Recommended basic AC power diagram

[s/v Jedi]

There have been so many questions and so much incorrect information posted online, that I decided to make some diagrams to bring order to chaos

This is the first one, a basic installation for American 120V 60Hz or European 230V 50Hz or any that is descended from those (basically world wide usable).

This basic diagram has an isolation transformer. This is because of the safety and protection it provides for the boat, the crew as well as swimmers around the boat. IMHO money saved by using a galvanic isolator instead of the transformer is not worth giving up the inherent safety from the transformer.

This transformer also allows to connect a 230V boat to a 120V shore power or a 120V boat to 230V shore power. It does not adapt the line frequency between 50 and 60Hz but allows many appliances to work.

The input breaker needs to be 30A for every boat. The breaker behind the transformer is 16A for a 230V boat and 30A for a 120V boat. Of course you need to order the correct Multiplus model for your voltage. I recommend the model with the larger transfer switches if multiple options are available. This allows the use of more power than the shore power can provide by using the Power Assist feature.

Inside the isolation transformer are two ground related jumpers. One connects the output Neutral to ground and this one needs to be installed. The other connects input ground to output ground and this needs to be REMOVED at all times except when hauled out and power is connected while on the hard (even then you can ignore it as it's just a code compliance thing).

If your code requires it you can use RCD breakers instead of regular ones.

The ships ground busbar is to be used for ground wires to all outlets, chargers, inverters, water heaters etc. I do not recommend to connect it to anything else so also not to any DC power, engine blocks, grounding plates etc.

This basic system already allows use of induction cooktops, microwaves etc. You can add a generator like a Honda 2200i by connecting it to the shore power inlet.

[Jammer]

nice. That is exactly what I plan to do on my next boat.


ABYC allows you to drop the grounding conductor from the shore power cable if the first 30a breaker is a GFCI breaker. This has the potential to save money and weight and make for a shore power cable that is physically easier to handle. Suitable two-conductor cable is available but you have to add your own end(s). https://www.awcwire.com/product/so-10_2 or Mcmaster has them with EPDM jacketing for more money, https://www.mcmaster.com/7081K17/

[s/v Jedi]

Originally Posted by Jammer

nice. That is exactly what I plan to do on my next boat.


ABYC allows you to drop the grounding conductor from the shore power cable if the first 30a breaker is a GFCI breaker. This has the potential to save money and weight and make for a shore power cable that is physically easier to handle. Suitable two-conductor cable is available but you have to add your own end(s). https://www.awcwire.com/product/so-10_2 or Mcmaster has them with EPDM jacketing for more money, https://www.mcmaster.com/7081K17/

Oh that’s news to me. Others here on the forum claim that shore ground is mandatory and not only that... they claim the isolation transformer must have a shield around the primary winding connected to shore ground.

I hope details come out in this thread

[Stu Jackson]

Originally Posted by s/v Jedi

There have been so many questions and so much incorrect information posted online, that I decided to make some diagrams to bring order to chaos >>>>>>>>>>>>>>>

Whew that's for sure! Thanks.


One nitpick" could you call it "Ship AC Ground" to avoid confusion, even though I know you said in the text to keep DC and AC grounds separate, and not connect the AC ground to the engine? And you did draw it in green, too. That's American color code. Do you know if it is the same in color in Europe?


Thanks again.

[tdgaffney]

Hello Jedi and TU. I am seeking confirmation. Paraphrasing my post #160 from the previous Thread:

“My shore power system includes a Galvanic Isolator and my 120vac Elec Panel includes a polarity indicator and an ELCI. Each of my 120vac outlets is a GFCI outlet. Coming back from these outlets, all the Black wires collate at the 120 Hot Bus, the Whites at the 120 Return Bus and the Greens at the 120 Ground Bus. These marry to the incoming shore power, the 120 Black-White-Green wires.


“Additionally, the Green Bus is connected to my Engine Block via connection to my 12vdc Ground Bus.”


In reply, TU, in post #162, replied, “Your system is ABYC correct.” (Thank You)


Now, here, I’m seeking confirmation. When plugged into Shore Power, the Shore Power Green wire, as described above, is connected to my 12vdc ground. Again, is that ok?

[s/v Jedi]

Originally Posted by Stu Jackson

Whew that's for sure! Thanks.


