Reverse Polarity

[thomm225]

Originally Posted by Blue Stocking

A lamp bulb is basically a resistance coil, so line/neutral is not that important, It is important with other electrical devices which have chassis grounds for instance. I stopped reading all the posts when it got screwy, but did anyone tell him if he is sharing the pedestal with another boat, it could be a polarity problem on the other boat feeding the neutral. Sorted this out in the boatyard just yesterday.

The example isn't talking about the bulb but the socket.....(as far as a person getting shocked are worse if in water etc)

again:

By contrast, a lamp socket connected to a reversed-polarity receptacle will have a ‘hot’ (ungrounded) screw-shell that is cycling at significant voltage to ground, while the spring-tab at the base will be ‘neutral’, and at zero volts to ground. Someone touching both the reverse-connected screw-shell and something grounded would become a conductor for significant current moving from 120V RMS ‘hot’ to zero volt ground

[leftbrainstuff]

Originally Posted by rwidman

Think about what you just wrote.

If your electrical connections have been fine at several other marinas, why would you think you need to reverse the wires on your plug for this marina?

Nothing changed on your boat traveling from the last marina to this one so why would you think the problem is on your boat or your shorepower cord?

What to try next? If the marina's electrician can't figure it out, your best bet might be to move on to another marina. But first, put all the wires back exactly how you found them.

+1. The first rule of A/B testing.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[letsgetsailing3]

Originally Posted by K_V_B

Oh. I will pay attention when I get on board a yacht if it has a polarity indicator, as this seems to be a reliable indicator for sub standard wiring...

But it's unlikely that I'll ever have a boat that is not CE marked, so yes, for me it will remain largely a non issue.

Fine for you, but maybe stop advising others that it's irrelevant, as it might not be on their boat. Boats with polarity requirements are only unsafe if their owners don't pay attention to it.

[btrayfors]

Here in the U.S., reverse polarity is dangerous and potentially lethal. Period.

Some examples have been given above. Here's another from personal experience.

A few years ago I hauled my boat for a bottom job. I plugged one of my 30A shore cords into the pedestal in the work area of the boat yard.

When I walked by my propeller and shaft, I happened to touch it and received a 120-volt shock! If the ground had been wet or I'd been barefoot or...any number of other scenarios....I"d likely have been ELECTROCUTED. KILLED. DEAD.

The boatyard's shorepower pedestal was wrongly wired....black hot and white neutral were reversed. This put 120VAC on my boats GROUND system (AC ground and DC ground on the boat were connected to a single-point .... the engine.... in one of the common and "approved" marine wiring practices).

It's pointless to argue whether the European system is better than the American system. The point is, we in North America have several HUNDRED MILLION people using the 120-volt system and it works pretty well for us. The best statistics available show about 50-60 accidental electric shock deaths annually in the U.S......not too bad with over 200,000,000 users!

I'd bet the rate of accidental deaths in 240-volt system countries is much higher, partly because of the increased lethality of 240VAC vs. 120VAC.

No matter. Our system is what it is. And the other systems are what they are.

Bill

[svlamorocha]

Originally Posted by btrayfors

The boatyard's shorepower pedestal was wrongly wired....black hot and white neutral were reversed. This put 120VAC on my boats GROUND system (AC ground and DC ground on the boat were connected to a single-point .... the engine.... in one of the common and "approved" marine wiring practices).

Bill

I understand electrical engineering and a few approaches to codes, but I am not sure I understand what "approved" wiring practice are you referring to. If I understand correctly what you wrote, then in your boat the (white if American boat) wire that was supposed to be NEUTRAL/groundDED (but was actually hot because of reverse polarity) was PERMANENTLY connected to the engine block. Did I get that right?

If so, then your installationbreached the common rule that neutral (white) and engine block/safety ground (green) should only be connected at the power source, which in this case was not inside the boat. (When you start the inverter or genset you should make that connection, but that is not relevant) Tests 6A, 6B and 6C in page 234 of Calder´s book goes would have helped detect this problem.

