Isolation Transformers

[c10ing]

Des Moines Marina dropped their shore power ground fault interruption from 100ma to 30ma. Could no longer connect to shore power in Des Moines Marina. They said I needed to install an isolation transformer. So did and now I can connect to shore power in Des Moines Marina.

[CharlieJ]

@c10ing
But the fault on your boat that caused the RCD to trip still exists.

[c10ing]

If you check the shore power green wire for voltage it should be zero, but I used to moor in a marina where the shore power green wire was 7 volts RMS above salt-water ground. In that case the problem was the shore power system.

[c10ing]

What's the best way to find AC leakage current? It has to be in one of the AC appliances. Most likely the water heater maybe. The only other AC appliances on the boat are the battery charger, inverter, and whatever is plugged in to a AC receptacle. Any ideas?

[AKA-None]

Originally Posted by c10ing

What's the best way to find AC leakage current? It has to be in one of the AC appliances. Most likely the water heater maybe. The only other AC appliances on the boat are the battery charger, inverter, and whatever is plugged in to a AC receptacle. Any ideas?

Or the wiring or the sockets themselves

[boatpoker]

Originally Posted by c10ing

What's the best way to find AC leakage current? It has to be in one of the AC appliances. Most likely the water heater maybe. The only other AC appliances on the boat are the battery charger, inverter, and whatever is plugged in to a AC receptacle. Any ideas?

or if your AC and DC grounds are joined or there is a fault in your inverter or your battery charger or if you have a non-marine grade inverter or if you have an automotive type battery charger ...

What is your concern with AC leakage ? Are you in fresh water ?

[c10ing]

Salt water/

[boatpoker]

Originally Posted by c10ing

Salt water/

Then AC leakage is pretty much irrelevant.

- There are no recorded incidents of electric shock drownings in salt water.
- AC current can cause corrosion in salt water but at such a slow rate that you
are unlikely to notice it in your lifetime.

[sinnerman]

If the erosion was that bad, and that fast it was probably AC leakage, not DC current leakage.

A galvanic isolating diode can only protect against DC leakage.

An isolation transformer will prevent both AC and DC leakage.
https://www.victronenergy.com/upload...formers-EN.pdf

You may have a problem in your AC wiring. Water heater is a good place to start looking.

Or your neighbor's boat has AC leakage and is using your boat as a path to ground (via your shore power ground wire ...)

BTW, this is one of the arguments against the ABYC recommendation of connecting your AC and DC grounds together.

If you connect them together you are offering up your engine/prop shaft (which are connected to DC ground) to now become a ground path for any stray AC currents in the water nearby...


My two cents.

cheers

[boatpoker]

Originally Posted by sinnerman

If the erosion was that bad, and that fast it was probably AC leakage, not DC current leakage.

Do you mean "corrosion" ? If so are you serious ?

[GrowleyMonster]

I installed an isolation transformer, a big heavy brute, on my boat. They are really hard to source these days. I don't think Charles makes them anymore. But, I am glad I did it. I have never needed the flexibility but it is cool to know that if I have to, I can switch back and forth between foreign and U.S. voltages, and the transformer is rated for 50Hz or 60Hz. Doesn't convert between them, of course, but my charger will tolerate 50Hz in a pinch, and I can run an awful lot of stuff off my big inverter.

I also installed a 2/0 copper ground bus fore and aft and I will probably be installing a large copper bar for that, one of these days. A good low impedence ground bus and good low resistance ground connections for equipment will do you good.

I never really trusted galvanic isolators. But then again, I don't trust walking under a ladder, either. But when a transformer fails, you know it immediately. When a galvanic isolator fails, you might not know it.

I have been really lazy about this lately, but my long standing habit is to at least check my shaft zincs once a month. If zincs seem to be just dissolving like sugar cubes, you got a problem. If they are lasting for years, it's no guarantee but it is a good sign. Or absence of a bad sign, to be more precise.

[boatpoker]

Originally Posted by GrowleyMonster

I never really trusted galvanic isolators. But then again, I don't trust walking under a ladder, either. But when a transformer fails, you know it immediately. When a galvanic isolator fails, you might not know it.
.

You could always buy a "Failsafe" galvanic isolator instead of one of the cheapies.

[CharlieJ]

@sinnerman
AC does not cause stray current corrosion on other than aluminum components.