Step down transformer for isolation on boat.

[Andrew Lippman]

I had two Swans both with isolation transformers. Mastervolt makes them. Each could step up or down. On my first boat, I modified it from Euro to US voltage and used the step down feature. Calder notes that an isolation transformer is the best option -- expensive but it does the job. I also had GFI (in euro-speak, RCDs) on both sides, shore and boat. Nautor seems to believe in using infinite relays and breakers, so my wiring was certainly complicated.

As I recall the shield is on the shore side. My boats were wired per normal standards: neutral connected to ground at the origin of a power source. That means the ground on the boat is not connected to shore ground.

I think this is an elegant solution and components are available from Victron and Mastervolt. Not sure I would go with SquareD, don't know enough about them. I may be able to resurrect the wiring diagrams.

[team karst]

Who demands that it be an isolation transformer in the first place? Most boats don't run any transformer; ie: zero isolation. The OP just needs to reduce V, correct?? much less $ to run a 3 terminal auto-xfrm.

[Andrew Lippman]

Isolation matters largely because of other sources and connections in a marina. For example, if some other boat or the marina wiring elevates the ground and that is connected to your ground, then there can be potential between your boat's keel and the water. This can cause galvanic corrosion.

I note that the Europeans approach this all very differently. In the 12/24VDC system, ground and DC return are isolated. They prevent corrosion by never connected anything electrical to safety ground. This is a real headache to do, for example, the VHF antenna has to be isolated at the masthead and the radio ground has to go through a capacitor.

The AC wiring on my boat seemed like normal code: A new neutral-ground connection on the secondary side, and the shield connected to shore ground. Same with the inverter: In invert mode, a new netural-ground when operating, and pass-through when on shore power.

My boat prints do not show all the RCDs, but there was one on the shore side and on the boat side.

[team karst]

Originally Posted by Andrew Lippman

Isolation matters largely because of other sources and connections in a marina. For example, if some other boat or the marina wiring elevates the ground and that is connected to your ground, then there can be potential between your boat's keel and the water. This can cause galvanic corrosion.
....
Fixed by a cheap galvanic isolator. But, why do you think mains isolation is mandatory? .

Yes, I agree with common mode transient suppression.

[s/v Jedi]

Originally Posted by rgleason

GBN ans svsagres had good suggestions.
https://diysolarforum.com/threads/sm...21#post-615689

Next we need a good galvanic isolator for a reasonable price.

If you mount a DIN rail box with ground fault breaker, then add this to the box as well: https://www.amazon.com/Protection-Pr.../dp/B08KVQZP69

As for the affordable galvanic isolator, I went for this $75 one: https://www.defender.com/product3.js...0032&id=605562

I believe Yandina is on this forum.

For optimum protection while on shore power, I use an EMS (Electrical Management System) that not only has surge suppression, but also a contactor and it will only pass power when it’s safe to do so, checking everything from under voltage, over voltage to frequency etc. This model is for a US 50A 120/240 connection, but there are many models incl. portable ones that go on the pedestal on the dock.
https://www.amazon.com/gp/product/B003AN1UA8

[rgleason]

Thanks Nick, very helpful.

[smac999]

Originally Posted by Andrew Lippman

I had two Swans both with isolation transformers. Mastervolt makes them. Each could step up or down. On my first boat, I modified it from Euro to US voltage and used the step down feature. Calder notes that an isolation transformer is the best option -- expensive but it does the job. I also had GFI (in euro-speak, RCDs) on both sides, shore and boat. Nautor seems to believe in using infinite relays and breakers, so my wiring was certainly complicated.

As I recall the shield is on the shore side. My boats were wired per normal standards: neutral connected to ground at the origin of a power source. That means the ground on the boat is not connected to shore ground.

I think this is an elegant solution and components are available from Victron and Mastervolt. Not sure I would go with SquareD, don't know enough about them. I may be able to resurrect the wiring diagrams.

The victron and mastervolt ones are not sutible for 50a 240v boats.

The victron is fine with 30a 120v boats. The mastervolt is not good for North America as the smaller one is only for 16a despite being labeled 3600watt. You have to buy the huge one for 30a

[goboatingnow]

Originally Posted by smac999

The victron and mastervolt ones are not sutible for 50a 240v boats.

The victron is fine with 30a 120v boats. The mastervolt is not good for North America as the smaller one is only for 16a despite being labeled 3600watt. You have to buy the huge one for 30a

In my opinion single phase 10 kw circuits shouldn’t be in smaller boats break the input into two. Best to aim the mains wiring for 3-4 kw maybe 5ke max.

