Wiring isolation transformers

[rourkeh]

I am wondering the proper way to wire the isolation transformer green ground wire on the output side. The instructions have a number of different wiring diagrams. Can you guys let me know what you have done. Cheers.

 

[SeaEric]

I'm adding isolation transformers this winter as part of a total re-do of the electrical on my 1966 41 TC. My personal participation in the project is mostly limited to scratching the check to the contractor. I do have a pdf diagram that describes the wiring. Its too large to upload here. If you PM your e-mail address I'll send it. It may be of some help to you.

 

[jim rosenthal]

Were you having an electrolysis problem where you are? That's a big project.

 

[krush]

Even if yours isn't a charles, this should work: http://www.charlesindustries.com/marine_manual/pm3201_1.pdf

A transformer is a transformer. Their diagrams look like they may be from ABYC anyway.

Good article: https://www.deimarine.com/media/wys...ation_vs_Isolation_Exchange_Article_10-20.pdf

 

[Maurice]

It's my understanding that a Galvanic Isolator prevents electrocution in the event that AC current escapes from the AC wiring on board (i.e. through a short in an AC battery charger), and the AC green ground wire should be bonded to the DC ground on board. It protects the hull, anodes and aluminum parts from galvanic corrosion when plugged into shore power. It is wired into the shore power grounding wire. They are two opposing semiconductor diodes. They prevent low voltage galvanic current leaving or entering the boat but easily allow 110 volts to pass through. Some may offer a monitoring panel -KCB Technologies in Canada ... if not discontinued.
The Isolation Transformer is completely different animal which completely separates the incoming AC power from the DC power on board. The AC power is transmitted electronically through the transformer. It prevents stray galvanic current from the dockside from reaching the boat, and prevents AC power from the dockside from posing a safety hazard for the crew. The AC ground wire is still connected to the DC ground to provide protection against faulty AC circuits on the boat.
By what I read, the galvanic isolator should be on any boat that plugs into shore power. It is lighter and less expensive that the transformer.
The AC and DC electrical systems are to be connected at one common grounding point.
There is a lot of easily understood info on the web about these devices, although I read where there may not be unanimous agreement where the ground wires should go. My opinion, get a qualified expert, and verify the qualifications.

 

[Passages]

My opinion, get a qualified expert, and verify the qualifications.

Mine too. I had and electrician spend a day on board scratching his head on the best way to tie my iso transformer. He called in HIS expert who still had to make a few phone calls.

They got it done but this is not a DIY project.

I ended up with a ACME 15 KVA iso xformer. Zincs lasting longer and I swear, my metered electric has gone down by a third. As an additional benefit, I don't have to worry about electrocuting my diver with stray current.

 

[oscarvan]

They got it done but this is not a DIY project.

I always laugh when I hear that. If there's a $60 dollar an hour person that does it, you can figure it out and I have, many times, over a broad spectrum of disciplines. And today with the world at your fingertips it is easier than ever to get the information, most of the time.

Now, $300 hour, you know orthodontists, divorce lawyers.... yes. You need to spend the money.

 

[krush]

I always laugh when I hear that. If there's a $60 dollar an hour person that does it, you can figure it out and I have, many times, over a broad spectrum of disciplines. And today with the world at your fingertips it is easier than ever to get the information, most of the time.

Now, $300 hour, you know orthodontists, divorce lawyers.... yes. You need to spend the money.

An electrician is not an electrical engineer, or an engineer with proper understanding of the system. However, none of the mentioned are needed, because you can just follow the ABYC standards.

 

[Boatsb]

There's a few issues.

When I add a buck boost transformer (usually automatic) it wires in like an isolation transformer. I usually see the need to update or increase wire size. I also add in breakers on the input (ELCI) and output (standard) specific to the power systems needs.

You don't just wire up a bunch of stuff and think it's OK.

 

[oscarvan]

An electrician is not an electrical engineer, or an engineer with proper understanding of the system. However, none of the mentioned are needed, because you can just follow the ABYC standards.

Exactly.

 

[Photolomy]

I would caveat that with "all of the standards", at least with respect to electricity. In other words you really need to understand the whole system and the standards applying to each piece.

 

[brettportzer]

I'm adding isolation transformers this winter as part of a total re-do of the electrical on my 1966 41 TC. My personal participation in the project is mostly limited to scratching the check to the contractor. I do have a pdf diagram that describes the wiring. Its too large to upload here. If you PM your e-mail address I'll send it. It may be of some help to you.

Where are they going?

 

[jim rosenthal]

Who makes isolation transformers, now? I had the impression Charles was out of that market, but perhaps my memory is mistaken.

 

[Boatsb]

I've used the ANG autoboost. Great product with both isolation and buck boost.

Haven't had any trouble with them.

 

[Jammin']

Defender still has some Charles units in stock.

 

[oscarvan]

Defender still has some Charles units in stock.

Good deals, only seeing 30A units though.

 

[SeaEric]

Where are they going?

There is space behind the bulkhead stbd side aft (behind the small sofa) which is adjacent to the shore power inlet. The units I'm using are being sourced from Bridgeport Magnetics.

 

[krush]

Who makes isolation transformers, now? I had the impression Charles was out of that market, but perhaps my memory is mistaken.

Any "normal" AC transformer is an isolation transformer. They don't need to be special "marine" units. I think I got an ACME transformer for my boat (NOS off ebay, has lots of taps for voltage adjustments).

 

[Photolomy]

Any "normal" AC transformer is an isolation transformer. They don't need to be special "marine" units. I think I got an ACME transformer for my boat (NOS off ebay, has lots of taps for voltage adjustments).

But does your average transformer have an electrostatic shield between the coils to use as a ground?

11.9.1.1. A metallic shield shall be located between the primary and secondary winding and be electrically insulated from all other portions of the transformer.
It shall be designed to withstand, without breakdown, a high potential test of 4000 volts AC, 60Hz, for one minute, applied between the shield and all other components such as windings, core, and outside enclosure.


11.9.1.2. A separate insulated wire lead or terminal identified as the shield connection is to be solidly connected only to the shield, and brought out for external connection
and shall be equal to or greater than the aggregate circular mil area of the largest transformer phase conductor(s).


11.9.1.3. The shield and its connection are to be of sufficient ampacity to provide a sustained fault current path for either the primary or secondary windings to ensure operation of the main shore power disconnect circuit breaker when subjected to a fault current level in accordance with ABYC TABLE V - B.

 

[jim rosenthal]

The Charles Marine units seem to cost roughly the same as Victron units I found for sale on line. And Charles is out of the transformer business; the units at Defender are closeouts. I think I'd buy Victron, in that instance. The ones from Bridgeport Magnetics are smaller and more compact. The prices of these seem to be coming down, good news esp if you have two incoming shore lines of 30A each, as I do, so I would need two transformers.