ELCI with Isolation Transformer and Inverter/Charger

[willston]

Hi guys,

I'm thoroughly stumped when it comes to how I should be wiring my AC mains isolation transformer and inverter/charger when it comes to ELCI's specifically. I've attached a screenshot of the primary control concepts drawing, where the irrelevant parts are faded. Basically what is happening is I have AC Shore power in, going to an Isolation Transformer and then to the Inverter/Charger. All loads are driven off the inverter with its built in ATS.

In the attached drawing I have 3 dual pole breakers, BP-B01, BP-B02 and BP-B03. I'm wondering which of those should be an ELCI, if any, and if any of these breakers are redundant/overkill. Wire run wise, the Isolation Transformer cable run is less than 8' from where power enters the boat. Physically the Isolation Transformer and Charger/Inverter are side by side, but if I have BP-B02 the run length turns to about 16'.

Outlets on the vessel will be GFCI's; however, larger loads like the hot water heater will not, which is where the ELCI comes in.

Side note: all loads are connected to the inverter output/ATS on the inverter charger, but large loads like the hot water heater are controlled by the main ECU disconnecting them during high current consumption times and when not connected to shore power. This is done because the inverter charger I have can boost power output up to 50a (Victron PowerAssist) allowing more load, meaning during high load times I don't trip my mains breaker(s), also allowing me to run the system off my 20a Honda Generator without overloading

[GordMay]

I highly recommend Steve D’Antonio’s PBB article: “The Complexity of Plugging in Theory, standards, and best practices behind installing and maintaining shore-power transformers”.

... if a transformer is located within 10'/3m (a measurement of the wire, not as the crow flies) or less from a shore inlet, although a conventional circuit breaker is required, an ELCI (equipment leakage circuit interrupter) device is not. While that satisfies the letter of the ABYC “law,” bear in mind that for overcurrent protection, every foot (30.5cm) of wire between the inlet and the transformer relies on the dock-mounted circuit breaker, one that may be deteriorated, inadvertently oversized, not ELCI-equipped, and whose condition is unknown.
Regardless of where the transformer is located, I [Steve D’Antonio] recommend that my clients install a primary ELCI circuit breaker as close as possible to the shore inlet. ...

Here ➥ https://stevedmarineconsulting.com/w...mers181-04.pdf

[shimari]

This might help - you need to have an ELCI or isolation transformer within 10' from the shore power entrance. Personally, I'd still add the ELCI even if the isolation transformer was within 10'.

https://shop.pkys.com/ABYC-standard-...ined_b_50.html

Edited - inserted wrong link

[s/v Jedi]

Originally Posted by willston

Hi guys,

I'm thoroughly stumped when it comes to how I should be wiring my AC mains isolation transformer and inverter/charger when it comes to ELCI's specifically. I've attached a screenshot of the primary control concepts drawing, where the irrelevant parts are faded. Basically what is happening is I have AC Shore power in, going to an Isolation Transformer and then to the Inverter/Charger. All loads are driven off the inverter with its built in ATS.

In the attached drawing I have 3 dual pole breakers, BP-B01, BP-B02 and BP-B03. I'm wondering which of those should be an ELCI, if any, and if any of these breakers are redundant/overkill. Wire run wise, the Isolation Transformer cable run is less than 8' from where power enters the boat. Physically the Isolation Transformer and Charger/Inverter are side by side, but if I have BP-B02 the run length turns to about 16'.

Outlets on the vessel will be GFCI's; however, larger loads like the hot water heater will not, which is where the ELCI comes in.

Side note: all loads are connected to the inverter output/ATS on the inverter charger, but large loads like the hot water heater are controlled by the main ECU disconnecting them during high current consumption times and when not connected to shore power. This is done because the inverter charger I have can boost power output up to 50a (Victron PowerAssist) allowing more load, meaning during high load times I don't trip my mains breaker(s), also allowing me to run the system off my 20a Honda Generator without overloading

Here is the diagram I made for a basic setup. No ELCI required. I believe ABYC recommends an ELCI when cabling between inlet and transformer is longer than three meters.

[CharlieJ]

S/v Jedi: Correct.

[willston]

Originally Posted by s/v Jedi

Here is the diagram I made for a basic setup. No ELCI required. I believe ABYC recommends an ELCI when cabling between inlet and transformer is longer than three meters.

Originally Posted by CharlieJ

S/v Jedi: Correct.