Please help me learn by explaining what standard permits the connection of neutral aka white wire in the US to the engine block (hence protective/safety ground aka green wire in the US that is always connected to the block ).

As far as I know neither NEC nor ABYC permits that but I would be happy to learn otherwise.

I clarify that I am not arguing against having the right polarity. I am just challenging the concept that in a properly wired boat reverse shore polarity BY ITSELF will make you get zapped when you touch something that is grounded to the engine..

Charlie

[rwidman]

A lamp bulb is basically a resistance coil, so line/neutral is not that important.......

This is an example of where a little knowledge can be worse than none at all as explained in post #46.

Most electrical appliances will work just fine with the polarity reversed. The problem is, they can be dangerous with the polarity reversed.

This is why we have polarized receptacles and reverse polarity indicators.

[btrayfors]

Charlie,

I agree with you re: the general recommendation that the green grounding wire and the white grounded wire only be connected at the source, normally the shore power source. Exceptions: onboard AC generator and/or inverter.

HOWEVER, there are many boats on which these wires are connected together at a single-point with the boat's DC ground. And, under some circumstances, this meets ABYC recommendations.

See, for example, this paragraph taken from West Marine's reprint of Stan Honey's excellent article on boat grounding:

Quote
AC Ground

See Practical Sailor August 15, 1995 for a detailed treatment of the green wire. The best solution is a heavy and expensive isolation transformer. The acceptable solution (for the rest of us) is to install a light and inexpensive Galvanic Isolator in the green wire, between the shorepower cord socket on your boat, and the connection to the boat's AC panel. Then, connect the grounding conductor (green) of the AC panel directly to the engine negative terminal or its bus.
Note that this meets the ABYC recommendation.

Unquote

(bolding mine)

Many marine electricians argue for this arrangement; many others don't.

Bill

[svlamorocha]

Originally Posted by btrayfors

Charlie,

I agree with you re: the general recommendation that the green grounding wire and the white grounded wire only be connected at the source, normally the shore power source. Exceptions: onboard AC generator and/or inverter.

HOWEVER, there are many boats on which these wires are connected together at a single-point with the boat's DC ground. And, under some circumstances, this meets ABYC recommendations.

See, for example, this paragraph taken from West Marine's reprint of Stan Honey's excellent article on boat grounding:

Quote
AC Ground

See Practical Sailor August 15, 1995 for a detailed treatment of the green wire. The best solution is a heavy and expensive isolation transformer. The acceptable solution (for the rest of us) is to install a light and inexpensive Galvanic Isolator in the green wire, between the shorepower cord socket on your boat, and the connection to the boat's AC panel. Then, connect the grounding conductor (green) of the AC panel directly to the engine negative terminal or its bus.
Note that this meets the ABYC recommendation.


Bill

Bill,

Ouch! Obviously I have understimated how far is the US from Europe on certain things. Can you then please clarify how can can it be true that this approach "meets the ABYC recommendation" that says:

"11.5.3.2.1. The shore power neutral is grounded through the shore power cable and shall not be grounded on board the boat."

Of course I am assuming that any neutral-to-ground connection at the inverter or genset is disconnected automatically when shorepower is coming in (as in all boats I work in that have gensets or inverters). What am I missing?

I understand that ABYC has an exception for boats with isolation transformers, but that could not get you zapped as you did. I look forward to learning something.

[rwidman]

Originally Posted by svlamorocha

Bill,

Ouch! Obviously I have understimated how far is the US from Europe on certain things. Can you then please clarify how can can it be true that this approach "meets the ABYC recommendation" that says:

"11.5.3.2.1. The shore power neutral is grounded through the shore power cable and shall not be grounded on board the boat."

Of course I am assuming that any neutral-to-ground connection at the inverter or genset is disconnected automatically when shorepower is coming in (as in all boats I work in that have gensets or inverters). What am I missing?

