Shore Power problem

[TravisTraverser]

I attached my shore power cable on my 1994 Larson 240 and have verified that I am getting 120volts at an outlet by using a voltmeter, however as soon as I plug a simple household fan into that outlet and switch it on, the main AC breaker throws . This applies with any other items within the boat (refrigerator, battery charger). <br />Is it likely that I have a bad main breaker? And could I verify that by bypassing the main breaker and wiring directly to the indiviual outlet breaker switch?<br />I am a novice when it comes to electricity.<br />Any and all help will be greatly appreciated

 

[Silvertip]

Re: Shore Power problem

ARRRRGGGG!!!! You never, ever want to bypass a protective device unless you are hell bent on burning your boat to the water line. Just so I understand the problem -- you say the main breaker trips. The main breaker turns off all AC within the boat. Individual breakers protect the various circuits. So which is it? The main breaker, or the breaker that protects the just the outlets you are attempting to use. The first thing to do is make sure the shore power is wired properly at its source. Reversed polarity and lack of or improper grounding can kill you so make darned sure you understand the consequenses. If shore power is wired and grounded properly, turn your attention to the boat. Circuit breakers do derate each time they are cycled so what was a 20A at one time may now trip at 15A. That alone will not create a problem for a fan but it could for higher current draw items. Do you have a big inverter or battery charger on that circuit?? If the circuit is not overloaded, it has to be either a wiring issue or a weak breaker. At most home improvement centers (electrical dept) you can buy a three prong plug with three LEDs in it for testing circuit wiring and grounding/reversals. Just a couple of bucks. Keep us posted.

 

[TravisTraverser]

Re: Shore Power problem

The Main breaker is the one that trips,. even if I just turn on the main breaker and the outlet breaker alone, with no other ones on, turning on the fan will trip the Main breaker. The outlet breaker still stays in the on position.<br />The reverse polarity light does not come on, but it does flash momentarily when the main breaker trips.<br />Would I still be reading 120 volts on the voltmeter if the polarity was reversed?<br />Thanks for the input, I promise not to burn the boat down.

 

[Paul Moir]

Re: Shore Power problem

Is the main breaker a GFI breaker?

 

[TravisTraverser]

Re: Shore Power problem

How could I determine if it is a GFI breaker? It is a 3 pole breaker with one toggle switch. The outlet has it's own GFI protection and it does not trip when the main breaker does.

 

[18rabbit]

Re: Shore Power problem

I think it is important your reverse polarity indicator is flashing when you flip the main breaker off.<br /><br />Yes, a lot of AC stuff will work with reverse polarity, some won’t. And yes, regardless of polarity the volts will read the same. Also know that unless you are using a voltmeter that is ‘true rms’ your AC voltage reading will be higher than expected, not really the voltage that you have, but I doubt that’s your problem if you are reading 120v.<br /><br />You can check for polarity with your voltmeter. At any wall plug/receptacle, the inlet for the smaller blade should be ‘hot’. Stick the red lead of your meter in there. The inlet for the larger blade is ‘neutral’, stick the black lead in there. It should read 120v (or there about) regardless of polarity. Leave the red lead in the smaller blade inlet, remove the black lead from the larger blade inlet and stick the lead in the round hole. It should read 120v if all is well. If the reading now goes to 0 you may have reverse polarity on the AC, and you need to do one more check. Remove both leads, and then stick the red lead into the inlet for the larger blade, and the black lead into the round hole. It should read 0, or there about with some millivolts. If you get 120v you definitely have reverse polarity.<br /><br />Btw, this is how your reverse polarity indicator works. It is a common light wired upstream of the main breaker with one leg on the neutral (same as larger blade inlet) and the other leg on the safety ground (same as round hole). When everything is working, there should be near 0 volts between those two. When the polarity is revered, there will be 120v between the two and the light lights up.<br /><br />Before we get to far into this I want to know why you have a 3-pole breaker? Monitoring of the hot (black) and neutral (white) is required, i.e. a 2-pole breaker. The safety ground (green) should NEVER be run thru a breaker. Do you have your safety ground (green) going thru that breaker? The AC wiring that you have, was it factory wired? Any idea how old it is?<br /><br />Btw, a GFCI breaker has a test button and a reset button on it like a (now) common bathroom outlet does. Your main breaker should not be a GFCI breaker.<br /><br />Edit: I’m thinking there is a combination of events that is happening here, and there are several possibilities for each event that will yield what you are experiencing. Your neutral line is maintaining voltage, it shouldn’t be, and when you flip the main breaker off the shortest path to ground for that voltage is thru the reverse polarity light to the safety ground. That’s the flash you are seeing.<br /><br />Start by checking the polarity of your boat’s AC. Either use your voltmeter of get one of those inexpensive testers that plugs directly into the outlet.

