AC Electrical Problem

[Prime Time]

Hi,
I am having trouble figuring out an AC electrical problem with my new boat.

The boat is on the hard, and I went to plug in the AC system so I could charge the batteries with a hard wired charger. The shore power was a 15 amp GFI outlet. I plugged in an extension cord and then an adapter to plug the cord into the 30 amp receptacle on the boat. Turning on the boat's circuit breaker, no problem. However, when I turned on the breaker for the charger, the GFI on land tripped.

I tried other shore outlets, same problem. There are 4 other breakers on this AC line: Port outlets, starboard outlets, water heater and a hard wired TV. Each circuit when turned on at the breaker panel tripped the GFI on shore with the exception of the TV breaker. There are a total of 4 110 outlets on the boat. 2 on port, 2 on starboard. One of each of them are GFI outlets. The GFI outlets will not reset. I am not sure how long this has been the case.

I have had the boat plugged in before without any problems, but I don't think the shore outlets were GFI types.

Any suggestions on how to trouble shoot this?

I have a second 30 amp receptacle/ breaker on board that powers air conditioners. No problem with these circuits.

Thanks,

Gary

 

[Alan Johnson]

GFI Tripping

I had a very similar problem. At my dock, we had work outlets only, 20 amp. GFCI protected outlets. When I am plugged into a standard 30 amp twist lock, the AC works fine including the GFI outlets in the heads and galley. If I plugged into the GFI outlet on the work dock and put it thru an adapter, I ALWAYS tripped the shore side GFI. I have found that boats should not have the shore power plugged into a GFI protected outlet and as long as you are using a 30 amp. twist lock, the electrical code does not require it as well.. After many hours of research, I fould my inverter/charger, a Freedom unit was the villian. To plug into a shoreside GFI circuit and not trip it, I had to disconned the chassie ground and the green ground from the shore side power. I sent the unit in for repair/evaluation and it was returned to me as working AOK. Again, this only happens when plugged into a shoreside GFI and not when I am into a twist lock.

 

[Prime Time]

Interesting

I can't understand why the GFI trips with some of the breakers but not the TV circuit.

I had a very similar problem. At my dock, we had work outlets only, 20 amp. GFCI protected outlets. When I am plugged into a standard 30 amp twist lock, the AC works fine including the GFI outlets in the heads and galley. If I plugged into the GFI outlet on the work dock and put it thru an adapter, I ALWAYS tripped the shore side GFI. I have found that boats should not have the shore power plugged into a GFI protected outlet and as long as you are using a 30 amp. twist lock, the electrical code does not require it as well.. After many hours of research, I fould my inverter/charger, a Freedom unit was the villian. To plug into a shoreside GFI circuit and not trip it, I had to disconned the chassie ground and the green ground from the shore side power. I sent the unit in for repair/evaluation and it was returned to me as working AOK. Again, this only happens when plugged into a shoreside GFI and not when I am into a twist lock.

 

[Don12364]

Two (of many) Possible Causes

From my own first hand experience on my boat:-
Modern switched mode battery chargers need a hefty filter on the mains input to prevent them radiating interference back up the mains lead. These filters are symmetrical in that they have sizeable capacitors between the hot and ground and also between the neutral and ground. So, whichever way they are connected there is always a current between hot and ground. If this current exceeds the rating of the GFI it pops. Beware you may have more than one such filter on board, each of which is not sufficient to pop the breaker but together, in parallel, they are.

Freedom Combis - In addition to the mains input filter described above also have an internal relay which, when the inverter is operating, connects the on board neutral to ground. This is the resting state.
When mains shore power is first connected the Freedom monitors this for several seconds and, if it decides the incoming power is the correct voltage etc. it will switch to this and open the neutral/ground connection. Unfortunately, until this time it held ground and neutral shorted. Because there is always some voltage between ground and neutral then a current flows. It is this current which trips the GFI.
(BTW I think my boat may be incorrectly connected re its neutral circuit - done by the builder or agent from new so others may be the same.)
I have taken out marina supplies all over because of this. My work around is this:-
1) To switch the inverter off at the mains on the main Navigation Panel.
2) Connect to shore power.
3) WAIT until the Mains On light on the Navigation panel lights; the Freedom having monitored the incoming voltage and given it the okay and opened the offending relay and passed the incoming mains supply through to the boats mains switch.
4) Switch on the mains switch on the panel.

Note:- The mains switch with the Freedom is after the inverter/charger so one is only switching its output.

As an afterthought. If anyone unplugs your shore power lead and then plugs it back in again you once again take the supply down because the on board mains switch was still on.

One can easily become non persona grata in marinas this way!

 

[Bill Roosa]

GFI basics

Don't know if this will help or not.
GFI circuit outlets want to see the entire hot AND neutral current going through them. They compare the two and determine if the amount of current going in is the same as that going out (I know it is AC but you get the idea). They are polarity specific. A hot side and a neutral side. If you boat has hot and neutral reversed everything will work fine but the GFI will trip. Check the adapter for correct polarity of wiring as it may be switching hot for neutral. The TV may be wired up with the wrong polarity so that may be why it is not tripping the circuit breaker.
I suspect the adapter is the culprit so check that first. If that reverses the problem (TV trips the GFI and everything else work OK) then you need to check the TV circuit for proper wiring polarity.

