Reverse Polarity

[svlamorocha]

Originally Posted by leftbrainstuff

I always check polarity of a new connection.

Often land based electricians of varying skill levels are engaged to fiddle with shore power.

You can either use a multi meter or one of the little colored light toolsm

There is misleading info in your post.

Bill´s problem was caused by a green wire that in fact was hot. He did not touch the white wire or the black wire; he touched the green wire (connected to the propeller).The polarity (defined as having neutral close to earth and hot far away from it) may or may not have been right, but that is irrelevant.

A "little colored light tool" (or a reverse polarity light, which is just an LED connected between neutral and green wires) will only detect a hot earth if the neutral is correctly wired. An electrician that gives you a hot earth is also likely to swap hot and neutral, , in which case your "little colored light tool" will not detect a problem.

In summary, the problem in this case is a hot green wire and one of those tools will not always detect that problem because it does not know what "real ground" is.

In order to be 100% sure you prevent Bill´s "hot green" problem with a green wire that comes from someone else (marina) you have to use a multimeter between green and real earth (as in a metal rod to connected to anything else) and read zero volts. Otherwise you can just connect your boat´s green to your own ground and rod and be done with it.

[DotDun]

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).

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

Originally Posted by leftbrainstuff

I always check polarity of a new connection.

Often land based electricians of varying skill levels are engaged to fiddle with shore power.

You can either use a multi meter or one of the little colored light toolsm

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

There are/were 2 issues with Bill's story, this is/was lost on most in this thread.

A neutral/hot reversal by itself would not cause Bill's propeller to be 120v potential above ground. The only way this can happen is with a second fault with the wiring on Bill's boat. Bill stated the reversal put 120v on the GROUND system of his boat, but he states the reversal was between hot (black) and neutral (white), not GROUND (green). So how did the 120v get on the GROUND (green)? The only way is if Bill's AC neutral (white) is tied to GROUND (green) (which is NOT code) on his boat, this is the second fault.

This has nothing to do with AC ground and DC ground being common as Bill states. (although this is a controversial topic for another thread).

So, it took 2 failures to put 120v potential wrt ground on Bill's propeller, not just the single reversal of white and black at the pedestal as stated.

[FlyingCloud1937]

Well,

There could be a double fault as you suggest, which is very possible in a boat/marine installation due to vibration, and corrosion.

It could also have been that the shore power was interrupted, and the inverter, is now the sources of power, with it's neutral to ground relay closed.

Or it could have been that he left the gen/shore power switch in the gen closed position, which would also tie neutral to ground.

But we would need an additional fault, as the source was not based on earth.

So we might assume that the boats earth/ground was broken either on the boat, or at the shore side connection.

Now all we need in any of these fault potentials is a voltage difference, for current to flow.

Everything can be referenced to ground, but with a 30 volt difference between the two ground references, enough current can flow to give a human a shock.

The further these potentials are a part the higher the current flows. Let's take a ground fault at zero to earth, and a high resistance limiting the same voltage to 60, one half of 120, the current in the ground deferential could cause an electrical shock/death, or fire.

Lloyd

Originally Posted by DotDun

There are/were 2 issues with Bill's story, this is/was lost on most in this thread.

A neutral/hot reversal by itself would not cause Bill's propeller to be 120v potential above ground. The only way this can happen is with a second fault with the wiring on Bill's boat. Bill stated the reversal put 120v on the GROUND system of his boat, but he states the reversal was between hot (black) and neutral (white), not GROUND (green). So how did the 120v get on the GROUND (green)? The only way is if Bill's AC neutral (white) is tied to GROUND (green) (which is NOT code) on his boat, this is the second fault.

This has nothing to do with AC ground and DC ground being common as Bill states. (although this is a controversial topic for another thread).

So, it took 2 failures to put 120v potential wrt ground on Bill's propeller, not just the single reversal of white and black at the pedestal as stated.

[K_V_B]

Originally Posted by tropicalescape

Grab something plugged in backward with wet feet after surfing and you find out why it matters,POW..

That's why people in Europe never sleep. It goes POW all the time...

Seriously now. Do you think that an appliance maker that build stuff that became deadly when plugged in backward would not have been litigated in to oblivion ages ago?


Sent from my iPad using Cruisers Sailing Forum

[K_V_B]

Originally Posted by rwidman

More often, they are dock hands or handymen at best. That brings us back to why we have reverse polarity indicators on our boats. Pretty much a complete circle.

More interesting is why we don't have reverse polarity indicators on our boat, the minority that does notwithstanding...



