Shore Power Cord Issue

Clay Greene · February 17, 2015, 01:09:08 PM

We woke up one morning last fall to find that our shore power cord, a Marinco EEL cord, had melted to our inlet. It took some work to get the plug disengaged. We had been running a heater overnight so we obviously were drawing some load and the heater was cycling on and off as it would reach the appropriate temperature. I cut the end off off the plug and found that only the white wire and the connection to the plug were badly melted. The green and the black wires looked fine. Having read Maine Sail's posts about the problems with the standard shore power cords, I replaced the inlet and the cord with the Smart Plug system.

My question is what would have caused the issue with just the white, neutral wire? Could it have been something other than a bad connection and arcing at that one prong of the plug? The EEL does not have a traditional locking ring but instead is a clamp with a locking tab, which I am pretty sure I engaged. I always leave plenty of slack in the cord so it does not get pulled with any boat movement. It may be a coincidence, but another slip tenant a dock over also said he had some charring/melting of his plug on the same night.

Any thoughts on this would be much appreciated. It is more a curiosity than anything at this point but something that has bothered me.

mark_53 · February 17, 2015, 01:20:13 PM

I had a similar problem but mine was the wiring on the power bus. It stated arching and went very brittle. I think heaters gain resistance as they get older. I replaced my heater and the wire and all has been fine since.

KWKloeber · February 17, 2015, 01:27:41 PM

Quote from: claygr on February 17, 2015, 01:09:08 PM
We woke up one morning last fall to find that our shore power cord, a Marinco EEL cord, had melted to our inlet. It took some work to get the plug disengaged. We had been running a heater overnight so we obviously were drawing some load and the heater was cycling on and off as it would reach the appropriate temperature. I cut the end off off the plug and found that only the white wire and the connection to the plug were badly melted. The green and the black wires looked fine. Having read Maine Sail's posts about the problems with the standard shore power cords, I replaced the inlet and the cord with the Smart Plug system.

My question is what would have caused the issue with just the white, neutral wire? Could it have been something other than a bad connection and arcing at that one prong of the plug? The EEL does not have a traditional locking ring but instead is a clamp with a locking tab, which I am pretty sure I engaged. I always leave plenty of slack in the cord so it does not get pulled with any boat movement. It may be a coincidence, but another slip tenant a dock over also said he had some charring/melting of his plug on the same night.

Any thoughts on this would be much appreciated. It is more a curiosity than anything at this point but something that has bothered me.

My understanding is that the EEL is the same basic connection (see RFC's article and forensics of the actual contact area of the locking blades.) If there's corrosion or otherwise a bad connection there's virtually no safety margin on the twist lock plugs, EEL or traditional style.

I hope all members know that there's a significant Smart Plug group purchase discount available for C34 owners.

Cheers,
Ken K

Clay Greene · February 17, 2015, 02:26:25 PM

Here are a couple of photos of the inlet.

KWKloeber · February 17, 2015, 03:34:37 PM

Quote from: claygr on February 17, 2015, 02:26:25 PM
Here are a couple of photos of the inlet.

Difficult to see inside the back-wired plug .... but from limited info, it looks more like a failure at the cord/wire/spade connection --- loose or corroded screw terminal?
Did the wire end end up getting welded to the buried end of the neutral terminal? That might indicate high resistance/arcing/heat there due to a broker wire or poor connection to the back of the spade.

I was told that the #1 cause of a house fire is electrical -- and the #1 cause of that is arcing at a terminal/connection. Makes sense. That's why new construction needs an Arc Fault Circuit Interrupter; like the GFCI we have all grown to know and love.

KK

mainesail · February 17, 2015, 04:36:39 PM

The EEL is nothing different. Yes it has a different locking mechanism, that still sucks, but the plug is still a NEMA L5-30. You have signs of heat burning evidence on both the hot and the neutral wires in those photos. The white just got hotter faster. Each wire, black & white, carry the same load, it is AC, it just amounts to which terminal got the most worn or had the most corrosion or made teh poorest contact when you plugged it in.

I will repeat this once again;

DO NOT ADD ELECTRIC HEATERS ON TOP OF YOUR OTHER AC LOADS!!!

If you must run an electric heater TURN OFF THE WATER HEATER FIRST.

In good shape these twist locks should never be loaded more than 24-25A as they age you'd be wise not to even approach 20A....

Want to play it safe buy a Smart Plug!!

Clay Greene · February 18, 2015, 10:00:04 AM

Just one other piece of information - the EEL cord was a year and a half old so it had been used for two six-month seasons. My guess is that it just may not have been seated properly in the inlet, so it was a combination of poor contact and the cycling loads from the heater. I don't think we would have even been able to run the water heater and the space heater at the same time without tripping the circuit breaker. We did always make sure that the space heater was the only AC load other than the battery charger, which would have been in "float" mode.

Lance Jones · February 19, 2015, 09:45:13 AM

I had similar incidents like yours. All during the winter. I was also running heater(s). I put in a second A/C panel when we were installing our air condition system. So, I put the ac on one panel and half of the outlets on each. We plug in low draw appliances on the new panel and high draw on the old panel. We haven't had ANY issues since.