120V System?shorting out

[wjob]

My 120V System which is supplied dockside by a new 15 or 20 amp GFI (can?t see the size) keeps tripping the GFI? Acting very strangely, seems to do something different every time I reset the GFI (tripping on very light loads?just 2 or 3 lamps). I?ve only tried the three circuits that power the various 120V outlets, one circuit seems OK, then 15 minutes later will trip the GFI (never trips the two 40 amp breakers that control the three circuits). Sometimes I can plug a lamp into an outlet with no problem, then when I plug a second one in it trips the GFI. There is no Isolation Transformer on the system. This problem started all of a sudden. I?ve cleaned the connectors on the shore line.

Thoughts please.

Thanks
Bill

 

[rbh]

Re: 120V System?shorting out

I wonder if you have a polarity problem somewhere?

 

[Kevinmcm]

Re: 120V System?shorting out

is the GFCI dockside or on the boat? Given the description of your symptoms (which were very helpful to a ten year electrician) it sounds like your GFCI is actually the culprit. They do weird things. A new one should fix your problem!

 

[wjob]

Re: 120V System?shorting out

Thanks all for the in-put. I'll be working on it later and will report my progress.

thanks
Bill

 

[wjob]

Re: 120V System?shorting out

Two possibilities, the GFI unit is bad (happens all the time) or you do indeed have a ground fault somewhere in the boat.

To do some basic testing get a good Volt Ohm Meter. With the shore power unplugged, open your electrical panel and check the resistance (ohms) from the main neutral to the ground terminal, it should read infinate resistance. Do the same test from the positive to the grouind, again it should read infinate resistance.

To test further, do the same as you have someone turn lights and appliances on and off. At no time should there be anything other than infinate resistance from the "hot" or the "neutral" to the ground.

Still have the problem after:

Putting in another new GFI

Followed the above instructions for OHM testing, and did get infinite resistance. But when I tested between hot and neutral at the main breaker got 22.7, the digital meter was set on the 200 ohms scale? Then I checked several of the different outlets and got infinite readings between hot and ground, and neutral and ground, but between hot and neutral, one outlet was 32.7 and the other was 27.6?

Again cleaned all connectors on the 30amp power cord to the boat and checked each for continuity.

This GFI will not re-set as long as I have any or all of the three individual breakers on for the three sets of outlets however it re-sets fine if they are off and the main 40 amp breaker is on? As soon as I turn on one of the three outlet breakers, it will trip?

I?m fine if I run an extension off the GFI and plug lamps and battery charger into it?

Any more thoughts?

Bill

 

[seabob4]

Re: 120V System?shorting out

Have you pulled your AC/DC panel down and inspected the wiring on the back side, in particular the the wiring feeding the GFCIs? Each breaker, regardless of what it controls, should have the black (hot) wire on the output side of the breaker, the white (neutral) off the outlets to a neutral bus NOT tied to the ground bus, and the green (ground) to the ground bus, tied into the 12VDC grounding system. It almost sounds like the neutral and ground buses got tied together...

 

[wjob]

Re: 120V System?shorting out

Thanks for the replies.

Re: seabob?s, I have not yet pulled the panel to look at the backside since it is not easy to do that but I will if I absolutely have to. This is a 1969 boat and has never given me this kind of problem, nothing has been changed that would have caused this, unless some wiring broke loose, which is always a possibility.

Re: Bubba?s, There is nothing plugged into the three breakers that are tripping the GFI. Regarding the polarity, the only thing that has changed is the replacement of the old dockside GFI and I?m sure I?ve done that correctly.

I?m going to do as you suggest, re-set my meter to the highest OHM scale and re-check the outlets. I?ll report back soon on this.

I?m also going to check for the stray voltages even though the closest boat that would use shore power is probably 50 yds away and their boat is gone right now anyway. When you said ?connect to the power outlet,? which outlet did you mean, any one on the boat or up on the dock?

Bill

 

[wjob]

Re: 120V System?shorting out

I re-checked the outlets using the highest OHM?s scale on my meter which is 2M?each outlet, each on a different circuit read about .080 from hot to ground and also from neutral to ground.

Bill

 

[seabob4]

Re: 120V System?shorting out

Bill,
The way a GFCI works is that it continually senses the amperage flowing back and forth between hot and neutral. If the return flow is less than it should be, the GFCI trips, as that means the current has another path to follow. Now that could be to ground, or it could be through you.

