AC Power Leakage

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Knot Salted

Knot Salted

Senior Member
Joined
Mar 16, 2015
Messages
322
Location
USA
Vessel Name
Knot Salted
Vessel Make
1981 Californian 34 LRC
I have a problem. Discovered safely with a meter, when fully connected (two lines) to shore power, KS appears to be leaking juice to ground. Marina and neighbors have been notified that we are operating on one line at a time to prevent leakage until corrected. Details follow:

She has five total 30A inlets and no generator. Inlets are typical ss capped Marinco and Furrion types.

One on port for AC Main.

Two to starboard, one dedicated for Air/Heat with external breaker, the other for AC Main.

Two at the bow, one dedicated for Air/Heat, the other for AC Main.


AC Main has a breaker at the panel, as does air/heat.

The boat came to me with the single port and two starboard inlets. I added the pair at the bow two years ago.

We only connect to one pair at a time depending on dock arrangement.

The symptom is: reading A~ with a clamp-on meter, I get zero on either inlet if only one line is in use. When air is running alone, all is zero. When anything on main is activated, I bump to .4 and up to 8.0 if heavy amps like fridge and water heater are added.

Each separate accessory breaker activated on AC Main reads zeros if the Air is off. I can run everything on AC Main, and still read zero until I turn on the air. - Again, the air/heat supply also reads zero until any single thing on AC Main supply is activated, building leakage from .4 up to 8.0 as more amperage on AC Main is used.

I have swapped supply lines and tried another pedestal on the dock. No change. Other boats around me read zeros.

Inverter battery supply is off, but it is connected into the AC side for cabin outlets under a separate breaker.


I have disconnected the bow inlets at the bus bars (last added, first out), and have the same issue when supplying via the original starboard inlets.

I do not know when this began. I have an aircraft electrician (friend of a friend) coming next week. Do not yet know when I can get a marine pro out.

Next, I plan to disconnect the inverter on the AC side and retest.

I may buy two new EEL power cords...

Running on one inlet line at a time for safety until resolved.
 
Last edited:
So your various inlets for each service are connected together without some sort of selector switch? So when plugged into on inlet, the others are hot? If so, that’s incredibly dangerous and should be rectified immediately.

As for the leakage, when you say you meter with the clamp on meter, where/what exactly are you metering? It it
Clamped around the ground wire only? Or clamped around the entire shore cord?
 
No isolator. Clamped around entire cord.
 
Start by turning every last breaker off in the boat and checking for current flow depending on which inlet shore power is connected to. If you still get flow, look for a ground wire from panel to the bonding system. Sometimes done on older boats.

If no flow, turn on inverter circuit. Sometimes people wire the inverter ground to the bonding system.

After that, turn breakers on individually until you see flow.

Boat sounds like a good candidate for a wiring makeover with a new 50 amp 220 volt panel and inlet wiring.

Ted
 
Last edited:
Knot Salted said:
No isolator. Clamped around entire cord.
Click to expand...


Thanks.


First, good for you for taking the time to check this. This is the kind of thing where a flunked survey would be a good thing, and you caught it first and can now fix it on your own time table.


I think one of two things is happening.


1) I suspect the most likely is that in your boat there is a common neutral bus or connection between the neutrals for the HVAC and the main power cords. With one cord plugged in, all the power comes and goes through that cord and all is hunky dory. But when you plug in the second cord, the neutrals for the two cords are interconnected on the boat and and the combined neutral current returns across both cords, but unevenly. If they will fit, you can test the theory by clamping your meter around both shore cords at the same time. My guess is the reading will be zero. To fix it you need to figure out where the two circuits' neutrals are connected, and separate them. BTW, if this is what's going on it's not super dangerous since none of the current if flowing back through the water. Regardless it's good to fix. This will trip RCD breakers, and can otherwise mask a much more dangerous situation.



2) I think less likely, and also far more dangerous, is that you have a significant return current path through the water. If you can clamp both cords at the same time and you get a non-zero reading, then the current is returning through the water which is super dangerous to swimmers, especially in fresh water which I think is where you are. But if this were the case, I think you would see a reading on at least one of the cords when used alone, and you are not. But stranger things have happened...


Getting back to your multiple inlets service the same on-board circuit, the only safe way to do that is with either 1) interlocking breakers that only allow you to turn on one at a time, or 2) a rotary selector switch wired such that each switch position connects only one inlet. Which ever you do, be sure to switch both the hot and the neutral, not just the hot. Blue Sea makes rotary switches and breakers for this, though I'm not sure they make triple interlocked breakers. But they might. In the mean time, you could make the boat safe by disconnecting all but one inlet per circuit. It might make operation inconvenient, but would address the exposed, hot terminals that you currently have.
 
