shore power cord problems

Two questions:

1. How do you prevent the condition shown in the pictures below? It used to happen to my sailboat, and it now happens to my trawler.
2. I hear RVs have surge protectors. Is that something I should add to my trawler?

The black carbon deposits are a sign of arcing (sparks). Both your cord and the inlet are beyond repair and should be replaced. Replacing one won't work, the other one will quickly ruin the new one.

How to prevent it? To start with, always, without fail, turn off the breaker on the dock pedestal before connecting or disconnecting the cord. If there's no breaker on the dock pedestal, turn off the main breaker on your boat before connecting or disconnecting the cord. Unplugging the cord when electricity is flowing is sure to generate an arc and that causes what you see.

Sometimes we see this damage on the male end of the cord and that's caused by a faulty outlet on the dock pedestal. That's more difficult to deal with because it belongs to the marina. Use a different outlet or ask them to replace it.

Other things to do: Don't drop the ends of the cord in the water, especially salt water. Don't leave them out in the rain when not in use.

Applying a coat of dielectric grease to the pins and sockets is a good maintenance procedure as it will shield the contacts from corrosion but still allow electrical contact. Dielectric grease is an insulator but the action of plugging in the plug wipes the grease from the actual contact surfaces.

Screwing on the ring helps hold the plug steady so it doesn't wiggle and loosen. Strapping the cord to the boat a foot or two from the plug also helps to remove strain and movement.

In the end, you should plan on replacing these things every several years.


I've never seen a surge protector on a boat or one in a catalog intended for a boat. I wouldn't worry about it.

That damage has nothing to do with surge.


The traditional twist lock 30 amp connector has a number of deficiencies in marine use: connector comes loose which reduces contact, contacts are too small to carry full current continuously, salt environment makes connections less reliable.


One solution is the Smartplug, a positive locking, enclosed connector with more contact area. See Home -.


Another is Marinco's EEL connector. See EEL Cordset, 30A 125V, Yellow, 50' | Marinco


David

Here is some interesting reading for you on this subject...
Rod is a very bright guy.
Bruce

Shore Power Cords - SmartPlug vs. 1938 Photo Gallery by Compass Marine How To at pbase.com

WesK said:

Applying a coat of dielectric grease to the pins and sockets is a good maintenance procedure as it will shield the contacts from corrosion but still allow electrical contact. Dielectric grease is an insulator but the action of plugging in the plug wipes the grease from the actual contact surfaces.

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How often do you apply this grease?

This is caused by resistance in the electrical connection while trying to draw a heavy load. Resistance can be caused by corrosion, arcing and loose wire connections. I recorded temperatures this summer on my standard 30 amp connection saw a 30 degree temp rise above ambient when carrying a 27 amp load for 30 minutes. Replaced the standard Marinco hull inlet and still had a 19 degree temp rise. Ordered a smart plug inlet $$. Replaced that inlet with a smart plug and had a 3.5 degree temp rise. We cruise full time and have been in about 30 different slips since the first of this year. About 80% of the time the power post breaker is on when we go to connect our cords. Naturally I turn it off before connecting, but this tells me that 80% of the time people are "hot plugging." That leads to arcing, arcing creates burns which have high resistance and that causes heat. I am also amazed at how many people do not close the cover on the hull inlet when under way. that allows salt air/spray etc lead to corrosion. Also am always surprised how few people use the locking ring to seal the 30 amp hull inlet: if you don't use the locking ring water gets in and creates corrosion. I use electric conductive pate on my plug spades if I am forced to plug into a suspect dock power pedestal. I have written about this for SAIL and Chesapeake Bay Magazine. Have a follow up article on the Smart Plug performance due out this winter.

https://dl.dropboxusercontent.com/u/9779634/cbm122015 plugging along.pdf

Have found that this problem is caused by using to many heavy amp devices,a/c and water heater on one circuit. Would replace both ends and try to regulate your loads so you don't draw too many amps. The ground wire cannot take the load of two heavy devices. Since watching my loads I have had no problems since.

Deckape said:

Have found that this problem is caused by using to many heavy amp devices,a/c and water heater on one circuit. Would replace both ends and try to regulate your loads so you don't draw too many amps. The ground wire cannot take the load of two heavy devices. Since watching my loads I have had no problems since.

