Using shore power on boat w/o AC power system

[dalepo]

I have a 22' boat with no AC inlet or power system, just a single 12v battery, used to power the radio and lights, that I keep charged with a small solar panel.

There are times when I work on the boat at the marina or sleep onboard when I'd like to use shore power to run small electric tools, a fan, phone charger, etc. I have an inverter, but I find that it runs the battery down faster than my solar panel can charge it up again.

The question is this: would it be safe to use an adapter to connect the 30 amp shore power outlet to a standard heavy-duty 15 amp extension cord and then run that into the boat through the hatch to power low-amp AC devices whle I'm working / sleeping onboard?

[RaymondR]

Generally not a problem but safer if the marina power tower has an earth leakage breaker installed.

[CassidyNZ]

I have a cable that plugs into shore power and has a 15A breaker with a plug socket installed on a box at the boat end. I use this to connect a very good battery charger as well as appliances (dehumidifier, vacuum cleaner, kettle, toaster) and power tools used on the boat. Nowadays I don’t use the battery charger any more because I now have a lot of solar and the batteries stay up without the charger.

I still use the cable when in marinas because the AC system on my boat is 110v and the world in which I live is 220v. The cable allows me to use local appliances on board.

[chrisr]

yep...we use to do this all the time on various race boats.

if staying onboard on the marina, just run a extension lead onboard to a powerboard, and plug in your heater, lights, kettle...whatever

not much different to camping (just don't get it wet !)

cheers,

[SV__Grace]

Sure, the pros do it all the time to work on boats dockside, and marina staff do as well.

I use an adapter like this for occasional use, but it's not meant to be plugged in all the time and outdoors in inclement conditions.

[thinwater]

Yup, cruised that way for years on my Stiletto 27. Still use that trick when working, sometimes.

[Coolerking]

Yup, we ran the Sears dehumidifier non stop on the SC70 I ran back in the day.
No problem at all

[oleman]

If I were the Captain and Chief Engineer I would install a rudimentary AC power distribution system so the next time I could just connect to Marina Power with out an issue. I feel the largest advantage would be to charge the DC system when the weather was not on my side.

[Lake-Effect]

Using a 30A -> 15A cheater cord is acceptable for temporary use (eg tools), and never leaving it connected and unattended. The danger of using normal 15A stuff on a 30A circuit, is that it's possible to have a fault that wouldn't trip the 30A breaker, but could still cause overheating and burning of 15A wires, plugs and outlets.

Similar to CassidyNZ, I put a 30A twistlock connector onto the cord of a powerbar that has a built-in 15A breaker. It's very unlikely that a short will develop on the 3 ft of cable between the 30A twistlock and the power-bar, and any 15A cords or devices plugged into the powerbar are protected by the powerbar's 15A breaker. It's a pretty safe arrangement, but not weatherproof. I could fabricate something more weatherproof if I intended to use 15A AC stuff more often.

[CassidyNZ]

Originally Posted by oleman

If I were the Captain and Chief Engineer I would install a rudimentary AC power distribution system so the next time I could just connect to Marina Power with out an issue. I feel the largest advantage would be to charge the DC system when the weather was not on my side.

You clearly don’t live/sail in New Zealand

Before you plug a boat into shore power here you have to provide the marina with proof that your AC installation has been checked/tested by an approved marine electrical contractor and verified as safe. It’s called an electrical Warrant of Fitness. And there is nothing rudimentary about it.

Better go with an extension cord suitably protected.

[CarinaPDX]

One easy, but a bit sloppy, way of solving the problem is to get a duplex 15A outlet, mount it in a junction box, and connect a 30A cord to the shore supply (the outlet stays inside the boat). Then buy an outlet strip with an integral 15A circuit breaker, or two if you need to run a heater as well, and plug them into the outlet box. It isn't really up to standards but should be safe. Ideally you would have a two-pole 30A breaker with two 15A breakers attached to two outlets but that is probably more than you wish to do for this. In fact it would be better to use GFCI outlets for the supply to protect against leakage. As others have said, using something low power and counting on the 30A breaker on the dock is not a good idea.

Greg

[SieveSailor]

The following advice may be obvious, but please, if you are going to run an extension cord onto your boat, at least make sure your extension cord is tied off on the boat side so that if it comes disconnected while plugged into shore power, it doesn't fall into the water as a live line.

[dalepo]

Thanks to all for this very helpful advice!