Proper Grounding for AC and DC

[Ike]

Yes ABYC Standards are voluntary but built into them are the Federal Regulations. (by the way when reading the Federal Regs, when they speak of the "ungrounded conductor" they mean the positive conductor, unless it's an old system with a positive ground.)

ABYC standards are the defacto standard for boat manufacturing and surveying in the US and many other countries around the world. Any boat built by an NMMA certified manufacturer is built to ABYC standards (80% of the boats built in the US and Canada) If you get a survey by any certified SAMS or NAMS surveyor they will use ABYC as the standard. If you get sued and taken to court the court will use the ABYC standard. If you take your boat in for work the technician will use ABYC standards, and if you say I don't want it that way, they will refuse to do it because it will void their liability insurance. Why all this? Because the ABYC Standards are the safest way to build boats. ABYC incorporates UL, SAE, NFPA, USCG, and ISO Standards, and it is ANSI certified. If you don't know what all that alphabet soup is about then you need to find out if you are going to do such things as wire your boat, or work on fuel systems. Even such mundane things as scuppers and dewatering ports, bilge pumps, and sill heights are covered by ABYC standards.

And yes there are some minor differences between EU (ISO standards incorporated into the Recreational Craft Directive, which the EU uses) But ABYC has been for many years the US (under a memorandum of understanding from the USCG and the state department) representative to ISO. They had significant input into the ISO standards and have harmonized them as much as possible. I have sat on many ABYC committees and some ISO meetings. And the differences are minor and accomplish exactly the same thing. And ABYC has adapted the Residual Current Device (one of the few differences) but calls it an ELCI and is currently looking at how that will fit into the shore power/onboard power system.

So lets get beyond this. If you don't want to follow the accepted industry standard that is your business as long as you are only putting yourself at risk. But if you take other people on your boat, or moor it in any marina you are placing others at risk.

And I agree with Nick that an Isolation transformer is the best solution if you have an AC system.

Sorry for the rant. But I have spent many years investigating and reviewing investigations of too many fires (most of which are electrical in origin) and deaths to not get worked up about this. I have spent a third of my life trying to get people to follow the ABYC standards, which go way beyond the Coast Guard standard that I was employed to enforce.

And there is one point about the standard that is definite. There should be only one ground point on a boat. All ground wires should lead to that one point. The engine block. The battery negative, the green wire (grounding wire) of the AC system, the bonding wires, the lightning protection system, all should ground to one point. Even if you have a ground buss, that buss should be connected only to ground at the engine block.

[cburger]

Well I am almost there just have to get the AC main grounded to the engine now and I will be compliant.

[s/v Jedi]

@Ike,

Yes, ABYC is the standard for the USA, but I don't think for many countries outside the USA although some will have basically copied it.

But when you speak of "the standard" here on this International forum, it sounds like if it were a world standard, while US yacht manufacture is of course just a fraction of the world's numbers.

I do not agree with you that the ABYC recommendations are always the best way to do things; especially for AC electrical installation, imho the EU guidelines are superior. What I mean with that is that they provide the same level of personal safety while also providing optimal protection for the boat and her systems. This might change as ABYC further adapts to new technology and start to appreciate the EU point of view on how to approach safety grounding. (they will catch up is what I mean). For example, I don't think they understand that GFCI like devices were developed as alternative to safety ground.

My AC electrical installation is "floating", ie. not referenced to ground. I don't use the shorepower ground and I also don't use the shorepower neutral if possible (isolation transformer). The installation creates a new ground with dynaplates and also a new Neutral which is not grounded (using auto transformer). This is not as recommended by ABYC, but it is safer nonetheless. It is also general practice in the US and elsewhere when extra safety is needed (electrics/electronics test benches).

I don't think we will see a world standard anytime soon, so we will keep the different ways to implement some things. They are probably all okay and often one will be better than the rest.

ciao!
Nick.

[donradcliffe]

Ike,

If you have investigated electrocutions in fresh water, you must be aware that the ABYC's insistence on connecting the DC and AC grounds has killed a number of swimmers, not to mention doing millions of dollars worth of damage through electrolysis. I personally don't know how you can live with your recommendations, given that knowledge.

The EU standards are far safer and effective. Until the ABYC overcomes its inertia, I can only say DON'T SWIM IN YOUR MARINA!!!

[goboatingnow]

Originally Posted by s/v Jedi

@Ike,

Yes, ABYC is the standard for the USA, but I don't think for many countries outside the USA although some will have basically copied it.

But when you speak of "the standard" here on this International forum, it sounds like if it were a world standard, while US yacht manufacture is of course just a fraction of the world's numbers.

I do not agree with you that the ABYC recommendations are always the best way to do things; especially for AC electrical installation, imho the EU guidelines are superior. What I mean with that is that they provide the same level of personal safety while also providing optimal protection for the boat and her systems. This might change as ABYC further adapts to new technology and start to appreciate the EU point of view on how to approach safety grounding. (they will catch up is what I mean). For example, I don't think they understand that GFCI like devices were developed as alternative to safety ground.

My AC electrical installation is "floating", ie. not referenced to ground. I don't use the shorepower ground and I also don't use the shorepower neutral if possible (isolation transformer). The installation creates a new ground with dynaplates and also a new Neutral which is not grounded (using auto transformer). This is not as recommended by ABYC, but it is safer nonetheless. It is also general practice in the US and elsewhere when extra safety is needed (electrics/electronics test benches).

