Shore Power Alternative

[Kevin]

ABYC Electrical Compliance Guide

In response to Sam, you can order the ABYC Electrical Compliance Guide, and another bookentitled "Boatowner's Illustrated Handbook of Wiring" by Charlie Wing from the webpage: www.abyc.com/newpage3.htmNigel Calder's "Boatowner's Mechanical and Electrical Manual" is another good reference.The ABYC standards are there to protect you fromshock, reverse polarity, limit the effects of a lightning strike and electrical current in the water from other boats due either to shorepower wiring faults or wiring faults on other boats (which is why no one ought to go swimming in a marina). As Ben has said, electrical wiring onboard that does not conform to ABYC standards will reduce to nil the chances of a successful claim related to electrical problems (on your own boat or causing a problem on another boat) against your insurance.Sam if you have a H23, then you have a steel keel and steel bolts attaching the keel to the sole of the fiberglass hull. With respect to the example of the microwave oven, it will likely function on reverse polarity as noted by another contributor BUT the cabinet is part of the grounding system for safety reasons and reverse polarity circumvents this protection. This will also hold for other but not all appliances.

 

[Mark Kissel]

Dear Confused - Part One

Hi Sam,For those interested, please read on. For you others, please forgive this lengthy reply; you can stop here.AC or alternating current has no polarity. It alternates between a maximum positive and a minimum negative voltage at a frequency of 60 Hertz (120 transitions per second) here in the US. Thus, a microwave oven and heater will operate in the same manner regardless of whether the line (black) wire or white (neutral) wire is the "hot" side.So why are there devices with polarized plugs? As Kevin mentions, for safety reasons.Let's take a look at a simple electrical circuit; a voltage supply, on/off switch, and electic motor. In this case, the voltage supply will be a 120 Volt outlet, properly wired and grounded. In order to power our motor, we must connect it to the outlet. We need the switch to provide a way to turn the motor on and off as required.Scenario 1: From the hot side (black wire) of the outlet, we plug in a wire. We then connect the other end of this wire to one side of the switch. From the other side of the switch, we connect a wire and run it to one side of the motor's windings. Then connect a wire to the other side of the motor's windings and run it back to the outlet's neutral (white wire) side. So we now have a loop from the hot, through the switch, through the motor, and back to the neutral.If the switch is open (off), there is no current flow through the motor's windings and nothing happens. Close the switch, current flows, and the motor spins.For now, let's leave the switch open. If we take a voltmeter and insert one probe into the neutral side of the outlet and place the other probe on the motor side of the open switch, we will read zero volts. In fact, we can place the other probe anywhere in our circuit except on the outlet side of the switch and still read zero volts. In other words, the motor windings and its wiring connections are at zero volt potential. Why? Because the neutral wire is also at zero volt potential.Scenario 2: Now we will make only one change. Let's reverse the two wires plugged into the outlet. The wire leading to the switch is at zero volt potential since it is plugged into the neutral side of the outlet. But look at the rest of the circuit...connected to the hot side of the outlet. Now the motor windings and its wiring are at 120 volt potential. If we close the switch, current flows and the motor spins.So what's the difference? In scenario 1 leave the switch open, grab a bare wire at the motor winding connection, and nothing happens. In scenario 2, leave the switch open, grab a bare wire at the motor winding connection, and you receive an electrical shock.Continued in "Dear Confused - Part Two"

 

[Peter]

Keep going Mark

Tell us about the part where the outer housing of electrical appliances used to be connected to the same (so-called) ground wire!! I got zapped by the fridge as a kid because the plug was in backwards. In those days, nobody thought AC even HAD reverse polarity. How could it if the current was changing polartity 120 times a second?As Mark pointed out, the problem was caused by the way devices were wired to the AC mains, not the current itself. Today, we know better, which is why we have three conductor wiring, polarized plugs, double-pole switches and GFI circuit breakers. These developments occurred because people were being shocked, burned or electrocuted.My feeling is that if you truly understand good electrical practice then do what you want and more power to you (no pun intended). If not, follow the appropriate standard.PeterH23 "Raven"

 

[Kevin]

Reply to Peter

Peter: Electrical appliciances such as ovens and clothes dryers in the United States still connect the cabinet to a single ground wire (as distinct from neutral). The appliance pigtails have only 3 prongs. Our cousins to the north in Canada use a pigtail with 4 prongs. That's right, 2 ground wires using a separate ground for the cabinet. So if the appliance shorts to ground, the cabinet is not "hot." This standard is also required in Canada for recreational vehicles. A light bulb is a pretty simple electrical device so why do I have a lamp with a two-prong polarized plug when the chassis isn't even grounded? Because that's the way the plugs are made today. On the other hand, I have a handheld electrical drill (AC motor) manufactured the same time as the lamp without a polarized plug. Should I worry. Nope. The drill is double insulated. The chassis is insulated from both lines (be they hot or neutral). Too bad Peter's fridge wasn't double insulated.