Click to expand...

That plug is used exclusively for the air conditioner (which died 3 weeks ago) so there is no way to regulate the amperage draw through that circuit.

Is there any information comparing the EEL plug to the Smart Plug? Casual observation shows more EEL Plugs around our local docks than Smart Plugs. They seem easier to use as you don't need to replace the boat or power post plugs. Thoughts?

djmarchand said:

One solution is the Smartplug, a positive locking, enclosed connector with more contact area. See Home -.

Click to expand...

Works for me!

Note the "thermostat" feature

seattleboatguy said:

That plug is used exclusively for the air conditioner (which died 3 weeks ago) so there is no way to regulate the amperage draw through that circuit.

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Why did the A/C die? Could it have been pulling a very high amp load before it died?

After you replace the cord (30a cords are cheap) and boat side receptacle, you need to meter the loads on that cord. If it's consistently at or over 80% of the 30a max load rating of you current cord, you should consider changing over to a 50a 250/125v cord system.

If you stick with the 30a cord, unplug both ends and check them regularly and spray all the contact points with Boeshield or something like it as needed. Or at least a few times a year.

hmason said:

Is there any information comparing the EEL plug to the Smart Plug? Casual observation shows more EEL Plugs around our local docks than Smart Plugs. They seem easier to use as you don't need to replace the boat or power post plugs. Thoughts?

Click to expand...

The EEL plug is certainly easier to use than the standard threaded ring plug, but it suffers from the same limited contact area of a NEMA L5-30 connection. See attached.

hmason said:

Is there any information comparing the EEL plug to the Smart Plug? Casual observation shows more EEL Plugs around our local docks than Smart Plugs. They seem easier to use as you don't need to replace the boat or power post plugs. Thoughts?

Click to expand...

The Eel plug has exactly the same "Guts" as the standards 30 amp hull inlet and cord end. So far as I can tell, his design was simply a way to make it easier for people to lock the plug to the hull inlet. It has no improved load carrying ability.

Capt.Bill11 said:

Why did the A/C die? Could it have been pulling a very high amp load before it died?

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Yes, that is very possible. The a/c tech who examined the dead Lunaire air conditioner said that the compressor was shorting to ground. There were also some scary melting wires in back of the control panel. It was not a happy a/c. I now have a new Ocean Breeze a/c sitting on the floor of my main cabin, waiting for me to install it this weekend.

Capt.Bill11 said:

If you stick with the 30a cord, unplug both ends and check them regularly and spray all the contact points with Boeshield or something like it as needed. Or at least a few times a year.

Click to expand...

So, inspect the shore power connector and re-apply the spray twice a year. Is that correct?

seattleboatguy said:

Yes, that is very possible. The a/c tech who examined the dead Lunaire air conditioner said that the compressor was shorting to ground. There were also some scary melting wires in back of the control panel. It was not a happy a/c. I now have a new Ocean Breeze a/c sitting on the floor of my main cabin, waiting for me to install it this weekend.

Click to expand...

Before you install the new AC, You really need to check and maybe replace wire and breaker between the dead 30 amp receptacle and the AC unit. If you cooked the receptacle and power wires within the AC, good chance there is overload damage elsewhere.

Ted

seattleboatguy said:

Two questions:

1. How do you prevent the condition shown in the pictures below? It used to happen to my sailboat, and it now happens to my trawler.
2. I hear RVs have surge protectors. Is that something I should add to my trawler?

Click to expand...

Newer boats have a breaker right after next to the boats shore power out let between the out let and the main panel selector switch to protect the cord and out let. Older boats do not have the breaker. We updated our electrical with a smart plug for addition safety.

Capt.Bill11 said:

If you stick with the 30a cord, unplug both ends and check them regularly and spray all the contact points with Boeshield or something like it as needed. Or at least a few times a year.

Click to expand...

This is good advice, and we consider it standard practice. If you cruise a lot you will sometimes get to marinas with questionable dock receptacles. Eventually one of them will overheat and damage your cord end despite the care you take of your own cord.

seattleboatguy said:

How often do you apply this grease?