Originally Posted by GordMay

I highly recommend Steve D’Antonio’s PBB article: “The Complexity of Plugging in Theory, standards, and best practices behind installing and maintaining shore-power transformers”.

Here ➥ https://stevedmarineconsulting.com/w...mers181-04.pdf

All of this is super helpful and a great read thanks GordMay. I'm going with one ELCI then after the transformer, its a little bit overkill per-say but for the extra cost of the breaker why not.

Thanks guys!

[goboatingnow]

I would fundamentally disagree that in Steve D’Antonio , diagram he shows the protective earth wire still be maintained through to the shower power earth and around the boat while an isolating transformer is in use.

Boat protective earth should be separated and returned to the source of power ie the transformer

[Statistical]

Originally Posted by willston

All of this is super helpful and a great read thanks GordMay. I'm going with one ELCI then after the transformer, its a little bit overkill per-say but for the extra cost of the breaker why not.

Thanks guys!

Is there a reason why after the transformer? It means anything on the shorepower side of the transformer is unprotected.

In your diagram in the first post I would make BP-B01 an ELCI. Not sure BP-BO2 needs to be an ELCI just normal overcurrent protection.

From ABYC-30

[s/v Jedi]

Originally Posted by willston

All of this is super helpful and a great read thanks GordMay. I'm going with one ELCI then after the transformer, its a little bit overkill per-say but for the extra cost of the breaker why not.

Thanks guys!

Please don’t, you’re just throwing money away. If you do use an ELCI it should be the first one, as close to the inlet as possible.

But with the transformer you don’t need it and behind the transformer it adds nothing.

Also, whatever they say and whatever you read: make sure that the ground terminal of the inlet is NOT connected to ground aboard. It should be connected to the input ground at the Victron transformer, but not to the output ground of the transformer. The transformer comes with a ground jumper to connect the two: hide it so you’ll never find it again.

ABYC doesn’t fully understand how isolation transformers work yet and they show info that connects shore ground to boat ground. Isolating these two is the primary function of the transformer and they manage to break it

[s/v Jedi]

Originally Posted by goboatingnow

I would fundamentally disagree that in Steve D’Antonio , diagram he shows the protective earth wire still be maintained through to the shower power earth and around the boat while an isolating transformer is in use.

Boat protective earth should be separated and returned to the source of power ie the transformer

Indeed, thanks for bringing it up, I already forgot that. This was discussed before.

[CharlieJ]

#7 & #9:
Suggest studying the two diagrams in Steve’s article. For apolarization xfmr the shore safety ground does come aboard and is connected to the boat’s safety ground bus.

For a conventional, iron core isolation xfmr shore safety ground is connected to the electrostatic shield between the primary and secondary windings. There is a neutral to ground bond established at the secondary. With this configuration the boat is electrically isolated from shore mains.

Interestingly, any AC leakage created by an iso xfmr equipped boat will not be sensed by a shore power pedestal that has been upgraded with a 30mA RCD.

[smac999]

Originally Posted by CharlieJ

#7 & #9:
Suggest studying the two diagrams in Steve’s article. For apolarization xfmr the shore safety ground does come aboard and is connected to the boat’s safety ground bus.

For a conventional, iron core isolation xfmr shore safety ground is connected to the electrostatic shield between the primary and secondary windings. There is a neutral to ground bond established at the secondary. With this configuration the boat is electrically isolated from shore mains.

Interestingly, any AC leakage created by an iso xfmr equipped boat will not be sensed by a shore power pedestal that has been upgraded with a 30mA RCD.

because a boat with a iso transformer can't leak current. the only place it can go is back to the transformer.

[Auspicious]

A thought based on the citations of ABYC guidelines: if you have a boat built to CE standards (which are regulatory while ABYC are not), you should make modifications in accordance with CE. Otherwise you end up with a boat built to mixed standards which leads to 1. unintended consequences and 2. a boat that is hard to sell.

[CharlieJ]

@Auspicious
True. However, the ABYC Standards (non-regulatory) are very nearly homogenized with the ISO Standards (regulatory).

[Auspicious]

Originally Posted by CharlieJ

@Auspicious
True. However, the ABYC Standards (non-regulatory) are very nearly homogenized with the ISO Standards (regulatory).

True BUT not completely. Bonding comes to mind as a difference, and there are some differences in current leakage detection.

I'm a little sensitive to this as the owner of a CE boat in the US.