Two 30amp 125v shore power service to 50amp 125v boat input

[btrayfors]

You have two 30A shore cords, each feeding a 30A circuit.

You want to be able to switch between shore power and generator power, without risk of backfeeding.

Two small Blue Seas double-breaker panels with slide lockouts will do the trick. This is what I do on my boat. Here's a pic:



The breakers are 30A each. The slide lockouts can be purchased separately and added to any Blue Sea Systems panel.

The Blue Seas part number is 8032. Here's a hires pic:



I get up to 30A on each circuit from either shore power or the generator, with no risk of back feeding.

I assume that if you're really wanting to get 50A on any one circuit you have the proper size wiring, i.e., AWG6?

Bill

[Le Tour]

Originally Posted by morningstar10

I think that's what I was visualizing. Two 30 amp inlets. The first inlet would go to the first 8466 panel 30A breaker with the output from the generator on the other 50A breaker to be selected on the panel by choosing between the breakers. The output of the both breakers on the 8466 would feed AC1 loads and the first breaker of 8499. The other breaker on 8499 would come from the second shorepower inlet. Both breakers on AC2 would feed AC2 loads.

Shore power to 2 inlets: AC1 to shorepower, AC2 to shorepower, 30 amp inputs feed the AC1 and AC2 loads. 60A total available.

Shore power to one inlet: AC1 to shorepower, AC2 to crossover, 30 amp from first inlet feeds both AC1 and AC2. 30A total available for both panels

Generator: AC1 to generator, AC2 to crossover, 50A total available for both panels. Is this right?

The only problem I have with this setup is what would happen if I accidentally left the second panel on the crossover breaker and plugged in shorepower cords to both inlets that were out of phase. I hope the breakers would trip and protect the system but can I count on that?
Or am I still unclear on your plan? Sure wish I had a picture of this. Calder's book has a lot of information but if this setup is in there I can't find it.

Morningstar10,

You will be fine, nothing will happen if you plug in two cords with the second AC panel switch set to be powered from AC1. The breaker wont trip because there is no fault. The power from the second cord will only go as far as the switch for the second panel and no further. The source switch maintains segregation. It will not allow you to turn on both source breakers simultaneously to feed the panel (doing so would connect the separate AC sources together). There is a physical cover over one of the breakers at all times only allowing one breaker (or source) to be active to feed the panel. This works just like the selection switch for your Generator and AC1 source. You can run your generator while plugged into AC. You generator is not in phase with the power grid, but it is also segregated thru the source selector switch. Both sources will not be connected to feed the panel at the same time. If you defeat the cover somehow, than you could have problems.

Please be aware that there is a lot left unsaid in this thread. For example, the second AC panel needs to be wired as a completely separate system. Most boats have a bus bar located in a convenient location for all return currents (the white or neutral wires). With only one AC source active at any time it is OK to have all returns go to a common bus. If you have two active AC sources, you cannot use a common return bus. You will need a separate return bus for all devices wired off the second panel (second AC source). The two systems need to maintain complete segregation. It goes without saying, be very careful with this. It would be good idea to diagram exactly what you would like to do. By drawing the diagram and understanding how each element works it will become clear. If it is not, than you may need to consult a marine electrician. This List Serve is an excellent source for quick information but it does not replace a couple hour consult with a marine electrician while viewing your schematic.

[Le Tour]

betrayfors posted a good picture showing the source selector switch. The black slide panel covering the generator breaker prevents the generator from powering the panel if the shore (AC1) switch is on and vice versa.

[Colin A]

Not sure if a diagram might help. The one attached is for a single panel with two separate AC systems (one for each 30 amp shore) it also has a gen transfer. The diagram only shows the customer wiring and not the jumpers used to connect the load select breakers but it should give you an idea what needs to happen.

[morningstar10]

OK i have it now. The problem wasn't with the explanations, just with my ability to vosualize. It's clear now. Thank you everyone for your help. Once it gets clear it seems obvious.

