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Old 02-11-2017, 02:47 PM   #1
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Big Marina Rewire & the new code

Since starting this trip Tuesday we have stayed two days each in the Field Club in Sarasota and the Sarasota YC. We left this morning for the short trip to Bird Key YC also in Sarasota. They recently reopened after a major renovation of their docks which included a total rewire.

When the dock master plugged us into 50 amp power the main breaker for all the power posts for the transient docks tripped. Dock master said that our boat must be back feeding power because the new system is required (by code) to trip if it senses a back flow of over 30 mila amps. Sort of a ground fault like deal he said. He had me turn off all the breakers on the boat and tried again. She blew again.

He said that there was nothing he could do and unless we wanted to run the gen set we should go elsewhere.

He was very apologetic and said that a significant number of visiting boats experienced the same thing as well as a few of the permanent party boats. Some of these were able to stay on line by starting with everything off...establishing power...and then turning on breakers one by one until the power tripped.

Is there anything they can do to fix this?

We left and putted over to Marina Jack's, bicycled to Whole Foods, and had a big plate of sushi for lunch. All was not lost...except out free night at Bird Key.
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Old 02-11-2017, 02:51 PM   #2
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This is a common situation. Hit the East Coast of the state first. You'll need to find the fault on your boat and if you don't have the electric knowledge get a marine electrician. Think of this as a free problem detection service from the marina, unfortunately not a free fix. The good news is that once you do fix the issue, you're good for all the marinas.
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Old 02-11-2017, 03:56 PM   #3
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This is a common situation. Hit the East Coast of the state first. You'll need to find the fault on your boat and if you don't have the electric knowledge get a marine electrician. Think of this as a free problem detection service from the marina, unfortunately not a free fix. The good news is that once you do fix the issue, you're good for all the marinas.
Could you please be a little more specific as to what you think might be the problem? Or any previous fixes you are aware of on boats that you have information?

Are you saying that a good marine electrician will know where to start looking? I sure do not mind hiring one.

I just checked my plug at the boat with 3 16K A/C's running and it was cool.

I posted this issue on my home YC forum and in the last hour have heard from three other boats that could not stay there for the same reason.
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Old 02-11-2017, 04:35 PM   #4
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I am no electrician or EE but this is what I know:

Some years ago, either the code was rewritten or newly interpreted to require GFCI (ground fault circuit interrupters) on each power pedestal. That means that if your boat has a ground fault (where slightly more/less current flows in the hot conductor as in the neutral conductor) anywhere on your boat, the GFCI will trip. In theory the hot/neutral current should be equal, but old, wet wiring lets a little current pass to ground and if so you have a gf and it will trip the GFCI.

I first saw this years ago when my 30 YO boat would trip the GFCI in a yard supply while it was on the hard. I never found the cause and I never subsequently plugged in to a marina's power with a GFCI. Later a buddy's old boat tripped the marina's new power supply when he plugged in. He never found the cause either.

You can isolate the circuit or circuits that are causing the trip by first turning off all breakers in the boat. Then if it doesn't trip when you plug in (if it does, you have a fault in the supply to the main breaker) then close each breaker one by one until one trips it. That is one with a problem.

I have never traced down one of these, but my approach would first be to check the offending breaker for any stray path to ground- maybe a piece of insulation or something that bridges hot to ground and due to salt air in the boat it has enough conductivity to trip the GFCI. Then look at each appliance or outlet connected to that circuit for the same thing.

I won't go into the reasons why (in a later post probably) but requiring a GFCI on a power pedestal is totally inappropriate. But it is the code apparently.

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Old 02-11-2017, 04:40 PM   #5
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As BandB says, these new protection devices are emerging more and more rapidly, and quickly indicating problems in boat wiring that has been previously unknown.

The marina guys description of the problem is a bit misleading. You aren't back feeding power. The new marina power is equipped with a residual current detection device, and that's what's tripping. It's similar to the GFI outlets that are now common in bathrooms, kitchens, and outside outlets, but it actually less sensitive.

What a RCD does is measure the current difference between the two power lines. In a properly working electrical system, the current in the two wires should always be the same. If there is a difference, then some of the current is finding it's way back to the power source through some other path, and that is potentially very dangerous. And it is definitely an indication that something is wrong, even if it isn't immediately dangerous. And RCD will trip at 30ma (30 thousandths of an amp), which isn't much, but is definitely enough to kill you.

