Dual Shore Power - What will run on single shore power?

[BOSCBIJI]

Howdy folks!

After scrubbing through the forum on this figured I'd tee up an opportunity of the power experts to provide some universal wisdom to us newbies. New R29 with dual shore power inputs:

If I plug in both shore power outlets, the entire panel is good to go. I know there's a limit on draw if I run a bunch of stuff and overwhelm the circuits, but the entire panel will be 'available' with shore power.

If I plug in just ONE of the shore power outlets, does only the side of the panel with the power chord plugged in work? In other words, the other side of the panel...its not powered?

Or if I plug in just ONE of the shore power outlets, would one side work with shore power and the other run off the inverter? Say plug in Shore Power 1...panel 1 works but then would panel 2 also be active just using the converter?

Essentially, if I don't care about AC/Heat and just want everything else to run on the boat (including the 120 outlets)...can that be done with one shore power connection or do both need to be plugged in?

I feel like the answer is: You're either funny inverter (no shore power plugged in) or you're all shore power (and if you only use one power cable you'll only get power to that side of the panel).

I know this is probably a 'no duh' question, but welcome any insights on this!

 

[S. Todd]

The second shore power input is only needed for the AC / Heat Pump units. I never plug that second one in if I don't need air conditioning or heat. If I am not using any other power hogging items (think water heater or microwave) it is possible to just use a splitter and then only run one power cord to the 30 amp outlet on the dock pedestal. Just using one of the AC units rather than both of them and I can still use the microwave.

 

[cominonslow]

We have a new R31 with dual shore power. For ours, when only one 30 amp dockside outlet is available, we leave shore power 1 plugged in (as those outlets can only be powered by shore power on the 31), and then we utilize the inverter to power the shore 2 side outlets. The other option is to utilize a splitter - just need to keep you load under 30amps total.

 

[S. Todd]

Based on the response from comimomslow it sounds like the newer Ranger Tugs actually do use the second power input for other than just the AC/ Heat Pump units. If that is the case with the R29 too, I recommend use of a splitter. It is the easiest way to get shore power to both inputs. We have never found it didn't work for us on our 2021 R29. Only one power cord needs to go to the pedestal which frequently only gives you one outlet and requires only one power cord to deal with when you are hooking up and unhooking to cruise.

 

[cominonslow]

Based on the response from comimomslow it sounds like the newer Ranger Tugs actually do use the second power input for other than just the AC/ Heat Pump units. If that is the case with the R29 too, I recommend use of a splitter. It is the easiest way to get shore power to both inputs. We have never found it didn't work for us on our 2021 R29. Only one power cord needs to go to the pedestal which frequently only gives you one outlet and requires only one power cord to deal with when you are hooking up and unhooking to cruise.

Correct. Shore power 2 powers all AC outlets on the new 31 in addition to powering the FWD heat pump. Shore power 1 powers main heat pump, water heater, and battery charger.

 

[DC3]

The Cutwaters have a slightly different configuration. Shore power 2 only powers the 2 AC units but has parallel switch to let you power both shore power 1 and 2 off a single shower power cable. You have to manage your power usage and only run 1 AC unit and probably not much else. But it removed the need for a splitter if only one outlet is available.

 

[DC3]

 

[Ozpilot]

View attachment 26939

I am looking to purchase a 2026 C-32. The online user manual on this lithium powered (no generator) boat does not show a parallel switch. The salesman is telling me it is not possible to power both buses from a single source. Correct?

It looks like to me is that in the case of a single source you can plug into shore power 1 and then use the inverter to power the shore power 2 bus. Of course you have to make sure you don’t exceed 30 amps.

 

[Full_O_Fish]

I am looking to purchase a 2026 C-32. The online user manual on this lithium powered (no generator) boat does not show a parallel switch. The salesman is telling me it is not possible to power both buses from a single source. Correct?

It looks like to me is that in the case of a single source you can plug into shore power 1 and then use the inverter to power the shore power 2 bus. Of course you have to make sure you don’t exceed 30 amps.
View attachment 27886

With the system you're looking at and describing, what you would want/need would be a 30a to dual 30a Y-adapter. This will plug into both shore 1&2, and be fed from a single cable from the pedestal. You will be limited to 30a total so you would have to do the math on which loads can be turned on simultaneously in order to not trip the breaker on the pedestal. The same Y-adapter could be plugged into the pedestal and then run two full length cables over to the inlets on the vessel, but you would still be subject to the same 30a max draw from the pedestal.

