Hot Shore Power Cord

[fissioneng]

Ever since I've owned the boat, the shore side of the shore power cord would get warm if both AC's run for a long time. It would get hot right at the plug after a long day. Knowing this was not a good thing, I finally took it apart and this is what I found. The insulation is completely burned off the red lead right where the cable compression clamp is. I assume it was that way from the start. Not sure exactly why the compression clamp would cause the wire to overheat, but it looks like it did. I cut it back a foot and reattached. It doesn't heat up at all now.

[dcate]

Just recently mine was warm enough it catch my attention. I too assumed it'd been this way awhile. Thanks for the starting place.

[GJH]

They should be cool to the touch, if you feel any warmth trouble is brewing. get in the habit of grabbing them when you by every day or two.

[Sailor John]

Wow. Scary stuff. Thanks for the call out! I'm off to check my power cords!
Sailor John

[Bob Bradley]

Same problem. I solved mine by replacing the inlets as well as the cord. The back side of them showed evidence of overheating as well. You may want to check yours out. I installed the new smart plugs, and I love them. Much more conductive surface than the old twist locks.

[Pascal]

I always check cords for heat as well but I usually check near the plug. Last december I noticed that one of the 2 50amp cord was warm but 3 or 4 feet from the plug . Moving away from the plug, it got hotter with temp peaking to almost too hot to touch about 15' from the end. That s one of 2 50 amp cable, this one is the house cord (no AC)

I cut the cable open and the N insulation was melted away over a few inches and all 4 NON TINNED wires were corroded from one end to the other! I replaced the whole 80' cable with tinned cable from Ward in FTL.

It looks like some of the marinco cable use in Glendinngs is not tinned!

I learned a lesson that day and now check for heat along the cable, not just at the plug.

http://i1048.photobucket.com/albums/s365/pgademer/25A3CC08-1A83-449C-A39C-915D117072BD-3416-0000027A417A0373_zps669312e7.jpg

http://i1048.photobucket.com/albums/s365/pgademer/168FE297-F20D-4BAE-9132-953796D0AF87-3416-0000027A3E744CFD_zpsf1256926.jpg

[Trojan]

Cut them off until you reach fresh copper, add conductive electical grease.Then attach them to a new plug. All power plugs need to be checked at least twice a year. Inside and out. This includes the back side of the input shore plug on the boat. It looks like the conections were loose and heated up. Tipical loose over heated connection. Just what causes boat fires. Power cords take a beating with all the bending twisting and vibration. Consider yourself lucky. Make sure the connection prongs are tight in the twist lock connection. If there blue or burnt in color,get new both connections. Don't use a burnt plug in a new connection or the new plug will be burnt again.

Bill

[fissioneng]

I cut the cable open and the N insulation was melted away over a few inches and all 4 NON TINNED wires were corroded from one end to the other! I replaced the whole 80' cable with tinned cable from Ward in FTL.

It looks like some of the marinco cable use in Glendinngs is not tinned!


As mentioned in another thread, I am finding that most pre-made power cords are not tinned and it is difficult to find tinned 6 AWG 4 conductor STOW cable. Ancor makes it for about $20/ft. Not sure where Ward's gets theirs. I did some web searches and didn't find much.

SmartPlug makes a 30 amp cord that is tinned. They've told me they're coming out with a 50 amp cord later this year, hopefully tinned.

[Pascal]

I paid $620 with tax for 80' of 50amp tinned cable at ward in dec. I orginally ordered the replacement from West Megayacht but it turned out the marinco cable was not tinned so I didn't accept it. My contact there couldn't get tinned right away so she called Ward and got me a good price there.

It s made for Ward and marked Ward on the putter insulation. Not sure what their regular price is

[Boatnut]

I always check cords for heat as well but I usually check near the plug. Last december I noticed that one of the 2 50amp cord was warm but 3 or 4 feet from the plug . Moving away from the plug, it got hotter with temp peaking to almost too hot to touch about 15' from the end. That s one of 2 50 amp cable, this one is the house cord (no AC)

I cut the cable open and the N insulation was melted away over a few inches and all 4 NON TINNED wires were corroded from one end to the other! I replaced the whole 80' cable with tinned cable from Ward in FTL.

It looks like some of the marinco cable use in Glendinngs is not tinned!

I learned a lesson that day and now check for heat along the cable, not just at the plug.

http://i1048.photobucket.com/albums/s365/pgademer/25A3CC08-1A83-449C-A39C-915D117072BD-3416-0000027A417A0373_zps669312e7.jpg

http://i1048.photobucket.com/albums/s365/pgademer/168FE297-F20D-4BAE-9132-953796D0AF87-3416-0000027A3E744CFD_zpsf1256926.jpg


Looks like a classic case of overload.

