Shore Power Cord Damage

[Mike Smith]

About every two years, I have to replace the female end of my shore power cord and the male AC receptical on Breezer due to electrical arching damage to one of the prongs - this is a fire hazard. I always twist lock the connection and screw the ring down tightly when we leave the boat. My 20A shore circuit breaker rarely trips, even though I run an air conditioner and battery charger full time. Before I call my electrician ($$$), What could be causing this damage and what can I do to fix it?
 
 Mike and Jan Smith
 S/V Breezer
 www.mikejansmith.com

[Ken Juul]

Arcing generally happens when contact is made or lost with an electrical load on the circuit.  Is your main A/c switch on the panel off when you connect?  Are the male prongs on the boat receptical straight?  If the one that is arcing is slightly bent it might be close enough to pass electricity but far enough to cause some arcing.  Is there slack in the line before the plug?  Even though it is screwed in tight, with little slack if it is stepped on it may put sufficient pressure on the plug to cause arcing.  My daughter had a bunch of college age guests on board, After a late night party in the cockpit I found some arcing on my plug.  Being stepped on is the only thing I can attribute it to.

[Mike Smith]

Ron & Ken & Vicki -
 The 20A breaker is on the dock, I have a 30A breaker on the boat.  I have a Sentry automatic charger which charges as needed.  Consensus is that I have been plugging and unpluging the power cord with the main AC breaker on.  Not a good practice.  I do everything else re: slack in the line, prongs are straight, etc.  Similar "stepped on" damage was done to the conection when I once asked a guest to disconnect the shore power cord, then didn't watch him do it. He pulled it out without first twisting the connector.  Broke the plastic insert, pulled out the wires. He said it was kinda hard to do.  Well, I'm off to swap out my Norcold reefer system.  Probably will have lot of questions toay!
 
 Mike and Jan Smith
 S/V Breezer
 www.mikejansmith.com

[Mike Smith]

On checking the shore power cord connection this weekend (boat side, female end), I found that my new cord was showing damage after only three days of use.  I checked the male plug and found that the white-wire prong was blackened with discoloration around the base, so I bought a new replacement insert.  On removing the old insert, the white wire insulation was showing discoloration back about 3/4" also.  Looks like a disaster ready to happen.  There is essentially no slack in the AC wire - I can get the insert out only about 2", so I am going to replace the cable and provide about 12" of slack for future work.  I have two questions:  (1) The existing cable is 10 gauge - should I go to 8 gauge? and(2) Should I wire the AC circuit directly to the shore side of the power transfer switch and from there to the AC distribution panel as it is currently done?  Thanks for any comments or suggestions.
 
 Mike and Jan Smith
 S/V Breezer
 www.mikejansmith.com

[Norris Johnson]

I had the same problem with my power cord, Mike. I found that some of my deck hands were plugging in with the power on. I replace the boat end of the PC and cleaned the boat receptacle with my dramel tool. No problem since. It's been two yrs.