One nitpick" could you call it "Ship AC Ground" to avoid confusion, even though I know you said in the text to keep DC and AC grounds separate, and not connect the AC ground to the engine? And you did draw it in green, too. That's American color code. Do you know if it is the same in color in Europe?


Thanks again.

Yes, it is generally preferred to have a separate AC ground, although the US likes to interconnect everything... which all stems from not having an isolation transformer. There’s gonna be a schematic without the transformer so that’ll be interesting

The colors:

US: L1=black, L2=red, N=white, Ground=green or bare copper
EU: L1= brown, N=blue, Ground=green with yellow stripe.

The EU has simpler shore power but mostly limited to 3.6kW while the US has a beautiful 12kW option widely available.

[s/v Jedi]

Originally Posted by tdgaffney

Hello Jedi and TU. I am seeking confirmation. Paraphrasing my post #160 from the previous Thread:

“My shore power system includes a Galvanic Isolator and my 120vac Elec Panel includes a polarity indicator and an ELCI. Each of my 120vac outlets is a GFCI outlet. Coming back from these outlets, all the Black wires collate at the 120 Hot Bus, the Whites at the 120 Return Bus and the Greens at the 120 Ground Bus. These marry to the incoming shore power, the 120 Black-White-Green wires.


“Additionally, the Green Bus is connected to my Engine Block via connection to my 12vdc Ground Bus.”


In reply, TU, in post #162, replied, “Your system is ABYC correct.” (Thank You)


Now, here, I’m seeking confirmation. When plugged into Shore Power, the Shore Power Green wire, as described above, is connected to my 12vdc ground. Again, is that ok?

No that is not okay. You will see your zincs dissolve quickly, followed by your propeller, shaft etc. But you’re ABYC compliant alright... even if it eats your boat.

The diagram I posted above is what you should have. There is another option using a galvanic isolator instead of an isolation transformer but I simply can not recommend it for your installation.

It’s rather simple to convert though as all the wiring from breakers to outlets etc. stay the same.

Edit: hold, wait a minute. You write you have a galvanic isolator... this should mean that the green wire from the shore power inlet is only connected to that isolator and nowhere else. If that’s indeed the case then you -may- be fine even though your installation doesn’t meet the higher standard of what I posted here. Example: your galvanic isolator could be malfunctioning without you knowing and putting you and/or the boat at risk. If you notice more zinc being eaten away than you are used to or than you would expect, then I recommend to upgrade to an isolation transformer (which really isolates shore ground from your boat... not half-half with tricks)

[tdgaffney]

I followed advice given in Practical Sailor's "Marine Electrical Systems." Quoting from Volume 2 - Grounding, pg 3:

DC GROUND
Every light or appliance should be wired with its own DC return
wire. Never use the mast, engine, or other metal object as part
of the return circuit.

The DC load returns of all branch circuits should be tied to
the negative bus of the DC distribution panel. In turn, the negative
bus of the DC distribution panel should be connected to the
engine negative terminal or its bus. Battery negative is also connected
to the engine negative terminal or its bus. The key factor
here is that the yacht’s electrical system is connected to seawater
ground at one point only, via the engine negative terminal or its
bus. ... ...

AC GROUND
The best solution for AC grounding is a heavy and expensive isolation
transformer. The acceptable solution (for the rest of us) is to install
a light and inexpensive galvanic isolator in the green wire, between
the shorepower cord socket on your boat and the connection to the
boat’s AC panel. Then, connect the grounding conductor (green) of
the AC panel directly to the engine negative terminal or its bus. Note
that this meets the ABYC recommendation, which is heartwarming.

Let me note that my boat's Shore Power first encounters the Galvanic Isolator, which the Green Wire passes through (Hot and Neutral pass by). Following that, Shore Power enters the 120vac Panel wherein the ELCI examines the Hot and Neutral to ensure their currents match. Also of note: Each 120vac outlet on the boat is GFCI protected and their Green Wires route to the Green Wire bus (and then to the 12vdc negative bus and on to the engine block); and zincs, props and shaft have had no apparent harm over the past three years.