I don't think we will see a world standard anytime soon, so we will keep the different ways to implement some things. They are probably all okay and often one will be better than the rest.

ciao!
Nick.

What's the purpose of a dynaplate in an isolating transformer situation no current can flow in it ever. Also if you don't connect on board AC ground to on board neutral. Faults can cause AC devices to go hot and the breakers will not trip I fully support your idea of floating isolated AC and agree that ABYC is behind the curve.

Dave

[goboatingnow]

.......l.

And there is one point about the standard that is definite. There should be only one ground point on a boat. All ground wires should lead to that one point. The engine block. The battery negative, the green wire (grounding wire) of the AC system, the bonding wires, the lightning protection system, all should ground to one point. Even if you have a ground buss, that buss should be connected only to ground at the engine block.

I couldn't disagree more and is not current practice as far as I can see. DC negatives should be communed close to the battery. This provides better DC performance and an electrically quiet bus.

Dave

[Blue Stocking]

So, there you go Roscoe, take your pick , and apparently, your chances.

[s/v Jedi]

Originally Posted by goboatingnow

What's the purpose of a dynaplate in an isolating transformer situation no current can flow in it ever. Also if you don't connect on board AC ground to on board neutral.

I agree that the ground isn't needed for AC safety in that scenario. The reason that it's around enters into the bonding and lightning safety systems, plus it was ABS approved when built.

ciao!
Nick.

[sdowney717]

Originally Posted by donradcliffe

Ike,

If you have investigated electrocutions in fresh water, you must be aware that the ABYC's insistence on connecting the DC and AC grounds has killed a number of swimmers, not to mention doing millions of dollars worth of damage through electrolysis. I personally don't know how you can live with your recommendations, given that knowledge.

The EU standards are far safer and effective. Until the ABYC overcomes its inertia, I can only say DON'T SWIM IN YOUR MARINA!!!

That is why the shore power source should be ELCI or GFCI protected, especially with fresh water marina. Wont that cut the power if a current leakage occurs and keep people from electrocution shock drowning?
And I mean at the shore power pedestal, not inside the boat. The shore cord is a source of a short. And it then protects everything downstream from the power source, cord and all.

[goboatingnow]

Originally Posted by sdowney717

That is why the shore power source should be ELCI or GFCI protected, especially with fresh water marina. Wont that cut the power if a current leakage occurs and keep people from electrocution shock drowning?
And I mean at the shore power pedestal, not inside the boat. The shore cord is a source of a short. And it then protects everything downstream from the power source, cord and all.

Yes and code in the EU requires RCDs in the marina supply post. I cant believe US marina don't install them. In fact recommendations in the UK code now suggest isolating transformers in the supply post should be installed, usually the next revision converts recommendations to mandatory requirements

Dave

[goboatingnow]

Originally Posted by Blue Stocking

So, there you go Roscoe, take your pick , and apparently, your chances.

I have to say Nick , I think lightening bonding to dynaplates is a complete waste of time, the wire just gets exploded. And anyway it's yours aluminium.

Dave

[s/v Jedi]

Originally Posted by goboatingnow

I have to say Nick , I think lightening bonding to dynaplates is a complete waste of time, the wire just gets exploded. And anyway it's yours aluminium.

Dave

I hate to say it, but with her previous owner, Jedi has proven the effectiveness of her lightning protection twice.

The wire does not get exploded. There is AWG-0 wire running straight (ie. no bends) from the foot of each mast to a bronze ground plate that is 1.5" thick and mounted right below each mast. This allows a controlled discharge to ground, without seeking thru-hulls etc. Not that it prevents extensive damage to elctronics, but it prevents getting holed by lightning.

Jedi is one of the fiberglass production Sundeers. The original prototype aluminium Sundeer is unique, only one of her around.

ciao!
Nick.

[donradcliffe]

Originally Posted by goboatingnow

Yes and code in the EU requires RCDs in the marina supply post. I cant believe US marina don't install them. In fact recommendations in the UK code now suggest isolating transformers in the supply post should be installed, usually the next revision converts recommendations to mandatory requirements

Dave

The best RCD protection is in the marina supply ON LAND, where it can protect against faulty wiring on the docks as well as the boats. Then a more sensitive RCD on the marina supply post. Once those systems are MANDATED, not recommended, you eliminate needless deaths every year.

See Marina Guard / Harbor Marine Consultants for a good discussion and an easy way to determine whether your or your neighbor's boat has a problem. I'm not affiliated with them, but I think they've got it right.

[goboatingnow]

Seems over the top to me, Its not a good idea to have RCDs on land, as you will get nuisance trips. Each pontoon finger has a trip and thats all thats neded. In many situations there may be group RCDs, but in my experience, thee often trip before the pontoon post and hence one fault takes out half the marina.

Dave

[donradcliffe]

The group RCD's can be set to a higher trip level than the supply RCD's to minimize nuisance trips and help locate the fault. They can also alarm in the harbormaster's office at lower than their trip levels. Looking at the database of Electric Shock Drownings (ESD), a number of people have been killed by degraded insulation and drooping wires upstream of the dock supply posts, and the technology is there to prevent those deaths.