Shorepower connections/leakage, starting with some simple tests

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@SteveK
SteveK said:
I was wondering if that is still a shock hazard then.
Click to expand...

Academically it is. Practically I do not believe so.
Some owners want to spend the money for an IT so they don’t have to deal with leakage. I won’t do those installations as the correct action is to clear the leakage. It really is not that hard.
 
This is the clamp tool I use, very sensitive, and well-suited for this sort of low current testing.

Clamp-on Tester 30031A/30032A (Leakage Current) | Yokogawa

With the caveat about false positives mentioned by Charlie J taken into account, one common error I see being made with this test is failing to note the difference in current flow with the power turned on and off. I often find high current, exceeding the 30 mA ELCI threshold, however, it's coming from a source other than the vessel I am testing, and only being conveyed back to its source via the test vessel's grounding wire. That's not harmful per se, unless you are a swimmer, but there's nothing you can do about it anyway since it's coming from another vessel. If the difference in leakage current between on and off is less than 30 mA, then your vessel's leakage is low and likely safe. Also, I'm not sure I'd fully rely on an ELCI not tripping to pronounce a system safe, I have seen them wired incorrectly. You can test an ELCI using one of these https://www.amazon.com/Extech-CT70-Circuit-Load-Tester/dp/B0058ELNFY?th=1 By changing the test threshold you can analyze trip current on GFCIs and ELCIs. It might be one of my most frequently used tools.

More here
December 2023 Newsletter – Leakage Current | Steve D'Antonio Marine Consulting
And here
 
Not quite good enough resolution. You need at least three decimal places on the amp scale, preferably four.
 
That is a fine multimeter but it’s not going to help you track down that last 30 milliamps that is tripping the ELIC.
 
This is what I use for AC leakage analysis. The newer version is available with a noise filtering feature.
20250913_102116_resized.jpg
 
That’s a great meter, especially with the filter. It’s a very specific use instrument though. Most people can’t justify getting something with such limited functions. A professional has no choice, have to have quality instruments,
Here’s one priced for the masses the has the required resolution: Amazon.com
 
Protecting the boat with anodes bonded to thru hull metals, I agree with.
Protecting on board passengers with GFI (GFCI), I agree.
Protecting swimmers from leaked AC into the water, I agree.

Seams to me that bonding the AC ground wire to the DC negative which is also connected to bonded metals in the water only serves to protect on board souls from electric shock should an AC hot touch an onboard metal. It provides an alternate ground that can kill swimmers.

My solution: Do not connect the AC ground wire to the DC negative. This eliminates the need for a galvanic isolator, the need for an isolation transformer, protects swimmers as any leakage either goes back to source or dead ends inside the boat.
 
Bmarler said:
That’s a great meter, especially with the filter. It’s a very specific use instrument though. Most people can’t justify getting something with such limited functions. A professional has no choice, have to have quality instruments,
Here’s one priced for the masses the has the required resolution: Amazon.com
Click to expand...
This meter seems to good to be true. I'm looking at this one too

 
SteveK said:
Protecting the boat with anodes bonded to thru hull metals, I agree with.
Protecting on board passengers with GFI (GFCI), I agree.
Protecting swimmers from leaked AC into the water, I agree.

Seams to me that bonding the AC ground wire to the DC negative which is also connected to bonded metals in the water only serves to protect on board souls from electric shock should an AC hot touch an onboard metal. It provides an alternate ground that can kill swimmers.

My solution: Do not connect the AC ground wire to the DC negative. This eliminates the need for a galvanic isolator, the need for an isolation transformer, protects swimmers as any leakage either goes back to source or dead ends inside the boat.
Click to expand...
"Dead ends inside the boat", the operative word there is dead, this approach could be lethal.

You can be forgiven for coming to this conclusion, others have as well, even some well known professionals.

