Dock Stanchion GFCI breakers and your boat

[Skybolt]

I am trying to be pro active with the issue of your boat tripping the dockside GFCI when you know there nothing wrong with your boat. BTW, that's never the case. My marina is about to upgrade the docks which means new GFCI power.

I have had issues this past summer with new docks and my boat tripping the pedestal GFCI. In checking out my boat I found issues that I never knew existed. I also haven't resolved this issue completely.

First what do I think I know about this? (From the dockside power perspective)
1. Ground (green wire) and Neutral (white wire) should never be connected together like in house wiring.
2. The ground wire should be connected to the DC ground.
3. There can not be more then 30mA of reverse current going back to the dock breaker.
4. There can not be an imbalance in voltage between the hot and neutral legs to/from the boat.
5. There should be a virtual open between the ground and neutral wires.
6. Hot to ground can not have any leakage, which causes this to occur.
7. The led(s) that show reverse polarity and power can cause issues as they bridge the hot and ground and neutral to a degree.
8. Just turning off all of the breakers will only stop leakage and not help with ground and neutral issues.

Is there more that needs to be taken into consideration?

30mA are they kidding me! How do you limit that when new electronics can produce that by itself when they are not rated for marine use, but ok, it is what it is. I think ultimately an isolation transformer will fix the dock breaker from tripping, but won't fix the boat issues.

This type of issue can take a very, very long time to resolve completely unless you get lucky. I am considering setting up a GFCI plug to go from a non GFCI outlet to the boat to be able to test this. I think a 50A hot tub box could be used if wired with marine plugs, just for testing. Although this will just tell you if it's fixed. Will just measuring revers current and ground/neutral resistance be sufficient?

So how do you test this without using the above? Find and fix any ground to neutral resistance, this could mean replacing electronics/appliances and entire wire runs. That will stop the GFCI from popping, but how to fix/find the hot to ground leakage current? That is the toughest one and I believe where the test GFCI will come in handy to isolate the offending lines. Turning breakers off will help isolate this issue but still a daunting task to resolve.

Older boats will see higher leakage current then newer ones as the jacketing deteriorates causing leakage, even though the lines are not shorted and to the observer appears to be nothing wrong with the wiring. Even when ohm'd out there will be nothing wrong in most cases. It takes voltage and current to cause leakage, very hard to find.

I started to investigate my issues and found a bad wire run that was only a few years old. It looked fine and worked as expected, but with the breakers off and the outlet pulled I found continuity between the ground and neutral causing a few volts to appear on the ground system. Man how long had that been going on. I replaced that run with a new wire and all is good.

I still have ~400mv between the ground and neutral at the panel when it should be close to zero. Just ordered a new ring current meter so I can see what that translates into. I am hoping if I can get the ground and neutral to look like an open and the reverse current to under 30mA I won't need the test cable. But man this is a daunting issue to track down. Not to mention a lot of up, down, plug, unplugging the boat. Removing needed led indicators and the like.

I am only posting this to help me think through the process of testing and see if anyone else has had to go through this. Before anyone ask's I do not have an inverter and only use the generator. At my panel there is a three breaker disconnect the switches the two hot leads and the neutral between the generator and shore power. My generator does have the ground and neutral connected as it was intended to be. ABYC and NEC dictate the neutral and ground should be connected only at the source. When on generator that is the source.

Is an isolation transformer the only real fix for this? And if I do add one do I also need an ELCI breaker on the boat as well? I just replaced my entire electrical panel a few years ago with all new Blue Sea ABYC compliant panels and the like. Man that could be upwards of 4K to get back what I already have. Not to mention replacing my panel again to do it right. Oh man this sucks!

 

[ttmott]

Orlando - A couple of clarifications.

• Ground fault protection has nothing to do with a "ground" conductor (the green wires). It has everything to do with electrical current leakage. All a Ground Fault protection device does is measure the current on the Hot leg and the current on the Neutral leg of a 120 VAC to ensure they are the same (within 30ma of each other). For 240 VAC applications the device measures the current between the two Hot legs to make sure it is the same. By default if the current isn't equal then there is current leakage somewhere else; which could be a ground conductor or through the boat's bonding system or directly into the water.
• For galvanic protection the grounding system on your boat must be isolated from the marina's electrical ground system until a trigger voltage is reached and then hazardous voltage can be dumped to the marina's electrical ground. This is for boats with galvanic isolators but not boats with isolation transformers.
• When a boat's generator is electrically switched to power the boat it must also switch/tie the boat's 120 VAC neutral to the boats grounding network. The generator is classified as a power source and consequently just like the utility drop at the marina the ground is tied to the neutral.
• Inverters like generators are classified as a power source and they must also switch the 120 VAC neutral to tie to the ground.
• I would say that 80 percent of Ground Fault trips are due to inverter or generator improper wiring and the balance to faulty electrical conductors or appliances. BTW standalone ice makers and cooling compressors are notorious.