I would also check to make sure your neutral and ground are NOT connected inside the boat while on shore power. This effectively makes the ground a parallel return path for normal neutral current. Its also a common problem.

Ken
 
KS, a few off hand thoughts:

Shore power, grounding and 40 year old electrical systems is a group of issues that Internet shopping can be in second place as compared to engaging a competent ABYC marine electrician.

Re-doing 110 volt grounds is surprisingly easy. Backing off to one incoming feed operable at a time sounds a bit more difficult. Redoing your electrical panel and breakers to specs more challenging yet. If you're handy, much of the wire pulling and elimination of old stuff is not too difficult. A capable marine tech can work up a compliant plan with you doing the grunt labor

Is the boat insured and subject to periodic survey? If so, electrical systems usually get a pretty thorough look over as major loss and liability is a primary concern of carriers.
 
All great thoughts and suggestions.

With all breakers off, there is no leakage flow though the wires using the bow or the starboard inlets. (where both lines can connect) Only an AC Main inlet is to port, never used.

I will be disconnecting the port and starboard inlets as they are not likely to be used again. If that changes, I will go to blue sea rotary switches.

The neutrals for AC Main and Air/Heat are not connected to the ground bus, but are in fact on the same bus together. This could well be the issue as Twistedtree suggests.

Not sure how to add a separate neutral without sharing a common point. ??

I will try both feeds together on the meter and hope for zeros. Will update. Thanks guys!
 
A couple of questions, how are you getting 2 power cords? is it split from a 220 volt feed? This would be a Y adapter that has 220 in and 110 out.... or is two separate 110 plugs at the pedestal? I can't imagine having that large of load imbalance with out it tripping GFI's somewhere... I would be looking at the integrity of the shorepower connections and making sure that current is not finding an easier return path in the common neutrals of both cordsets.
 
I agree with whomever said the neutrals between the two 120V inlets are connected. I don't think it's a problem, I think you are just seeing the difference in current between the two hot leads. This issue will only be observed when there is current on both hot leads and is only present because the two hot leads are 180 degrees out of phase with each other. Try making one input have low current and the other have high current, you should see a big current on the neutral wire. While still monitoring the neutral current, add load to the low current inlet. If the neutrals are indeed connected, the current on the neutral will decrease as the current increases on the "low current" inlet. If the current on both hot leads is the same, there will be no current in the neutral, the odds of this happening with 120V loads are incredibly slim though.
 
KS
Not knowing your current cruising grounds, as you visit other US marinas be prepared for the new GFIC electrical codes. The docks so equipped are very unforgiving at a threshold of 30ma stray current.

We redid our grounds a few years ago by establishing one neutral buss, tying all 110s and two galvanic isolators to it and then establishing only one ship's ground point. This redo allowed us to conform with new 30ma GFIC docks and avoid a big, cumbersome, heat generating and not cheap isolation transformer.

Charlie J who at times posts on TF is a real pro at compliance with new code installations and necessary vessel redoes.
 
Last edited:
I am doing the HAPPY Dance!!!!
It was indeed the imbalance of loads passing through the common neutral.
When both lines are in the meter I GET ZEROS!!!

Thanks Twisted, for the Ah Ha moment!

Thanks to all of you.

Improvements will be made and monitored, but I can keep $2K in the bank one more day -knock wood...
 
I would simplify the system to begin with, unhook all the inlets but 2, 1 for each shore power. Now check that all the neutrals for each inlet go to the same neutral bus. You need 2 neutral busses if you only have 1 then you need to add a second neutral bus bar. The 2 neutral bus bars should not be connected together on the boat. Do this and then recheck for current leakage. You will probably be good then. Also check things like voltmeters that the neutrals are not hooked to the wrong bus bar on neutral. I did one boat where a PO had replaced an outlet and reversed the ground and neutrals on the outlet. You can make a tester by taking an old shore power cable and stripping the insulation so that the 3 conductors are exposed. Then clamp onto the hot and neutral conductors and you would look for 0 showing that all the power going out on the hot lead is returning on the neutral lead. That is what you want to see.
 
Ka_sea_ta said:
A couple of questions, how are you getting 2 power cords? is it split from a 220 volt feed? This would be a Y adapter that has 220 in and 110 out.... or is two separate 110 plugs at the pedestal? I can't imagine having that large of load imbalance with out it tripping GFI's somewhere... I would be looking at the integrity of the shorepower connections and making sure that current is not finding an easier return path in the common neutrals of both cordsets.
Click to expand...

