[C320-list] Shore power system

[Ron Squires]

Scott,
I agree with you about the latent danger in having neutral and safety ground buses connected onboard a boat. Every reference I could find on the topic echoed the same advise. Since the installation appears to be original, the only scenario that makes any sense to me is that the jumper that that should have been removed to split the bus bar wasn't taken out. And then the boat was never connected to a GFCI source, until now.
As to the point you brought up about the RCI test switch being shown as a dead short on the '99 schematic, I noticed that as well. The '93 schematic and actual layout does not have the test switch. The RCI light is simply connected between the neutral and safety ground wires at the shore power inlet breaker. Granted there is no way to know if the RCI light is working until you get an actual reverse current hookup condition. And if the light is nonfunctional, you wouldn't realize the condition until you check the RCI on the main panel.

Ron & Michelle
#26 1994 "Island Time"

_/) Sent from my iPhone 5

On Jul 22, 2013, at 10:16 PM, Scott Thompson <surprise at thompson87.com> wrote:

> Ron, Calder's book lays out several reasons why it is dangerous to bond AC neutral (white) to AC green (ground) on board, with limited and specific exceptions that apply only if you have a generator or inverter, and even in those cases there should be no connection between neutral and ground when connected to shore power. So I would definitely disconnect the two buses from each other. Since neutral and ground are supposed to be bonded together on shore, the unsafe conditions would only occur if something else went wrong, but this is a boat so that is to be expected and anticipated.
> 
> Do you know whether the conditions you describe are new, or is it possible that they have been there all along? Incorrect wiring at the shore power inlet on the stern (i.e. reversing hot and neutral) or plugging in the shore power cable incorrectly (possible with some older connectors, especially if worn) would certainly cause the symptoms you describe given that the two buses are tied together.  I keep my boat on a mooring and only "plug in" to shore power a few times each year. If your previous owner did the same then possibly a wiring problem went undetected for a long time.
> 
> Two observations that may be helpful or not:
> 
> 1. My boat developed persistent "reverse polarity" a few years ago. That is, out of the blue the light started coming on no matter which dock outlet or marina I connected to. I replaced the power inlet on the stern and the problem went away. A bad neutral connection can mimic reverse polarity by creating a voltage drop between the neutral bus on board and the other end of the neutral wire back on shore, since the latter is bonded to ground.
> 
> 2. The AC wiring diagram for the reverse polarity light and test switch in my manual makes no sense to me, and I suspect it is wrong. For example, it appears to show a direct connection between AC hot (black) and AC ground (green) at one of the switch terminals. I would not count on the diagram being correct. That said, mine also shows no connection between the AC neutral bus and AC ground bus.
> 
> Scott Thompson
> Surprise, #653 (1999)
> 
> On 7/22/2013 8:20 PM, Ron Squires wrote:
>> Warren thank you for responding, I was hoping for replies from owners of mid-nineties boats. The only wiring I am addressing in this post is the 120v system. On our boat the neutral (white wire) and the safety ground (green wire) buses are connected via the over the top of the separators jumpers used on these type of terminal strips. To be clear the terminal strip has twelve positions, all of them are connected via jumpers. Four positions are white wires and six are green wires, with two unused in between. This does not match the 1993 schematic included in the owners manual, nor any other schematic I have been able to locate. All the opinions I have read conclude that these two buses should not be connected on a boat, only "at the power source". I'm not talking about those boats carrying a gen-set, but those like ours using a shore power cord and on shore source. The ABYC recommendation to connect the safety ground (green wire) and 12v negative (black wire) buses is not at issue here. I see no indication that these two are connected on our boat.
>>  Ron & Michelle
>> # 26 1994 "Island Time"
>> 
>> _/) Sent from my iPhone 5
>> 
>> On Jul 22, 2013, at 6:02 PM, Warren Updike <wupdike at hotmail.com> wrote:
>> 
>>> To be clear, when you say, "neutral bus" do you mean the negative (black)
>>> side of the DC service?  When you say, "safety ground bus" do you mean the
>>> frame ground (green) side of the AC service?  If the answer to both is yes,
>>> then this is a normal and recommended connection.  Our 1994 hull also has
>>> this connection.  This is not likely contributing to your problem.  Nor, is
>>> it a reason why your GFCI is tripping.  If everything else is OK, there
>>> should be no voltage across the green/white or green/black wires of the AC
>>> service that would trip the GFCI.
>>> 
>>> I think you should find your problem along the lines suggested by others.
>>> Check every point of connection between the dock and the AC breaker.
>>> 
>>> Warren & Pattie Updike
>>> 1994 C320 #62 "Warr De Mar"
>>> 
>>> -----Original Message-----
>>> From: Ron Squires [mailto:rsquires77 at netzero.com]
>>> Sent: Monday, July 22, 2013 10:35 AM
>>> To: C-320 List
>>> Subject: [C320-list] Shore power system
>>> 
>>> This is our first season with this boat. When we connect to the shore power
>>> supply we encounter two problems, so far. First is we get a reverse current
>>> light, second when turning on the main AC breakers in order first the one at
>>> the inlet then the one the panel, the GFCI at the supply point trips.
>>> 
>>> What we have noted already while investigating is that the neutral bus and
>>> the safety ground bus are connected on the single shared terminal strip via
>>> what look to be original jumpers.
>>> The boat does not have an isolation transformer.
>>> 
>>> I can't believe this boat has been miswired this long without someone
>>> questioning the buses being connected.
>>> Can anyone think of a reason they would have, or should be connected on the
>>> early series boats(hull #26)?
>>> The buses being connected does explain the GFCI trip but not the reverse
>>> current light. We have checked the source and cord with a polarity checker
>>> and they are OK.
>>> We need to dig deeper into the AC system, will we find any more surprises
>>> with the system on a boat with an early hull number?
>>> 
>>> _/) Sent from my iPhone 5
> 
> 
>