Sent from my iPad using Cruisers Sailing Forum

[DotDun]

Originally Posted by FlyingCloud1937

Well,

There could be a double fault as you suggest, which is very possible in a boat/marine installation due to vibration, and corrosion.

It could also have been that the shore power was interrupted, and the inverter, is now the sources of power, with it's neutral to ground relay closed.

Hmm, the inverter doesn't work if there is a 120v potential on the shorepower. Even then, the inverter opens the shorepower neutral/hot when it's putting out 120v.

Originally Posted by FlyingCloud1937

Or it could have been that he left the gen/shore power switch in the gen closed position, which would also tie neutral to ground.

And the transfer switch leaves the shore power neutral connected to the boat while in 'Gen' position??? If so, it's a huge problem. The transfer switch opens (at minimum) the H and N, hence the N/G tie in the generator is of no consequence.

Originally Posted by FlyingCloud1937

But we would need an additional fault, as the source was not based on earth.

So we might assume that the boats earth/ground was broken either on the boat, or at the shore side connection.

Now all we need in any of these fault potentials is a voltage difference, for current to flow.

Everything can be referenced to ground, but with a 30 volt difference between the two ground references, enough current can flow to give a human a shock.

No, the only source reference to earth ground is shorepower, neither the generator or inverter is reference to earth ground with the boat sitting on blocks.

You need to trace back to the source.

Originally Posted by FlyingCloud1937

The further these potentials are a part the higher the current flows. Let's take a ground fault at zero to earth, and a high resistance limiting the same voltage to 60, one half of 120, the current in the ground deferential could cause an electrical shock/death, or fire.

Lloyd

[deblen]

Originally Posted by svlamorocha

I am familiar with land and boat wiring in various places including the US approach. I have also sailed boats to places with different systems.

Now we are not talking about safety and grounding but it is still a great topic.

I do not like US-style 240V appliances in US boats taken outside the US. It just complicates things too much at the time of getting shorepower or running off a genset.

You can get 120V heater elements and Splendide washer-dryers that work great. Benefit is that you only need two current-carrying wires from shore (L and N) and "one-voltage-at-a-time" genset.

If there is a need to split load into two sources then I prefer a) split into two buses and feed each bus separately from a) separate shore cables (which can be at 0, 120, 180 or whatever number of degrees away form each other) ; b) one from shore and one from genset or c) use modern inverter-chargers with "power assist" and "power control".

The Antares boats have a nice implementation of a) and b) but not c).

If you do not mix load voltages then you can easily run that boat in foreign marinas with a single iso transformer that doubles as step-down. If you had a 240V dryer on a boat with 120V minor appliances it would get much more complicated because the dryer could not be fed by the same iso transformer unless the trafo had two simultaneous taps (can yo find such a trafo?) or you connected the dryer ashore and losing the isolation.

We are only left with the frequency problem but that is for another thread!

By the way, you remind me of the strange setup at Crew´s Inn in Trinidad with two 127V hots at 120 degrees form each other. It worked fine for those who understood that 2x127V was 220V (not 254V) in that case, but the rest worried a lot!

Hell-I'm sorry I brought up the N.A. dual 240/120 requirement at this time.
I mentioned it only because I thought you & KVB were close enough to solving the hot ground problem.Lets get back to a safe grounding interface.
I don't care if you don't like N.A. 240V stoves on a boat.Fact is they are there & will stay there.
So will the N.A. 120V small appliances & 240V heaters.
And no way are N.A. boats going 3 phase.
And yes-leave freq.conversion out at this time.
We have to deal with things as they are-not as we would like them to be.
Also,lets stick with current ABYC/NEC code & assume all N.A. boats are wired to current code.It would be impossible to cover past or incorrect wiring.

So-best I can tell so far-to have my boat "plug & play" safely:

1. I need a Transformer with 240V primary (L1 & N) x 120-0-120 L1 N L2 secondary
2. I do not bring land Green (safety earth) aboard,because it could be floating above 0V,due to defective marina ground.
3. I conn. my boats N to my boats AC Green(safety earth)(against code @ present) at boats shore power dist. panel ?-by using txfmr,I can't get a hot neutral by reversal of shore L1 & N.
4. I use a 3 pole RCD at panel, conn. to L1 N L2 to detect any un-balanced flow.Will this detect a hot G also?
5. I conn. my AC Green to Water-somehow?? It has to conn. to real Earth somewhere,& I can't see lugging a load of 8ft ground rods & driving one at each stop.
6. DC neg-already conn.to engine block,in most cases.ABYC says conn. this to AC Green.

Disregarding frequency 60hz/50hz at this time
Disregarding generators & inverters internal to boat-your comments please.