FWIW

 

[Prime Time]

Clarification

I have proven so far that there is not a polarity problem with the shore power or how the boat is wired.

The adapter works fine when I use it on my other 30 amp inlet for the a/c

The problem is not just related to the battery charger but even if that circuit is left open, just closing the circuit breaker to the 110 AC outlets on board throws the GFCI on shore.

 

[walt]

Good information posted already! Sounds like you know its not the battery charger as the problem occurs when its not even plugged in.

What is common about the three circuits you have the problem with: Port outlets, starboard outlets, water heater . Do these share for example a neutral or ground run that the TV circuit does not? What if you disconect the earth ground on the water heater (just for a test)..

As mentioned by others, somehow you have a leakage path from either the hot wire to ground (in the US, black to green) or from nuetral to ground (white to green). The leakage path is likely "small" since you dont blow the marina fuse plugged into a non GFCI outlet.

If its DC leak, you should be able to simply take an ohm meter and check for resistance (not plugged into shore power of course). Ie, if things are wired correctly, you should see infinite ohms from black to green. Given that these can trip as low as 5 ma, a 22K ohm parasitic resistance could cause the trip (assuming RMS).

If its an AC leak (such as Danalex described) the ohm meter wont detect it.

 

[Benny]

Based on my experience GFI interruptors do not like boat battery chargers. No GFI interrupt on a 30 or 50 amp lock outlets. Not sure if they would do any good on a dock anyways. If I were you I would run the extension cord inside the cabin and plug in a portable battery charger.

 

[walt]

Don’t know if you have solved your problem yet .. but another idea.

Donalex's post was interesting regarding the input filtering of switchmode devices (such as a modern battery charger). The issue is there is typically filtering on the AC lines to ground at the AC input (so the FCC will allow you to use the device without it jamming radios, TV, etc) and this filtering is typically symmetrical - i.e., the same amount of filtering on both hot and neutral lines to ground.

However, the AC voltage on the hot and neutral lines are NOT symmetrical with respect to ground. The hot wire to ground is much higher voltage than the neutral wire to ground. So the ground leakage current is also much higher from the hot wire to ground – and this is the imbalance the GFCI is looking for. Generally, this filtering (capacitance) is significantly too small to trip GFCI. I have a small 5 amp switchmode battery maintainer run off GFCI plug with no problem.

You mentioned an extension cord because the boat is on the hard. An extension cord also has “symmetrical” parasitic capacitance from hot and neutral to ground and once again, because the hot voltage with respect to ground is much higher than the neutral voltage, the extension cord also contributes to the imbalance.

So there is some possibility that a very long extension cord is also contributing to your problem... As Donalex pointed out, a single device might not trip the GFCI.. but the device affects all add up and the extension cord is one of the devices.

 

[Dan Johnson]

Gary...

I'd buy one of those inexpensive (under $10) plug-in circuit testors at your local home center and recheck each of your 110 outlets. One could be shorted (neutral to ground) or wired in reverse (I found one of my home kitchen outlets wired wrong this way) with something plugged in, causing the shore GFI to pop due to the voltage drop coming from a long extension cord providing the power while in the yard.

Whoa! Reread your original post. Check out how each of the GFI outlets onboard are wired. I also found one in my house that was wired in reverse--line feed wired into the protected side and the protected side wired into the line feed (so much for licensed electricians working in new housing developments). Once tripped I couldn't reset it--that's how I found it.

 

[Prime Time]

Not the cord

Thanks for the post.

I have eliminated the cord as the problem 2 ways.
-I plugged a toaster into the cord and no issues
-I plugged the cord and adapter into my second 30 amp inlet for the Air Conditioning and no problems

Don’t know if you have solved your problem yet .. but another idea.

Donalex's post was interesting regarding the input filtering of switchmode devices (such as a modern battery charger). The issue is there is typically filtering on the AC lines to ground at the AC input (so the FCC will allow you to use the device without it jamming radios, TV, etc) and this filtering is typically symmetrical - i.e., the same amount of filtering on both hot and neutral lines to ground.

However, the AC voltage on the hot and neutral lines are NOT symmetrical with respect to ground. The hot wire to ground is much higher voltage than the neutral wire to ground. So the ground leakage current is also much higher from the hot wire to ground – and this is the imbalance the GFCI is looking for. Generally, this filtering (capacitance) is significantly too small to trip GFCI. I have a small 5 amp switchmode battery maintainer run off GFCI plug with no problem.

You mentioned an extension cord because the boat is on the hard. An extension cord also has “symmetrical” parasitic capacitance from hot and neutral to ground and once again, because the hot voltage with respect to ground is much higher than the neutral voltage, the extension cord also contributes to the imbalance.

So there is some possibility that a very long extension cord is also contributing to your problem... As Donalex pointed out, a single device might not trip the GFCI.. but the device affects all add up and the extension cord is one of the devices.

