Shore Ground NOT Connected to Isolation Transformer

[goboatingnow]

Given here RCBOs are cheap I would always have one fitted right behind my shore power cable entry. If fitted this allows no shore earth to come in contact with an isolation transformer.

RCBOs can be less usefully fitted to the output side of the transformer as the existence of sneak return paths is virtually eliminated by taking earth ground out of the equation. But I’d still fit them anyway albeit they are less effective. MCBs of course should be fitted to the output side

[Lake-Effect]

Originally Posted by s/v Jedi

No, that does not increase safety. The reason for the jumper is that by hauling out you now fall under regular code shoreside installation, where they don’t recognize isolation transformers.

Connecting the grounds INCREASES safety. If the iso transformer is a properly-rated plastic-encased toroid installed by an expert Jedi, the improvement is marginal. But not all marine iso transformers are encased in non-metallic enclosures, or installed by expert Jedis.

I guess for hospitals etc. where they do use them, they have separate code sections to allow it.

You guessed wrong; the grounds are still connected.

Iso transformers for hospitals.

Is it too much to ask a self-proclaimed expert to have a bit better grasp on their area of expertise, and to not broadcast opinion as fact?

[Lake-Effect]

Originally Posted by s/v Jedi

With that I fully agree that the NEC is backwards like nothing else. But that doesn’t mean the ABYC shouldn’t have recognized ELCI breakers 20 years earlier.

Yes, it's all the fault of the ABYC.

Since 2011, efforts have been underway from both the building code side and from the boat building side to address safety issues due to stray electrical current in and around docks and marinas. The National Electrical Code Article 555 addresses electrical shock drownings caused by leakage of electrical current from A/C shore power facilities on docks and marinas. Concurrently, the American Boat & Yacht Council (ABYC) section E-11.11 has made changes to address A/C power leakage from boats into surrounding waters that endanger people.

(source)

As an expert, you already know that the ABYC has been leading the awareness campaign for Electric-Shock Drowning.

[goboatingnow]

Originally Posted by Lake-Effect

Connecting the grounds INCREASES safety. If the iso transformer is a properly-rated plastic-encased toroid installed by an expert Jedi, the improvement is marginal. But not all marine iso transformers are encased in non-metallic enclosures, or installed by expert Jedis.


You guessed wrong; the grounds are still connected.

Iso transformers for hospitals.

Is it too much to ask a self-proclaimed expert to have a bit better grasp on their area of expertise, and to not broadcast opinion as fact?

Connecting the grounds does NOT increase safety. That’s self evident if you study fault current paths

In fact it decreases safety as reintroducing earth referenced currents increases the potential for coming in contact with a fault return path

The is issue of a plastic or metal case iso traffo is a red herring. It’s merely one or many shock potentials.

[s/v Jedi]

Originally Posted by Lake-Effect

Connecting the grounds INCREASES safety. If the iso transformer is a properly-rated plastic-encased toroid installed by an expert Jedi, the improvement is marginal. But not all marine iso transformers are encased in non-metallic enclosures, or installed by expert Jedis.


You guessed wrong; the grounds are still connected.

Iso transformers for hospitals.

Is it too much to ask a self-proclaimed expert to have a bit better grasp on their area of expertise, and to not broadcast opinion as fact?

My gosh you need to work at your stance even more than me. You are name calling, please read up on Ad Hominem and how this is completely counter productive for discussion, and not allowed on this forum.

So here some points for consideration:

- all toroidal transformers that I have seen are insulated.

- show me how ground is beneficial behind an isolation transformer(no links, just explain it) or stop promoting it.

- I skip from one thing to another too quickly; I know I need to improve my communication skills. It’s how my brain works and I need to take more time to formulate my writing.
Here I commented on how a ground is of no safety value behind an isolation transformer, then skipped to why it is required to install a ground jumper when you’re hauled out (code does not recognize isolation transformer) and then on to hospitals (but there are many shoreside installations with isolation transformers) where they are used so probably code does recognize them there. I never said that hospitals don’t use ground and I never meant to imply that. Hospitals only use isolation transformers in parts of their installation, like ICU’s because it is too expensive for the whole facility and the added level of safety isn’t required for most of it.