There are two separate 30 amp 120V lines. No Y adapters. --Thanks!
 
Comodave said:
I would simplify the system to begin with, unhook all the inlets but 2, 1 for each shore power. Now check that all the neutrals for each inlet go to the same neutral bus. You need 2 neutral busses if you only have 1 then you need to add a second neutral bus bar. The 2 neutral bus bars should not be connected together on the boat. Do this and then recheck for current leakage. You will probably be good then. Also check things like voltmeters that the neutrals are not hooked to the wrong bus bar on neutral. I did one boat where a PO had replaced an outlet and reversed the ground and neutrals on the outlet. You can make a tester by taking an old shore power cable and stripping the insulation so that the 3 conductors are exposed. Then clamp onto the hot and neutral conductors and you would look for 0 showing that all the power going out on the hot lead is returning on the neutral lead. That is what you want to see.
Click to expand...

Will do. Thanks Como.
 
Knot Salted said:
I am doing the HAPPY Dance!!!!
It was indeed the imbalance of loads passing through the common neutral.
When both lines are in the meter I GET ZEROS!!!

Thanks Twisted, for the Ah Ha moment!

Thanks to all of you.

Improvements will be made and monitored, but I can keep $2K in the bank one more day -knock wood...
Click to expand...


That's great news.


To correctly handle the neutrals, you need to separately gather the neutrals for the HVAC circuit, and only connect them to the HVAC inlets. Then gather all the rest of the neutrals and connect them to the main shore inlets. That forces the current to return through the same cable that it came in on.


The biggest issue at this point is that as soon as you plug into two ECLI outlets they will pop and you will be without power, and perhaps the scorn of the whole dock if there is a common breaker.


There is also a bit of a risk that you will overload whichever neutral is carrying more of the load.
 
One of the marinas near here doesn’t have individual breakers for each slip so they have 1 for the whole dock that trips at 100 mAmps of leakage. So if your boat is leaking very much it would take out the whole dock.
 
Comodave #18:
More to the point, if the boats on the dock are already leaking 96mAAC, and the transient boat shows up with a nominal 5mAAC leakage (which I see regularly), the pier head panel RCD will trip and the transient boat will be the bad guy!
 
Absolutely. That is what I was getting at without the numbers. A friends boat did just that until we rewired it.
 
twistedtree said:
Thanks.


First, good for you for taking the time to check this. This is the kind of thing where a flunked survey would be a good thing, and you caught it first and can now fix it on your own time table.


I think one of two things is happening.


1) I suspect the most likely is that in your boat there is a common neutral bus or connection between the neutrals for the HVAC and the main power cords. With one cord plugged in, all the power comes and goes through that cord and all is hunky dory. But when you plug in the second cord, the neutrals for the two cords are interconnected on the boat and and the combined neutral current returns across both cords, but unevenly. If they will fit, you can test the theory by clamping your meter around both shore cords at the same time. My guess is the reading will be zero. To fix it you need to figure out where the two circuits' neutrals are connected, and separate them. BTW, if this is what's going on it's not super dangerous since none of the current if flowing back through the water. Regardless it's good to fix. This will trip RCD breakers, and can otherwise mask a much more dangerous situation.



2) I think less likely, and also far more dangerous, is that you have a significant return current path through the water. If you can clamp both cords at the same time and you get a non-zero reading, then the current is returning through the water which is super dangerous to swimmers, especially in fresh water which I think is where you are. But if this were the case, I think you would see a reading on at least one of the cords when used alone, and you are not. But stranger things have happened...


Getting back to your multiple inlets service the same on-board circuit, the only safe way to do that is with either 1) interlocking breakers that only allow you to turn on one at a time, or 2) a rotary selector switch wired such that each switch position connects only one inlet. Which ever you do, be sure to switch both the hot and the neutral, not just the hot. Blue Sea makes rotary switches and breakers for this, though I'm not sure they make triple interlocked breakers. But they might. In the mean time, you could make the boat safe by disconnecting all but one inlet per circuit. It might make operation inconvenient, but would address the exposed, hot terminals that you currently have.
Click to expand...

I’m also thinking a shared neutral buss.
 
twistedtree said:
Thanks.


First, good for you for taking the time to check this. This is the kind of thing where a flunked survey would be a good thing, and you caught it first and can now fix it on your own time table.


I think one of two things is happening.


