AC DC common ground

[mitiempo]

Originally Posted by goboatingnow

Agreed but the point is major standards bodies disagree about the importance. ISO feels that whole boat RCD protection removes the need.

Personally I don’t want any path for external current into my dc system and “ protective earths “ in marinas area often nothing of the sort.

It should be pointed that ISO standards are legal requirements in the EU. ABYC in the US is a recommendation

"...protective earths in marinas are often nothing of the sort."
That is the reason for a secondary path to earth in case of a fault.

While ABYC is only a recommendation surveyors are heavily guided by the ABYC standards and insurance companies listen to the surveyors.

[donradcliffe]

It is a contentious issue, and a serious safety hazard to swimmers in fresh water marinas. I for one do not agree with the ABYC rule, because for every internal short in a battery charger, I encounter at least 10 shore power systems with a non functional safety ground. The European RCD system is more failsafe and protective.

In addition to the serious corrosion issues, the AC/DC connection will cause spurious trips to RCD breakers in modern marinas. One of the known problems is the reverse polarity indicator, which IS another connection between ground and neutral on the boat.

[goboatingnow]

In reality in European Marinas , ( and I spent a lot of time in a freshwater marina ) there are multiple RCDs in the circuit , typically the boat , the pontoon Pilar , the pontoon and the marina feed

Often a trip cause One or all them to trip.

I’ve never heard of swimmers being electrocuted ( on my side of the pond anyway ) not withstanding that it’s more likely the sewage would poison them first.

[boatpoker]

Originally Posted by goboatingnow

In reality in European Marinas , ( and I spent a lot of time in a freshwater marina ) there are multiple RCDs in the circuit , typically the boat , the pontoon Pilar , the pontoon and the marina feed

Often a trip cause One or all them to trip.

I’ve never heard of swimmers being electrocuted ( on my side of the pond anyway ) not withstanding that it’s more likely the sewage would poison them first.

ESD is a fresh water phenomena. There are no recorded incidents of ESD in salt water.

[goboatingnow]

Originally Posted by boatpoker

ESD is a fresh water phenomena. There are no recorded incidents of ESD in salt water.

Err I mentioned freshwater. That’s where I was based

My experience is that the minute a live wire protected by an RCD hits freshwater , it trips , ie within the rated 30ms.

[smac999]

Originally Posted by donradcliffe

It is a contentious issue, and a serious safety hazard to swimmers in fresh water marinas. I for one do not agree with the ABYC rule, because for every internal short in a battery charger, I encounter at least 10 shore power systems with a non functional safety ground. The European RCD system is more failsafe and protective.

In addition to the serious corrosion issues, the AC/DC connection will cause spurious trips to RCD breakers in modern marinas. One of the known problems is the reverse polarity indicator, which IS another connection between ground and neutral on the boat.

The ac to dc ground SAVES swimmers in the water. The bond is the only thing that allows a normal ac breaker to trip if the ac hot shorts out in the boat to metal. Ie against the engine block or a through hull. and is exactly why the rule was added. I was on a boat a few months back where the ac hot was shorted to a through hull and the boat was leaking 15a into the water. Had that bonding system been tied to ac ground as it should it would be dead short and trip ac breakers.

Elci and isotransformers are better options though.

The rev pol indicator has nothing to do with the ac - dc ground bond.

[smac999]

Originally Posted by boatpoker

ESD is a fresh water phenomena. There are no recorded incidents of ESD in salt water.

Most ocean marinaras here are at river bottoms and have lots of fresh water in them. The fact that the ocean freezes In the marina in the winter proves that.

[Kolchac]

You must NOT connect!

[CharlieJ]

@Kolchac #38:
Your location shows as the USA. On what do you base your entirely incorrect opinion?

[CharlieJ]

@goboatingnow #28:
My quote of ISO 13297 was in reply to the comment up thread by @roland_stockham #9:

May have changed but in Europe it was forbidden to connect the A/C ground to the DC neutral.

I was pointing out that this connection was not forbidden.

BTW, there are very few boats built before 2016 in my area that have been retrofitted with ELCIs. Also, marinas in my area (Gulf of Mexico) are very slow to upgrade to the latest requirement for RCD's/ELCI's in the shore power system as required since 2011 by the National Electrical Code.

[boatpoker]

Originally Posted by smac999

Most ocean marinaras here are at river bottoms and have lots of fresh water in them. The fact that the ocean freezes In the marina in the winter proves that.

Please provide link to an incident of ESD in salt water.

[boat driver]

good deal of confusion on this thread-
aside from the various country government agencies involved, technology itself has a good deal of variables-
but bottom line- if you have a doubt in your vessel wiring or the vessel is tripping ground fault breakers ashore may I suggest contacting a good vessel surveyor or a reputable marine electrician and asking/understanding the reason why.
I can suggest multiple reasons for the tripping as vessels get more complex and more so- multiple electrical "leaking" as vessels go through upgrades and maintenance. It is not a single technological expense solution generally. (isolators are good but retrofit can be covering a problem)
I can example a vessel wired during manufacture where a single outlet was grounded to the steel hull (like a car), another vessel with the wiring AC and DC all the same color.
I can example a high end manufacture that has vessels wired based on their local code. (Boat show some popped the gfi shoreside some did not).
Then west marine had a series of invertors that had a motherboard short that appeared in sail drive units deteriorating.
The lesson here is find out why.

[goboatingnow]

Originally Posted by mitiempo

"...protective earths in marinas are often nothing of the sort."

That is the reason for a secondary path to earth in case of a fault.



While ABYC is only a recommendation surveyors are heavily guided by the ABYC standards and insurance companies listen to the surveyors.

No it’s an argument for fitting RCDs. These are specifically fitted to detect abnormal current return paths . The ABYC ac protective earth dc connection is in my view dated , ignores RCDs and can be a huge source of impressed current

[CharlieJ]

@goboatingnow #43:

The ABYC ac protective earth dc connection is in my view dated , ignores RCDs and can be a huge source of impressed current

What exactly do you mean by "...a huge source of impressed current"?

[AndyEss]

Originally Posted by smac999

Most ocean marinaras here are at river bottoms and have lots of fresh water in them. The fact that the ocean freezes In the marina in the winter proves that.

Huh?
Fresh water freezes at 32deg F, seawater at about 29deg F. Surely parts of Canada have occasional winter air temperatures colder than 29?
Ice on water (by itself) says next to nothing about its salt content.
Or is the Arctic Ocean actually a freshwater lake? That polar ice pack that stretches from North America to Asia and Europe is still real.