[morningstar10]

But now that it's clear I wonder if there isn't an easier way? If I just had two panels, one from each of the two inlets, each with source selection, couldn't i wire each shorepower inlet to a different panel, the generator to both panels and if I needed to feed both panels from one inlet I could do it with a Y connector to the two inlets. is that what btrayfors was suggesting?

[Le Tour]

Originally Posted by morningstar10

But now that it's clear I wonder if there isn't an easier way? If I just had two panels, one from each of the two inlets, each with source selection, couldn't i wire each shorepower inlet to a different panel, the generator to both panels and if I needed to feed both panels from one inlet I could do it with a Y connector to the two inlets. is that what btrayfors was suggesting?

I don't see an immediate problem with that, but you will already have all you need without purchasing the Y connector. It is cleaner to hard wire it as discussed. The Y is just another piece of gear to carry around and the shore power connectors tend to fail because the connection is not as solid as a properly crimped connection in a dry space. Once you price the Y connector from Marinco or Hubble I think you will agree (probably ~$200) with the original plan. If you want to purchase a connector, better to buy a 50 amp to 30 amp adapter. Some guest marinas have 50 amp and 30 amp service for the same slip. Most don't have two 30 amp services for the same slip. If you have an adapter you can use your two 30 amp shore power cables to power both of you AC panels.

If you wire with the Y and assuming your generator is 5KW you probably don't want to use 30 amp breakers on each panel since that would exceed 6000 Watts load to the generator.

[morningstar10]

Have the whole thing wired up and everything works great with one exception. My 50A 240V ELCI keeps tripping. Seems to only happen when I'm off the boat. Also seems to only happen when the Victron charger/inverter is on. Faster when the inverter is on, slower when it's on charger only. Usually trips overnight. No idea how to trace the problem. About to bypass the ELCI.

[FlyingCloud1937]

That will be do to an imbalanced load on the phases.

Lloyd

Originally Posted by morningstar10

Have the whole thing wired up and everything works great with one exception. My 50A 240V ELCI keeps tripping. Seems to only happen when I'm off the boat. Also seems to only happen when the Victron charger/inverter is on. Faster when the inverter is on, slower when it's on charger only. Usually trips overnight. No idea how to trace the problem. About to bypass the ELCI.

[morningstar10]

How do you get a perfectly balanced load? Have most of the load on L1 including the inverter/charger, galley and microwave. L2 has air conditioning.

[FlyingCloud1937]

Inductive and rectified loads cause a phase angle shift, along with unbalanced loads causes more current to flow in the neutral, which causes the ELCI to fault.

You can use a transformer, or you can get a scope and work out the loads. What inverter do you have? and What is the Power Factor?

Lloyd

Originally Posted by morningstar10

How do you get a perfectly balanced load? Have most of the load on L1 including the inverter/charger, galley and microwave. L2 has air conditioning.

[morningstar10]

I have a Victron Multiplus. Are you talking about an isolation transformer? I don't know the power factor. How would I find it?

[morningstar10]

I can measure each load easily but they're intermittent. The microwave operates rarely, the AC operates almost continuously, the inverter/charger fluctuates. How can they be balanced?

[rcmpegasus]

What you are describing is almost exactly what I just installed. Two 30 amp lines, two separate AC panels and selectors and lockouts. Either shore power can power either AC panel or both. Each AC line has a Victron multiplus. If no shore power generator can power both panels.

I'm real happy with the system, lots of redundancy and flex ability. My only issue was that the learning curve on operation of it is steep. Once I got my head around it, it was fine but training crew to understand it is not straight forward.

[FlyingCloud1937]

That's a good looking 360 panel. Who did your design/install?

Lloyd

Originally Posted by rcmpegasus

What you are describing is almost exactly what I just installed. Two 30 amp lines, two separate AC panels and selectors and lockouts. Either shore power can power either AC panel or both. Each AC line has a Victron multiplus. If no shore power generator can power both panels.

I'm real happy with the system, lots of redundancy and flex ability. My only issue was that the learning curve on operation of it is steep. Once I got my head around it, it was fine but training crew to understand it is not straight forward.