[Pascal]

Never popped any breakers... Cables are protected by breaker on pedestal, breakers where the cables enter the boat plus master breakers at the panel. Never saw more than 50 amps on the panel meters which are visible from the galley and saloon

[fissioneng]

Never popped any breakers... Cables are protected by breaker on pedestal, breakers where the cables enter the boat plus master breakers at the panel. Never saw more than 50 amps on the panel meters which are visible from the galley and saloon

Same with me. I usually only see 30 amps per leg. In my understanding, the heating is caused by localized high resistance (caused by corrosion or loose connections) at amperages much below the fuse/breaker ratings (think of a light bulb filament). This is how the Hatteras power boxes we all have can catch wires on fire without tripping breakers or blowing fuses. Same thing can happen with the little fingers that hold the bullet fuses.

[Pascal]

I know the neutral carries the total of the two hots but I would assume that those shore power cables are sized to accommodate that cumulative load, in other words the neutral would be sized to carry that load and the equally sized hots are oversized

Otherwise it is a risk every boat is facing

[Boatsb]

I know the neutral carries the total of the two hots but I would assume that those shore power cables are sized to accommodate that cumulative load, in other words the neutral would be sized to carry that load and the equally sized hots are oversized

Otherwise it is a risk every boat is facing


Boatnut put it in plane and simple terms. It is designed to run a split load with both 125 and 250the where the 250 volt systems do not use the neutral. When you use mostly 125because volt items like multiple chargers and ac units it will overlaid the neutral.

In a perfect t world the dock and the boat should have 3 pole breakers to protect it properly.

[Boatnut]

I deleted my post by accident. I'll not bore you by redoing it.

pascal, I have no idea why the wires are all the same size, obviously the rating of the cable, is determined by the ampacity of the neutral conductor.

[Pascal]

I deleted my post by accident. I'll not bore you by redoing it.

pascal, I have no idea why the wires are all the same size, obviously the rating of the cable, is determined by the ampacity of the neutral conductor.


Exactly, the cable should be able to handle a full load on both legs regardless of on how many 240v loads are run

While on larger boats ACs are often 240valong with other loads, on many boats incl my 53 almost everything is 120v making the N conductor work harder.

[fissioneng]

On my boat, the neutral doesn't come aboard. It is provided by the polarization transformer so at least I should never have an overload problem in the neutral in the shore power cable. The output of the transformer has a 3 pole 50 amp breaker, so the neutral is protected.

So, to keep my onboard neutral safe, the sum of both hot lines should be no more than 50 amps?

BTW, My AC's are 240 volt and together draw about 25 amps with the pump running.

Doesn't the neutral overload potentially occur in your house?

[Boatsb]

On my boat, the neutral doesn't come aboard. It is provided by the polarization transformer so at least I should never have an overload problem in the neutral in the shore power cable. The output of the transformer has a 3 pole 50 amp breaker, so the neutral is protected.

So, to keep my onboard neutral safe, the sum of both hot lines should be no more than 50 amps?

BTW, My AC's are 240 volt.

Doesn't the neutral overload potentially occur in your house?



If you specify a 4 conductor 4 gage cable at 50 feet it will handle all of the 110 loads. When people buy on price manufacturers make things as cheap as possible so most are 6the ga.

[thoward]

http://i205.photobucket.com/albums/bb123/knottymaid/Boat612007-28.jpg

[Jaxfishgyd]

Has anyone tried or have any of the "Right angle adaptors" that are out there?? I see Marinco and a few others makes them for 30 amp......Would be a good addition for my boat if they are trustworthy

[Nonchalant1]

Very frequently, the dock power tower plug being corroded or poorly aligned will cause your plug to heat up. That means the the dock's plug is heating up too. I have sen 2 brand new 50/240 plugs burned up because the dock's power receptacle was bad. Then they both burn up before the power blows because the heat is created without exceeding either your boat's or the dock's 50 amps. If it gets hot enough you may havr to cut off 15 ft. or more of your cord to get back to clean copper, which means too short a cord and you spend $400 or more getting a new one. If your cord plugs are OK, alert the marina and/or move to a different dock plug.

One of the 2 new plugs that burned up was mine. After it has all melted together, the marina just says they don't know what caused it and theyll pay for their plug and I'll pay for a new 30 ft. 50/250 cord. Ouch!

[madhatter1]

The nuetral does not carry the load of the 2 hot legs. The load consumes the power from the hot leg and there is minimal amperage on the nuetral. In a building 3 20 amp phases will be run with one equally sized nuetral. The double culprit is corrosion. One dock side and one on the boat. With corrosion on termination points there is resistance. Resistance equals a voltage drop. This voltage drop can only be measured under a load. A voltage drop does not change the load. Say the load draws 15 amps at 240V. 240 X 15 = 3600 watts. The load always uses 3600 watts. Add in corrosion on the dock and the boat and drop the voltage to 200 volts (measured under a load) and now you draw 18 amps through a conductor. Keep the voltage drop going and eventually the cord overheats. Most likely the wires in the boat are OK. Re-do all terminations that feed the panel. Plug into a known good power source. If the voltage at the mains is close to the voltage at the load while running the load then the boat is good. If not the terminations on the load need to be re-done at each end. Once all is good aboard 1/2 the problems go away. Once all this is corrected and proved out the next time the cord gets hot a meter on the mains showing a voltage drop will accuratly point to the shore power provided.

