers, RCDs, and GFIs.

where will the draining water go?

Some sort of hood over the supposedly water tight outlet cover might help. I have not been happy with the normal water protected outlet covers. There must be something better. Is the outlet really necessary?

bayview said:

where will the draining water go?...

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The same place it would have gone if there was no electrical box. We are not talking about a major flow of water, just a slight drip. If it can't accumulate, there will be no problem.

Obviously, it's best to seal the box as well as possible. The vent in the bottom is just in case the seal is not perfect.

Congrats on finding the short. I thought High Wire would have carried his current meter test suggestions further but for future trouble shooting, purchase a clamp on amp meter. Harbor Freight has a few of them all under $20.

An amp meter probing in the branch circuit can isolate the path of the shorted condition. Not all conductors in the branch will have current flowing only the conductor feeding the short.

A schematic of your boat's wiring is also helpful isolating these sometimes difficult to locate problems. In any case, nice to have a happy ending without having to call/pay an electrician.

foggysail said:

............... An amp meter probing in the branch circuit can isolate the path of the shorted condition. .

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Not in this case because the direct short tripped the breaker before any measurement could be taken. If you have a direct short, the actual amperage is not important.

Now an ohm meter could have determined that there was a direct short, but with the breaker tripping immediately, that's pretty obvious.

The ohm meter would help to isolate the particular circuit where several are joined together as in his case.

As far as a schematic, that's going to show the electrical components but not necessarily where they are physically located. Most of our boats are small enough that it's easier to just look for the problem with our eyes (and sometimes, our nose).

Dave
I am proud of you. I have been a professional electrical troubleshooter for all my life. I am 70 years old. I did not answer your posts because I do not have the skills to talk you through the troubleshooting procedure without knowing your background, I do not want you to kill yourself or burn down your boat. You did a fine systematic job of half splitting the problem down to the cause. Those same skills can be applied to most systems on the boat. Thanks for sharing your experience will the forum.
Cliff

Good find, you dodged a bullet (boat fire). Although I hate being the sand in your bathing suit here:

"At this point I had been working on this for 10 hours straight. I was tired and sore from crawling around with my bad back and knees, I was shaky from lack of calories, and it was too dark to see anything up on the boat deck anyway. So I went home."

Far from me being a paragon of virtue but working with AC takes awareness and a real fear of death. I think you probably have both but you professed your ignorance too. Just be careful, working by yourself on dangerous systems when you are tired and sore, people tend to cut corners.

Everything electrical or moving machinery, spinning shafts, batteries etc.

Stay safe and enjoy your boat!