I really like the GFCI concept and application in the marine environment as it makes things safe, forces boat owners to correct deficient electrical things, and as a side benefit eliminates electrolysis on the boat's underwater metals and bottom paints.

 

[Skybolt]

Tom, I understand most of what you posted, and as usual you did it in a much neater fashion then I did and more concise.

I do have one question from the 50Amp perspective and cannot get clarification on this. All I have ever read states both 110v legs must draw equal current to not pop the breaker. Is that literal or are they just referring to each leg independently referenced to neutral? I have just guessed it means both legs independently referenced to neutral because otherwise it's always going to pop the breaker. The reverse current (leakage) is really hard to find, but how/why are ice makers an issue?

 

[hughespat57]

Tom, I understand most of what you posted, and as usual you did it in a much neater fashion then I did and more concise.

I do have one question from the 50Amp perspective and cannot get clarification on this. All I have ever read states both 110v legs must draw equal current to not pop the breaker. Is that literal or are they just referring to each leg independently referenced to neutral? I have just guessed it means both legs independently referenced to neutral because otherwise it's always going to pop the breaker. The reverse current (leakage) is really hard to find, but how/why are ice makers an issue?

You have 99+% of it right. And a +1 to @ttmott additions.

If the fault is simple like in the shore cord or the feeds it is fairly easy to find. However the fault can be in many locations. And this is why turning off multiple breakers may not always isolate the fault.

See my posts here http://clubsearay.com/index.php?threads/tripping-the-breaker-at-the-dock-pole.109214/
See #16 for an overview and #25 for a drawing why it can be very deceiving at times what circuit has the fault.

 

[Skybolt]

You have 99+% of it right. And a +1 to @ttmott additions.

If the fault is simple like in the shore cord or the feeds it is fairly easy to find. However the fault can be in many locations. And this is why turning off multiple breakers may not always isolate the fault.

See my posts here http://clubsearay.com/index.php?threads/tripping-the-breaker-at-the-dock-pole.109214/
See #16 for an overview and #25 for a drawing why it can be very deceiving at times what circuit has the fault.

Yeah I left out the bit about the Zinc Saver, but thanks.

You know Tom really is a rocket scientist!

 

[carterchapman]

You know Tom really is a rocket scientist!

I have proudly named him a "steely eyed missile man"...with credit to Chris Craft in Apollo 13!!

 

[Skybolt]

I have proudly named him a "steely eyed missile man"...with credit to Chris Craft in Apollo 13!!

I like it! Very nice.

 

[ttmott]

The 50 amp 250 VAC connection is four wires. 120 volt Hot (Black), 120 Volt Hot (Red), Neutral (White), and Ground (Green). There are three prongs on the plug with the shell being the ground or four prongs on the plug depending upon the arrangement.
The 120 Volt hot legs are 180 degrees out of phase sine wave which gives us that peak to peak voltage differential of 240 Volts.
If your boat does NOT have an isolation transformer the 120 Volt appliances use the white for the neutral with one of the two 120 Volt hot legs and that, obviously, gives us 120 VAC. If your boat does have an isolation transformer the shorepower neutral is not used; the transformer derives the neutral on the secondary windings.

Ok, so we can have current simultaneously on all three legs - Hot, Hot, and Neutral depending what is operating on the boat. If all current was being provided and returned on those three legs then we can say there is no leakage. Remember in an alternating current system the current flows one direction then reverses and flows the other at a rate of 60 times per second, hence 60hz. So, the Ground Fault Interrupter is looking at all three legs and summating the total current expecting all current sent is equal to all current returned up to a mismatch of 30 milliamps. In the case of a boat with an isolation transformer where the neutral isn't connected the Ground Fault Interrupter still looks at all three legs and even though there is no current on the neutral it's summation sees all current accounted for on the two hot legs so still all is good.