 

[TravisTraverser]

Re: Shore Power problem

Thanks to Upinsmoke and 18Rabbit for the in depth review of my problem. I will be sure to check for reverse polarity per the instructions. <br />The main breaker was factory installed in 1994 when the boat was built, on inspection all wiring is in almost prisitine condition. I called it a 3 pole breaker because it appears to be constructed of 3 seperate breakers, each with their own terminals, but one common switch on the center breaker unit.<br />Would the fact that the boat has an electric range and fridge along with a water heater have any impact on what type of breaker would be used?<br />Thanks again for the lesson in electricity.

 

[Silvertip]

Re: Shore Power problem

OK, we have a picture emerging here. Range, fridge and water heater are high amperage devices. Were any of these running when you experience the problem. And I guess another question is, did this problem just surface? Did you change slips? One test you might make is to flip off all breakers except the MAIN and the breaker for the circuit you plug the fan into. If the problem now goes away, you have an excessive load problem. If this is a new problem AND you just changed slips -- I'd really be wary of shore power wiring. If not, we need to think some more and right now my head hurts.

 

[18rabbit]

Re: Shore Power problem

LakeLubber – You are asking a lot of good questions. Will try to keep up with you.<br /><br />Your breaker is likely a 3-pole breaker with a single actuator for all three poles. Multi-pole, single actuator breakers are sort of common on boats. In other works, it would be ok. Not ok is having your safety ground (green wire) routed thru one of the three poles on your main breaker. Please check that out and let us know. And is that main breaker a 30-amp or 50-amp?<br /><br />All of those items you mentioned should each be on its own breaker, probably a single-pole breaker for each. I don’t think that is your problem. The water heater is a big-ticket item, it is going to suck down 12-amps, but the fridge only wants about 1-amp, and the range is probably off. One of those box-looking 20-inch fans is only 2-amps, so we are only 1/2 the way to throwing a 30-amp breaker. Oh, your battery charger probably isn’t pulling more than 2 or 3 amps.<br /><br />Btw, breakers may degrade as they are used, but depending on the type of breaker you have, it is rated for something like a minimum of 5,000 duty cycles to 10,000 duty cycles before it fails to meet spec. In other words, you can stand there and flip your main breaker on and off all day and your fingers will fall off before the breaker wears out. It is unusual but breakers do occasionally die prematurely.

 

[amirm]

Re: Shore Power problem

This sure is puzzling. <br /><br />Do you by any chance have a high power (>1500 watts) inverter/charger? If so, you may want to power that off before going too far. It should have its own on/off switch. That way, we know that is not causing any problems.<br /><br />The other thing is to use your neighbor's shore power outlet if he/she is not there to see if you have the same problem. I often find that one slip may have a reverse polarity but the other does not.<br /><br />If none of this does anything, then I would think the only calprit would have to be the main A/C breakers, as unlikely as that is.<br /><br />Amir

 

[waterone1@aol.com]

Re: Shore Power problem

Lakelubber....yes, replace the main breaker.