Also, your link shows that the installation is done according to IEC regulations, which is the International standards committee that I referenced before. You act and say it is NEC code so why does your link say IEC? (See attachment)

I hope you can continue this discussion in a civil manner. If you keep throwing personal insults then I’ll ignore it completely.

[goboatingnow]

Originally Posted by Lake-Effect

Yes, it's all the fault of the ABYC.

Since 2011, efforts have been underway from both the building code side and from the boat building side to address safety issues due to stray electrical current in and around docks and marinas. The National Electrical Code Article 555 addresses electrical shock drownings caused by leakage of electrical current from A/C shore power facilities on docks and marinas. Concurrently, the American Boat & Yacht Council (ABYC) section E-11.11 has made changes to address A/C power leakage from boats into surrounding waters that endanger people.

(source)

As an expert, you already know that the ABYC has been leading the awareness campaign for Electric-Shock Drowning.

Europe has virtually no instances of electro shock drowning

Why , because of the widespread shore use OF RCBO including mandatory use on marina pillars.

The US would be better advised to follow suit rather then the ABYC tying itself in knots trying to fix on a boat what should be mandatory in the NEC.

US house wiring standards are frightening To a Northern European !!!

[Lake-Effect]

Originally Posted by goboatingnow

Connecting the grounds does NOT increase safety. That’s self evident if you study fault current paths

In fact it decreases safety as reintroducing earth referenced currents increases the potential for coming in contact with a fault return path

You haven't considered all possible faults, and all possible paths.

The US would be better advised to follow suit rather then the ABYC tying itself in knots trying to fix on a boat what should be mandatory in the NEC.

Well, exactly. How is this the fault of the ABYC, again?

[s/v Jedi]

Originally Posted by Lake-Effect

Yes, it's all the fault of the ABYC.

Since 2011, efforts have been underway from both the building code side and from the boat building side to address safety issues due to stray electrical current in and around docks and marinas. The National Electrical Code Article 555 addresses electrical shock drownings caused by leakage of electrical current from A/C shore power facilities on docks and marinas. Concurrently, the American Boat & Yacht Council (ABYC) section E-11.11 has made changes to address A/C power leakage from boats into surrounding waters that endanger people.

(source)

As an expert, you already know that the ABYC has been leading the awareness campaign for Electric-Shock Drowning.

At least I know that they are 20 years behind the rest of the world. You can say they are “leading” but you really mean in the US only. You just wrote something else showing the US was 30 years behind, pointing fingers to the NEC which is also an American institute.

[goboatingnow]

Shoreside codes allow isolating transformers but insist on output common earth. This is because a risk always exists that the output comes in contact with non isolated earth referenced mains.

In fact U.K. site transformers are wired like this to reduce the shock voltage to 55V



This is not a situation that exists on a boat.

[s/v Jedi]

Originally Posted by goboatingnow

Shoreside codes allow isolating transformers but insist on output common earth. This is because a risk always exists that the output comes in contact with non isolated earth referenced mains.

In fact U.K. site transformers are wired like this to reduce the shock voltage to 55V

Attachment 260519

This is not a situation that exists on a boat.

Exactly, the Brits are pretty smart with that as well. See how both outputs are hot, something most US installers are fearful of even though their 240V outlets are the same…. and how ground is on a center tap and this tap isn’t used for anything else than grounding. 55V is very survivable, the avg person from my generation was supposed to be tolerant of 48V DC which is much tougher than AC.

So, when a hauled out boat installs the ground jumper in the transformer, it is 100% up to code in the US? That’s great news, I never found any NEC code describing it.

[Lake-Effect]

Originally Posted by s/v Jedi

My gosh you need to work at your stance even more than me. You are name calling, please read up on Ad Hominem and how this is completely counter productive for discussion, and not allowed on this forum.

I'm sorry, you crowned yourself an expert, yet you continue to project your opinion (often a very well founded one) as fact. Turn up the humility just a little maybe? "I think" this is safer, "to the best of my knowledge" this is so, etc?