[Boatsb]

Rememder most of these boats are not 240V systems. they are 2 120 systems running at 180 phase to allow for some 240 items to run. In a 120 V system the N is used and is equal to the leg.

[SKYCHENEY]

Rememder most of these boats are not 240V systems. they are 2 120 systems running at 180 phase to allow for some 240 items to run. In a 120 V system the N is used and is equal to the leg.

I'm not sure you can say that most of these boats don't have true 240v loads. All of the larger Hatts (50'+) from the mid 1970's and newer have 240 A/C units, 240v water heaters, 240v battery chargers, 240v stoves, and 240v clothes dryers.

The problem is more likely with the retro-fitted boats that originally only had 2-30amp 120v inlets.

[Boatnut]

The nuetral does not carry the load of the 2 hot legs. The load consumes the power from the hot leg and there is minimal amperage on the nuetral. In a building 3 20 amp phases will be run with one equally sized nuetral. The double culprit is corrosion. One dock side and one on the boat. With corrosion on termination points there is resistance. Resistance equals a voltage drop. This voltage drop can only be measured under a load. A voltage drop does not change the load. Say the load draws 15 amps at 240V. 240 X 15 = 3600 watts. The load always uses 3600 watts. Add in corrosion on the dock and the boat and drop the voltage to 200 volts (measured under a load) and now you draw 18 amps through a conductor. Keep the voltage drop going and eventually the cord overheats. Most likely the wires in the boat are OK. Re-do all terminations that feed the panel. Plug into a known good power source. If the voltage at the mains is close to the voltage at the load while running the load then the boat is good. If not the terminations on the load need to be re-done at each end. Once all is good aboard 1/2 the problems go away. Once all this is corrected and proved out the next time the cord gets hot a meter on the mains showing a voltage drop will accuratly point to the shore power provided.

Although the above post is basically correct, IMO it could confuse those not familiar with electricity.

The current is carried through the two hot legs, with no current in the neutral. This is true, in fact neutral if often not is not brought into the boat, and in a 240v system is not needed or used.

The neutral comes into use when 120V is used. One leg of 240v referenced to neutral gives 120v. Now the neutral is a current carrier, with the neutral carrying the same current as the one hot leg.

The green wire is a ground always, it should not carry current, is a safety ground, and should be wired accordingly.

A couple of areas IMHO that can cause premature failure of power cords.

The biggest culprit of course is corrosion, which can be pretty much eliminated with proper regular maintnenece, and the use of a good high voltage vapor compound, ie: Dow Corning No. 4 on the plugs.

Next comes the shore power itself, many marinas especially the older ones, are providing 208v, not 240v. Keeping the load constant, and lowering the volts, results in higher current. This is not typically a problen, except when heavy loads as on charter boat are used.

Last but not least are those very popular adapters where you use 2 30amp legs to produce 240v. In this case 2 30amp legs are used providing a possible 60 amps of service, which obviously overloads the 50 amp cable.

[Boatsb]

Nut, you missed one at the end.

2 30 amp 120 volt cords into a n adapter will give you only 30a amp 220 volt. 60 amps 110 volt is its equivalent.

[SKYCHENEY]

As pointed out previously, the boats with the isolation transformers don't even bring the neutral on board and thus it cannot be overloaded on the cord.

[Boatsb]

As pointed out previously, the boats with the isolation transformers don't even bring the neutral on board and thus it cannot be overloaded on the cord.

Only if they have the isolation transformer set up that way. On the many hatts that was the standard but never underestimate the stupidity of the previous owner.


Also many of the smaller boats and convertibles dont have them.

[SKYCHENEY]

Only if they have the isolation transformer set up that way. On the many hatts that was the standard but never underestimate the stupidity of the previous owner.


Also many of the smaller boats and convertibles dont have them.

Its pretty easy to check. Just pull the inlets on the boat and take a look to see if there is a neutral. You should probably do that to make sure you don't have any corrosion and that the lugs are tight anyway.

The smaller boats are mostly 30amp 120v with just polarization transformers.

[Boatnut]

Nut, you missed one at the end.

2 30 amp 120 volt cords into a n adapter will give you only 30a amp 220 volt. 60 amps 110 volt is its equivalent.

Scott, Your correct, what was I thinking. Thanks for setting things straight.

To comment on the neutral thingie. The only time neutral is needed is to have 120v. If you have a 4 wire system as incomming power to develope 120v, you may have a problems with stray current, and be prone rapid zinc loss. The reason for this is that there can be a potential difference between the green safety grouind and neutral. The amount of this difference is due to the distance from the distribution center. The further away from the distribution point the higher the stray voltage voltage may be. If you have isolation transformers, There is no need for the neutral, the 120v is developed by the isolation transformer secondary winding.

This brings up a point I noticed in another thread. Someone was talking about their house power went through an isolation transformer, and the air conditioning did not. A scenerio I don't understand because there is a good chance they are bringing a ground aboard also, therefor destroying the isolation effect of the system.

PS: It's Mr. Nut to you Scott. LOL