GFIC Wiring

[CarinaPDX]

I just checked: the ABYC does not require the DC negative to be grounded - only that if the DC system is grounded it must be the negative side. So apparently an isolated AC system needs to have neutral and ground connected to the DC negative (at the engine or bus) but not necessarily to the seawater ground. Strange.

Greg

[goboatingnow]

Originally Posted by svmariane

Oops...Did I mention ABYC specs in the example? Let me check....

You mentioned " code"

Furthermore could you point out the relevant " code" that requires isolated supplies to have GFCIs. aBYC refers to shore power , the OP said inverters.

This is the very point I make , the codes are derived from house practice or poor practice in relation to available technologies or are inadequate when applied to certain systems ( like aluminium vessels with fully isolated mains ) , yet they get parroted out without any clear understanding of their weakness. ( and this isn't even a statutory code neither )

Dave

[goboatingnow]

Originally Posted by CarinaPDX

I just checked: the ABYC does not require the DC negative to be grounded - only that if the DC system is grounded it must be the negative side. So apparently an isolated AC system needs to have neutral and ground connected to the DC negative (at the engine or bus) but not necessarily to the seawater ground. Strange.

Greg

Not strange

Here's the European practice , which I beleive is more logically thought out. Unlike ABYC , this is a statutory code

Mandatory whole boat ELCI, in the boat , on shore power feed into the boat ( as well as mandatory ELCI , on the shore power pillar )

No connection between protective earth and DC negative , no requirement for either system to be seawater bonded.

Hence fully isolated on board power is possible via magnetic coupling ( generators , invertors , isolating traffo )in such cases no fault path exits between hot ( live ) and the earth. ,no possible swimmer shock , you can hold the hot wire in your hand and stand in the sea if you like ( just like a bird on a 40kv line !!)

Neutral and protective earth connected at power source , ie at mains utility ,etc, at onboard neutral for isolated generators.

No further localised GFCIs

Advantages

Fully isolated supplies possible
No load dumping between AC and DC systems
Reduction in impressed current corrosion potential
No ground loops
Whole boat RCD protection ,
Pillar supply protection ( shore power cable in the water issue )

Not saying one way or another , but its a more consistent approach.

Disadvantage
Relies on whole boat RCD ( same as house code )

Dave

[DotDun]

Originally Posted by svmariane

Situation: the insurance company requires a recent survey, and then the hired surveyor writes down that the vessel has no GFCI(s) installed and needs them to meet code.

What would you recommend, that the owner install the GFCI units or just lie about doing so to the insurance company?

I would hire a different surveyor.

[CarinaPDX]

Dave- Most of what you call for is currently recommended by ABYC: the ELCI at the shore power entrance and isolating transformer. They do cop out and allow for a galvanic isolator instead of the iso transformer, but at least when talking to an ABYC rep they do prefer the transformer. Disconnecting the sea water connection is also allowed if not recommended - I will give that some more thought.

I agree with the underlying point: standards bodies don't always get things right, or at least they can set some strange priorities. I have never agreed with the idea of connecting all of the underwater fittings together (bonding) and then to a zinc; it does sell a lot of zinc but otherwise accomplishes little. Better to isolate each fitting - which is usually the default on non-metal boats anyway.

Greg

[DotDun]

Originally Posted by FlyingCloud1937

A generator even though isolated, is connected to mother earth, by the fact that it is sea water cooled, this is a high Resistance connection. So in a fault situation, where the unsuspecting touches a live fault in one hand an a better connection to mother earth in the other hand, an x mA across the heart is psooible.

This is easily measured. But not worth it on my boat. My genset is connected to the input of my isolation transformer.

Originally Posted by FlyingCloud1937

because it's very likely that anything isolated is not, and now you have 2 problems. 1. Ions will find the path to ground, any path...ground=mother earth. 2. multiple pathes to ground set up the possibility for different potentials to ground and thereby circulating currents in the earth ground. which creates all manor of corrosion issues.

Huh? You are claiming that my isolation transformer and my inverter is likely not isolated and magically connected to a earth ground somehow?

[FlyingCloud1937]

oops

Lloyd

[FlyingCloud1937]

Originally Posted by DotDun

This is easily measured. But not worth it on my boat. My genset is connected to the input of my isolation transformer.

so if it's sea water cooled, then yes it's connected to mother earth. So in reality it's not isolated.

the Neutral to safety bond (ie source) in tact is the opposite end of the the same earth ground at the pedestal, but the sea water is the interconnect.

Huh? You are claiming that my isolation transformer and my inverter is likely not isolated and magically connected to a earth ground somehow?

any AC/DC device can fault, which will lead to not being isolated.

What AC/DC devises? oh like battery chargers, inverters, ac/dc refrigeration.....etc

Lloyd

[FlyingCloud1937]

Originally Posted by FlyingCloud1937

so if it's sea water cooled, then yes it's connected to mother earth. So in reality it's not isolated.

the Neutral to safety bond (ie source) in tact is the opposite end of the the same earth ground at the pedestal, but the sea water is the interconnect.





any AC/DC device can fault, which will lead to not being isolated.