Note: The above is for discussion only.Leave code & unsubstantiated opinions out of it.Purely an exercise.
Thanks/ Len

[FlyingCloud1937]

Would you like a minute to re-think.

I'll give you that anyways.

Now go back and re-read what I said.

Then as a good debater, thinking an argument from both sides, come back with a for and against.

I'll bet you find the answerer to my riddle, before I answer back.

Lloyd

Originally Posted by DotDun

Hmm, the inverter doesn't work if there is a 120v potential on the shorepower. Even then, the inverter opens the shorepower neutral/hot when it's putting out 120v.



And the transfer switch leaves the shore power neutral connected to the boat while in 'Gen' position??? If so, it's a huge problem. The transfer switch opens (at minimum) the H and N, hence the N/G tie in the generator is of no consequence.



No, the only source reference to earth ground is shorepower, neither the generator or inverter is reference to earth ground with the boat sitting on blocks.

You need to trace back to the source.

[FlyingCloud1937]

You do realize that Schenider, is the corp.... that purchased Xantrex (formerly aka TRACE)...and before that (Heart) the one and only worst hated inverter/charger marine dc supplier in the industry.

Lloyd

Originally Posted by svlamorocha

Nope; the RCD trips in 1/20th of a second and that is too fast for my clamp.

Jokes aside, the RCDs used where I live are rated at 30mA and 300 miliseconds. To be fair, according to the guys who have the toy to test them (Fluke 1650 series) they typically trip a bit below 30mA (standard requires no trip below 15 and 100% trip at 30, all in 300 miliseconds). In addition, it could be that the current was lower and it took longer given the curve of the device. Still, this is good evidence that 30mA nominal RCDs save people.

The confusion in what they teach in the US (I used to work for a large company in the US and saw visiting European safety guys explain this) is that they quote mA figures without the corresponding duration. Yes, there is a small probability of ventricular fibrilation at 40mA (see curve C1 in attached graph) but only after FIVE SECONDS. Therefore a 30 mA RCD that trips at nominal current within 300 miliseconds is good enough to save you from ventricular fibrilation (or any muscular reaction for that matter). Of course, I am talking about a proper whole-house DIN-rail-mounted RCD made by Schenider or the like, not one of those cheap outlet-mounted things.

[K_V_B]

Originally Posted by deblen

1. I need a Transformer with 240V primary (L1 & N) x 120-0-120 L1 N L2 secondary
2. I do not bring land Green (safety earth) aboard,because it could be floating above 0V,due to defective marina ground.
3. I conn. my boats N to my boats AC Green(safety earth)(against code @ present) at boats shore power dist. panel ?-by using txfmr,I can't get a hot neutral by reversal of shore L1 & N.

Are you sure this is against code? This image is straight from the ABYC standards:



This diagram shows N and PE tied together at the secondary, so the code does allow it.
The only thing missing here in my opinion is an RCD on the boat side of the isolation transformer. But you have included one so:

4. I use a 3 pole RCD at panel, conn. to L1 N L2 to detect any un-balanced flow.Will this detect a hot G also?

Here in Europe we have two pole and four pole RCDs. I haven't come across a 3 pole one myself, but they exist.
This will not detect a "hot" PE, bu you will not have this problem...

5. I conn. my AC Green to Water-somehow?? It has to conn. to real Earth somewhere,& I can't see lugging a load of 8ft ground rods & driving one at each stop.
6. DC neg-already conn.to engine block,in most cases.ABYC says conn. this to AC Green.

You basically bond all the metal on your boat together. The idea is to protect you. If you were to inadvertently touch a metal part of the boat together with a live wire the RCD will trip.

Disregarding frequency 60hz/50hz at this time

That is largely not an issue anyway.

My ideal system, for a boat that is supposed to be able to go anywhere would look different however. (Maybe I'll have that boat build one day...)

a) I would not connect the boats' AC system to shore power at all.
b) The AC system would be centred around a combi inverter/charger with power assist like Victron or Mastervolt make. Add in a small genset and a big battery bank. I have this way clean, 240V 50Hz wherever I go.
c) Shore power is only connected to a single device: A battery charger that has a wide input range. Chargers exist that will accept anything between 90 and 400V, AC and DC...

For a simple boat that only sails on one side of the Atlantic wiring to CE standard would be sufficient. Ie, having a RCD at the point of entry. But I would add a galvanic isolator.