If your boat is tripping an RCD, then some portion of the power coming into the boat is getting back to the shore power source through a path other than the intended power line. The return path is most likely through the ground wire that is also part of your power cord, or through you boat's bonding system and metal parts in contact with the water, and back through the water. The later is when things can become very dangerous to swimmers.

Turning off all your on-boat breakers is a first diagnostic step. If the RDC doesn't trip, then the problem is in one of your boat's circuits. Turning breakers back on one at a time until the RCD trips will help narrow down where the problem lies.

In your case, the breaker still tripped, so the problem is in the wiring before all your breakers. Most likely you have a connection on your boat between the shore power neutral and ground wires. There should not be a connection when on shore power. When the two are connected, the return current splits up and follows both the neutral and the ground back to the power source. The RCD sees that the line and neutral currents are different, and trips.
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Old 02-11-2017, 05:55 PM   #6
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Could you please be a little more specific as to what you think might be the problem? Or any previous fixes you are aware of on boats that you have information?

Are you saying that a good marine electrician will know where to start looking? I sure do not mind hiring one.

I just checked my plug at the boat with 3 16K A/C's running and it was cool.

I posted this issue on my home YC forum and in the last hour have heard from three other boats that could not stay there for the same reason.
I think you have a fault and it could be in many places and a good marine electrician would know how to trace it and fix it. That's as specific as I can be because I wouldn't know how to trace it myself, would have someone else do so.
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Old 02-11-2017, 06:00 PM   #7
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What Twistedtree said nails it. I have had to run this problem to ground for several customers. The marina has taken the cheap way out and put one RCD on the dock. So one boat with a leak and the whole dock goes out. Here on the upper east coast we have seen this problem for two years. The best but most expensive solution is to put the RCD in each power post. That way only the troublesome boat trips out.

There have been a number of electric shock drownings in fresh water locations due to AC current leakage into the water. The RCD solves that problem. The standards organizations have applied the freshwater solution to saltwater marinas although the issue is a freshwater problem.
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Old 02-11-2017, 09:17 PM   #8
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Does your boat have a Galvanic Isolator between the shore power inlet and the circuit breaker panel?

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Old 02-11-2017, 09:27 PM   #9
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There have been a number of electric shock drownings in fresh water locations due to AC current leakage into the water. The RCD solves that problem. The standards organizations have applied the freshwater solution to saltwater marinas although the issue is a freshwater problem.
This is true, but even thought electric shock drowning isn't an issue in salt water, and there may be no immediate electrocution threat, the RCD tripping is still indicative of a wiring safety issue in your boat. You have essentially lost the safety shield that your ground system provides, and/or will be the victim or cause of major electrolysis damage. In all ways, the problems exposed by RCD devices are important to correct.
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Old 02-11-2017, 09:33 PM   #10
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Is there any sort of plug in device or test that one can do beforehand, to make sure our boats meet the standard? So you don't wind up tripping the power to an entire dock of boats, maybe on arriving after the marina crew have left for the day, and left you facing a lynch mob of angry boaters without shore power.
From what I have read elsewhere the fault can be as small as the wiring to the LED lights that show a circuit breaker is on.

From the OP
"Sort of a ground fault like deal he said. He had me turn off all the breakers on the boat and tried again. She blew again."
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Old 02-11-2017, 09:35 PM   #11
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Does your boat have a Galvanic Isolator between the shore power inlet and the circuit breaker panel?

Ted
This is another good point. I have heard of some galvanic isolators who's control panels can cause RCDs to trip. The LEDs that indicate line power shunt enough current to ground to trip the RCD.

This is another way that a single RCD per dock is potentially problematic. If each boat has a tiny, but acceptable amount of leakage - say 1-2 milliamps, and you have 20-30 boats on that dock, they can collectively trip the RCD. Even though all boats are individually working just fine, if you hook up enough of them, it pushes things over the edge. The last boat in trips the breaker, and gets blamed for everything.
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Old 02-12-2017, 06:57 AM   #12
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If turning off all the house breakers doesnt work, try the breakers on the noisemaker , even tho its not running.
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Old 02-12-2017, 07:47 AM   #13
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In your case, the breaker still tripped, so the problem is in the wiring before all your breakers. Most likely you have a connection on your boat between the shore power neutral and ground wires. There should not be a connection when on shore power. When the two are connected, the return current splits up and follows both the neutral and the ground back to the power source. The RCD sees that the line and neutral currents are different, and trips.

