Reverse polarity light on

[Mity]

hi, I own a Hunter H320 2001. I have the reverse polarity light going on only when I turn my water heater on. I did all the tests recommended by Nigel Calder and all passed.
I notice between the white and ground 11vac when I turn the water heater on.. the ac voltage also drop from 116 to 106.
I checked the water heater and it seems ok.

I have no more clue!
Any ideas ?

Thanks for your help!
Michel

 

[FastOlson]

I am suspicious of that (original equip?) water heater. After our marina changed over to the new GFI 30 amp shore power outlet posts, we had a boat of about that age that could no longer draw power because the new and sensitive breaker would not hold.
It turned out that his AC water heater had some small leakage from neutral to ground. Per a couple of marine electricians that I know this is a common problem due to the "marine" water heater elements in all of our boats being no different or better than the same parts in a home water heater. Corrosion from the damp marine air gets to them.
Maybe not your problem, but given the symptom, certainly worth some follow up diagnosis.

 

[Rich Stidger]

I would opinion that the problem is a leakage resistance between the white (neutral) and the ground (green). In addition it could be excessive resistance in the white wire path. Check all of your water heater connections back to the AC panel switch.

 

[Johnb]

The reverse polarity light indicates a difference in voltage between neutral (white) and ground (green). You say that when you turn on a heavy load the light comes on and the voltage difference is 11 volts. This indicates a poor connection somewhere in the neutral circuit. Wherever that is it is almost certainly also getting (very) hot. Take a good look at all the wiring points and also the connectors, and while you are about the live as well.

 

[BigEasy]

The reverse polarity light indicates a difference in voltage between neutral (white) and ground (green). You say that when you turn on a heavy load the light comes on and the voltage difference is 11 volts. This indicates a poor connection somewhere in the neutral circuit. Wherever that is it is almost certainly also getting (very) hot.

Recently had a reverse polarity situation. I traced the problem to the 30 amp AC power inlet on the transom, that was corroded & showed signs of overheating. Took that opportunity to replace it with a "Smart Plug" and was good to go. One interesting aspect was that all of the gfci outlets onboard were dead and the gfci resets were inoperable. As Rich mentioned in a previous post, the gfci outlets must have been detecting leakage between common & ground.

 

[justsomeguy]

Took that opportunity to replace it with a "Smart Plug"

How's the dockside connection?

 

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[BigEasy]

How's the dockside connection?

If you are referring to the smart plug conversion of the power cord and receptacle, I think it's one of the best improvements that I have done. If you are referring to the dock power pedestal receptacle and the mating end of the power cord, they both checked out ok--no problems there.

 

[jssailem]

With you Big Easy on the Smart plug.

Just a quick look at Maine Sails gallery of shame images convinced me.

 

[Mity]

Thanks everyone,

I have checked the resistance between the white and ground, I read an open circuit when all ac breakers are close and open. I followed all the wires to the water heater and they are all good. The resistance of the heater should be 9 ohms based on 1500w and it is what I measured.

Johnb you were right. I did find 2 wires corroded and melted on the white connection in the distribution panel. The previous owner did not use marine grade and the 12 and 8 gage melted. I replaced those and the Ac breaker (magnetic breaker and it did heat a bit), I still have the reverse polarity light on with water heater.

I also notice yesterday when I turn my charger on the voltage between the white and ground was 4 vac but keeping my meter on it I notice the voltage dropping very fast. After about 3 minutes the difference was .5. However for the water heater the voltage stay steady at 11.23vac.

I'll check again all the white connections to see if I find something.

 

[Ron20324]

I wonder if the ground is being crossed with the AC via the water in the tank?

 

[jssailem]

What about a short in the heater element?

 

[Rich Stidger]

This could be a classic case of two problems. The fact that there is a neutral to ground voltage with the battery chargers suggests that it is not just the water heater that is the problem. Check that there is no corrosion on the shore cable connections on both ends. I have had a dim reverse polarity light when I was using an extension cord with slightly corroded contacts. All plug and socket contacts need to be bright and clean.

 

[walmsleyc]

Just last week, my ELCI started tripping when I turned on my Seward water heater.

After some investigation, with the heater element disconnected from all AC connections, the resistance of the element was correct, but there was about 300Kohms between the element contacts (though it as highly variable) and the metal element threaded "plug" (ie. ground). I don't think 300Kohms would was tripped the ELCI, but perhaps when 120AC is applied, the resistance varied somewhat to allow ~30mA of current leakage to ground.

I ordered a new element and removed the old one. On the old one, there was sludge, rust brown stuff, around the base of the elements right at the threaded plug that was likely the cause. Since it may have been original to the boat (30 years old), I just tossed it. New element has NO conductance between ground and the elements and the ELCI no longer trips.

HIGHLY recommend having an ELCI install on your boat.

Question: Would it be wise to also have a GFCI installed to protect the water heater circuit? It has a lower trip point than an ELCI (5mA instead of 30mA), and would add some redundancy and a even better level of protection.

FYI, the element I removed was FULL length (did not have the 180deg fold in it) and was about 12" long, and because of the confined space could not get it out without bending it as I extracted it. The replacement element is of the folded type, and fit in easily (about 6-7" long).

Chris

 

[Mity]

Just did more tests.. since I suspected the water heater I cut the white wire to see if my issue resided and yes it did. Then I decided to remove all the connection to the white buss bar, one at a time to see if I could find the one leaking to ground, no luck either.
What I notice is whenever I drain lot of current (above 10amps) the light goes on. The voltage do go down now and it is no more 11vac. I change the extension cord and now have 30amps rated cord. I have a varistor for the reverse polarity check and the voltage on it is the same as the one on the white wire. The varistor is connected between the ground and shore white wire true a breaker.. will continue investigating.

 

[JimInPB]

If you have about 10 volts show up between ground & neutral then ground is not well bonded to neutral. If at the same time, the voltage on the hot leg also changes by about 10 volts, then you are probably not seeing a voltage drop due to high load on thin wires, you are probably seeing a floating neutral. The fact that you only see it when the water heater is on, does not mean that the ground to neutral connection failure originates in the water heater. It only means that the imbalanced draw created by the water heater makes the floating connection show itself.

If you have a 220vac service with 110vac tapped off one side of the 220, then one leg of the 110v is probably going high by 10v when the other goes low by 10v. If your boat only has a single 110v feed, then some other boat in the area is probably seeing the 10v change in the other direction on his 110v feed.

Somewhere, there is a bad ground connection &/or a bad neutral connection. This needs to be fixed first. After your floating neutral issue is addressed, you may also need to do something about leakage current in the water heater.

A lot of older boats can’t take power from the newer current-leakage protected power posts because they have current leakages that have existed for years without the owner knowing about it. When a boat owner swears that there must be a problem with the new dock posts because his boat was fine last week on power from another dock, the first thing that I think to check is leakage current. I saw this issue on a beautifully kept older yacht that was in Key West for Quantum Race Week this past year. This problem is not limited to scows.

Ground leakage is pretty easy to measure if you have a clamp-on ammeter that reads down to milliamps. Just zero the meter in free air, then clamp it around your entire power feed cable (like the meter instructions tell you not to do) & the reading should indicate leakage current.

Ground fault issues on boats can be a serious problem if the leakage current is sent to the surrounding waters. 2 volts per foot of water is enough of a voltage gradient to kill a swimmer.

 

[Mity]

Thanks Jim, I'll do more testing.