How can I find the ground fault in my boat?

[Qsilverrdc]

Update - some progress was made over the weekend.
Three images of my panel board. Remember this is a 1988 boat.

Front of panel

Back side

Hull side

So I used my clamp meter around the shore power cord at my dock everything running.
The reading was .85 amps. I have 2 plug ports on my boat and use a Y splitter. When I measured current there I got 2.55 amps on one and 1.7 on the other. I thought this is strange. The readings on the Y splitter should be the same. This is because of different loading at the panel. Line 1 with Converter, Galley, AC pump, Forward AC draws more current. Then the Line 2 side, but the combined (l1+l2) current is shared on the neutrals of the Y, because they are common on the buss.

I unplugged the shore power cord from the pedestal and the boat. I used my meter to check for open and crossed wiring. The cord checked normal as I expected it would.

Next I opened the main panel on board. I did some continuity checking between the neutral bus (white or right in image) and the safety grounding buss (green on left in image). 0 (Zero) ohms of resistance. Confirmation that I have a neutral bond somewhere.

I began by removing neutrals at the bar and found the heavy white wire on the left is bonded. The rest on their own show about 14 mega-ohm reading to ground. That is about .01 ma. Great the problem is found.

The problem is the heavy white wire is the generator neutral. So I did a little research and found these excerpts.

For shore power (source ashore), the neutral and ground are bonded in the shore power infrastructure ashore, and MUST NOT be connected together on the boat. For generators, the neutral and safety ground MUST be connected together at the frame of the generator (source onboard).... In the past some boat manufacturers have used switches that do not transfer the neutral. This is a hidden, silent, non-symptomatic wiring error.


So looking at my panel breakers you can see they only transfer the Hot wire. By default my boat will trip the ground fault because it was built that way. The generator neutral is bonded to ground (as required) and also always connected to shore power neutral. This creates the fault. I have disconnected the generator neutral temporarily to fix the ground fault problem.
I re-checked the amps and both legs of the Y are the same and the cable reads 0 (zero) now. Not leaking current but not fixed as I can't use the generator.

Now I need to figure out a permanent fix.

Thoughts are welcome, Richard

 

[ttmott]

Update - some progress was made over the weekend.
Three images of my panel board. Remember this is a 1988 boat.

Front of panel

Back side

Hull side

So I used my clamp meter around the shore power cord at my dock everything running.
The reading was .85 amps. I have 2 plug ports on my boat and use a Y splitter. When I measured current there I got 2.55 amps on one and 1.7 on the other. I thought this is strange. The readings on the Y splitter should be the same. This is because of different loading at the panel. Line 1 with Converter, Galley, AC pump, Forward AC draws more current. Then the Line 2 side, but the combined (l1+l2) current is shared on the neutrals of the Y, because they are common on the buss.

I unplugged the shore power cord from the pedestal and the boat. I used my meter to check for open and crossed wiring. The cord checked normal as I expected it would.

Next I opened the main panel on board. I did some continuity checking between the neutral bus (white or right in image) and the safety grounding buss (green on left in image). 0 (Zero) ohms of resistance. Confirmation that I have a neutral bond somewhere.

I began by removing neutrals at the bar and found the heavy white wire on the left is bonded. The rest on their own show about 14 mega-ohm reading to ground. That is about .01 ma. Great the problem is found.

The problem is the heavy white wire is the generator neutral. So I did a little research and found these excerpts.

For shore power (source ashore), the neutral and ground are bonded in the shore power infrastructure ashore, and MUST NOT be connected together on the boat. For generators, the neutral and safety ground MUST be connected together at the frame of the generator (source onboard).... In the past some boat manufacturers have used switches that do not transfer the neutral. This is a hidden, silent, non-symptomatic wiring error.


So looking at my panel breakers you can see they only transfer the Hot wire. By default my boat will trip the ground fault because it was built that way. The generator neutral is bonded to ground (as required) and also always connected to shore power neutral. This creates the fault. I have disconnected the generator neutral temporarily to fix the ground fault problem.
I re-checked the amps and both legs of the Y are the same and the cable reads 0 (zero) now. Not leaking current but not fixed as I can't use the generator.