 

[Skybolt]

So I measured my leakage current today and it's not as bad as I would have thought, but still bad none the less, ~500mA. I have seen other boats up in the volt's range. But to your point @ttmott The appliances are the issue here. When I turned off the ice makers and galley appliances everything went to zero except for the older AC unit. But all of the galley appliances are new this year, and they were not cheap units either. New Microwave, Kenyon Cook top, Summit side by side and Summit wine/beer fridge.

The ice makers are the worst as mentioned. When the cockpit one is turned on it lowers the cabin ones leakage current, not quite sure how that works but it does. They both make ice and keep it frozen real well. No reason to suspect anything is wrong.

So I guess the only way I am going to get this fixed is to install an isolation transformer so the boat can plug into a newer dock's GFCI. After what I witnessed today on my own boat, I can only imagine what is really going on in other boats. I have all new appliances in the galley that produce ~250mA of leakage current. I am using that as a marker because I ran new Anchor 12ga three wire for the galley. So I know that isn't the issue and the appliances are new, so not going to replace them again for this. I guess house hold appliances are not designed for use on boat's in anyway. I would think getting through UL would make them safe for boats by definition. But I guess not.

I am going to go over the entire AC wiring this winter and check everything to make sure it's safe and not damaged in anyway. And start sourcing a new isolation transformer. I was really hoping that my battery charger was causing issues, but that was one of the only things that wasn't.

 

[carterchapman]

@ttmott - Tom thank you so much for sharing this. If we got into a Computational Fluid Dynamics discussion of supercritical wing design, I cold participate, but OMG, I am so lacking in EE knowledge! I blame myself, but I would love to put the blame on Vanderbilt and Princeton's Engineering Schools (to no avail!!).

You make me realize how much I do not know...

 

[Wanderer 290]

I do have a question??? Assuming all or most neutrals go to a common buss bar and all or most grounds go to a common buss bar then if a 110 device has a short neutral to ground internally ( converter for example ) but the breaker for the device is off the gfi will trip because of the short between the neutral and ground buss bars that is actually occurring up line at the faulty 110 device?

 

[Skybolt]

I do have a question??? Assuming all or most neutrals go to a common buss bar and all or most grounds go to a common buss bar then if a 110 device has a short neutral to ground internally ( converter for example ) but the breaker for the device is off the gfi will trip because of the short between the neutral and ground buss bars that is actually occurring up line at the faulty 110 device?

Yes, that is correct. There are two main rules that must be maintained. On a boat Neutral and Ground must always stay isolated from each other when on dock power. When on generator they become one in the same. The neutral and ground are usually connected on a generator and the neutral then needs to be lifted at the panel when the generator is not in use. This is one reason that the ship to shore rotary switch on newer boats has so many wires on it.

EDIT: I should note that the above is for non isolation transformer boats. On isolation transformers neutral and ground are essentially the same, as with the generator. Because they are power sources.

 

[ttmott]

@ttmott - Tom thank you so much for sharing this. If we got into a Computational Fluid Dynamics discussion of supercritical wing design, I cold participate, but OMG, I am so lacking in EE knowledge! I blame myself, but I would love to put the blame on Vanderbilt and Princeton's Engineering Schools (to no avail!!).

You make me realize how much I do not know...

Hey Carter - this may help; I copied the graphic from the "internet". This is a typical split phase household/dock 240 volt supply waveform frozen in time. The Red is one phase of 120 volt and black another phase of 120 volt. They are out of phase from each other by 180 degrees (shifted by 1/2 wave). The line through the middle is the neutral (0V). The peak to peak is shown higher in this graphic but the Veff is the Root Mean Square (RMS) value we typically associate by measurement. The little transformer inset is an isolation transformer where the left primary windings are the two 120 volt hot legs and the secondary shows that tap in the middle of the windings which is the derived neutral.

 

[Wanderer 290]

So the point in my prior question is…
If a shore power gfi fault occurs it can be because of any electrical device onboard be it an outlet, refrigerator, etc. Additionally, sufficient moisture present between 2 male prongs on a plug can cause a gfi fault. Therefore troubleshooting and identifying the “problem” can be laborious…

 

[Skybolt]

So the point in my prior question is…
If a shore power gfi fault occurs it can be because of any electrical device onboard be it an outlet, refrigerator, etc. Additionally, sufficient moisture present between 2 male prongs on a plug can cause a gfi fault. Therefore troubleshooting and identifying the “problem” can be laborious…

And that is why I posted this thread, because it is next to impossible to fix it all and keep it under 30mA leakage current. The new regulations passed in 2007 that didn't take place until 2014 are why Isolation transformers are being used on boats. I can guarantee new boats would have this issue if it were not for isolation transformers.

