Boat using 30 Amp shore power, I recently had some arcing on the connection from power cord to boat socket. Have replaced both the connectors.

I am NOT an electrician by any means but have heard of arc fault breakers, I have not been able to locate 30A arc faults breakers (I suspect they are not available) and was wondering if I could split the input to 2 x 15amp arc faults which would then be connected together again to feed my power panel?

or does anyone know if and where I can get a 30A arc fault breaker?

in the last few weeks I know of several boat fires that killed, and after my arcing event I dont want to be the next.

Thank you for any help or advice you can offer. Once I have some more knowledge I will approach a certified marine electrician to install it

Thanks again, stay safe Scott

  • Is your shore power 30A/120V or 30A/240V? Is there GFP on the shore power receptacles you're using? – ThreePhaseEel Mar 6 at 20:24

You're barking up the wrong tree. Fix the sockets. Don't create arcing.

If you have sockets that are arcing while in normal use, then the plug or socket is defective and simply needs to be repaired. You saw it happen, you know it happen, cash out your 401(K) and head to West Marine and get another socket or plug.

If it arced while you were plugging or unplugging it, well heck - that's normal when the boat is drawing a load when you yank out the plug or plug it in. You shouldn't do that. Turn off the supply disconnect before messing with the plug, and then, you won't have that problem. It would also suffice to turn off the boat-side disconnect (or all the breakers if it doesn't have a master disconnect/breaker).

Disconnect switches often look exactly like circuit breakers. They are simply breakers rated for switching duty.

Now, if you want AFCI protection inside the boat, you can feel free to get AFCI circuit breakers on all your 15A or 20A individual circuits. If you have an obsolete or cheesy 120V distribution board in the boat that does not accommodate AFCI breakers, get one that does. You may want to think about industrial-grade "bolt-on" (bolt-down) breaker panels and breakers. They're used in factories to keep unauthorized personnel from opening up panels and messing with breakers because the bolt-down bolts are hot... but they also work great when dealing with vibration or shock.

Mind you, AFCI breakers operate by "listening" to the power line and identifying that characteristic crinkle-crunch sound of a bad headphone jack or of connecting speakers with the power on. They can't help hearing what's on the supply side of the breaker. So even if the arcing is "before" the AFCI breaker, they will often trip anyway. E.G. when you unplug the boat hot.

So... don't create arcing.

Why that won't work

As far as combining breakers... 30A is not made up of dual 15A. OK, imagine you wire two 12V batteries nose to tail, and you call the middle neutral. You then have +12V and -12V - use them both and you have 24V. Now if you have a 24V, 30 amp load - is it drawing 15A from each battery? No. It's drawing 30A from each battery. Likewise a 240V/30A load.

Regardless, you're not allowed to combine 2 small breakers to substitute for a big one, so you can't use two 15's to get a 30. Manufacturers will do that for very large breakers (gang four 100A to get a 200A/240V breaker), but they do it under controlled conditions and the whole assembly is tested and UL-Listed.

Even more than that, that doesn't work with AFCI breakers - because they monitor the neutral wire for current imbalance, both of the above cases will trip them.

  • Yeah, getting the marina to put in GFP to current Code would shut down a lot of these smokey shenanigans (in addition to pulling the plug on leaky boats) – ThreePhaseEel Mar 6 at 21:25
  • Wow thank you so much for the time to give so much detail Harper. I have replaced the shore power plug as well as the receptacle / socket and yes both were very expensive. Youre right I had unplugged a few times without killing the power and the boat is 30 years old, so Im sure someone before had done the same. The socket and pins we all pitted. I was just looking for a way to prevent arcing at the plug again or inside the boat for extra safety. Thank you again, I very much appreciate your time and knowledge Have a great day – Scott K Mar 6 at 22:32

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