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Old 06-09-2012, 12:10   #1
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A Marina in Need of Advice

Hi i work at a hotel and marina in south eastern Massachusetts. Having no experance working on a marina doing maintenance often offers a lot of learning experances. The boaters on our marina are complaining that recently they are going through a lot of zinc. I read the thread that addressed burning through zinc : Zincs and the 'Hot' Marina I have tested the power pedestals as "EngNate" mentioned with a pencil zinc and a multimeter and it ranged between 120m DC and 140m DC. I am not sure exactly what that means though. it seems from what i have read to be good. Am i correct in saying this implies that it is not a hot dock? The boats here are well kept, 1/3 of the boaters here spend every weekend living on their boat (some stay all week). Please help, my boss is on my back for answers.
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Old 06-09-2012, 12:15   #2
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Re: A marina in need of advise

experience*
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Old 06-09-2012, 12:17   #3
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Re: A Marina in Need of Advise

ACK "A MARINA IN NEED OF ADVICE" wow i cant spell today at all...
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Old 06-09-2012, 12:20   #4
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A marina seeking advice...

A marina seeking advice...
Hi i work at a hotel and marina in south eastern Massachusetts. Having no experance working on a marina doing maintenance often offers a lot of learning experinces. The boaters on our marina are complaining that recently they are going through a lot of zinc. I read the thread that addressed burning through zinc : Zincs and the 'Hot' Marina I have tested the power pedestals as "EngNate" mentioned with a pencil zinc and a multimeter and it ranged between 120m DC and 140m DC. I am not sure exactly what that means though. it seems from what i have read to be good. Am i correct in saying this implies that it is not a hot dock? The boats here are well kept, 1/3 of the boaters here spend every weekend living on their boat (some stay all week). Please help, my boss is on my back for answers. (I am new to online forums)
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Old 06-09-2012, 12:24   #5
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You should contract with a reputable electrician who is familiar with marinas and ground leakage. In the long run it will prove less expensive than chasing faults that you may not fully understand.
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Old 06-09-2012, 12:24   #6
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I have replied to your other thread
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Old 06-09-2012, 12:36   #7
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Re: A marina seeking advice...

I worked as an electrical apprentice for 5 years and went to school for 4 years learning code, but i only worked in residential. I want to understand it myself. Its been a while since i was in school and i havent done much other than maintenance since i stoped doing electrical full time. I am hoping someone can give me a little help. (but spelling it out for me is O.K. too)
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Old 06-09-2012, 12:47   #8
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Re: A marina seeking advice...

Quote:
Originally Posted by Landlover View Post
I worked as an electrical apprentice for 5 years and went to school for 4 years learning code, but i only worked in residential. I want to understand it myself. Its been a while since i was in school and i havent done much other than maintenance since i stoped doing electrical full time. I am hoping someone can give me a little help. (but spelling it out for me is O.K. too)
I can't help (it's all electrickery to me ) - but a free thread bump might help attract those who know about such things (and there are a fair few here - so worth checking back in)........

......but nonetheless, just to say that fair play to you (and the Marina) for actually wanting to get this sorted. and IMO you are going about it the right way in trying to also understand WTF is going on and not simply going down the waive a cheque route at someone who knows (or claims to).....will likely be cheaper for the boss as well .
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Old 06-09-2012, 12:49   #9
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Keep on mind that a hot dock can be caused by one boat. It may even be a piece of equipment plugged in on an otherwise good boat.

Beyond that you should be plenty able to find a ground with current, I'm less qualified than you and have found leakage with persistence.
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Old 06-09-2012, 12:52   #10
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Re: A marina seeking advice...

You should also consider the risk that a "hot dock" may be the result of a "hot boat" in the vicinity of the boats with the zinc problem. A boat may be "leaking" current into the water through improperly wired equipment such as bilge pumps, or a leaky power cable immersed in the water between the pedestal and the boat.
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Old 06-09-2012, 14:05   #11
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Re: A Marina in Need of Advise

Threads combined.
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Old 06-09-2012, 14:35   #12
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Re: A Marina in Need of Advise

Does your power system have ground fault detection?

It would seem if you had a hot boat on your system it would be tripping all the time.