I understand that ABYC has an exception for boats with isolation transformers, but that could not get you zapped as you did. I look forward to learning something.

If the boat has an isolation transformer, that would be considered the "source" and that would be where the ground and neutral conductors feeding the boat would be connected together. The ground must continue to the source feeding the transformer (the marina's ground). Otherwise there is no actual ground.

[Blue Stocking]

Originally Posted by rwidman

This is an example of where a little knowledge can be worse than none at all as explained in post #46.

Most electrical appliances will work just fine with the polarity reversed. The problem is, they can be dangerous with the polarity reversed.

This is why we have polarized receptacles and reverse polarity indicators.

That little knowledge is 50 yrs in the field. I was using example from extreme ends of the range, but you are doing a good job, so, have at it

[btrayfors]

Charlie,

My purpose here is not to argue for or against connecting the green grounding wire to the DC negative ground (usually the engine) on a boat. Nor is it to argue for or against ABYC recommendations or advisories.

Rather, I was just pointing out a personal experience in which a reversed polarity situation could have been life-threatening.

As for "authoritative" views on making such a connection on the boat, there are several which come to mind. You can Google for more. Over many years, Don Casey, West Marine, professional boat builder magazines, and others have argued FOR the connection, claiming it is important to reduce the possibility of electric shock drowning.

For example, it was listed as #4 in West's article, "Ten Deadly Conditions on Boats":

Quote.......

4. No “Green Wire” or poor-quality connection between DC negative and AC safety ground.

Without a good connection between DC negative and AC safety ground, stray AC current may enter the DC ground system. When this happens, AC current may enter the water around a boat and injure or kill swimmers near the boat. The green wire is the safety ground wire that connects the DC negative ground block to the AC safety ground bus. The purpose of this wire is to provide a lowest-resistance path to ground for any stray AC current that finds its way onto the DC ground system. There have been cases of AC current entering the water around a boat through the engine shaft and killing swimmers near the boat. For more on how to prevent this, see our West Advisor on ELCI/GFCI Electrical Shock Protection.

Unquote

Whatever you and I may think about the practice of connecting the green grounding wire to the boat's DC ground (usually the engine), the fact remains that this is fairly commonly done.


Bill

[deblen]

Earthing system - Wikipedia, the free encyclopedia

Earthing is done differently in different countries around the world.
The neutral is not necessarily earthed,in the N.A. way.
OP asked about Malaysia. If the earth conn. at the marina is bad,the neutral will float,in the marina.
If you plug your boat into this,with it's green & neutral commoned,as it should be,& connected to the water(engine earth),the Rev Pol lamp could light.

Safest & simplest bet in foreign countries is a 230V battery charger IMHO.

[FlyingCloud1937]

The plain simple fact that the US uses polarity, is if a fault develops between the earth ground, and the neutral, in an appliance/fixture. Whereby the case could become energized.

The idea behind, having the earth ground, bonded to the neutral is to cause the circuit breaker to trip, as the US doesn't use double pole isolated CB's. If this weren't the case and a fault developed between neutral and case, then the CB might not trip until a human, created the circuit. Which can cause death and has.

Early on the US didn't have polarized circuit requirement. Then after mounting injuries and death toll the NEC instituted the polarized circuit rules.

Now we have double insulated power tools, which when first introduced didn't have polarized plugs. But as of today you won't find any double insulated power tools that don't also have a polarized plug. This is an NEC, and UL requirement in the USA.

Now onto US wire boats. We have the same requirements as the land based AC requirements, because AC aboard grew out of the same codes as they developed overtime on the shore side.

The reason a US boat is polarized is the same as a US land based system is polarized. " It's the FAULT POTENTIAL" On a boat this fault potential is magnified by the fact that boat wiring suffers from corrosion, so a fault potential can exist, due to development of corrosion in the safety ground of each circuit. One day it works and the next day it doesn't, a fault in the neutral to case can put a human at great risk, because of the unknown fault, that only appears after electrocution.