Hopefully, those better versed in electrical systems find this system acceptable. Otherwise, I would appreciate advice on what to change. Thanks in advance. Tom

[s/v Jedi]

Originally Posted by tdgaffney

I followed advice given in Practical Sailor's "Marine Electrical Systems." Quoting from Volume 2 - Grounding, pg 3:

AC GROUND
The best solution for AC grounding is a heavy and expensive isolation
transformer. The acceptable solution (for the rest of us) is to install
a light and inexpensive galvanic isolator in the green wire, between
the shorepower cord socket on your boat and the connection to the
boat’s AC panel. Then, connect the grounding conductor (green) of
the AC panel directly to the engine negative terminal or its bus. Note
[/I] that this meets the ABYC recommendation, which is heartwarming.

Let me note that Shore Power first encounters the Galvanic Isolator, which the Green Wire passes through (Hot and Neutral pass by). Following that, Shore Power enters the 120vac Panel wherein the ELCI examines the Hot and Neutral to ensure their currents match. Also of note: Each 120vac outlet on the boat is GFCI protected; and zincs, props and shaft have had no apparent harm.


Hopefully, those better versed in electrical systems, find this system acceptable. Otherwise, I would appreciate advice on what to change. Thanks in advance. Tom

Even though I think I agree with the part about DC, this thread is about AC so I’m ignoring it.

The galvanic isolator is a device that inserts semiconductors in series with the earth conductor. It exists of an anti-parallel circuit of multiple diodes. This means that low DC current can not pass, while AC currents can pass.

The blocking of low voltage DC current is what is supposed to protect the underwater metals. This actually works to some extent... the worrying bit is that when it’s real bad, it doesn’t work anymore. Also, by conducting AC current, it does not provide any additional safety for people aboard, nor swimmers around the boat. The reason I recommend against it is that for a 3.6kW shore power setup, great options with isolation transformer are readily available. The RCD breaker and gfci outlets improve safety but are not a replacement for an auto transformer.

The best thing to do for your boat is buy a bigger anchor. The 2nd best thing is buying an isolation transformer if you use shore power.

In case I haven’t been clear: buy an isolation transformer whenever questions arise around zinc anode performance, light shocks from touching things aboard etc. For people who don’t have a galvanic isolator: don’t even consider buying one, get the transformer

[Jammer]

Originally Posted by s/v Jedi

Oh that’s news to me. Others here on the forum claim that shore ground is mandatory and not only that... they claim the isolation transformer must have a shield around the primary winding connected to shore ground.

I hope details come out in this thread

Here you go. This is an excerpt from Charles Industries literature that references the ABYC diagram. They have exited the marine isolation transformer business but the document is still relevant.


I believe it's a recent addition to the E-11 standard.

[s/v Jedi]

Originally Posted by Jammer

Here you go. This is an excerpt from Charles Industries literature that references the ABYC diagram. They have exited the marine isolation transformer business but the document is still relevant.


I believe it's a recent addition to the E-11 standard.

Wow, this is even more relaxed than Victron who brings shore ground to the transformer to “protect” the inlet wiring.

Let’s see if one of the ABYC members can confirm this change

[tanglewood]

ABYC (and the diagram posted above) allows for elimination of the neutral in a split phase when used with an isolation transformer.


It does NOT allow elimination of the green wire ground. I'm not sure where that notion came from.

[tanglewood]

Originally Posted by tanglewood

ABYC (and the diagram posted above) allows for elimination of the neutral in a split phase when used with an isolation transformer.


It does NOT allow elimination of the green wire ground. I'm not sure where that notion came from.

Crap, I see what you are saying now. I'll have to ask, though I think the RCD provides the same protection as the ground in this case.

[Paul L]

Seems like if you are going to discuss the importance of the ground jumpers in the text they should be on the diagram too.

[tanglewood]

OK, I checked the ABYC E-11 versions back to 2012, and also the current draft that just went through public review.


None of them permit a disconnected ground from the shore cable. It has to be



1) connected directly to the ship's ground if there is no isolation transformer and no galvanic isolator, or


2) connected to the galvanic isolator is equipped, or


3) connected to the isolation transformer's shield if so equipped.


So whatever that drawing is, what it's showing hasn't been allowed for at least 9 years.


Any chance there is a date on the document you pulled that drawing from? It certainly has the form of the ABYC drawings, but it's clearly an old one. How old, I don't know.