Electrical Problem

[NYSail]

Hello all, I am thinking I have a ground fault problem on my boat and need a marine electrician as I have minimal knowledge of how the systems are run.

I keep my boat on Long Island New York in Pt. Jefferson area (North shore). I was refered once to a regular electrician, however he did not give me the confidence that he knew about marine DC / AC systems.

Thanks!

 

[Tim R.]

Any well regarded boat yard should be able to help. They are usually very knowledgable in the 12/24v stuff. Conventional electricians usually are not.

What is the problem? We have lots of smart folks here.

 

[NYSail]

Hello....When I bought the boat 4 years ago, I had a stainless steel housing for my centerboard cable that looked like swiss cheese......welder said it appeared to be from significant galvanic corrosion. He completely rebuilt the peice for me. Also, when going over the boat....I found an unattached ground wire with one end attached to the engine mount (with other wires connected there) and the other end sitting in the bilge. I never found where this needs to be connected so it remains unconnected, however now neatly bundled and not sitting loose in the bilge. This year at haul out, yard said my prop looked funny like it might be getting "zapped" and also showed me that my cotter pin holding my prop nut was almost completely disolved. Zincs were still viable on the shaft (2) although my bow thuster zinc was completely gone.

One other thing, last year I was working on the boat while on the hard I had the boat shore plugged in to AC power recharging batteries using an adapter. I then ran an extension cord from an outlet in the boat and plugged my sander into it. While sanding the strut I felt an electrical current....very noticable but not enough to knock me down or anything. I checked the electrical cord running to the shore outlet and found the ground plug had fallen off. When I replaced the cord, the strut did not have an electrical current. I always wondered why I was getting a shock from the strut.....and now think something may be miswired.

My problem is that I do not know much about electrical grounding. I have many books, however just do not want to apply my interprutations. These situations may not mean anything and maybe the problem had been solved by the previous owner (new charging system was installed 1 year prior to purchase)...however I thought I would have a pro come and give me an opinion.

Thanks

 

[RAD]

Call me about this, I might be able to help and I'm local
516 592 7780

 

[sailingdog]

Checking for a DC ground fault is usually pretty simple on a boat. I've posted directions for doing so on another forum and can do so here if you'd like to take a shot at diagnosing this yourself. It does require that you know how to at least use a volt-ohm meter.

 

[NYSail]

Would love to see the method as always love to learn

Thanks!

 

[sailingdog]

NYSail-

Here it is:

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.

Any questions, let me know.

 

[Don S/V ILLusion]

The above won't adequately check for a grnd leak unless you are either very lucky or very careful, e.g., even a voltmeter left in the circuit will provide a false reading as it acts as a shunt to grnd.

The is a better desc in Calder's manuals too long to quote here.