 

[TravisTraverser]

Re: Shore Power problem

This boat is on my private dock, this is the first time I have tried to use shore power since purchasing the boat in March and I am hooking it up to a standard 15amp grounded outlet.<br />All the other individual breakers are off except the outlet breaker and it still flips the main breaker. I reversed the polarity on the shore power cord and exactly the same thing happened.<br />I have verified that the power cord will power the fan before it gets to the shore power cord.<br />This shore outlet is the only one available on my dock.<br />My only other alternative other than replacing the breaker would be to pull into a marina and use their shore power and see if it does the same thing.<br />I certainly appreciate all the input and have learned a lot in the process.

 

[TravisTraverser]

Re: Shore Power problem

By the way, the first thing I did when this problem arose was to turn off the battery charger to see if it was the culprit, but it still flipped the brekaer with only the fan on.

 

[Boatin Bob]

Re: Shore Power problem

I think your idea to pull into a marina is the quickest way to eliminate either the boat or your dock shore power wiring as the culprit. Do that first to see where the problem is and then try some of the other good ideas mentioned above.

 

[18rabbit]

Re: Shore Power problem

The quickest way to eliminate your dock’s power as part of the problem is to use your voltmeter and check it for reverse polarity as I described above.<br /><br />If the safety ground (green wire) on your boat is routed thru one of the 3 poles on your main breaker, then that needs to be fixed before you start probing around inside the AC panel. There should be nothing between that conductor and shore power, except a galvanic isolator. If you don’t have a GI, then there should be nothing between the safety ground and shore power. This is not a minor safety issue.<br /><br />Main breakers don’t have 3 poles, so maybe your main breaker isn’t really a main breaker. How many amps is your main breaker rated for? It is written on the breaker itself somewhere. It might be that the previous owner stuck a smaller breaker in there.<br /><br />Somehow voltage is allowed to sit on the neutral line up stream of the main breaker. But if it were as simple as shore power with reverse polarity, the indicator light should be lit when the main breaker is switched off…unless your boat’s safety ground is on one of the 3 poles of the main breaker, in which case it would not light up until you flipped the main on…unless neutral and safety ground are tied together on the boat, which is one of the appropriate wiring scenario for marine electric. If that is the case, your reverse polarity lamp is useless, and your boat has a major AC electrical safety issue: the safety ground going thru a breaker.<br /><br />The reason the safety ground may be going thru the main breaker is to allow you to disconnect the path for stray dc in the water (common around marinas) that will work it’s way thru any metal on your boat below the water line, up thru the boat, and out the safety ground. The actual flow of the stray dc current on that path isn’t an issue, but it causes galvanic corrosion of subsurface metallic parts on your boat that will eventually sink it, some boats in as fast as a day or two. There needs to be a way to trap that stray DC current and that is what a galvanic isolator does. It allows you to maintain a connection to shore power without allowing the stray DC current to flow thru your boat to the shore power’s safety ground. Whether or not your safety ground is on the main breaker, you need a GI on your boat.<br /><br />Lakelubber, I am going to suggest you avoid using your shore power and the AC on your boat until you get this sorted out. There is a potential for your boat to burn if the neutral and ground are tied together and you engage reverse polarity shore power. Essentially, somewhere on your boat part of the AC wiring may be acting like a glowing red coil in a heater. If there is enough resistance where neutral and safety ground are connected, 30-amps may not get thru there, which would explain why the main breaker doesn’t flip until another load is placed on your AC. Note: resistance = heat…the more resistance you have, the more heat you get. DO NOT connect your boat’s shore power until you have this figured out!<br /><br />If what I am thinking is correct, you have the following issues to fix:<br /><br />1 – reverse polarity at shore power.<br />2 – your safety ground is routed thru the main breaker.<br />3 – neutral and the safety ground are connected together.<br />4 – you need to install a GI on your boat.<br /><br />The flashing reverse polarity indicator can be explained as a 3-pole breaker with a single actuator. When you flip the breaker off, one of the 3 poles is disconnecting a fraction of a second sooner than the other poles. This is causing the AC to seek another path, in this case that path would be the wiring for the reverse polarity lamp…there may be as much as 29.9amps of 120vac whipping thru that little bitty wire for a fraction of a second when you flip the main breaker off.<br /><br />Of course, not seeing the boat, I could be off in left field somewhere and none of the above applies.<br />

