How to determine if my boat has an electrical "leak" - SailNet Community
 
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post #1 of 9 Old 04-20-2007 Thread Starter
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How to determine if my boat has an electrical "leak"

In another thread where I solicited opinions on what might have caused my rudder to break I posted a picture of the upper portion of the stainless steel rudder shaft which showed copper deposits on the end. This was 4 weeks after the incident and I have been in a marina and hooked up to electricity the whole time. I used the air conditioning units much of the time and the only other AC use was charging of cellphone, shaver, notebook, VHF and other small battery devices.

All I have onboard as diagnostic equipment are two multimeters which (surprisingly) read the same.

The boat electrics are:
- 220v AC system
- 220v Generator (used for 5 minutes runtime in the 4 weeks, just started it to see if it was still functioning correctly)
- 4 house, 1 engine batteries connected to a Cristec CPS600 charger.
- Alternator attached to engine. (used for about 2hr tt in 4 weeks, bags of ice @ $4 were better than running the engine to cool the beers)


I would very much like to hear suggestions as to what I can do in order to determine if I have an AC or DC "leak" given the instruments I have available. Or, if not, what I would need to get in order to do so. Or if I should sail to St. Maartin and find a pro to do this analysis for me.


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post #2 of 9 Old 04-20-2007
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I don't think you can do it with the instruments/tools you have at hand, because I believe you need a silver/silver chloride test electrode to do the testing with for galvanic corrosion issues.

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I found This article that seems to make sense and would allow me to use a multimeter. Is it misleading (apart from telling me how to catch more fish by charging my boat electrically)?


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post #4 of 9 Old 04-20-2007
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Zanshin-

If you want to test to see if you have a DC-based ground leak, the test for that is rather simple. The steps for seeing if you have a DC-ground leak are as follows:

First—the preliminary diagnosis test:


1) Turn off all equipment and disconnect any solar panels
2) Disconnect the positive side of the battery banks.
3) Leave the main battery isolation switch turned on for the bank in question
4) Set the meter to VDC mode, range appropriate for your battery bank
5) Connect the meter between the positive terminal and the disconnected cable

The meter should give no reading. If it reads XX volts for your XX VDC system, one of two things is happening.

1) You've left some equipment connected and turned on. This could be a bilge pump, a power feed to a stereo for the radio's memory and clock functions, or a hard-wired fume detector.

2) If you've disconnected all the "hard-wired" equipment and still get a reading, then you've most likely got a ground leak in your boat's DC system.

The Ground Leak Check:

1) Set the meter in Ohm mode and set it to the lowest range (x1).
2) Connect the leads of the Ohm-meter (or multimeter in Ohm mode) to the disconnected positive lead and the negative terminal of the battery.

The meter is now reading the resistance of any circuit to ground that exists in the boat's wiring. The reading on the Ohm meter display can help you identify the cause of the leak.

0-10 Ohms means it is most likely a piece of equipment left on
10-1k Ohms is a low-drain piece of equipment left on, or a serious ground leak
1k-10k Ohms is a minor leak
10k+ Ohms is an insignificant leak

How Big is The Leak?

The ammeter function of the multi-meter can tell you what the current leakage is. If your meter can read up to 10 Amps DC, then you can use it to measure amperage for leaks down to about 1.3 Ohms resistance on a 12 VDC system, or 2.6 Ohms for a 24 VDC system.

To see how big the leak is, put the probes on the positive battery post and the disconnected cable. The meter readings can be interpreted as shown:

<1mA — insignificant leakage
1–10mA — minor leakage
10mA–1A — major leak or some equipment left on
>1A — Usually some equipment left on.

I'm not sure how to test for a ground fault in the AC side of your boat. I hope this helps.

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post #5 of 9 Old 04-21-2007
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If Your hooked into shore power 220v you should have a four wire plug.
Two hots a nuetral and a ground. Test for continuity At the end of your cord that plugs into the dock with the cord pluged into the boat touch one lead to the nutral leg and one to the ground and see if you get a reading. plug it bck into the dock unplug the boat and test for voltage at the neutral and ground for the dock. To be right there should be no voltage here.
wooa 220 US or euro? I HAVE NOT BEEN SHOCKED BY EUROPEAN CURRENT YET meaning i no nothing about it.

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post #6 of 9 Old 04-21-2007
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I bet it's mostly simple metal fatigue hastened by an undersized designed diamater shaft that caused this failure. But this has already been posted elsewhere. Heck, mostly everything will break, fail, fall apart, rust, or if it hasn't, then it will get stolen eventually. An emergency rudder isn't a bad thing aboard, but the price of that replacment rudder would make Howard Hughes ghost choke. I think that I would skip carting a second one of those aboard. I don't think that you will find galvanic corrosion, unless I misunderstand the design of your rudder. What are the dissimilar types of metal near or at the breaking point? Working with steels in a machine shop for some years it was unbelievable the "stuff" that would show up in assorted varieties of metal including thompson shafting round stock. Some of the impurities were incredable. Quality control can go missing at times.
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post #7 of 9 Old 04-21-2007
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It is very advisable to have an isolation transformer between shore power and your ship's AC electrics. There is always a danger in the polarisation of both the shore neutral and earth lines that may raise your ship's "earth" to a significant DC voltage. I have observed typically 9V.
Try using your volt meter between your DC earth, then +ve, and water (hang a wire over the side, or use your SSB ground plate), with and without AC plugged in (and I mean take the AC wire back on board).
You may need to experiment with switching various DC circuits on an off to find which ones are opening up a pathway (if that is the case).
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post #8 of 9 Old 04-21-2007
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If you are looking for gross current leaks, and absolute lab reference accuracy is not an issue, I would think that picking up 50' of tinned stranded wire or any reasonable guage (even 18-22g) and using it to extend the voltmeter leads (so you can measure, say, from the engine ground or shaft up and out and around the outside of the hull) would be meaningful.

You will still be measuring the voltage from "here" to "there" and if there's stray voltage/current, you'll still be measuring it, no?

In theory there's some current from your zincs, you'd have to find out what that's supposed to be and take it into account. As a practical matter, if you ran some tests while your boat was just anchored out, and then repeated them in the marina...you'd have some good comparison points showing whether there was excess current in the marina.

And in theory...since a "neutral" wire on the AC box is supposed to be at ground, I have to wonder if you just dropped a line form neutral into the water, if the GFI tripped, wouldn't that mean the neutral and ground had a problem?
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post #9 of 9 Old 04-22-2007
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This is why I hire a marine electrican and not a shoreside electrican.
But what I understand is that the shoreside ground and the vessel's ground should be isolated from each other. Vessel's ground and neutral are not quite the same.
But you know you have problems as I have found (the hard way) when you get a shock from the housing of any electrical equipment you may have on board. I have been shocked from searchlights (was turned off) and Fathometer's housings (off or on). So you may have to check for leakage at each piece of electrical/electronic equipment you have on board.
But doing a electrical survive before calling the electrican will help him in running down the problems. Or at least a starting point. Because that starting point maybe just the first link on a chain of related problems.
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