1) I suspect the most likely is that in your boat there is a common neutral bus or connection between the neutrals for the HVAC and the main power cords. With one cord plugged in, all the power comes and goes through that cord and all is hunky dory. But when you plug in the second cord, the neutrals for the two cords are interconnected on the boat and and the combined neutral current returns across both cords, but unevenly. If they will fit, you can test the theory by clamping your meter around both shore cords at the same time. My guess is the reading will be zero. To fix it you need to figure out where the two circuits' neutrals are connected, and separate them. BTW, if this is what's going on it's not super dangerous since none of the current if flowing back through the water. Regardless it's good to fix. This will trip RCD breakers, and can otherwise mask a much more dangerous situation.



2) I think less likely, and also far more dangerous, is that you have a significant return current path through the water. If you can clamp both cords at the same time and you get a non-zero reading, then the current is returning through the water which is super dangerous to swimmers, especially in fresh water which I think is where you are. But if this were the case, I think you would see a reading on at least one of the cords when used alone, and you are not. But stranger things have happened...


Getting back to your multiple inlets service the same on-board circuit, the only safe way to do that is with either 1) interlocking breakers that only allow you to turn on one at a time, or 2) a rotary selector switch wired such that each switch position connects only one inlet. Which ever you do, be sure to switch both the hot and the neutral, not just the hot. Blue Sea makes rotary switches and breakers for this, though I'm not sure they make triple interlocked breakers. But they might. In the mean time, you could make the boat safe by disconnecting all but one inlet per circuit. It might make operation inconvenient, but would address the exposed, hot terminals that you currently have.
Click to expand...

I agree with option 1 as the most likely case, I've seen this many times with twin 30A inlets, either wrong from the builder, or at some point someone paralleled the neutrals.

Also reiterate Peter's comments on multiple paralleled inlets, incredibly dangerous. Given the choice, and while more bulky, I prefer slide lock breakers over rotary switches, the former are more reliable and can be switched under load, many rotary switches are not designed to do this, which means you need to de-power before switching.

Paneltronics can make virtually any slide lock breaker arrangement desired.
 
Need break out

Comodave said:
I would simplify the system to begin with, unhook all the inlets but 2, 1 for each shore power. Now check that all the neutrals for each inlet go to the same neutral bus. You need 2 neutral busses if you only have 1 then you need to add a second neutral bus bar. The 2 neutral bus bars should not be connected together on the boat. Do this and then recheck for current leakage. You will probably be good then. Also check things like voltmeters that the neutrals are not hooked to the wrong bus bar on neutral. I did one boat where a PO had replaced an outlet and reversed the ground and neutrals on the outlet. You can make a tester by taking an old shore power cable and stripping the insulation so that the 3 conductors are exposed. Then clamp onto the hot and neutral conductors and you would look for 0 showing that all the power going out on the hot lead is returning on the neutral lead. That is what you want to see.
Click to expand...

Measuring around the entire cord is not very useful. Need to measure as stated above with a breakout.

Here is a good primer on the ins/outs for measuring leaks. Also, be sure you are using a proper meter. The correct ones cost around $300.


https://www.fluke.com/en-us/learn/blog/electrical/beyond-the-basics-electrical-problems-at-a-boat-dock

https://www.marinadockage.com/technical-bulletin-understanding-ac-leakage-current/
 
Sir, the best way way to measure the leakage on your boat is to make an adapter to you shore power cords. it is important to have access to the wire inside the cord for the correct measurement of leakage (L-N-G). Electrical 101 for boats is that Neutral and Ground are never connected on the boat however on they can mistakenly be switched on older boats. place the line wire and neutral wire only in the clam on meter first (this reading should be closer to zero mA with everything off on the boat). while monitoring the meter, start individual system to locale the culprit system that has N &G switched.
good luck,
 
pattormey said:
Measuring around the entire cord is not very useful. Need to measure as stated above with a breakout.

You can tell a great deal by measuring the entire cord, it's done routinely and successfully. If leakage, an imbalance, is present only with the vessel energized, that's definitive proof of a problem on the vessel that belongs to that cord. If the leakage does not change with power turned off, then the leakage is from another vessel, and only using this vessel as the conduit back to the source.

I use this meter https://tmi.yokogawa.com/us/solutio...p-on-tester-for-leakage-current-30031a30032a/
Click to expand...
 
Solved

Thanks to all of you for your knowlege and thoughts.

No ground/neutrals interconnected on board.

Imbalance between two power cords sharing a neutral bus was the culprit on the readings.

Whew!!!
 
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