In addition to it being a violation of ABYC Standards, hard no on this for several reasons. Primarily, the DC negative (and DC grounding, lightning and bonding systems all) need to be common with AC safety ground, so a ground fault to any of these will be cleared by a short, and a tripped circuit breaker. If these systems are not common, and grounded to the neutral ashore (not on the boat, other than at a source of power like a genset, inverter or shore power transformer only when they are the source of power), it's possible to energize an engine block or other hardware for instance, and have it remain energized. A person could then complete the path back to the source by touching the engine and something that is grounded. I've experienced this exact scenario when a block heater hot wire chafed to an engine block and energized it. I touched it and then my sleeved arm brushed a seacock, and I received a shock. If I had not been wearing a sweatshirt, I might have been electrocuted. There was no connection between the AC safety ground and DC negative aboard the vessel.

More here

Safe Shore Power and Electrocution Prevention | Steve D'Antonio Marine Consulting

Neutral to Ground Demystified | Steve D'Antonio Marine Consulting

 
@Steve DAntonio
Thank you for a well worded reply as always. Having worked with live wires I am familiar with the shock sensation. BTW, I actually read your links.

It depends.
My understanding is that ABYC introduced the standard to connect AC ground to the bonding system, which includes the DC negative connected to the engine and which is also connected to the bonding system to provide an alternate route to AC ground in case the AC ground to shore should fail in order to protect the person working on the engine or nearby.
it's possible to energize an engine block
Click to expand...
If a AC hot were to energize the engine (or any other metal) the bonding system would still allow the current to leak to the water, correct.
This circuit is on a GFCI and with the hot leaking to water (possibly 5mA) the return on neutral is not balanced so the GFCI will trip and open the circuit.
Is that not correct?
 

When I had a leakage issue I chose this one. A bit pricey, but good.

I read an old post from Charlie J and then did the steps and about 3 hours later it was resolved. I had 4 amps of leakage..lol.
 
I have never seen a leakage meter that was less than $285 before. I am intrigued by this $85 one.
 
SteveK said:
@Steve DAntonio
Thank you for a well worded reply as always. Having worked with live wires I am familiar with the shock sensation. BTW, I actually read your links.

It depends.
My understanding is that ABYC introduced the standard to connect AC ground to the bonding system, which includes the DC negative connected to the engine and which is also connected to the bonding system to provide an alternate route to AC ground in case the AC ground to shore should fail in order to protect the person working on the engine or nearby.

If a AC hot were to energize the engine (or any other metal) the bonding system would still allow the current to leak to the water, correct.
This circuit is on a GFCI and with the hot leaking to water (possibly 5mA) the return on neutral is not balanced so the GFCI will trip and open the circuit.
Is that not correct?
Click to expand...
Only if the engine block were bonded (more correctly called DC grounded). However, only normally non-current carrying blocks (and other chassis) should be bonded. If the engine block is part of the DC negative circuit for the starter and alternator, i.e., non-isolated ground, then then it should not be bonded, in which case it could become energized. Bonding, DC grounding and AC safety grounding conductors should never normally carry current other than that which is associated with cathodic/corrosion protection.

I routinely encounter bonding wires on normally current carrying engine blocks. This is not only non-compliant, it can be dangerous if the conductor is too small to carry cranking/fault current from the starter or starter positive wire respectively. If the DC negative cable is compromised or disconnected, the bonding wire will overheat if called upon to carry cranking or fault current.

More here Feature: Risks of Undersized Bonding/Grounding Wires – Editorial: You Have Enemies? | Steve D'Antonio Marine Consulting

If the engine block is bonded, this is what it should look like.
050325_452.jpg
 
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More often than not this is what I encounter for engine block grounding wires. Regardless of whether or not the engine block can or should be bonded, this undersized wire is a fire hazard. If it carries fault current from a starter wire, it will overheat, if it carries cranking or charging current, due to a wiring defect, it will overheat. I have witnessed this first hand after start batteries were replaced. The tech doing the replacement dropped one of several negative cables behind the battery box. When he returned the next day to install the new batteries, he didn't notice the dropped cable. When he started the engine, I was in the ER, the block bonding wire, which was AWG8, momentarily carried the cranking current, it instantly vaporized, which caused the wiring harness it was strapped to to catch fire.

