Shore power possible short

Jay,

Had to respond here. Your "shore power" must be grounded. Otherwise, all your ac on board will be ungrounded whether it is properly wired or not. Then you want a GFCI device. In fact, by code, your outdoor receptacle is supposed to be GFCI protected...but you should have one on board anyway. This can save your life. Cheap insurance. Your charger should have a "bonding" lug on the outside of the case which is supposed to tie into your DC ground system. The point of this is to provide a path to the shore power ground (which you don't have) to protect swimmers from stray electrical currents when you are plugged in to the shore power at a marina.

Rusty
 
Just came in from working on this problem.

Randy from the shore power connection on into the boat the system is c-dory installed with a Quest charger so is grounded when connected at a marina.

At the present the boat is sitting on a blocked trailer with power coming from my outside shed, which is essentially my homes electrical system. The unusual circumstance that is either compounding the problem I'm experiencing or possibly is the problem is my home is the old two wire system. Think old home in rural Wyoming shed and electric outlets installed about l930. The old style two wire system only has a neutral and hot vs present being neutral, hot and ground, which is whats in the boat and the West Marine 30 amp marine cord going to it and is connected to the shed power with a two prong adapter. So into the boat's neutral, hot and ground is only going neutral and hot, and at the present you're right the boat is not grounded.

Yesterday I was getting 110 VAC from motors to actual dirt ground. The boats breaker control was saying the polarity was ok, but as Bob Austin said without a ground it may not be working. So tonight checked the polarity at the shed and found the neutral and hot reversed at the shed outlet. Thought Eureka!! problem solved. But when I again checked the motors to ground the voltage was now just under 60 VAC, so then went back to the shed outlet where the boats ground comes back into the two plug adapter and found that ground to register the same just under 60 VAC, that I found between the motors and the dirt ground. The additional very strange factor is this voltage only registers on the meter if the meter ground probe is put on the outlet and the positive probe to dirt ground and it works the same at the motors the negative probe must must on the moter and positive meter probe to dirt ground to register the voltage. The meter registers a normal hot 120 VAC with either probe to hot or ground.

I can and will ground the plug at the shed outlet, so the boats AC is grounded when plugged in as Randy and others have suggested, but can I install a GRCI with my present home 2 wire system.

Jay
 
Have a look at this article - pretty good on the 2-Wire versus GFCI accomodations. http://ecmweb.com/mag/electric_replacing_wire_ungrounded The bottom line is you can but you MUST mark the GFCI as non-compliant (unless you drop in a ground somewhere in a subpanel perhaps or you remove the 2-wire and go 3-wire from your service panel). Marking the GFCI as non-compliant is what's required from my understanding. I've done a bunch of old 2-wire to 3-wire upgrades - tons of work.
 
