Basic Shore Power Question

[JLR]

On my 43, I have an option of one 50 amp/240v power cord or a single 30 amp power cord. On my panel, assuming I have it set to shore power, I have a choice of 120v or 240v. Here's my question. If I am running the 30 amp cord only, on the panel, do I need to have 120v selected or can I select 240? In other words, can I run anything that is 240V from my one 30 amp line? I think my AC might be 240v and/or my block heaters since they are connected to what I believe is a double breaker. Thanks.

[fissioneng]

On my boat, if you plug in 120 volts, the polarization transformer will turn it into 240 volts for your 240 loads. I can run one 240 volt AC unit when on 120 volts. You can run as much as you want on 120 or 240 as long as you don't exceed the 30 amp rating of the 120 volt shore line. If you don't have a transformer, it might not work like this.

You need to set the switch to 120 when plugged into 120.

[JLR]

That is what I was hoping. I was concerned about the compressor on the AC unit and the motor on the AC pump not being happy with just the one thirty amp line and the selector set to 120v.

[Genesis]

Yes, it will power both sides if you have the transformer in your boat, BUT....

Remember that a 30A/120V cord delivers approximately 1/4 of the watts of a 50A/250V one! That is, if you need 240V (e.g. for your AC unit) you have 15 amps (total for 240V), not 50!

[fissioneng]

Remember that a 30A/120V cord delivers approximately 1/4 of the watts of a 50A/250V one! That is, if you need 240V (e.g. for your AC unit) you have 15 amps (total for 240V), not 50!

Certainly. My AC pump is 120 volts and when I run a 240 volt 16K AC unit and the 120 volt pump, I can't run anything else in the boat but a few lights. I blew a 30 amp fuse when I turned on too many things. Definitely no water heater or stove.

[Jaxfishgyd]

Mine had a 30 amp for boat use and 50 amp for the AC's... but all 120V... After replacing the old units in 2000, I was only drawing 22 amps so replaced the 50 amp plug on the boat and went to 30 amp service... Now 14 yrs later, have had zero problems with this set up... and makes it a LOT easier when stopping at any marina where most only have 30 amp service for the size slip I need