 

[RAD]

I found a similar problem with a friends Catalina when on the hard and discovered that the main circuit breaker had both the neutral (white) and hot wire going to it and it also had something to do with the reversed polarity system, puzzled cause he never had the problem before only when plugged into a GFI outlet so I removed the white wires from the breaker and tied them together temporary for the winter and all was well

 

[Prime Time]

wow

I am surprised your friends system would work like that regardless of a GFI. That hot to neutral without any load would create quite a short??

I found a similar problem with a friends Catalina when on the hard and discovered that the main circuit breaker had both the neutral (white) and hot wire going to it and it also had something to do with the reversed polarity system, puzzled cause he never had the problem before only when plugged into a GFI outlet so I removed the white wires from the breaker and tied them together temporary for the winter and all was well

 

[RAD]

I think I wrote it the wrong way... the main circuit breaker is a double pole breaker with both hot and neutral and by removing the neutral from the breaker kept the breaker/polarity warning system from seeing this neutral and also keeping the gfi from tripping, I believe the ground wire is touching the neutral some where and thats what causing the gfi to trip, on this boat I could not get the main to stay on with out tripping the gfi and on your boat its the down stream branch circuit so your in better shape to isolate the problem... possibly the neutral is touching ground some where?

 

[Prime Time]

I see now

I see what you are saying now. Thanks.

I think I wrote it the wrong way... the main circuit breaker is a double pole breaker with both hot and neutral and by removing the neutral from the breaker kept the breaker/polarity warning system from seeing this neutral and also keeping the gfi from tripping, I believe the ground wire is touching the neutral some where and thats what causing the gfi to trip, on this boat I could not get the main to stay on with out tripping the gfi and on your boat its the down stream branch circuit so your in better shape to isolate the problem... possibly the neutral is touching ground some where?

 

[Prime Time]

Problem Resolved but why??????

So, I was at my boat trying to trouble shoot the AC system. To review, when I plugged my boat into a shore based GFCI outlet, it tripped even if the main AC breaker on board was in the off position. I had a 100 foot cord plugged into the 15 amp GFCI outlet. To this, I used a 15 - 30 amp adapter to connect the boat's 50 foot 30 amp cord, which was connected to the boat's AC inlet.

-I checked the grounding of all the AC circuits, and there was a low resistance to each.
-Using the ohm meter again, checked to see if there was a neutral to ground connection at the boat's AC inlet, nothing. Infinite resistance.
-I checked the extension cords for shorts, nothing.

To make life a little easier, I placed a second GFCI outlet box with a short cord at the end of the 100 ft extension cord located on the boat, so I could reset it rather than climbing off the boat. The 15-30 amp adapter was pugged into this box and then the boats 30 amp cord plugged into the adapter.

Miracle of miracles, this cured the problem. The AC system could be turned on and the GFCI box on land or the new one at the end of the 100 ft cord would not trip. We checked the new box and confirmed that it was working properly with a good ground.

So, it seems the shore based GFCI did not like having 150 feet of extension cord connected to it but 100 feet was ok with the secondary GFCI placed before the last 50 feet of extension cord. Any ideas why??

 

[tommays]

It would only take a TINY problem with the cord (6mA) to trip a GFI and they do wear OUT

At work they dammage cords a LOT and you might get a short tiny tingle and it will trip the GFI OR there is not much point in having the device

 

[sailingdog]

There is a very good reason for the boat to have the double pole main AC breaker with the hot and neutral wires each wired to one of the breakers. The reason is simple—if there is a reverse polarity situation in the main shorepower source, and you don't have the neutral line running through a breaker, the boat's AC system can still be hot even though you have the Main AC breaker "shut off".

Disconnecting the neutral wires from the breaker are merely a hack solution and doesn't solve the fact that there is something wrong with the wiring on the boat if the GFIs are tripping or the reverse polarity light is on, and leaves the boat with a serious shock hazard if it should ever be plugged into a shore power post with reversed polarity.

I'd also point out that the neutral and ground wires are usually tied together on the shore-side of the AC system at some point.

I think I wrote it the wrong way... the main circuit breaker is a double pole breaker with both hot and neutral and by removing the neutral from the breaker kept the breaker/polarity warning system from seeing this neutral and also keeping the gfi from tripping, I believe the ground wire is touching the neutral some where and thats what causing the gfi to trip, on this boat I could not get the main to stay on with out tripping the gfi and on your boat its the down stream branch circuit so your in better shape to isolate the problem... possibly the neutral is touching ground some where?

 

[woodster]

my ac hot leg and my nuterl and my ground are on a three block breaker and that says to me that all the wires are controlled throught the three gang main breaker ....for what its worth i think that is as good as it gets ....as far as controling the shore power source in concerned ....

comments are welcome

regards
woody

 

[Ron20324]

my ac hot leg and my nuterl and my ground are on a three block breaker and that says to me that all the wires are controlled throught the three gang main breaker. Comments are welcome.
woody

IIRC, through the years, wisdom has shown it's not a good idea to have a circuit breaker on the ground wires. NEVER. That has been mulled over through this forum.