The telling part here is that you say when you turn the outlet breakers on, the GFCIs trip NOW. That says there is a fault behind the panel which has developed after all this time (since '69) and you need to get behind there and to some investigative work...

 

[Lrider]

Re: 120V System?shorting out

Any corrosion that builds up and touches grounded parts can cause the GFIC to trip, it's just like the one you have in the bathroom. I found some corrosion in the boat I am looking at the could do that if it was a 120 circuit

 

[wjob]

Re: 120V System?shorting out

Yes, I am comfortable working with it.

Bill

 

[seabob4]

Re: 120V System?shorting out

Actually I'd love to see a pic of the panel and then one with the backside exposed. It would be interesting to see how a panel was wired in '69 as opposed to today. I used to wire all the panels at Stamas Yacht for 5 years, so I kinda know what they SHOULD look like...

 

[wjob]

Re: 120V System?shorting out

Thanks for all the help! It is much appreciated. I have the covers off both
the main panel and the sub panel that houses the receptacle breakers. I will post a picture of all this (with the exception right now of the back of the panel) within the next hour.

Bubba, do those readings I took at the receptacles with the OHM scale set to the 2M, which showed .080 from hot to ground and about the same from neutral to ground tell us anything?

I am and have been a great booster of Stamas for many years. Their boats, wiring, etc. were always first class. Mine is a ?69 42ft Chris Craft Sport fish, one of their very early glass boats and it too was/is high quality. I?ve got 8V53 Detroit?s in it plus a 32V System and a 6.5 Kohler diesel generator. I?m 75 years old and all my life I?ve spent a lot of time on the ocean, I use to skipper sport fishermen up in NJ for many years. I owned at one time a 1970?s vintage 26ft Stamas with the twin OMC out drives and it was an unbelievable sea boat.

Be back soon with the photos.

Bill

 

[seabob4]

Re: 120V System?shorting out

We await. Would love to see pics of the boat as well!

 

[wjob]

Re: 120V System?shorting out

Having a problem getting photos to load up. Going to re-take and try another program. I'll be back shortly.

In the meantime have attached some during Hurricane Wilma

Bill

 

[seabob4]

Re: 120V System?shorting out

Bill,
I use photobucket, resize them to large, and they come out like this, with a simple copy and paste...

 

[wire2]

Re: 120V System?shorting out

I re-checked the outlets using the highest OHM?s scale on my meter which is 2M?each outlet, each on a different circuit read about .080 from hot to ground and also from neutral to ground.

Bill

.08M is 80k ohms that shouldn't be there. Since it's on each of 3 circuits, the common denominator would appear to be the panel. Does it go to infinity when the breakers are turned off?

 

[wjob]

Re: 120V System?shorting out

This is a relatively new camera to me and for some reason my computer not allowing me to easily upload attachments to the forum site. Bubba and Bob, if you could email a private message to me, including your email addresses, I think I can email the pictures to you. In the meantime, I?m going to try my old camera again, taking these damn pictures for the third time but the quality won?t be nearly as good, so the email would be the best bet.

Thanks
Bill

 

[wjob]

Re: 120V System?shorting out

Readings (all taken on the 2M OHM scale) really get screwy, with dock cord unplugged and breakers off in the #1 Dock Box (two 40 amp breakers) and in the 115 VAC Load Center Box (house the 3 receptacle breakers):

At Galley outlet (on one breaker):
Looking straight into outlet, left slot to ground reads .096, right slot to
Grnd. is Inf.

At Port outlet (on one breaker):
Looking straight into outlet, left slot to ground reads .096, right slot to
Grnd. is Inf.

At Stbd. Outlet (on one breaker):
Looking straight into outlet, left slot to ground reads Inf., right slot to
Grnd. Is .096

At the Load Center Box
Hot to Grnd - Only the Stbd Outlet Breaker reads .096, Other two are Inf.
Neutral to Grnd - All read .096

At #1 Dock Box
Both hot to Grnd and neutral to grnd are Inf.

What does this tell us?

Bill

 

[seabob4]

Re: 120V System?shorting out

Bill, and guys,
Sorry I'm late in posting pics, got caught up in some other stuff. Here's what Bill's AC box looks like...

So let's take a look...