Click to expand...

I apply it periodically to the cord that I use when traveling. For my home cord, I reapply it any time I remove my cord from the dock pedestal. Since I have to use an adaptor on my 30 amp cord since I have a 50/120 plug on the boat, I use the grease on that connection as well. It is cheap and easy to apply. I keep it I. A drawer on the boat that is easy to get at so I don't have to go hunting for it.

http://www.homedepot.com/p/CRC-3-3-oz-Technician-Grade-Di-Electric-Grease-05105/203283187

FWIW, I think that for 30amp services, the Smartplug is a great investment.

Dielectric grease is an insulator, non-conductive... Yes, it will keep air out of the joint but won't pass electricity. Better choice would be a conductive grease.

Phil Fill said:

Newer boats have a breaker right after next to the boats shore power out let between the out let and the main panel selector switch to protect the cord and out let. Older boats do not have the breaker. We updated our electrical with a smart plug for addition safety.

Click to expand...

I don't understand the theory behind this. If you have a 30 amp breaker next to the shore power outlet, and then another 30 amp breaker a few feet away on the main panel, it would seem kind of redundant to me. Why do the newer boats have both?

I use Kopr-Shield, a conductive grease. But you must be very judicious with it. It is conductive and you can create a short circuit if you get sloppy with it. With our hull inlets, we can leave the cords attached. I put Kopr-Shield on the boat end, screw down tight on the locking ring and check for temperature rise anytime I see I have a heavy load. I put Kopr-Shield on the plug on the shore end as needed, depending upon the power post at today's marina.


CP8-TB Thomas & Betts Kopr-Shield Compound, 8-Oz

O C Diver said:

Before you install the new AC, You really need to check and maybe replace wire and breaker between the dead 30 amp receptacle and the AC unit. If you cooked the receptacle and power wires within the AC, good chance there is overload damage elsewhere.

Ted

Click to expand...

That's a good thought. I'll take a close look at the entire wire run between the shore power connector and the new a/c.

seattleboatguy said:

I don't understand the theory behind this. If you have a 30 amp breaker next to the shore power outlet, and then another 30 amp breaker a few feet away on the main panel, it would seem kind of redundant to me. Why do the newer boats have both?

Click to expand...

Not sure all newer boats have them....but but I think newer boats conforming with ABYC suggestions need to have a breaker within so many feet of the boat power inlet....10 feet rings a bell....

So if the main panel is too far away, there is a breaker right next to it...and really new boats mave have the new whole boat ground fault system (ELCI ?) right there.

stubones99 said:

Dielectric grease is an insulator, non-conductive... Yes, it will keep air out of the joint but won't pass electricity. Better choice would be a conductive grease.

Click to expand...

Oh dear. Now, an electrical novice like myself has to choose between dielectric grease and conductive grease? It reminds me of my sailboat days, when I had to choose between a dozen different ideas of what was the "proper" way to establish the ground plane for my new single sideband radio.

This is an ABYC requirement that there be overcurrent protection which breaks both the hot and the neutral conductors,and be located within 10 feet of the hull inlet.

If the inlet is near the panel, then the panel breakers suffice. On most boats it is more than 10 feet from the inlet to the main distribution panel.

hmason said:

Is there any information comparing the EEL plug to the Smart Plug? Casual observation shows more EEL Plugs around our local docks than Smart Plugs. They seem easier to use as you don't need to replace the boat or power post plugs. Thoughts?

Click to expand...

The only difference in the EEL is the grip clamps or locking mechanism to attempt to hold the plug into the socket. It is still a NEMA 30A plug. In my experience the EEL is that it is not much of an improvement, other than convenience factor, in holding the plug in place over the threaded rings. Easier & more convenient to lock, sure, better not really...

seattleboatguy said:

Oh dear. Now, an electrical novice like myself has to choose between dielectric grease and conductive grease? It reminds me of my sailboat days, when I had to choose between a dozen different ideas of what was the "proper" way to establish the ground plane for my new single sideband radio.

Click to expand...

Don't use either.

Why would you use one grease that could inhibit conductivity or one that can cause a short because is so conductve?

Just use Boeshield or something like it and rest easy.