Wiring shore/generator switch and galvanic isolater

[smokey73]

Sorry for the long post: I'm hoping Maine will be able to clarify a few things.

I believe he considered the Sterling Crossover Switch (SC50) as a possible good fit for a shore power/generator/inverter supply switch. I also saw a comment Maine made in another thread about how the green and neutral wires should be connected for multiple power input sources. My confusion is that the wiring diagram from Sterling does not seem to match Maine's recommendation.

1. Attached is the wiring diagram from the Sterling spec sheet. It seems to show that the green wires from all three possible sources Shore, Generator, and Inverter are connected (un-switched) to the load side green wire going to the boat? It also appears to show the common (neutral) wire connected when the switch is in the selected position. This seems to be at odds with Maine's recommendation. Am I missing something?

2. I'm also a little confused where the new Galvanic Isolator would be wired into the circuit? Any help would be appreciated:

Quote from Maine at Compass Marine in an earlier thread:

[FONT=&quot]Quote:[/FONT]
[FONT=&quot]Originally Posted by Jeff Jellick [/FONT][FONT=&quot] [/FONT][FONT=&quot][/FONT]
[FONT=&quot]
Yes, I have added a 3 - position selector switch, that allows me to switch between, Shore Power, Generator, or Invertor. So, to answer your question, when I am running off the Invertor, I cannot be connected to Shore Power. I added this as a safety option.[/FONT]
[FONT=&quot]Jeff,

Be 100% sure this was done correctly, the vast majority of transfer switches I see installed are done incorrectly.

When on shore power AC NEUTRAL and GROUND ARE NOTconnected on the boat

When using INVERT AC NEUTRAL & GROUND ARE connected on the boat

[/FONT]
[FONT=&quot]
When using GENSET AC NEUTRAL & GROUND ARE connected on the boat[/FONT]

 

[Maine Sail]

Jeff,

• When unplugged from the dock and the switch is in generator position there needs to be a neutral to ground bond on the boat. This is usually at the generator end.

• When unplugged from the dock and the switch is in inverter position there needs to be a neutral to ground bond. This is usually at the inverter end.

• When on shore power there should be NO neutral to ground bonds on-board the vessel, only back on shore.

Testing:

• With switch set to shore power, but unplugged from shore, check continuity between neutral and ground. There should be no continuity between neutral & ground.

• With switch set to inverter, but unplugged from shore, there should be continuity between neutral & ground.

• With switch set to inverter, but unplugged from shore, there should be continuity between neutral & ground.

 

[smokey73]

Does the Sterling wiring diagram accomplish your discussion

Jeff,

• When unplugged from the dock and the switch is in generator position there needs to be a neutral to ground bond on the boat. This is usually at the generator end.

• When unplugged from the dock and the switch is in inverter position there needs to be a neutral to ground bond. This is usually at the inverter end.

• When on shore power there should be NO neutral to ground bonds on-board the vessel, only back on shore.

Testing:

• With switch set to shore power, but unplugged from shore, check continuity between neutral and ground. There should be no continuity between neutral & ground.

• With switch set to inverter, but unplugged from shore, there should be continuity between neutral & ground.

• With switch set to inverter, but unplugged from shore, there should be continuity between neutral & ground.

Maine, Thanks for your rapid response. Jeff posted the original post awhile back - I just quoted him -this is Smokey73.

I am not sure your answer addressed my question. The Sterling wiring diagram that was attached to the original post seems to show all the three power sources hooked up the same way to the boats electrical system. If that is the way to wire it then how would it accomplish the different objectives with regard to the ground and neutral as described in your message? The Sterling diagram seems to show all three grounds tied together to the ships ground (un-switched) plus when the switch is in each of the various positions, the lower connection on the load side (labelled 10) is the ships neutral connected to the respective power supply neutral. It seems that this would make all the connections the same with regard to neutral and ground.