 

[Mark Kissel]

Dear Confused - Part Two

Okay Peter, let's talk about the cabinet.Let's take our simple circuit and install the motor in a metal box with just the shaft sticking out. We'll also cut holes in the box to mount the switch and to pull the black and white wires out for the outlet. We have now solved the problem associated with scenario 2. With all bare wire connections inside, we can't physically touch a "live" wire and be shocked. If it were a perfect world, we could stop here.Consider scenario 2 for a moment. What happens if the motor's winding breaks and comes to rest against the metal motor housing...connected by metal screws...to our metal box. Remember, the motor and all of its wiring is at 120 volts in scenario 2. So we now have a metal box at 120 volt potential. Assuming our feet are in contact with a surface (earth, water, etc.) at zero volt pontential, and we touch the cabinet with our hand, a circuit path is formed through the skin (a pretty fair conductor) of our body and current flows. A rather clinical way to say we get a nasty shock, or worse, electrocuted.So how do we resolve this problem? What if we attached another wire to the metal box and connected the other end to the ground opening in our outlet? Let's call this a ground wire. Now we have a really good (copper) conductor with a circuit path from the box to ground. If that wire breaks loose in the motor's windings and 'short circuits' against the motor housing, the ground wireprovides an almost perfect path for current flow. Why? Because the ground wire offers very little resistance to current flow. In AC circuits, resistance is known as impedance. What happens if we touch the metal box now? Our body now forms a parallel connection with the ground wire. But, because our body has a much higher impedance than copper wire, very little current flows through our body. The resulting shock is usually anything from a tingling sensation up to minor burns. There is little chance of electrocution. Problem solved now? Not exactly.Because we have now attached a ground wire that allows current to flow from our damaged motor windings to ground, a secondary (and likely a much more serious) problem can develop; overheating. The motor windings might fail in a manner that causes overheating and develops into a fire.To solve this problem, we can attach a breaker to the outlet supplying power. If the short circuit allows an almost zero impedance path to ground, the current quickly rises and overwhelms the rating for the breaker, causing it to trip (turn off). Now is the problem solved? Not exactly, again. Grrrrr. Now what?In rare circumstances, a short circuit may develop with a fairly high impedance path to ground. This keeps the current draw below that required to trip the breaker. However, part of the short circuit path may involve a component that normally expects to "see" a much lower current level in normal operation, and now is suddenly overwhelmed. This component may then heat up and ignite.Should you rush right down to your boat and check the polarity of your shore power outlet? No. But it IS a good idea to check and make sure it is proper. If you are unsure or do not want to do this yourself, any qualified (liscensed) electrician can do it for you. Check references.So, Lee, now you know all the deep dark dangers of the "Reverse Polarity Syndrome". The bottom line is if your polarity is correct, you stand very little chance of being injured or starting a fire. If your polarity is INCORRECT, you still stand very little chance of being injured or starting a fire, but the risk does increase. You decide.Kevin, lamp plugs are polarized to minimize the chance of the socket base and harp from becoming energized.Ben, if you deny claims based on whether or not a system meets ABYC standards, I would think you'd be setting up a lot of "bad faith" civil suits filed by your insureds. I bought the boat, you insured it, I pay my premiums, a fire occurs due to a faulty ignition switch. The problem is determined to be a non ABYC approved installation by the manufacturer. Pay my claim, you can subrogate against the manufacturer to get your money back. End of discussion.Sam, I'm no fighter pilot, just a dumb old country boy with a little bit of education.Mark KisselKittiwake 98H240

 

[Kevin]

Thanks to Mark for Part Two

Mark: Thanks for your very clear discussion in part two and noting the hazard associated with the socket and harp for the lamp that requiresa polarized plug. - Kevin.

 

[Sam Kurtz]

So, Where's the Danger and What's the Standard?

I have a Hunter 26 a Guest battery charger mounted to the side of the compartment it is in a plastic case that I am not sure I could get into if I were inclined to anyway. It has a molded plug that I plug an extension cord into. Occasionally I also plug in a fan or a light. I use one of those little yellow gadgets that determine if your circuits are correct once a month or so to check my GFI I will probably buy another one to put on the boat so that I do not have to dig around in the junk drawer to find it every time. Here is the $64 question how is a $350 shore power installation safer than my $30 10 gauge extension cord? None of the other posters who were trying to frighten everyone has mentioned what in fact the standard is. Do I somehow need to ground my boat? I have no metal or any holes at all under the waterline and do not intend to install one. The only other thing I can think of for Lee to do on his is to maybe box in the microwave so that the metal cabinet is not exposed but I do not think I would bother.Wasn't the a guy who had a 260 up in Atlanta who was an electrician and had installed a shore power setup on his? Would be nice to hear his thoughts on this.

 

[Michael Bell]

Perhaps I can simplify this…

Check with your marina. They might not allow you to use an extension cord.

 

[Kevin]

Reply to Sam

Sam: If you have no metal on your boat below the waterline, how do you dissipate the energy of a lightning strike to the mast on your Hunter 26? My Hunter 23 came from the factory in 1985 with the mast step plate on the deck bonded to the steel keel with 8 gauge wire. - Kevin.

 

[Crazy Dave Condon]

Electrifying

28 posts and this makes 29. Boy I did not think this would go into outer space but I think the message has gotten across on what ever you do, be careful as water and electricity do not mix. Can we put this to rest. Thank you.Crazy Dave Condommmmmmmmmmmmmm