Where the conversation gets complicated is with what type of inverter has been installed on the vessel and what features have been enabled. Some products such as victron inverter/chargers can actually supplement shore power in order to supply intermittent loads without tripping the supply breaker. An example would be using the above mentioned Y-adapter you could draw 20a on shore 1, and set the input limit of the inverter for 8a so it will only draw 8a making a net 28a which will not blow the breaker. However if all of shore 2 needs to actually draw 20a for a bit (running the microwave, and other outlets, etc) then the inverter will supply 12a + 8a to cover the load, then go back to charging the batteries once the demand is back below the 8a programmed limit.

Another option, if there are dc-dc chargers which have been programmed accordingly between the engine and house banks, then in theory you can do what you described. Plug into only shore 1 and make sure the battery charger is turned on, which will charge the engine/thruster batteries. Once the charge voltage is high enough the dc-dc charger(s) will begin charging the house batteries via the engine battery charger (oversimplification). If the inverter is turned on it will pull from the house batteries and give power to all shore 2 loads, but it will be pulling very likely more power from the house bank than the dc-dc are putting in (just depends on how many devices or loads are on). So if you're not careful, you could potentially draw your house bank down to a point that it shuts off internally either from the inverter low voltage cutoff or the lithium battery BMS.

 

[Ozpilot]

With the system you're looking at and describing, what you would want/need would be a 30a to dual 30a Y-adapter. This will plug into both shore 1&2, and be fed from a single cable from the pedestal. You will be limited to 30a total so you would have to do the math on which loads can be turned on simultaneously in order to not trip the breaker on the pedestal. The same Y-adapter could be plugged into the pedestal and then run two full length cables over to the inlets on the vessel, but you would still be subject to the same 30a max draw from the pedestal.

Where the conversation gets complicated is with what type of inverter has been installed on the vessel and what features have been enabled. Some products such as victron inverter/chargers can actually supplement shore power in order to supply intermittent loads without tripping the supply breaker. An example would be using the above mentioned Y-adapter you could draw 20a on shore 1, and set the input limit of the inverter for 8a so it will only draw 8a making a net 28a which will not blow the breaker. However if all of shore 2 needs to actually draw 20a for a bit (running the microwave, and other outlets, etc) then the inverter will supply 12a + 8a to cover the load, then go back to charging the batteries once the demand is back below the 8a programmed limit.

Another option, if there are dc-dc chargers which have been programmed accordingly between the engine and house banks, then in theory you can do what you described. Plug into only shore 1 and make sure the battery charger is turned on, which will charge the engine/thruster batteries. Once the charge voltage is high enough the dc-dc charger(s) will begin charging the house batteries via the engine battery charger (oversimplification). If the inverter is turned on it will pull from the house batteries and give power to all shore 2 loads, but it will be pulling very likely more power from the house bank than the dc-dc are putting in (just depends on how many devices or loads are on). So if you're not careful, you could potentially draw your house bank down to a point that it shuts off internally either from the inverter low voltage cutoff or the lithium battery BMS.

Very informative. Thanks.

I have an aviation background. Aircraft design involves a lot of redundancy. In electrical systems it’s common to have two buses that are independent and powered from different sources.

As an example many twin engine aircraft have two independent buses each powered by a generator on each engine.

However there is always the option of powering both buses from a single source in the case of generator or engine failure. Of course it may be necessary to shed electrical load to remain within the limits of the remaining generator.

My understanding is that’s what the parallel switch does. What I don’t understand is why that switch was eliminated when the generator was taken out.

 

[Rode Trip]

I'll add that what you probably want is a 50amp to two 30 amp splitter (not a 30 amp to two 30 amp). The 50 amp plug at most marinas is 240 volt, 50 amp so you can pull one leg of the 240 for each of your shore power legs. Just remember you're limited to 50 amps and not 60.
You probably have a pass through inverter/charger which will sense if there's AC voltage on the bus that it's powered from and be a DC charger when it senses that voltage. If there's no AC power on that bus, then it will feed that bus through the inverter from the batteries. I don't know whether that's Bus 1 or Bus 2 on your boat.
The reason there is no parallel switch for the two AC buses is so that you don't accidentally parallel the inverter output with the shore power on the other bus.
One bus fed from a 30 amp shore power connection. The other bus fed from either a 30 amp shore power connection or the inverter output. You need to figure out which bus feeds your inverter/charger.