[FlyingCloud1937]

I don't know....weenk

read this and tell me

http://www.google.com/url?sa=t&rct=j...85970519,d.cGU
Now, let’s clear up some of the terminology
confusion when it comes to these devices.
The ABYC Standards refer to two types of
transformers: Isolation and Polarization. To
be designated an “Isolation Transformer” by
the ABYC Standards, it must have a metallic
shield installed between the primary and secondary
windings that is electrically insulated
from all other portions of the transformer.
This shield must be able to withstand a
4000VAC potential for one minute applied
between the shield and all other components
including windings, core and the outside
enclosure.

Lloyd

Originally Posted by K_V_B

Are you sure this is against code? This image is straight from the ABYC standards:



This diagram shows N and PE tied together at the secondary, so the code does allow it.
The only thing missing here in my opinion is an RCD on the boat side of the isolation transformer. But you have included one so:


Here in Europe we have two pole and four pole RCDs. I haven't come across a 3 pole one myself, but they exist.
This will not detect a "hot" PE, bu you will not have this problem...



You basically bond all the metal on your boat together. The idea is to protect you. If you were to inadvertently touch a metal part of the boat together with a live wire the RCD will trip.


That is largely not an issue anyway.

My ideal system, for a boat that is supposed to be able to go anywhere would look different however. (Maybe I'll have that boat build one day...)

a) I would not connect the boats' AC system to shore power at all.
b) The AC system would be centred around a combi inverter/charger with power assist like Victron or Mastervolt make. Add in a small genset and a big battery bank. I have this way clean, 240V 50Hz wherever I go.
c) Shore power is only connected to a single device: A battery charger that has a wide input range. Chargers exist that will accept anything between 90 and 400V, AC and DC...

For a simple boat that only sails on one side of the Atlantic wiring to CE standard would be sufficient. Ie, having a RCD at the point of entry. But I would add a galvanic isolator.

[FlyingCloud1937]

I don't know?????????????????????????????????????????????? ?????????????????????????????????????????????????? ??????????????????????????????????
[quote]Here’s a question
to keep in mind while reading this
article: Would you deliberately disconnect
the green grounding wire from receptacles
or appliances in your home?[/qote]

Originally Posted by K_V_B

Are you sure this is against code? This image is straight from the ABYC standards:



This diagram shows N and PE tied together at the secondary, so the code does allow it.
The only thing missing here in my opinion is an RCD on the boat side of the isolation transformer. But you have included one so:


Here in Europe we have two pole and four pole RCDs. I haven't come across a 3 pole one myself, but they exist.
This will not detect a "hot" PE, bu you will not have this problem...



You basically bond all the metal on your boat together. The idea is to protect you. If you were to inadvertently touch a metal part of the boat together with a live wire the RCD will trip.


That is largely not an issue anyway.

My ideal system, for a boat that is supposed to be able to go anywhere would look different however. (Maybe I'll have that boat build one day...)

a) I would not connect the boats' AC system to shore power at all.
b) The AC system would be centred around a combi inverter/charger with power assist like Victron or Mastervolt make. Add in a small genset and a big battery bank. I have this way clean, 240V 50Hz wherever I go.
c) Shore power is only connected to a single device: A battery charger that has a wide input range. Chargers exist that will accept anything between 90 and 400V, AC and DC...

For a simple boat that only sails on one side of the Atlantic wiring to CE standard would be sufficient. Ie, having a RCD at the point of entry. But I would add a galvanic isolator.

[FlyingCloud1937]

Originally Posted by K_V_B

That is largely not an issue anyway.

My ideal system, for a boat that is supposed to be able to go anywhere would look different however. (Maybe I'll have that boat build one day...)

a) I would not connect the boats' AC system to shore power at all.

b) The AC system would be centred around a combi inverter/charger with power assist like Victron or Mastervolt make.

Where will the power for shore side assist come from?

c) Shore power is only connected to a single device: A battery charger that has a wide input range. Chargers exist that will accept anything between 90 and 400V, AC and DC..

For a simple boat that only sails on one side of the Atlantic wiring to CE standard would be sufficient. Ie, having a RCD at the point of entry..

Why

But I would add a galvanic isolator.

[K_V_B]

Originally Posted by FlyingCloud1937

Where will the power for shore side assist come from?

I would not plan to use shore side power assist. I would plan on having a large enough inverter, and use gen set to assist if needed.

Why

What is the problem?

[K_V_B]

Originally Posted by FlyingCloud1937

to keep in mind while reading this
article: Would you deliberately disconnect
the green grounding wire from receptacles
or appliances in your home?

I would not. Even though until the mid 90ies ungrounded receptacles were still permitted in the country I was then living in (The Netherlands).

But I am not proposing not having a proper grounded system.