Now I need to figure out a permanent fix.

Thoughts are welcome, Richard

Now that's interesting; the transfer switches in my boat switch both hot and neutrals specifically due to the generator combining the neutral and ground. The only point the grounds and neutrals are to be bonded is at the facility main disconnect panel or at the utility provider interface which is all before any GFCI device. In the case of a generator powering something the generator must combine the neutrals and ground just as if the generator was the utility provider. I have a schematic of my boat I can send you if you desire.

 

[ttmott]

400 DA Schematic. The red items are modifications to my boat FYI.

 

[Qsilverrdc]

Now that's interesting; the transfer switches in my boat switch both hot and neutrals specifically due to the generator combining the neutral and ground. The only point the grounds and neutrals are to be bonded is at the facility main disconnect panel or at the utility provider interface which is all before any GFCI device. In the case of a generator powering something the generator must combine the neutrals and ground just as if the generator was the utility provider. I have a schematic of my boat I can send you if you desire.

Would love to have the schematic.

I have been looking into replacing the airpax marine breaker out with 2 - 3 pole and switching the neutrals. About $100 for each breaker and a slide interlock at $35. Plus some wire. So that is about $250 for parts. I don't know if the mounting spacing is the same.

Richard

 

[ttmott]

Would love to have the schematic.

I have been looking into replacing the airpax marine breaker out with 2 - 3 pole and switching the neutrals. About $100 for each breaker and a slide interlock at $35. Plus some wire. So that is about $250 for parts. I don't know if the mounting spacing is the same.

Richard

I pasted it and if you click in it you should be able to access on photobucket. You really need four 2 pole transfer switches with the slide lockout. Might want to give Flounder Pounder a call; they may have everything and are very reasonable. Look to 1995 and later SR's.

 

[Qsilverrdc]

I took some time to do a schematic of my AC side.
Not too complicated, but not up to current ABYC standard.
The generator is "bonded to safety ground" as required by National Electric Code (NEC) and American Boat and Yacht Council (ABYC)
The problem is it is always bonded, and that is creating the ground fault situation this whole thread is about.
I am trying to figure the best solution, that does not cost too much for this problem.
The ABYC current requires neutrals to be switched with the Hots.

Full size here http://i64.tinypic.com/a9o8ls.jpg
So when I look at this diagram.
On Shore power 30 amps for each leg (60 total) would be available.
On Generator each leg has 50 amps. That would be 100 amps total if the generator could deliver.
My generator is 6.5kw so about 54 amps at max rating. (so why not 2 - 30 amp breakers for the gen.)
I assume so they could put a larger generator in? Maybe that's just how it was done in 1988.
I drew the diagram with a single 30 amp feed to a 30 amp cable to a Y splitter as I currently keep my boat.
I would guess the intent was for 2 - 30 amp cords, or a 50 amp cable split down.

 

[Qsilverrdc]

Here is a fix I was thinking about.
I would remove the existing 2 pole interlocked breakers and replace with 3 pole interlocked breakers. [blue sea]
I don't think this works, because the combined neutral passes thru the breaker and will trip at 30 amps.
The original design is 60 amps, 30 for each side. (I know I run on a single 30 amp shore cord.)
If I replaced the breaker with a 3 pole 60 amp then the design power (returning on neutral) would be the same. I am just not sure about the line side wire gauge to the branch breakers, as exists, if it is rated for 60 amps.
It should be rated at least for 50 amps, as the generator circuit can deliver 50 amps to each leg.

This is about $400 of repair and parts if done myself.

Anyone have other thoughts?

 

[ttmott]

Do you have two 120VAC lines coming into the boat or one? Looks like one from this drawing... That's a lot of load for one 30 Amp shore line....

 

[Qsilverrdc]

Do you have two 120VAC lines coming into the boat or one? Looks like one from this drawing... That's a lot of load for one 30 Amp shore line....

No, I only run 1 - 30 amp cord. Probably if I want to run stove and AC at same time I would need 2 - 30's. Have never needed 2 lines, but I don't use water heater or stove. Never have tripped a 30 amp pedestal.

 

[Mike Blake]

Why don't you use the 2 30AMP lines? Just curious?