[s/v Jedi]

Originally Posted by goboatingnow

In my opinion single phase 10 kw circuits shouldn’t be in smaller boats break the input into two. Best to aim the mains wiring for 3-4 kw maybe 5ke max.

It’s the standard in North America. Next one up is 100A.

The 50A service is 12kW, 6AWG wiring, works like a charm.

So this is why we have two shore power connections. The first one is 3.6kW using the Victron isolation transformer so it can use either 120V/30A or 240V/50A and whatever input, make it into a 240V/15A output. This setup is in all my diagrams: a standard 30A breaker on its input and a 15A breaker on the output (no RCD required)

The second shore power is 12kW 240V/50A. I take all four conductors from shore: L1, L2, N and Ground and feed that into a Progressive EMS. When that decides it’s good to go, it will close the contactor and the power becomes available on its output terminals. Here I take L1 and L2 to the big selector switch and Ground to a Yandina galvanic isolator and the output from that to my ships ground. Neutral is left unused.

So this 12kW input is only to be used where shore power is in top notch condition, mainly our slip in Port Canaveral, but I would use it in similar marinas.

In high end European marinas I could take a 32A hookup, but as I want 60Hz aboard, the 3.6kW is more than enough as I’ll just make 24V 70A from it to feed an inverter.

[DShant]

I know not very much about electrical things. Just enough to get into trouble. I recently had a survey requested for insurance purposes and the Surveyor put in this new requirement I had not seen before.



"To conform to new electrical code A.B.Y.C. & N.F.P.A, an E.L.C.I. (Equipment
Leakage Circuit Interrupter) (or RCD) should be installed to prevent AC leakage from boats into surrounding waters that endangers swimmers."


This thread has educated me a bit but I am still at a loss as to how to deal with it. I have three 50 amp cords coming in three different locations to two isolation transformers. I have had all kinds of different recommendations by electricians and others about how to deal with this on my old boat. Not really sure what to do and not really happy about the requirement.



I don't see many swimmers in my marinas and I have never heard of a swimmer getting electrocuted.

[smac999]

the guideline is for new built boats, built after the code was made like 6 years ago. and likely boats that are rewiring would have to follow current guidelines.

there is no requirement to update an existing boat to current codes. you'd be changing stuff every year if had to do that. and houses would be torn down every 5 years.

if the isolation transformers are within 10' of the shore inlet there is also no requirement to have elci breakers with the current code either.

the elci breaker requirement is for new boats without isolation transformers.


but if you are required to add them, then you would need 3 of them, one for each input... and they are not cheap

[goboatingnow]

Good idea to fit them anyway they add significant additional safety to those onboard too

[skipperpete]

Originally Posted by DShant

I know not very much about electrical things. Just enough to get into trouble. I recently had a survey requested for insurance purposes and the Surveyor put in this new requirement I had not seen before.



"To conform to new electrical code A.B.Y.C. & N.F.P.A, an E.L.C.I. (Equipment
Leakage Circuit Interrupter) (or RCD) should be installed to prevent AC leakage from boats into surrounding waters that endangers swimmers."


This thread has educated me a bit but I am still at a loss as to how to deal with it. I have three 50 amp cords coming in three different locations to two isolation transformers. I have had all kinds of different recommendations by electricians and others about how to deal with this on my old boat. Not really sure what to do and not really happy about the requirement.



I don't see many swimmers in my marinas and I have never heard of a swimmer getting electrocuted.

Is your vessel under survey ?( coastguard inspected). If so this could be the reason the surveyor suggested the RCD. Also note the difference between “should be installed” and “must be installed”, either way it’s good practice to have a professionally installed RCD.

[goboatingnow]

Originally Posted by skipperpete

Is your vessel under survey ?( coastguard inspected). If so this could be the reason the surveyor suggested the RCD. Also note the difference between “should be installed” and “must be installed”, either way it’s good practice to have a professionally installed RCD.

The are easy to fit by a non professional.

[Bowdrie]

Originally Posted by DShant

I don't see many swimmers in my marinas and I have never heard of a swimmer getting electrocuted.

It took years to identify, and is much more prevalent in fresh water.
This incident served as a major push for upgrading of marina/boat wiring.

https://www.youtube.com/watch?v=sM1GF7Bli4k