Dangerous Marina Electrical Problem?

[jimmcgee]

I’m starting to think there may be a dangerous electrical problem in our marina.

There are twenty slips on our dock. All were under water during hurricane Sandy.

Earlier this summer two boats had their battery chargers burn out and another had the plug and inlet on his Marinco power cord burn up.

Two weeks ago I came to the marina and found the 30A breaker to my slip tripped and my batteries dead, I assumed the batteries had been run down by the fridge after the breaker had blown. I let the batteries recharge over the next week, but when we went to start the engine they barely had enough juice to crank it. The batteries were 37 months old and hadn’t been abused. I replaced them with new batteries which seem to be OK so far.

This weekend another boat had the inlet plug burn up. They were running their reverse cycle AC in heat mode and the plug smoked while they were at dinner.

Of the boats that had their chargers smoked one was 20+ year old trawler, the other was a newer (approx. 5yr old) Silverton 38. The boats that smoked their plugs were an Egg Harbor and a Silverton, both 90’s vintage. My boat is a 95 Catalina 30. So we’re talking a variety of boats. And it’s been an odd year, a lot of the regulars really haven’t been around much because of the weather and we've been away a lot so there may be others I haven’t heard about.

Even so four out of 20 burning up chargers or plugs seems pretty unusual. I’m not sure if my batteries are related to any of this.

After Sandy the marina left the dock wiring in place after having it checked by an electrician and only replaced the breakers in the power posts.

I’m looking for some guidance here before talking to the marina owner who is not a technical guy. What is the likelihood this is related to salt water submersion? Is just replacing the breakers safe or is it a hazard? Any thoughts on what could be causing these problems?

Finally, I know an isolation transformer provides galvanic isolation by blocking DC transmission; are marine isolation transformers also designed to filter voltage spikes and to deal with surges and sags?

 

[tkanzler]

Finally, I know an isolation transformer provides galvanic isolation by blocking DC transmission; are marine isolation transformers also designed to filter voltage spikes and to deal with surges and sags?

No, they're just transformers, with isolated grounds most likely. The power on the load side is treated as a new source (Separately Derived System, or SDS, in NEC-speak), but it's going to pass surges and sags.

And since it's going to be of some size, it's likely it's 120/240V input with 120/240V output. That means it's wired in an Edison 3-wire (or split-phase) arrangement, like your house, and it sounds like you may have a floating neutral problem. If you lose the neutral, the voltage between either of the two hots and the neutral is unstable, and will move around + or - depending on which of the two hots you reference, and what the relative loading is on each side. One side will read over, and the other under, but switching large loads on and off will make the voltage readings move - when one side goes up, the other goes down, potentially by a lot with a large load unbalance between the two legs.

My first guess would be corroded neutral connection somewhere, probably near or at the transformer(s), due to salt water immersion. Check the voltage under load, and also check the voltage of the neutral to ground. N-G may not show much if the whole secondary center tap of the transformer is floating while the neutral and ground are still bonded, but the voltage between either hot and neutral will potentially be all over the place.

And yes, if it's a floating neutral, it's dangerous. Potentially deadly, in fact.

 

[Rich Stidger]

Keep in mind that the Seaside Heights boardwalk fire started due to electrical damage from the salt water immersion during hurricane Sandy. IMHO it's not a stretch to think that your marina has suffered similar damage.

 

[Maine Sail]

#1 Battery chargers burn up, new and old ones. They are often sized incorrectly for the DC loads running while at the dock and the charging so they wind up in bulk far too often and for far too long. Unless these boats also sunk the charger incidents are likely isolated. Low voltage can cause issues with some chargers but usually for them to just cut out and stop working as they should. How many of the burned up chargers were UL Marine chargers?

#2 Burned out shore inlets or cord plugs are also very, very, very common. The Marinco/Hubbell/NEMA plug standard, IMHO, is a very poor choice for marine applications and unfortunately we have been using it for years and years and years, with lots of problems.

Burned up inlets or plugs is caused by corrosion/resistance and lack of service/maintenance/cleaning of the connections run rather rampant. Were these issues at the boat end or pedestal end? They are most often at the boat end but pedestal corrosion is not uncommon...

Resistance caused by old worn out plugs and corrosion.

This guy was trying to run his AC on this plug... It was charred.. Go figure...

#3 Do any boats, more than one, have the reverse polarity lights on?

#4 Has anyone clamped their shore cord to look for an imbalance in the cord. A good quality AC clamp meter with good low current resolution can simply be clamped over the entire cord. It should read 0A.. Most cheap AC clamp meters do not have the resolution to do this so you may need to finds someone that has one. The one below is very accurate at both low DC and AC current, but you certainly pay for it.