I see that Eaton makes a ground fault monitor. Its just a box with a red green and yellow light.
Marina Ground Fault Monitor

I like the Bender Marina guard. It has more lights.
http://www.benderrelay.com/datasheet...0book%20V2.pdf

They have a good method for detecting the fault if its a customers boat.
1. Install the ground fault detector.
2. If it shows a fault, walk around the docks turning off breakers or disconnecting boats until the fault disappears.
3. The last boat disconnected is the culprit.

An alternative is to shut off all the boats, and turn each one on until the problem appears.

When done turn on all the boats, so the frozen food doesn't go bad. And of course notify everyone before you do this.

Me: I'm and Electrical and Software engineer, but I only sail, don't work in a marina.
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Old 06-09-2012, 14:49   #13
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Re: A Marina in Need of Advise

Let me provide a few comments. My degree is in electrical engineering, but I am actually a bit rusty when it comes to the basics. Since differing metals placed in salt water create a battery electrons migrate from one electrode to the other. But not only do electrons migrate but also some of the electrodes metal will dissolve and migrate to the other. We use zincs since they act as a primary electrode and break down in the process protecting the ‘good’ metal on our boats. As current increases, the overall process increases or speeds up. So increased current means the zincs break down quicker. Often a boat with experiencing hastened zinc reduction the issue is due to bad wiring particularly open or bare wires or connectors especially in the bilge which adds to the current flow through the zincs due to the ‘leaking’ current. In the case of shore power, voltages and currents are increased and if there is ‘leaking’ zincs will be lost faster. And the goal in the case of a ‘hot’ dock is to locate increased current or current loss causing the premature zinc reduction.
There are a few likely causes. From the marina standpoint, the areas of direct responsibility are in the wiring and pedestals. Specifically check if each circuit isolated (any voltage/current on circuits not in use) and if each neutral and ground clean and properly grounded (check for high resistance and/or voltage drops). Unfortunately for the marina the usual culprit in a **‘hot’ dock is a wiring issue with one of the boats or improper shore power hookup. On a recent visit to a local marina I noticed one guy had what appeared to be a basic extension cord running from a pedestal into his boat with it running through the water between boat and doc.
A few thoughts on troubleshooting and isolating the issue. There should be a region of the marina that appears as hot (more zincs being rapidly depleted compared to others). Of course this depends on observations and reports from the customer base. If you have individual meters on the pedestals than you may be able to find a specific circuit and/or boat with a high usage. If there is no noticeable concentration of zincs being lost the issue most likely is either dock wiring where one or more circuits are compromised and serving multiple locations, or a frequently overlooked issue – power spikes or surges. Surges tend to be very difficult to troubleshoot since they are intermittent and are the result of a boater’s equipment.
Once the issue(s) is found, the fixes should be straight forward. From the marina standpoint, addressing bad wiring or pedestals is normal stuff. Adding surge protection, especially at the pedestals, may be rather effective but may be costly. The use of a monitoring box(es) that record usage and max power may prove beneficial not only to help isolate issue location(s) but also to assist if the issue lies with a boat and not directly the marina.
Sorry about being long winded.
Hope that helps, at least to get the thoughts focused.
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Old 06-09-2012, 15:39   #14
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It still amazes me that US docks don't fit ground fault interrupters ( RCBOs) to each pedestal as a matter of course

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Old 09-09-2012, 11:06   #15
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Re: A Marina in Need of Advice

GFIs on the dock only see half the problem. A hot boat leaking DC into the water or injecting DC current into the ground lead will not trip a GFI.

With years of experience I can say that running round and measuring the voltage in the water, even with the right equipment, will give you a mountain of data that defies analysis, even by experts.

If a particular boat is having problems thier first line of defense is an isolation transformer but since most can't afford the cost, space or weight a Galvanic Isolator is $100 of insurance well spent.

If the AC Voltage across the isolator is greater than about 0.75 volts then the methods suggested above for isolating the culprit can be used. I've measured as much as 5 volts AC on a marina ground. While the hot wires were 10 gauge or heavier the ground wire was only 16 gauge. It only takes one miswired boat returning current via the ground instead of the neutral to create havoc on the light gauge ground wire.

The most common cause of boats putting AC current on the ground is a combination of two things. First is a not uncommon wiring error (especially if the boat is using a domestic house breaker box) where the neutral and ground are connected together. This is WRONG. Then if that boat has a faulty shore power connection and loses the neutral the problem is compounded when the current flows back in the ground lead.
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