First a little AC electricity 101. The 'hot' provides power to the load and the neutral returns it to the source. That is at least for a half cycle. It then reverses the direction of current flow. That happens 120 times a second (60 cycle AC). For the circuit to work it does not need to be grounded and indeed it isn't in some applications. To provide a measure of safety, one side of the source is bonded to ground (that would be the neutral). For those of you who are wondering, the midpoint of a typical 240 volt transformer winding is bonded to ground which gives you two legs of 120 volts to ground or 240 volts between the legs. We however are only concerned with one half of the winding or 120 volts. In the interest of safety the Americans run a third wire out to the shell or frame of the load called the ground. In Europe they take only two wires to the single phase load which is 1/3 of a 3 phase 220 volt ungrounded delta system. I've never been to Europe but I've hooked up some of their machines that make it over here. Back to our problem, we have three wires going out to a typical modern load i.e. your battery charger. Here are a few ideas that could be your source of stray voltage. First you could have a completely normal functioning 3 wire circuit and still pick up stray voltage. In this scenario you could have your house panel feeding your garage and your garage panel feeding your load. If your load is between your house and garage you could set yourself up as a shorter return path back to the source (house) as a parallel resistor. Then you would only feel a tickle as most of the current would return through your power cord to your garage and then back to the house. Remember electricity takes the path of least resistance but it can take multiple paths and not violate any laws of nature. This is unlikely but it could happen if you have low skin resistance. The next scenario is you have a weak link in your neutral connection. If there is a higher than normal resistance anywhere in the neutral conductor and you have leakage in the load or circuit then you can become a parallel pathway in that circuit by touching a conductive part in that circuit. You would need to check all neutral connection points in main panels, sub panels, meter bases, and branch circuits. Check to make sure the the neutral buss is bonded in your main panel. If you are feeding the load from a sub panel make sure you have a good ground that is separated from the neutral buss by it's own ground rod or preferably a separate ground wire from the main service or both. Now the old two wire 110 volt systems. There was no ground reference. There was no ground wire. As old fuse boxes were replaced with circuit breakers, grounds were generally established thru the new panels and meter bases. That would give you a reference to ground but no return path through a ground wire. GFI outlets are allowed by code to replace old two wire receptacles. First off a GFI outlet will not eliminate stray voltage. All GFI will do is trip if the power leaving the receptacle does not equal what is returning to it through a load. If there is an unbalance of 3 to 5 milliamps the GFI will trip because it maybe going through a human being. You can feel and measure that potential without tripping the GFI as long as you are not consuming more than 3-5 milliamp trip threshold of the GFI. The next question would be where is the stray voltage coming from that I'm getting from my boat. Any portion of that circuit that is wet and touching metal parts would do it. It could be a partial short that is bleeding through compromised insulation that is worn or pinched. Could be a interwinding short in the filament transformer of your battery charger. Could be induced voltage from any inductor that you have on board such as fans, heaters, or dual voltage refrigerators. If it tickles you I doubt it is induced. Buy one of those cheap outlet testers that you plug into a three wire u-ground receptacle. It should tell you if you have the hot and neutral reversed in your old two wire system. Find a friend or neighbor who has a three wire system and plug the tester into their outlet. If your tester reads correct polarity plug your boat into it and see if you still have problems.
Forrest
 
Forrest excellent explanation. Your last statement is why I previously suggested doing further tests with a power supply known to be correctly wired and grounded. I'll bet Jay finds the boat is wired correctly. I personally don't like to give to much advice on 110 volt wiring via the net because it doesn't take much of a mistake to kill someone. In Jay's case a home wired 75+ years ago will probably have alot of additions to the system that could create problems. This stuff isn't rocket science but you can quickly create a unsafe condition if not careful.
 
The batteries are charged again and the charger is in float mode, so made one more test to ground and that sneaky voltage is still there on its way from motor to ground if a route is provided. Winter hit here with a vengeance today, so this problem will have to wait to spring to be solved. Thanks all for the help and suggestions. Will hook to a known good three wire system and if that and making sure all wires and connections are good determine the problem is likely in the charger will replace it next. Only about six months or so to spring, when I can unwrap boat and get on with this.

I understand the reluctance of some to give to much direct advice over the Internet on something that could turn hazardous and sure appreciate all the advice given in what ever form.

Jay
 
I should add a little information about meters and semi-conductors before I return to lurk mode. First most digital multi-meters have an FET (field effect transistor) on the input for measuring voltage. They therefore don't consume any power. What does that mean? It means they will measure phantom voltages such as static electricity or induced voltages that have no amperage associated with it. In other words digital multi-meters lie on occasion. Examples would be static when you park your car under transmission lines, walk across carpet in dry air or measure voltage on de-energized wires that are in close proximity to energized AC or pulsating DC circuits. A potential to ground can be measured or felt but is dissipated when you become the same potential. How can you tell if it is not a phantom voltage? Use a solenoid type voltage tester or a D'Arsonval type of meter that consumes power during measurement. Second, most all semi-conductors leak. It's just a matter of how much. A leaking triac can pass enough current to power a small electrical device. A burden resister can be installed on the output to dissipate the leaking current. Semi-conductors are involved in all modern electronic devices.Good luck and I'll leave you with a final thought conveyed to me by an old electrician to me when I was a young apprentice full of questions, "Sometimes electricity can be a funny thing".
Forrest
 
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