Arcing in 30 amp shore power cord? (Picture)

[Lake-Effect]

Originally Posted by Jammer

There have been various product proposals for a shore power connection with a temperature sensor that will disconnect the boat in the event of overheating, before there is a risk of fire. I'm only aware of one that made it to market and it was withdrawn due to problems with build quality.

That's not really a solution, just early detection of failure.

The problem is the usual connector - it seems to be a poor match for the weight and rigidity of most shorepower cables, its twist-lock is inadequate, and the contact area is minimal for the rated max current, especially as the connectors age and wear.

For many boats who don't have heavy AC loads, they may never experience a problem; they usually aren't drawing enough current to start the contact heating. And you can prolong the life of the contacts by using a contact cleaner/protectant (as per Frankly), and by never connecting/disconnecting "hot" - the boat and pedestel breakers should be off first - so you don't cause arcing at the connectors.

The Smart Plug is a step in the right direction, but then you still have the same old plug at the pedestel end.

[Rumrace]

I’m happy you unplugged it. You need to replace your boats plug in and check the hull ground wire. I think the green stuff got your ground.

[phorvati]

This is a classic example of an arc fault. This is series arc, so low current, not enough for Circuit breaker to trip and also no mismatch for GFCI, ELCI to trip. this is part of the reason UL mandated Arc Fault Circuit Interrupters AFCIs in homes, granted this is at a dock. I wonder if UL marine AFCI is coming as a mandate soon because ELCI cannot catch this.

If terminal is oxidized enough contacts develop semi-conductive path for small arc to develop. It becomes carbonized over time and the path is ripe for creating even more arcing which if left un-attended leads to heat buildup and ultimately fires. The more arcing the more carbon buildup and conditions escalate. Conditions need to be just right. Happens in home wiring (over decades)if improper torque is used for securing wires to wall fixtures or circuit breaker panels. In salty environment its a lot easier for those conditions to develop.

UL test AFCIs by creating this type of carbonized arcing samples in the test lab, to verify AFCI "work". It's very difficult to make them, so a lot of samples get thrown away, a bit of a witch craft.

[Cheechako]

Not uncommon. I used to replace my cord every year living aboard as we ran a small space heater in winter. The end would look similar to that and if you inspected the internal copper wiring it as black.

[Mauruuru]

both the cord "female" end connector and the boat "male" connector should be replaced when this kind of heat induced failure is seen. It may well be that the problem is starting in the male connector due to a damaged or previously overheated contact.

[thesaltytar]

Originally Posted by Frankly

Get a tube, mine must be 30 years old and has been smeared on a lot of electrical connections over the years.

That's actually a very good idea. Not to remedy the existing issue (as you noted at the top of your comment) but helping the conductivity over time will likely lengthen the lifespan of the plugs.

I used to do something similar with the little ends of halogen light bulbs because the vibration of the engine would shorten their lifespan. Improving their contact lengthened their lifespan.

Also... I do have a smart plug and stand by it, bit it's just a better design doing the same job and susceptible to the same failures over perhaps longer time.

[Nate24]

This is certainly a fire hazard. One of the reasons this occurs I haven’t seen mentioned yet, is that some folks do not cut the AC panel breaker off, and the Pedestal breaker off prior to attaching or detaching the SP cord. This leads to pitting on both the cord, and the inlet connection. Over time, that can lead to the same issue.

Good to see you are pulling the inlet connection. I would also suggest cutting back the AC wire if there is any charting at all. Sometimes, a new AC wire to at least the breaker will be necessary. Can become a bigger job, the further the deterioration is.

[mcon12000]

I concur with the others that suggested you replace the inlet on the boat and unfortunately the new cord also needs to be replaced.

Now the best solution is to ditch the L5-30 style connector on the boat side of the cord. Many use the Smartplug but I use a 30amp watertight pin and sleeve that moves the point of failure to the shore side of the service.

[Shaneesprit]

Replace the plug.
Chances are the plug is worn / damaged from the arcing - cleaning an arc is not good enough.
No Electrician worth his salt would try and clean that up.

[BoatBumm]

I’ll also vote strongly for the SmartPlug. My solution to occasionally needing the conventional inlet was to leave it in place and wire the SmartPlug inlet next to the original in parallel. I can thus use either one as needed.

BUT, BUT, BUT a conventional 3-prong inlet has male prongs in there, and those prongs will be “hot” when the parallel wired SmartPlug is use. My solution to that was to cut a cylinder of high density foam to fit the inside diameter of the old inlet, and slice 3 slots in that foam cylinder using a handheld jig saw blade to accept the prongs. That cylinder just lives in the old inlet since I rarely need it. There’s a pull cold loop of light cord to remove that insulating cylinder when needed.

I’m sure a surveyor would have a conniption fit over what I did. “That’s Unsafe! Violates standards!”

But it works.

[captainwd40]

That is the neutral pin being armed.

You either have a floating ground or forgot to install the jumper on your inverter.

An electrician can easily diagnose and fix your problem.

Cheers!

[GrowleyMonster]

Originally Posted by CSY Man

Hello from Florida:
Plugged in my 30 amp cord to run the 10,000 BTU A/C: Strong smell of burnt something.
Disconnected the cord and noticed black soot marks on the female end.
Cleaned the male contacts (They were already clean, no corrosion, but black from the arcing)

Different day, different marina AND different cord, same result: Arching and burned smell.
What is going on?
(No breakers popped on the boat or on the dock pedestals, the A/C was working normally.)

A short in the vessel's 110 volt system? (If so, breakers should have popped)

I would say that your male connection is bad, not making good contact. High resistance and current equals heat. Sometimes lots of heat. Replace the receptacle.

[CSY Man]

Yes, replacing the inlet for sure, just curious what triggered it..
(Pulled out the old one, no corrosion, probably just old age)

Got an exact replacement from the same maker, $90.00

[CSY Man]

One guy got upset about the above question/thread and sent me a nasty message, probably full of himself and rum 'n coke.

For those who are concerned about fires and being in the same marina as me:
Shore power are hardly ever being used, nor do I visit marinas more than once or twice per year.
Got a nice solar panel and an 80 amp alternator.

Just curious what happened to my shore power cable and why the arcing..

Thanks for the informative advice and information, much appreciated

[Sailmonkey]

Originally Posted by CSY Man

One guy got upset about the above question/thread and sent me a nasty message, probably full of himself and rum 'n coke.



For those who are concerned about fires and being in the same marina as me:

Shore power are hardly ever being used, nor do I visit marinas more than once or twice per year.

Got a nice solar panel and an 80 amp alternator.



Just curious what happened to my shore power cable and why the arcing..



Thanks for the informative advice and information, much appreciated

Whoever sent that message to you must be unaware that most boats with 30a shore connections and any load greater than 18-20 amps have melted connections.