Shore power process

TickledPink

Having now had my fv250 for a few weeks and encountered stress levels way up there, I figured I'd put it on to shore power then spend some time calmly getting to know my new boat.
With everything turned off, including batteries, I hooked up the boat, then the dock and then switched the shore power and battery charger breakers on getting green lights. All good. 
Except, the red light next to reverse polarity is lit up. Should I be worried?
As this is my first hook up, I openly admit I haven't got a clue what I'm doing but am happy to learn.
Do the batteries have to be on to charge?
Do the batteries need to be on to use 12v items or does the shore power cover everything? 
I'm hoping by summer, I'll be able to relax on my boat but so far I'm considering valium as a boating companion 

aero3113

Whenever you‘re plugged into shore power you want to have your battery charger on. Shore power will give you power to all of your 110 volt items (refrigerator,range,microwave and outlets) when you turn the main breaker on. Everything 12 volt comes from your batteries. Others will chime in about the red light, it happened to me once and it was a issue with the receptacle on the boat. I’ve read could also be an issue with the shore power cord or tower at the dock.

TickledPink

Thanks that explains a lot. So just to clarify, I don't need to have batteries turned on to charge them, just the battery charger switch?

Pat310

Definitely will charge with batteries turned off.  As far as reverse polarity light it usually means the hot and neutral legs of the shore power are reversed which, from what I understand, if the neutral is tied to the ground on the boat can put current into the water around the boat. Not sure how that works with European power as I know you are in UK

Liberty44140

Any time I’ve had the reverse polarity light on all of the boats I’ve owned it’s been due to a bad connection or cord. Sometimes just a loose plug in, sometimes a bad cord, sometimes a bad converter if I’m trying to use a 30 to 15a converter. Check your connections and cords for that one.

Ian

I have seen it also where the shore power outlet is wired wrong or the earth isn’t making the right connection. Where I store I had issues with a couple of outlets I’d plug into in spring but no issue anywhere else. I’d check with someone else’s cord that shows correct operation and also another outlet or stanchion. 

LaRea

> ... the red light next to reverse polarity is lit up. Should I be worried?

Yes - find the cause and get it fixed.  

Check that the power cord connectors are clean and do not look burned or melted.  Try different power cords and/or plugging into different power pedestals.  For about $20, you can get a power receptacle tester to confirm the wiring of the shore power pedestal.  

If none of that works, it could be a problem with the boat's wiring.  We've been seeing a handful of connector failures in some boats that age.  On my boat, the symptom was a persistent reverse polarity light.  Details here:

https://rinkerboats.vanillacommunities.com/discussion/13379/hazard-warning-anderson-powerpole-connectors-in-shore-power-wiring

TickledPink

Thanks everyone. I went back to the boat this morning and the reverse polarity light was off. Just a hitch? Definitely something to keep an eye on. 
Anyway, all good so thanks again for all the great advice.

Willhound

For some reason my 270 would occasionally throw a reverse polarity light when hooking up shore power but would go away after a bit. Never did find a cause. Sometimes switching battery charger off and then back on again would clear it. I suspected a bad connection at the charger but despite checking repeatedly it ever changed.

MH342

If I remember correctly, the reverse polarity light is usually an LED (or regular bulb with diode) between the neutral and ground.  It lights up if the neutral (which should be the same voltage as ground … near zero volts) is a higher voltage than the ground. This would happen if the hot and neutral were reversed because then neutral would be hot at 120. But It can also happen with a bad connection on the neutral which causes a voltage drop somewhere on the return path to the dock. The voltage drop downstream results in a higher voltage difference at the panel between neutral and ground. 

The thing to watch out for in this scenario is that it would only light up at higher currents because the more current, the higher the resistance & voltage drop in the bad connection. At low or zero draw, the voltage drop nears zero and there would be no voltage difference from neutral to ground to light the bulb.  The bad connection would be somewhere between the panel and the dock.  If nothing is running the bad connection could still be present but not showing and indication. 

On my prior boat I actually found (by luck) a loose screw terminal on the negative bus behind the panel, resulting in “only” a charred screw and slightly melted wire insulation.  I was back there doing something else and noticed the melted wire. Who knows how long ago it had worked loose but was lucky to find it. Lesson learned that day … always take every opportunity to look at everything you can anytime you crawl through the boat on a project, keep your eyes peeled and question anything that looks off, or starts acting differently!

rasbury

I hit the like but don't understand any of it...

MH342

Sorry ras. Basically the light can come on if the voltage on your neutral is not zero (or near zero). If it’s easy for power to flow back to the dock, then your neutral will be near zero … the same voltage as ground … and everything is good. If it’s hard for the power to return to the dock due to a bad/high resistance connection, then the voltage in the boats neutral will increase. An analogy would be a narrow restriction in a river. As the river flow increases, the water backs up and the water level upstream (which is the neutral voltage on your boat) will increase. Since the water only backs up with high flows, the light may only come on if there is a high consumer driving a lot of current. 

The water analogy is Current = flow, voltage = water height or pressure, Resistance = a narrow point in the river. 

davidbrooks

Reverse polarity isn't typically an intermittent issue unless you have something bad about to happen.  Loose or burnt connections or wired incorrectly are what i would typically look for. I have had this show up from a mis wired shore receptable, a burn connection on the boat side or even a bad shore cable.  I would recommend starting at the dock electrical box and work your way to the boat.  Use a polarity tester as mentioned before but just look for loose or burnt connections.  if you see any burn marks or corrosion then that would be a time to replace.

rasbury

Electricity fascinates me but for some reason just can't grasp it- and then I look at circuit boards...I can do the very basic stuff but trouble shooting or installing things unless it's a direct swap I'm lost.

LaRea

davidbrooks said:

Reverse polarity isn't typically an intermittent issue unless you have something bad about to happen.

@davidbrooks speaks truth here.  If it shows up and goes away once, fine.  If it comes back, it's a warning that you should take seriously.