Useful post.

Does the last para suggest that maybe SeaSalt's issue could be as simple as a shorepower cord problem? Different cord, all fixed?

-Chris
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Old 02-12-2017, 08:16 AM   #14
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Useful post.

Does the last para suggest that maybe SeaSalt's issue could be as simple as a shorepower cord problem? Different cord, all fixed?

-Chris
I hope so. In my continuing habit of throwing money at whatever my current boat is...I plan to install a Glendinning Cable Master in the space where the former owner had just placed a new Village Marine No Frills 450 water maker, which I will never use. It is coming out and will be on the market.
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Old 02-12-2017, 10:27 AM   #15
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I hope so. In my continuing habit of throwing money at whatever my current boat is...I plan to install a Glendinning Cable Master in the space where the former owner had just placed a new Village Marine No Frills 450 water maker, which I will never use. It is coming out and will be on the market.

Could be easy enough to diagnose with a borrowed cable and a tester capable of sensing RCD?

We had a Cablemaster retrofitted; works great.

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Old 02-12-2017, 12:29 PM   #16
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I just completed, as the prime contractor, the installation of a new 600 foot main dock with 70 foot side tie slips. I contracted the electrical for a 150 KVA transformer and 2 x 50/125/250 outlets at each slip plus other amenities like a party deck at the outer end. Each power tower has it's own GFCI as we are in fresh water and stray current can be deadly. We had one incident when an older steel hulled boat came in and complained that our power was no good. I don't think so but he was sure it was not him,,,,,,




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Old 02-12-2017, 01:46 PM   #17
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Useful post.

Does the last para suggest that maybe SeaSalt's issue could be as simple as a shorepower cord problem? Different cord, all fixed?

-Chris
Very unlikely. If the ground and neutral are bonded on the boat, I expect it would be in or around the main electrical panel. It could also be at the generator, and not being disconnected when on shore vs gen power. Or inverters are another possible location.

For the shore power cord to be at fault, the wires in it would have had to become crossed somehow, which I seriously doubt. Not impossible, but far from the first place I'd look. I think the easiest way to test would be to plug in the cord with the boat end disconnected. If the cord itself is bad, it should trip the RCD.

Another more subtle cause could be built up dirt and salt at the inlet fixture, or the cord ends, allowing enough leakage current to trip the RCD.
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Old 02-12-2017, 02:16 PM   #18
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My first guess would be the shore power circuit. Not the cord itself but the plugs and sockets. Open them up and see if there is any corrosion present. It is very common for some green corrosion to make a high resistance leakage path between wires.
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Old 02-12-2017, 05:26 PM   #19
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Let me make a case against pedestal GFCIs.

First, I guess I can accept them in fresh water situations. A fault to ground PLUS a faulty ground can cause a hot boat. If the ground is good, then there should be no chance of a potential at the boat's external metals. But if you have a hot leaking to ground inside the boat and the ground is open, ie not connected to shore, then the thru hulls and prop shaft can be hot and with the low conductivity of fresh water, I can see how electrocution could happen if someone is swimming nearby.

But salt water has good conductivity and any such double fault should not build up potential on the external metals as it will bleed to (real) ground.

But the reason for GFCIs often stated is that they protect occupants. Well if so, why don't we have GFCIs on the incoming power to our houses. The NEC only requires circuits in the kitchen, bath and outside outlets to be protected by GFCIs. Boats are just floating houses (ignoring the underwater metals situation discussed above) and all boats built during the last 20 years have GFCIs protecting the outlets in the galley and head.

The shore power supply is analogous to the feeder from your power company that ties in to your main electrical panel. The only difference is that the shore power cord can be disconnected.

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Old 02-12-2017, 06:32 PM   #20
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I think it's because a shore power connection has all the same qualities as an external outlet. In fact, that's exactly what it is, just a bit higher power than your typical outside house outlet. If our boats were hard wired like a house, I'd agree. But since we plug them in while standing in a wet environment, it seems reasonable to be that they should be protected the same as other outside outlets.
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