 

[Qsilverrdc]

Here is another thought with just adding a two way neutral transfer switch. (partial circuit shown)
I looked at this as it is close to the ABYC standard, if switched together with the main. Maybe should have an off position. A-Off-B type switch rated 100 amps.

So the main switch (breaker) has 3 states. generator, shore and off. The neutral switch has 2 states generator and shore. Other states are shore power connected or disconnected. If the main switch is off, then no current can flow, so that state can be ignored.

Starting with dock side connected, reverse polarity, main off. Switch to generator, no current. Switch to shore, no current. Mains now set to shore on (reversed). Switch to generator, no current. Switch to shore, current available, neutrals hot. [Conclusion on reverse polarity on shore power] no new issue created.

Dock side connected normal, main off. Switch to generator, no current. Switch to shore, no current. Mains now set to shore on. Switch to generator, all current will pass the generator neutral bond to ground - Fault. Switch to shore, current available correct operation for shore power mode.

Dock side connected normal, main now set to generator on. Switch to shore, no current open neutral. It is possible that a neutral path thru the shore power ground to the marina side source bond (not shown) could be created. - Fault

Dock side disconnected, main now set to generator on. Switch to generator, correct operation for generator. Switch to shore, no current open neutral.

So this option creates 2 potential faults.
Fault 1 - Use shore power with neutral switch to generator.
In a marina with ground fault this should cause a trip. 100% of the current is passing on the hot and ground.
In other marinas, I don't know what would happen. Guess it depends on the ground condition. I have to believe the boat would be leaking current to the water in this case.
Fault 2 - Use generator with neutral switch set to shore while plugged into shore power.
In a marina with ground fault this should cause a trip. 100% of the current is passing on the ground and neutral legs of the shore power back to the source neutral ground bond.
In other marinas, I don't know what would happen.

 

[Qsilverrdc]

Why don't you use the 2 30AMP lines? Just curious?

Never on the boat when I bought it I guess. I just hooked up the 30 amp "Y" adapter to the boat, a 50' cable and a 25' cable extension to reach my pedestal. Didn't have much else on the boat to get power. It has always worked so I never even considered something else.

Rich

 

[Mike Blake]

Never on the boat when I bought it I guess. I just hooked up the 30 amp "Y" adapter to the boat, a 50' cable and a 25' cable extension to reach my pedestal. Didn't have much else on the boat to get power. It has always worked so I never even considered something else.

Rich

I have the same setup. I always have used 2 cords and everything works just fine.

 

[Qsilverrdc]

So I would like to thank all for the suggestions and advice.

In short I will be removing the 2 interlocked 2 pole breakers on the current panel, and replacing with 2 interlocked 3 pole breakers. 30 amps shore and 50 amps for generator. Schematic below or http://i67.tinypic.com/11hz42v.jpg

The reason is the neutrals need to be switched with the power. Currently they are just joined on the neutral buss. Any AC power source on the boat like an inverter or generator must have the AC neutral bonded to the safety ground at the source. When on shore power there must be no bonding of the neutral to the ground.

The system was originally designed for 110 volt or 220 volt and has 2 - 30 amp shore power receptacles on the boat. To get full 60 amps of power the hookup must be to 220 (240) volt with the phases 180 degrees out of phase. One way is to use a 50 amp 120/240v cord Y-split to 2 - 30 amp ends at the boat. This would be considered the "normal" hookup for my boat. Since the 220 volt phases are 180 degrees out the neutral will never see more then 30 amps, even though the system is drawing 60 amps (30 amps for each phase). Another connection could use a 50A to 2 -30A splitter and 2 - 30A cords to the boat.

If only 30 amp plugs are available at dock, then a single 30 amp cord to a 30 to 2 - 30amp Y at the boat (my current hookup). If 2 - 30 amp plugs that are out of phase are available at the dock, then 2 cords would also deliver 60 amps.

So I have purchased 2 "C"-series 3 pole breakers, one 30A and one 50A for about $195 delivered.
I also purchased a sliding lockout for "C" series breakers for about $35. A few more supplies, splices, wire, shrink tube, soldering tools, etc, will also be needed.

Richard