Also, where would the galvanic isolator be wired into the system?

I attached the Sterling wiring diagram below again>

 

[sailerhlf]

Smokey 73, Your diagram shows 240 V power. Is your inverter, generator and shore the same power voltage? What voltage is your boat using? 240 V or 120 V? This is very important. 240 V needs black and white lead and neutral. 120 V to neutral from black or white. That is why 240 V needs 4 wires.
Howard

 

[sailerhlf]

Smokey 73, I apologize for assuming that the wiring was 240V. Looking at the wiring diagram closer, it looks like 120V. The switch is insulated up to 240V. Sorry for the misinformation. Howard

 

[sailerhlf]

Smokey 73, I believe the reason for no continuity between neutral and ground is safety. If the neutral is broken between the shore and boat then the return power would go through the ground and through the water back
to shore neutral through ground. That would be a source for electrocution of a swimmer near the boat ground.
Howard

 

[smokey73]

clarification needed?

Smokey 73, I believe the reason for no continuity between neutral and ground is safety. If the neutral is broken between the shore and boat then the return power would go through the ground and through the water back
to shore neutral through ground. That would be a source for electrocution of a swimmer near the boat ground.
Howard

I understand that. The thing is, looking at the wiring diagram provided by Sterling I don't see the connections as described by Mainesail as to when neutral and ground are connected and when they are not. The Sterling diagram seems to show all three power supplies connected the same way so how would in one case neutral and ground not be connected and in the other two neutral and ground be connected? I'm just confused by that aspect, not the concept.

 

[Charles Erwin]

Your diagram shows switching for the black (hot) and white (neutral) only.
Safety green does not pass through the switch.

In other words - safety green is always connected to every possible source permanently - no switching involved/allowed. This means safety green is always connected to the shore power transformer (in the parking lot) via the shore power cord, to the inverter located on the boat via the cable to the inverter; to the generator on the boat via the generator cable.

Safety green is also "bonded" to neutral at each source - think of the source as the power maker in use.

Shore power in use - Safety green is bonded (fastened) to neutral at the transformer in the parking lot.

Generator power in use - Safety green is bonded to neutral at the generator on the boat.

Inverter - Safety green is bonded to neutral at the inverter on the boat.

If this is still not clear - please tell us what part is confusing.

Charles

 

[smokey73]

Your diagram shows switching for the black (hot) and white (neutral) only.
Safety green does not pass through the switch.

In other words - safety green is always connected to every possible source permanently - no switching involved/allowed. This means safety green is always connected to the shore power transformer (in the parking lot) via the shore power cord, to the inverter located on the boat via the cable to the inverter; to the generator on the boat via the generator cable.

Safety green is also "bonded" to neutral at each source - think of the source as the power maker in use.

Shore power in use - Safety green is bonded (fastened) to neutral at the transformer in the parking lot.

Generator power in use - Safety green is bonded to neutral at the generator on the boat.

Inverter - Safety green is bonded to neutral at the inverter on the boat.

If this is still not clear - please tell us what part is confusing.

Charles

Okay - I think I've got it. The only question I have now is should the Safety Green from the Generator be attached to the other Green wires on the boat side of the galvanic isolater or should the green wire from the Generator be wired to the other green wires on the shore power inlet side of the galvanic isolater? Or does it no difference either way? The current green wire (with no generator installed) goes from the shore power connection to the galvanic isolater then to the boat. With no galvanic isolator its easy, attach all the green wires together as shown in the Sterling diagram, but with the galvanic isolator where does the green wire connection go?

 

[mitiempo]

The only question I have now is should the Safety Green from the Generator be attached to the other Green wires on the boat side of the galvanic isolater or should the green wire from the Generator be wired to the other green wires on the shore power inlet side of the galvanic isolater?

Generator output - all three wires - go to the main AC panel. The green to the AC ground bus. The black (hot) and white (neutral) go to the source selector switch.