This is what it should look like:

It should NEVER look like this. People die at readings like this...

#5 You will want to conduct your own testing, safely, with proper test procedures, and equipment, and then bring your findings to the marina. It may be very that the docks have some corrosion if they submerged so you will need to check each boat loaded and unloaded. Did the pedestals submerge or just the docks? Anything below the dock should be water tight, not that it really is though.

I do find both marina issues and boat issues but the ratio is on the order of 90% boat and 10% marina... This ratio I would expect to change after a flood.

Charlie Wing's book Boatowner's Illustrated Electrical Handbook - Second Edition gives the full run down for a DIY on how to test your marine AC & dock pedestal wiring..

Don't simply rule in the marina and rule out the boats.... It is a system and both need to be checked. Best to have done your homework before going to marina management.

 

[jimmcgee]

#1 Battery chargers burn up, new and old ones. They are often sized incorrectly for the DC loads running while at the dock and the charging so they wind up in bulk far too often and for far too long. Unless these boats also sunk the charger incidents are likely isolated. Low voltage can cause issues with some chargers but usually for them to just cut out and stop working as they should. How many of the burned up chargers were UL Marine chargers?

#2 Burned out shore inlets or cord plugs are also very, very, very common. The Marinco/Hubbell/NEMA plug standard, IMHO, is a very poor choice for marine applications and unfortunately we have been using it for years and years and years, with lots of problems.

Burned up inlets or plugs is caused by corrosion/resistance and lack of service/maintenance/cleaning of the connections run rather rampant. Were these issues at the boat end or pedestal end? They are most often at the boat end but pedestal corrosion is not uncommon...

Agreed, but what got my attention is the frequency. I've not heard of a single electrical issue in three years at this marina. This year 20% of the boats on the dock (excluding mine) have had a significant electrical problem. I consider any electrical problem that smokes, burns and is a risk of fire to be significant.

All four involved the dockside power. All four occurred on the boat side of the connection.

Three of the four were older boats so I can't comment on what they did or didn't have installed. I would hope the 5 year old Silverton would have had a proper Marine UL charger. For that matter I would hope the same was true for the mid-90's boats.

I'm still not sure my issue is related as the symptoms are different.

#3 Do any boats, more than one, have the reverse polarity lights on?

Mine did not come on this weekend - at least not that I noticed. I don't know about the others.

#4 Has anyone clamped their shore cord to look for an imbalance in the cord. A good quality AC clamp meter with good low current resolution can simply be clamped over the entire cord. It should read 0A.. Most cheap AC clamp meters do not have the resolution to do this so you may need to finds someone that has one. The one below is very accurate at both low DC and AC current, but you certainly pay for it.

#5 You will want to conduct your own testing, safely, with proper test procedures, and equipment, and then bring your findings to the marina. It may be very that the docks have some corrosion if they submerged so you will need to check each boat loaded and unloaded. Did the pedestals submerge or just the docks? Anything below the dock should be water tight, not that it really is though.

I do find both marina issues and boat issues but the ratio is on the order of 90% boat and 10% marina... This ratio I would expect to change after a flood.

Charlie Wing's book Boatowner's Illustrated Electrical Handbook - Second Edition gives the full run down for a DIY on how to test your marine AC & dock pedestal wiring..

That's part of the reason for my post, looking for some information on how to find out if something really is going on. I have Charlie Wing's book, I'll read through the section on testing and I may be able to borrow a meter.

It's my understanding that the pedestal's were completely submerged by the storm surge. I saw pedestals on one of the other docks that had burns on them two days after the storm so I'm wondering the power may have been on during the storm and those pedestals shorted during the surge.

As for everything being water tight below the docks, well let's just say the water and power installations are quite old.

I don't know if this is related in any way but a slip neighbor got zapped diving on a fouled prop in his slip last year by stray current in the water.

Don't simply rule in the marina and rule out the boats.... It is a system and both need to be checked. Best to have done your homework before going to marina management.

I'm not going to go in half cocked. I want to have some idea if there is really a problem and if it is really a hazard before talking with the owner. He's not a bad guy but I know money is tight and he's not going to want to investigate unless he knows something is seriously wrong.

 

[jimmcgee]

My first guess would be corroded neutral connection somewhere, probably near or at the transformer(s), due to salt water immersion. Check the voltage under load, and also check the voltage of the neutral to ground. N-G may not show much if the whole secondary center tap of the transformer is floating while the neutral and ground are still bonded, but the voltage between either hot and neutral will potentially be all over the place.