 

[Silvertip]

Re: Shore Power problem

Let's try a couple more things. Nobldy asked, but is circuit you are trying to run the fan on the ONLY circuit that pops the main breaker?? If it is, then shore power very likely is not the problem. If the plugging the fan into any other circuit pops the breaker, that sends us back to shore power. Otherwise, here is another sequence to try. 1) Disconnect from shore power. 2) turn off the main breaker. 3) turn off all breakers. 4) make sure every appliance on that problem circuit is disconnected. 5) using an ohm meter, measure between the load (output) side of the circuit breaker on the problem circuit to earth ground, then repeat for neutral. It should measure OPEN circuit on both tests. If not, that circuit has a problem or there is still something connected you are not aware of. It may also be a bad outlet or a wiring problem. You might go so far as to remove the outlets to check if reversed or improper wiring is present on the GFI outlet for that circuit. The smaller of the two slots on the outlet are the hot side. Wider slot is neutral, and the round hole is safety ground. I'm beginning to think this is a faulty or miswired GFI. Keep trying, but most important, be methodical.

 

[cp]

Re: Shore Power problem

You're getting lots of good help above, but now that you've told us that "...this is the first time I have tried to use shore power since purchasing the boat in March and I am hooking it up to a standard 15amp grounded outlet." a different train of thought comes to mind.<br /><br />Because 3-pole breakers such as you've said you have on your boat are normally used for 240v service, where the 3 poles break the 2 'hot' wires and the neutral with the gnd remaining connected always, the question arises: Are you connecting 120v into a circuit intended for 240v?<br /><br />Did the shore power connector on your boat come with the boat? Does it look (pin configuration) exactly like the shore power connector on your dock? Did the shore power cable come with the boat, or did you make one up with connectors to suit? If the boat's shore power connector is not the same as the dock's we may have found the problem. For some info on shore power connector and cable pin configurations see the below link:<br /><br />Shore Power Connectors/Cables<br /><br />Hope this helps; good luck.

 

[Silvertip]

Re: Shore Power problem

I thought of that too, but even if that's the case, half the circuits on the boat would not work if he's feeding the boat with 120. Neutral is neutral as far as the boats concerned and providing the hot from shore is indeed feeding either leg of the breaker panel -- provided that is indeed a 240 panel. What's not been answered here is whether the problem circuit is the ONLY circuit that trips the Main breaker. We really need to know more about the boats wiring.

 

[18rabbit]

Re: Shore Power problem

I presume a Larson 240 is a 24ft boat, not likely to be 240v or 50-amp/120v. And given that it is a 1994 with factory installed electrical, I suspect the third leg of the main breaker is for the safety ground, as a GI was not as common 11-years ago.

 

[TravisTraverser]

Re: Shore Power problem

Everything trips the main breaker; battery charger, fridge, water heater, etc.<br />Each time one of the individual breakers is turned on for any appliance or outlet and load is appled to that appliance the main breaker trips.<br />This is definitely a 120v breaker and the boat shore power connector is labeled as 120v, the shore power adapter came with the boat and appears to be in great condition, but subsequent to the problem occuring, I purchased a new shore power cord and still get the same problem, so I eliminated a problem with the cord and I reversed the polarity to se if that was the issue, but I still get a tripped main breaker.<br />I will put an ohm meter on the breaker, as suggested and see if that sheds any light.<br />Meanwhile, I appreciate all the knowledge that has been flowing my way.