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-   -   N28-2 factory AC wiring (https://www.sailnet.com/forums/newport/305642-n28-2-factory-ac-wiring.html)

MitchK 12-06-2017 11:40 PM

N28-2 factory AC wiring
 
All, as I was going through the boat over the past several weeks, I discovered the AC wiring leaves a lot to be desired. So much so, I refuse to use it until I can get it re-wired properly. I had found the nut/bolt and tape splices up in the bow, but what I have discovered at the main breaker has me scratching my head. There are three wires coming from the shore power plug, but when they get to the factory push button breaker, they connect the common and ground together, and have the hot going to the breaker. I think this is not a good thing. Anyway, I have already ordered up some 12-3 marine wiring, and some 10-3 for the run from the shore power plug to where the new Paneltronics AC panel will be installed. I will also be ordering a galvanic isolator to help eliminate any ground currents. Fortunately, the N28-2's AC circuit needs are pretty minimal, so I am only installing a three circuit panel. Anyway, thought* the wiring issue might be something others might want to be on the lookout for.

Mitch*

CaryMcDonald 12-07-2017 03:31 AM

Re: N28-2 factory AC wiring
 
Be sure to NOT inspect your mains box at your home, or office; you'll find the neutral strapped to ground there as well.

The goal is to insure that a 'free' hot wire that becomes loose, or otherwise conductive to the 'world' will encounter either 'ground' or neutral (which is the SAME thing), and 'almost' instantly blow the mains. The 'ground fault' interrupter wall sockets do the same thing, only much more rapidly, and with a 'trickle' of amperage (If it detects a current even 'through you', it will trip before you are 'tripped' for instance).

Let's say you disconnect the grounding to the your boat's panel neutral... and a Hot side line gets to your engine, or 'ground'. It now has made your entire (formerly floating 'ground' hot; but assuming salt water, then the boat NEXT to you, (and the power company, and the nearest building that has a copper spike bonding THEIR neutral to Earth Ground, (read: nearby saltwater harbor water), will be conducting to YOUR (formerly floating ground), NOW HOT through at least the prop and propshaft... and then issues will occur. If your sink is 'floating', for instance, yet now becomes 'hot' while your engine 'grounded through the prop', then feeling the 'difference' between them could be hazardous to your health... but probably not. Using a properly plugged in power tool from dock-side on your 'craft' (with an active hot on your 'ground', could be fatal however.

[But while we are speaking to 'grounding' however, it would be polite to mention your DC system, usually 24VDC. Your motor starter may dictate the choice of positive or negative ground; FACTOID: Boats will see MUCH LESS corrosion at terminals, and all things 'metal' if you can make the choice of a POSITIVE ground. Airplanes, 4-20 Current Systems, telegraph design during era's gone by, teletype, and MANY Eurpean cars used POSITIVE instead of a Negative ground, which was adopted by U.S. Car Manufacturers 'just to be different.' Go figure.]

BillMoran 12-07-2017 05:57 AM

Re: N28-2 factory AC wiring
 
The simple fact is that when everything is working properly, the neutral and ground wires are the same.

The reason they are different is to perform different functions when things go wrong. Since your house wiring is only designed to protect you from things that go wrong _within_ the house, then connecting the ground and neutral wire at the breaker box makes some sense.

However, boat wiring is more complex because a boat floats in electrolyte, and as a result you need to protect yourself and others from more types of electrical interactions than can occur in a house.

You should fix the wiring up to be more correct. If you can budget for it, also get yourself an isolation transformer or some other device designed to protect you from wiring problems with your dock neighbors as well.

I know I harp on this a bit, but Nigel Calder's book does a great job explaining how this works ... much better than I ever could.

boatpoker 12-07-2017 09:07 AM

Re: N28-2 factory AC wiring
 
Quote:

Originally Posted by MitchK (Post 2051306218)
All, as I was going through the boat over the past several weeks, I discovered the AC wiring leaves a lot to be desired. So much so, I refuse to use it until I can get it re-wired properly. I had found the nut/bolt and tape splices up in the bow, but what I have discovered at the main breaker has me scratching my head. There are three wires coming from the shore power plug, but when they get to the factory push button breaker, they connect the common and ground together, and have the hot going to the breaker. I think this is not a good thing. Anyway, I have already ordered up some 12-3 marine wiring, and some 10-3 for the run from the shore power plug to where the new Paneltronics AC panel will be installed. I will also be ordering a galvanic isolator to help eliminate any ground currents. Fortunately, the N28-2's AC circuit needs are pretty minimal, so I am only installing a three circuit panel. Anyway, thought* the wiring issue might be something others might want to be on the lookout for.

Mitch*

You are absolutely correct ! ABYC E-11 Prohibits neutral / ground bonding on boats for a very good reason. Your AC ground and DC negative are (should be) bonded. Therefore joining the AC neutral and ground will introduce AC into your DC system. This is the cause of Electric Shock Drowning (just google it). Even working on your DC system on such a vessel can result in AC electrocution.

Nut/bolt tape splices are also contrary to the same standard.

If the builder has done things like this, what other stupidity have they perpetrated.

I suggest you have an electrical survey done by an ABYC Certified Marine Electrician.
or ...
PM me with your email address and I will respond with ta pdf. of the full ABYC E-11 electrical standard.

BillMoran 12-07-2017 11:29 AM

Re: N28-2 factory AC wiring
 
Any advice on how to _find_ an ABYC electrician? Google doesn't seem to understand and simply provides me with a list of house wiring experts. I'm guessing I could ask around my marina and eventually find someone.

boatpoker 12-07-2017 11:33 AM

Re: N28-2 factory AC wiring
 
Quote:

Originally Posted by BillMoran (Post 2051306586)
Any advice on how to _find_ an ABYC electrician? Google doesn't seem to understand and simply provides me with a list of house wiring experts. I'm guessing I could ask around my marina and eventually find someone.

ABYC find a Certified technichian

MitchK 12-07-2017 09:12 PM

Re: N28-2 factory AC wiring
 
All, thanks for the replies.

In my home, you are correct in that the common and building ground are tied together, but not at the breaker panel. They are tied together at the meter base where the electrical utility comes in. It is isolated like that for a reason.

The main reason I am not using the installed AC system, is like you said, What else did they do. I did find a splice in the AC wiring up in the bow that has the same nut/bolt/electrical tape connection, so I just do not trust it not to do bad things.

I do understand ABCY codes, along with the NEC, that is why I am re-wiring the system. With the common and ground (AC) tied together, it makes it impossible to isolate the boats electrical system from the marinas electrical system. I have not yet determined if the AC ground and DC -12 are tied together. Hopefully this weekend I can find out.

Fortunately, the electrical systems on my Newport are pretty simple. I did rebuild the DC panel and add individual fuses for each of the DC circuits. The AC circuit only has 4 or 5 receptacles. I will also be adding boxes behind the receptacles with wire restraints.

Mitch


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