- show me how ground is beneficial behind an isolation transformer(no links, just explain it) or stop promoting it.

If there is any risk of shorepower AC energizing boat metal or any part of the DC wiring, the connection between boat ground and AC ground provides a low-resistance return path for that potential, and it should trip conventional overcurrent devices as well as all leakage-current-detecting devices (GFCI, ELCI RCD, etc). Without this return path, the fault remains until something (or someone) creates a leakage path sufficient to trip the above leakage-sensing devices. Which themselves sometimes fail, or are installed wrong. This should be obvious.

You correctly point out that the risk of this happening from a properly-installed, non-metal-cased iso transformer is very small... but it is not zero. There are several other places besides the transformer where hot shore AC can come into contact with boat metal.

I hope you can continue this discussion in a civil manner. If you keep throwing personal insults then I’ll ignore it completely.

I'm using a label you anointed yourself with. Step off the pedestal a little, share your opinion, and stop issuing proclamations.

People read and often follow what's posted here. If it's wrong, incomplete or misleading, that's a problem.

[goboatingnow]

Originally Posted by s/v Jedi

Exactly, the Brits are pretty smart with that as well. See how both outputs are hot, something most US installers are fearful of even though their 240V outlets are the same…. and how ground is on a center tap and this tap isn’t used for anything else than grounding. 55V is very survivable, the avg person from my generation was supposed to be tolerant of 48V DC which is much tougher than AC.



So, when a hauled out boat installs the ground jumper in the transformer, it is 100% up to code in the US? That’s great news, I never found any NEC code describing it.

The primary reason ,as I said , for shoreside /land based continuous ground is the real risk of contact with non isolated earth referenced supplies , so in this case the power tool body will trip the non isolated supply whereas were the grounds separated this wouldn’t happen.

However this shock risk is almost impossible on a boat as the shore side terminates at a specific and unique point and no non isolated ships supply network should therefore exist.

The discontinuous earth is very advantageous on a boat as protection from impressed corrosion and other issues associated with shore side supply.

[goboatingnow]

So, when a hauled out boat installs the ground jumper in the transformer, it is 100% up to code in the US? That’s great news, I never found any NEC code describing it.

Look a little closer , article 647 deals with “ derived power “ and requires continuous grounding

[goboatingnow]

Originally Posted by Lake-Effect

You haven't considered all possible faults, and all possible paths.



Well, exactly. How is this the fault of the ABYC, again?

I have considered all fault paths

Let’s analyse

With a discontinuous ground and an isolating transformer

1. Let’s assume the common GRP
boat ( metal boats are another thing entirely )

2. A residual cutout device affixed at the entry point of the shore power

3. Sea water is not part of any intentional connection

4. Underwater metals are not bonded or connected to any dc or ac common point or anode ( they may have individual dedicated anodes )

6. Other then the connection to the isolating transformer , there is no other shore mains network in the boat live.

A. Shore power faults : handled by the residual device and minimised by no mains network on board.

B on board shocks can only occur where the user is directly inserted into the output side circuit. No shock potential exists with reference to onboard metals or other normally unconnected materials

( iso “ earth “ is NOT connected to anything
other then directly mains fed equipment )

C. The inadvertent introduction of a third party shore referenced mains fault is extremely unlikely and can be discounted

D OUPUT side RCBO devices can be fitted to handle inadvertent shock paths where unconnected metal objects inadvertently get connected to boat side earth but the MCBs will handle this anyway but I’ll still fit an output sIde RCBO.


This system is safe for swimmers , is safe against single point failures and also against sone double point failures offers the greatest protection against impressed current corrosion and represents the best compromise

[Lake-Effect]

Originally Posted by goboatingnow

I have considered all fault paths

Let’s analyse

With a discontinuous ground and an isolating transformer

....And more hoops to jump through than a Vegas lion act.

You haven't considered all paths. How bout a frayed shorepower cable, or a busted inlet? Without a return ground, RCDs etc don't trip (fault remains) until there's a leakage path.

You seem to have forgotten the primary reason why AC circuits and devices include a ground.