What AC/DC devises? oh like battery chargers, inverters, ac/dc refrigeration.....etc

Lloyd

let's try this experiment in a different light. say lightning.

here we're floating on our yacht on the sea, with the heavens above, and the mother earth below the seabed.

now in the analogy we are isolated, ie floating.

what happens when the heavens provide us with electrical ions...ie a lighting strike.

because we are floating we should expect no issue right...? that's what I thought.

the very same laws of physics apply to any electrical ions onboard, it's all good until we have a fault.

then floating(isolation) isn't floating anymore.

Lloyd

[FlyingCloud1937]

Originally Posted by DotDun

This is easily measured. But not worth it on my boat. My genset is connected to the input of my isolation transformer.

You do realize that an isolation transformer only stops dc from flowing and that all AC can find it's way back to shore side ground through the ISO.

So it matters not which side the generator is connected, ...unless you also happen to run the generator while connected to the shore side pedistal.

Once disconnected, an ISO in series with the gen, is no different than an ISO in parallel with the gen.

Lloyd

[FlyingCloud1937]

Originally Posted by DotDun

This is easily measured. But not worth it on my boat. My genset is connected to the input of my isolation transformer.



Huh? You are claiming that my isolation transformer and my inverter is likely not isolated and magically connected to a earth ground somehow?

now that i think about it a little more.

The fact that you have your gen connected to the input side of your ISO, you have now bypassed the ISO, so that everything on your boat while connected to shore pedestal is a direct connection to mother earth, and all dc VA's can now bypass the ISO.

Why/how is this...because the gen is bonded neutral to earth, and the fact that the gen is connected to the dc bat/ships ground for starting.

You have now bonded the gen to dc, and AC shore side. thereby bypassing the ISO.

You are connecting the gen in parallel with the shore side earth (Huh? You are claiming that my isolation transformer and my inverter is likely not isolated and magically connected to a earth ground somehow?)

It's not magical, it was by your own design, it's called a circuit.

lloyd

[goboatingnow]

now that i think about it a little more.

The fact that you have your gen connected to the input side of your ISO, you have now bypassed the ISO, so that everything on your boat while connected to shore pedestal is a direct connection to mother earth, and all dc VA's can now bypass the ISO.

Why/how is this...because the gen is bonded neutral to earth, and the fact that the gen is connected to the dc bat/ships ground for starting.

You have now bonded the gen to dc, and AC shore side. thereby bypassing the ISO.

You are connecting the gen in parallel with the shore side earth (Huh? You are claiming that my isolation transformer and my inverter is likely not isolated and magically connected to a earth ground somehow?)

It's not magical, it was by your own design, it's called a circuit.

Lloyd , I dont know what youre smoking , but save some for me!

Seawater cooled gennys do Not have by default the neutral connected to the case. They produce a output that is not earth referenced. ie there is no path via the planet to the neutral ( unless you create one deliberately).

Similarly inverters use magnetic coupling to create a AC output

IN particular isolating transformers ARE specifically designed to produce an un-grounded isolated , ie no earth return path . Here every building site uses 110V ( yes in 230VAC land) portable power tools fed by a 230 to 110V isolating traffo ( the ubiquitous yellow isolating traffo). WHy ,to ensure that the worker never has a ground path to earth, hence irrespective of all safety devices, he can touch the hot wire, while standing in a pool of water


Bonding neutral to protective earth , in itself may or may not produce a connection to sewater and hence the earth. even connecting the protective earth wire to DC negative ( done under ABYC to bring things like engine blocks into the protective AC wire protection), in itself do not guarantee a path to seawater.

I am not aware that ABYC mandates a DC path ( or AC earth path to seawater locally on the boat).

Where you to install a isolating transformer following such a supposed code, ie where a deliberate and proper seawater connection was established to neutral for on board sources of AC, you would deliberately undoing the very isolation you just gave "charles industries" large wallops of green-backs for.!!. It make no sense .( nor is it actaully required under ABYC).

My understanding from reading the ABYC recommendations over the years is the 5mAGFCI/ 30mA ELCI is required for shore power installations, ABYC is quite quiet on on-board AC generation , especially isolated ones.

Hence my original comments stands, RCD,( as a generic term) give little ( note not none) additional protection where no low resistance path to the planet is available.

furthermore the protection produced by using an isolated on board AC generator is significantly greater then that supplied by destroying the isolation , merely to create a situation where RCDs can function

Creating a risk, in order to enable a particular safety device to protect you from it does not make any sense at all.


Dave

[goboatingnow]

The fact that you have your gen connected to the input side of your ISO, you have now bypassed the ISO, so that everything on your boat while connected to shore pedestal is a direct connection to mother earth, and all dc VA's can now bypass the ISO.

generators are onboard power sources, they should never be connected to the input side of a isolating transformer. They are connected into the on board AC circuits INSTEAD of the isolating transformer by using a transfer switch. ( in the same manner as inverters etc)

[DotDun]

Originally Posted by goboatingnow

generators are onboard power sources, they should never be connected to the input side of a isolating transformer. They are connected into the on board AC circuits INSTEAD of the isolating transformer by using a transfer switch. ( in the same manner as inverters etc)

The shorepower / generator transfer switch connects to the input of the IT.

[goboatingnow]

Originally Posted by DotDun

The shorepower / generator transfer switch connects to the input of the IT.

Why, it has absolutely no function in that regard, The output of a generator is isolated, unless you make it not so.

ANyway , this has no bearing on the substance of my comments,

Dave