• Untitled Document

    Join us on March 29rd, 7pm EST

    for the CBEC Virtual Meeting

    All EYO members and followers are welcome to join the fun and get to know the guest speaker!

    See the link below for login credentials and join us!

    March Meeting Info

    (dismiss this notice by hitting 'X', upper right)

Reverse Polarity light.

Captain Crunch

Member II
Hello all, I installed a new Blue Sea systems AC panel in my boat in the spring All was well until I arrived at my boat last weekend and the AC power was off. It seems the female shore power plug on the marina side of things was worn and burnt, taking my extension cord with it. Fine.... things wear out. I connected a new male end to my extension cord and plugged it in to the neighbors shore power. As I started to put my AC loads back online, 1500w heater, water heater,and battery charger the reverse polarity light slowly started to illuminate. What I mean by this is when I flick on my main 30A breaker no light at all. Flick on the battery charger, you can just see a tiny bit of illumination. The outlet plugs with the heater plugged in a little more, and by the time the water heater is brought online the light is on although I think a little dimmer then full on. The water heater seems to illuminate the light the most. I metered out all the wires from the marina to the outlets and everything is as it should be. I even opened everything up and rewired all the outlets just to make sure. The problem hasn't corrected. Has anyone had this experience with reverse polarity lights on AC panels. Any insight here would be much appreciated.
 

HughHarv

Hugh
Reverse Polarity

A reverse polarity tester should light up instantly if there's a problem, regardless of load. More current equals more load, is the panel warm? Maybe the light is heat sensitive?
 

Captain Crunch

Member II
From what I can tell from what I read on the subject is there is too much resistance in the neutral wire and this is slowly illuminating the reverse polarity light as I put the heavier loads of the space heater and the water heater online. The boat is wired with an 8-2 conductor from the shore power plug to the panel and each branch circuit is 14-2. Both appliances are on their own 15 amp breakers. All connections meter out perfectly. Should this suggest there is a problem on the marina side of thing? Loose neutral somewhere down the line? I want to cover all my bases before I get a marina maintenance guy to start tearing things apart. I understand that a loose neutral problem will not trip a breaker and just cause fire with 30A fueling it.
 

jkm

Member III
14-2 is only rated for 15 amp total load. 14-2 is adequate for lighting, not appliance grade wire.
How many amps are on each circuit?



John
 

HughHarv

Hugh
neutral connection

I had a few residential trouble calls related to a loose neutral, this was years ago mind you, and my memory is fuzzy. They residents called because they kept frying t.v.'s, etc. As I recall, the measured voltage at various outlets didn't measure up to line voltage.

The neutral wire (aluminum in this case) was corroded at several outlet connections and at the main buss. If this was the problem I would think you would get a low or no voltage reading somewhere.

In one junction box, I stripped the wire back to new metal and reconnected, voltage problem solved there. Had to do the same on every outlet and breaker box connection before I was done.
 

Mike.Gritten

Member III
I'm no AC wizard, (chime in you electrical gurus) but why are you only running 2 conductor wiring for your AC? To me, this sounds like the problem. If you have no ground wire (just hot and neutral) I'd be concerned. When I redid our wiring, I replaced it all with 3 conductor marine-grade wiring and have none of the reverse polarity issues you describe. Read Nigel Calder's book (the "bible" on our boat!) and see what he has to say on this topic.
 

jkm

Member III
14-2 is a three wire configuration, hot, neutral, and ground for at least the last 25 years. Though I would not be surprised if your wiring is old you may have not the ground.

An open neutral will cause all sorts of havoc as Hugh said.

John
 

jkm

Member III
Voltage drop table for 110v and 3% drop max:
http://www.cerrowire.com/default.aspx?id=51


re: "14-2 is a three wire configuration"
John, in my local chandlery, 14-2 Marine Grade Boat Cable by ANCOR is 2 wire; 14-3 is three wire.

Sorry Chuck I stand corrected

I still live in the world of residential development where 14-2 is three wire and 14-3 is four wire.

I've never looked at wire in the ship's store. I'll check it out and see if Obama can fix it!




John
 

Captain Crunch

Member II
Hey guys, What I meant by 14-2 is a neutral, hot and ground. Im not used to including the ground.(residential wiring terms) The wiring installation is brand new installed by me. I have a 30 amp main with 3 branch circuits on 15A breakers. Hot water heater on one, 1500W space heater plugged into the outlets on one, and a battery charger on the last circuit. A large load but the system is wired to handle it. Im almost positive the plug melted down because it was old and there was a bad connection on the prongs, the neutral prong looked to be the hottest. The reverse polarity light is still a mystery. Ive read a few things that suggest that the neutral conductor isn't large enough. Does this make sense with the way 3 conductor 14 awg is designed. One book says I have some issues to address but doesn't go any further into it. Anyways thanks for the replies. Any more thoughts would be gladly accepted.
 

Randy Rutledge

Sustaining Member
I think you are running single phase 120 but are you running two phase 240 or single phase 120. If you are running single phase 120 the ground issue would just result in low or no voltage but if it is two phase a floating ground will cause the voltage to go very high on the low load leg and burn stuff.
 

dave_g

Member II
The reverse polarity indicator is wired between the AC Neutral and the Ground. When everything is correct, all of the AC current flows in the Hot and Neutral wires (never in the Ground). Back on shore, the AC neutral and the Ground are connected together, so the voltage between neutral and ground should be 0 (or a very very low voltage).

In order for the reverse polarity indicator to light up, there must be a voltage difference between the neutral and the ground. This can be a reult of wiring the Shore HOT conductor to the Boat Neutral wire (the reverse polarity condition the light is meant to show) or as a result of increased resistance in the neutral wire between your AC panel and shore (which sounds like your condition). As you turn on appliances, the current in the neutral wire increases. Because of the resistance in the Neutral wire, this current creates a larger voltage drop in the neutral wire and thus a larger voltage difference between the neutral and the ground wires, causing the indicator to glow brighter.

On your boat, I would check all of the AC connections and wires from the panel back to the shore power connection, focusing on the neutral conductor. An ohmmeter should be sufficient to find the problem. My first suspect would be your extension cord.

Dave
 

Sven

Seglare
The reverse polarity indicator is wired between the AC Neutral and the Ground.
...

Ah, thanks for the very clear explanation !

So simple and functional that I could see wiring one as a DIY project (with great care) but probably using a meter rather than a light.



-Sven
 
Top