Now on a US boat all metal objects are recommended to be bonded, this ties the earth of the AC and the ground of the DC into one system, and one potential. There is also good reason to do this in a polarized system on a boat. Any device such as a battery charger or inverter, has both AC and DC in a fault condition, the ground could become energized on the DC ground, in a reverse polarity situation. It would take a double fault, but it does and has happens, that's how the the rules change. It takes a certain number of accidents and deaths for this to to become rule.

It's just like a dangerous intersection or cross walk, society has to count x number of injuries and maiming of Humans, before it decides the rules need some safety changes.

In the US we have determined that it only takes 15 millivolts across the hear to put you into defib. That's why all US GFCI's are rated at the same.

I agree with the use of 30 millivolt RCCB/ELCB's as now promulgated by the ABYC for shore power entrance circuits. As I also agree with the GFCI additional requirements in wet areas. Protecting the whole boat with a RCCB/ELCB's will shut the whole boat down in a fault, but if a fault develops in the GFCI circuit, then that circuit alone will be rendered safe, and won't shut the rest of the ship down.

In this manner we can protect the humans.

Now onto the OP's problem, we don't have enough information to diagnose. We don't know if it is wired to US standards or CE standards. So all of the trouble shooting is just throwing **** against the wall hoping to find something that sticks.

We are only probably less then a couple of years away from the ABYC/ CE boat standard to become the same.

Lloyd

[svlamorocha]

Originally Posted by btrayfors

Charlie,

My purpose here is not to argue for or against connecting the green grounding wire to the DC negative ground (usually the engine) on a boat. Nor is it to argue for or against ABYC recommendations or advisories.

(snip)
Whatever you and I may think about the practice of connecting the green grounding wire to the boat's DC ground (usually the engine), the fact remains that this is fairly commonly done.


Bill

Bill

Thanks a lot for for all this. I take as good the US preference for protecting swimmers in a marina, and taking green across the transformer. All that said and given there is an isolation transformer , one way of seeing all this is that the green-to-engine connection or the shore neutral that is far from earth are not the problem; in this case the problem is that the green coming from shore is far away from earth so your engine (and your washing machine chassis, microwave chassis, etc) end up hot relative to earth. You are not long enough to touch real earth and the microwave or washing machine but your prop can zap you while painiting the bottom.

Given an isolation transformer with green that goes across that you said there was, you could easily fix that by having a TT earth system ashore by which the green is not connected to neutral ashore but instead it goes to a ground rod that is only connected to the green wire.

That is what the do in some land-based 3rd world codes I am familiar with. In the 3rd world you can have neutral that is several volts away from earth in your house, hence you cannot rely on service neutral for safety. Given that marinas in the USA have 3rd world wiring then we may just as well adopt third world earth practices (my name for TT system) and take all shore greens to a rod!

Did I miss something? I look forward to some more learning!

Charlie

[smac999]

Originally Posted by btrayfors

Here in the U.S., reverse polarity is dangerous and potentially lethal. Period.

Some examples have been given above. Here's another from personal experience.

A few years ago I hauled my boat for a bottom job. I plugged one of my 30A shore cords into the pedestal in the work area of the boat yard.

When I walked by my propeller and shaft, I happened to touch it and received a 120-volt shock! If the ground had been wet or I'd been barefoot or...any number of other scenarios....I"d likely have been ELECTROCUTED. KILLED. DEAD.

The boatyard's shorepower pedestal was wrongly wired....black hot and white neutral were reversed. This put 120VAC on my boats GROUND system (AC ground and DC ground on the boat were connected to a single-point .... the engine.... in one of the common and "approved" marine wiring practices).
ll

rev pol wouldn't cause that. you had other issues. or maybe hot and ground swaped at yard. not hot and N.


the green ground is attached to dc ground for safty, and allows the main breaker to trip if something is wrong on the boat. (hot wire shorted to engine etc) otherwise you'd electrocute yourself in the boat.