Because this is so common, and because so many industry pros see bonding and grounding wires as passive and not at risk of causing any hard as long as they are present, it is ignored. This is a textbook example of 'normalization of deviance', much like the incompatible threads of inline ball valve and through hull "seacock" installations has become so commonplace.
050125_085.jpg
 
@Steve DAntonio I can agree if that green awg8 is carrying start current it would likely fry. But why would it if located on engine block and not the DC negative battery terminal? Usually the DC neg is a larger cable, the #8 bonding size wire has no circuit to carry back to the battery unless more than one location of the bonding system is connected to the battery negative, like say the other engine which the jumper wire between engines would encourage. I was wondering why the schematic had the jumper.
 
Not sure I fully understand your question, and my example was a single engine application, however, in the scenario I described...
  • The engine block is a normal current carrier.
  • The DC negative cable that supplies the starter is accidentally disconnected at the battery.
  • The bonding system is (correctly) common with the DC negative system and thus the (incorrectly applied) engine block bonding wire is common with the DC negative.
  • The engine block bonding wire carries cranking current and overheats.
Re. the "jumper", there has been a great deal of debate about this cable, and diagram 14C, in the ABYC Electrical Project Technical Committee for the past two years; one of the results of which was the two new ground diagrams, grounded and isolated DC systems. Suffice it to say, if you are referring to this wire, ABYC E-11 diagram 14C, here is the language associated with it...

11.5.2.5.1
In multiple inboard engine installations, which include auxiliary generators
with crossover (parallel) grounded cranking motor systems, the engines shall be connected with a large enough conductor to carry the cranking motor current. This cable and its terminations shall be in addition to, and independent of, any other electrical connections to the engines including those required in E-11.5.2.4 (see DIAGRAM 14 C).

Diagram 14C represents a non-isolated ground engine(s) installation, i.e., the engine blocks are current carrying. For isolated ground engines, the negative cables would be connected to the starter negative posts, or a negative distribution bus, off the engine. The engine blocks can be optionally bonded/grounded, however, if not bonded/grounded, they could become energized with AC hot, and present an electrocution hazard.
 
@Steve DAntonio #54
To build on Steve’s excellent explanation, there are some very fine points involved that require careful study and understanding prior to doing anything. Note that there are boat builders that are not getting this right.
 
@Steve DAntonio
My post 53 was saying the #8 green was the bonding system connection to the DC- thru the engine negative wire back to DC- post which is connected to the AC GND and thus a hot touching the block would trip the GFI.

If the main starter negative was disconnected that green wire would not be a source to DC- unless another point of the bonding system was also connected to DC- and created a circuit. To avoid this the bonding should connect to DC- at the main DC- bus and not on the engine block.

I wondered about the jumper wire in Diagram 14C as a second source of DC- and if the starter DC- was disconnected from the block that jumper would still allow a circuit for the starter.
 
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I've tried to explain this as best I could, but I'll try one more time.

"If the main starter negative was disconnected that green wire would not be a source to DC- unless another point of the bonding system was also connected to DC- and created a circuit."

The bonding system and DC negative are common for ABYC compliant systems. They are connected, usually behind the panel.

The start battery negative terminal can and often does have more than one negative cable. If the one that goes to the starer is removed, there is often a second and even third one one that parallels that terminal with the other onboard battery negatives, and the negative bus, and then the bonding system. This is why it was so easy for the tech to miss hooking up the starter negative cable. If there was no cable on the battery negative, he would have noticed that. Now you have a complete circuit to the starter, albeit via a bonding wire.

You are assuming the AC wire that chafes on the block is supplied from a GFCI. A hard-wired block heater (where I've encountered such faults, one after an engine overheated and melted the 120 VAC wire) is not required to have any such protection, it can but it's not mandatory, nor are any other hard-wired AC appliances. Only outlets in machinery spaces are required to be GFCI protected. And, all of this assumes a fully ABYC compliant vessel.

I hope that's clearer now.
 
I’ll bet Steve has the same feeling.
 
NoRain said:
I’ll bet Steve has the same feeling.
Click to expand...
your comment suggests you agree with his explanation based on assumptions of facts not in evidence. perhaps you want to discuss it, maybe another view can break the unresolved.
Look close at the Diagram 14B where a dotted line goes to ground bus, then to main bus and tell me how that bonding green wire on the engine is used as return to DC-. It assumes a second not shown bonding wire direct to the DC- because the attached one no longer has a path once the DC- is disconnected.
 
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