And yes, if it's a floating neutral, it's dangerous. Potentially deadly, in fact.

Maine Sail, does this sound like a possible cause?

 

[kloudie1]

Marina I just moved from had some residual damage from salt water from Katrina. One of the neutral busses had bad connections that have since been corrected. I was awakened by a fan inside the boat running at higher speed and hooked up volt meter to inside connection. Found volts at 135, spiking to 145 at times.. I shut everything down and the next day talked to the guy who was correcting the connections at the buss. He said it had been going on intermittantly for 5 or so years but finally it had gotten bad enough to find. I had never considered that I could have high volts at the boat.. usually low volts from bad connections.. Fortunately, I got no damage that I know of, from the incident.

 

[CarlN]

Mainsail,

In the "learn something new every day" department, I've never known of putting a clamp meter around the cord for this type of diagnostic. How good a meter do I need? I find Exetech AC only clamp meters on the internet for $60. Do I need a higher end one?

I guess I should get the book you mentioned, but how is the 2 amp imbalance in the cord potentially deadly? Does it mean a hot ground/neutral?

It also seems that it would be a good idea for me to set my Victron charger to give an alarm if voltage ever spikes. Maybe it does this already.

 

[Johnb]

Unless you already know what you are doing, the knock on effects in terms of death and destruction are just too severe to start learning, or buying your own testers etc. I totally agree that the problems will most likely lie with the individual boats rather than the professionally installed and maintained marina power system, but if that has been dunked it really should be re tested.

Tkanzlers comment makes sense to me, the neutral may be floating. A lot of boats protect against excessive neutral to ground voltage but that only triggers at 60+ volts. If the docks were protected by GFCI's that would create a lot of confidence.

To lighten this up a bit I have attached a picture I found amusing.

 

[Maine Sail]

Mainsail,

In the "learn something new every day" department, I've never known of putting a clamp meter around the cord for this type of diagnostic. How good a meter do I need? I find Exetech AC only clamp meters on the internet for $60. Do I need a higher end one?

The two meters used most in the industry are the Yokogawa 300-31 (AC only) or the Extech 380942 (AC/DC). Both are excellent leak testers but quite expensive. AC/DC resolution, at low or mA currents, in a clamp meter, is not easy to do and thus they can be pricy. I like my Extech 380942 but the Yokogawa 300-31 has bigger jaws and can clamp 50A service more easily. I use my for lots of DC leak testing as well, the Yokogawa can't do this, and the size of it is good for tight spots.

My Extech just barely fits over a 50A service so this is where the Yokogawa shines for AC use.. When I bought mine the Yokagawa's were back ordered and I needed DC too.. Fluke has nothing in the type of tester other than an Amprobe unit, Fluke owns Amprobe. However I am not a huge fan of that leak tester.

You would want a meter capable of measuring AC out to the hundredth of an amp, at a bare minimum but preferably mA level out to the thousandths, with some level of accuracy. You may be able to find one but it is not the level of tool I use so can't really steer you very well on that...

What's going down the AC hot and back the AC neutral wires should match perfectly. If they do match then the reading, when clamping the entire cord, will be 0.000A. If there is an imbalance between hot and neutral , caused by leakage, then the meter will give a reading. This reading is what is leaking to Earth and causing the imbalance between hot & neutral. In a worst case scenario you are looking for a max leakage, under load, of of 0mA to 3mA (0.003A).. Anything above 3 mA of leakage and the terminations, wiring, cord set, inlets etc. need to be examined carefully.

 

[jimmcgee]

Wow, you weren't kidding about the price. I'll talk with an electrician I know and see if he has one of these. Otherwise I think it's time to recommend the marina have someone look at the system.

Thank you,
Jim

 

[tkanzler]

What's going down the AC hot and back the AC neutral wires should match perfectly. If they do match then the reading, when clamping the entire cord, will be 0.000A. If there is an imbalance between hot and neutral , caused by leakage, then the meter will give a reading. This reading is what is leaking to Earth and causing the imbalance between hot & neutral.

But just to clarify, if there is an improper connection between the neutral and ground system in the boat, and the boat's metal in contact with the water isn't bonded (or there isn't any metal in contact with the water), then there could still be parallel neutral-ground current in the cord, which won't show up on a clamp-on meter.

Since the only place the neutral and ground should be bonded is in the service equipment of the marina, or at the first disconnect after an isolation transformer, it's possible for a neutral-ground 'short' to put current on the ground without leaking into the water and registering on the meter. A simple continuity test between the neutral and ground on the shore power cord should show the presence or absence of such an unintended connection.