So Tom, this question is for you. Isolation transformers stop and protect the dock from leakage current and since the neutral is created from the ground, is there any leakage current going in to the water now?

 

[carterchapman]

Hey Carter - this may help; copied from the "internet". This is a typical split phase household/dock 240 volt supply waveform frozen in time. The Red is one phase of 120 volt and black another phase of 120 volt. They are out of phase from each other by 180 degrees (shifted by 1/2 wave). The line through the middle is the neutral (0V). The peak to peak is shown higher in this graphic but the Veff is the Root Mean Square (RMS) value we typically associate by measurement. The little transformer inset is an isolation transformer where the left primary windings are the two 120 volt hot legs and the secondary shows that tap in the middle of the windings which is the derived neutral.

Fields and waves still give me night sweats!!!

 

[ttmott]

So Tom, this question is for you. Isolation transformers stop and protect the dock from leakage current and since the neutral is created from the ground, is there any leakage current going in to the water now?

First, even in household appliances there should be zero leakage, so if one of your new units is bleeding current to the ground you need to get that sorted out. 30ma is current, you could have a high voltage potential at the appliance chassis which is a shock hazard. You can for each appliance, as a test, pull the ground off and see if that stops tripping the GFCI. Installing an isolation xfmer doesn't correct the safety problem. Boat manufacturers did not install isolation transformers to avoid meeting the code for ground fault isolation.

An isolation transformer is the best electrical solution for a boat; it does several things that benefit the boat's electrical configuration.
First, it electrically isolates the boat completely from the marina's power supply and thus eliminates the primary cause for galvanic corrosion. The primary windings have no electrical conductivity to the boat. The shorepower ground is tied to the transformers iron core to provide a path to ground should there be a fault in the primary windings. That iron core is insulated and isolated from the transformer's chassis.
Second, it dampens electrical noise and spikes so the boat is a stable voltage and frequency environment.
Third, as the transformer is classified as a power source the secondary winding center tap neutral (for 120 VAC) is now also the boat's AC power ground so having to switch neutrals for generators and inverters goes away. All of the boat's neutrals still need to be isolated from the boat's ground except at one point - the main neutral buss bar. All GFCI devices and all appliances must be installed after that ground/neutral tie. The below picture from my boat shows that tie on the primary ground and neutral buss bars. The heavy white wires are the neutrals from the isolation transformer center tap and the generator. Note they are not switched....
Fourth, as with an isolation transformer there is no electrical path to the shore systems there is no need for galvanic isolators. In fact the isolators need to be removed so there is an unimpeded electrical conductivity throughout the boat's AC ground, DC ground, and bonding systems.
Fifth, some isolation transformers have an automatic buck/boost feature in which they can raise and lower secondary voltage if there are issues with the shore power like being at the end of the dock.

The down side - if the marina does not have split phase 240 volt power you are dead. Connecting 120 volt shorepower, no matter how it is configured will not power your boat. They are expensive; you will have to invest a couple of boat bucks for a 15 to 20 KVA unit. They are heavy, like 150 pounds.

 

[ttmott]

The reverse current (leakage) is really hard to find, but how/why are ice makers an issue?

Ice makers - They are usually installed in a wet/moist environment and all of the electrical is below the water source/ice. Ripe for water and corrosion on the electrical connections and switches. It doesn't take much to get to that 30ma current leakage.

 

[Nater Potater]

And that is why I posted this thread, because it is next to impossible to fix it all and keep it under 30mA leakage current. The new regulations passed in 2007 that didn't take place until 2014 are why Isolation transformers are being used on boats. I can guarantee new boats would have this issue if it were not for isolation transformers.

If I'm reading all of this correctly (thanks for everyone's input!), on my older ('92) boat, I should install an isolation transformer to be able to use the newer shore power pedestals, and then focus on GFCI/safety issues in the boat itself. Yes?

 

[ttmott]

Here is another tidbit that many overlook. If your boat has dual 30 amp 125 VAC shore power connections, there should be two independent neutral buss bars in the boat. As people change and modify their electrical systems, they may connect the hot leg to one side but the neutral to the other side. It's easy to do because neither are labeled very good. This simple error even though will work just fine for most loads, it will assuredly trip the dock GFCI.
Heck, on my last boat installing an inverter I found that SR actually mixed up one of the circuits.