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Old 03-02-2020, 03:37 PM   #81
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Guys new to this stuff. When I inspect the old style plugs should i put any type lubrication on the plugs/posts?
Thanks Mike
Yes, See post #65
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Old 03-02-2020, 03:42 PM   #82
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The Smart Plugs are not immune to problems. There have been several fires. The issue is workmanship. The wire connections are screw terminals. When you put it together you torque it down and then leave it for half an hour or so and then re torque them. And then after a month or so check the torque again. If the connection is not tight, tight tight, it will become a high resistance connection. As others have said, resistance=heat.

We've used Smart Plugs for several years and have found another weakness. The OEM Hubble and Marinco ends are potted. The Smart Plugs are not. Our plugs are on the transom. We used to keep the plugs attached all the time, with the locking mechanism tight. this was acceptable and endorsed by Smart Plugs. But on the transom you get a lot of salt spray and mist. The attached pictures show salt bridge which built up inside one of my plugs after 2 years and 12,000 nautical miles. The plugs were not running warm. The problem showed up when we tripped the ELCI device at a marina we have stayed at many times. The boat next to us also had a smart plug so I asked to try his cord. It did not trip the device. When I took the Smart Plug apart there was moisture inside and a bridge of salt between the hot and ground. .
Looks like little baby busbars inside. On large busbars, both the material of the bolts and the torque is highly critical. The bolt thermal expansion needs to be close to the busbar expansion factor.
I might be tempted to pot such a plug; Haven't seen one up close yet though.
This picture is a great example of conductive condensate, and lack of creepage distance to accommodate.
My parents lived in a home a block from the ocean; one day a garage outlet strip spontaneously caught fire with zero load. Same issue.
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Old 03-02-2020, 03:58 PM   #83
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I’m getting ready to retire from 45 years as an electrical power engineer and a boater for 39 years. The limitation on the amount of current a thermo-magnetic breaker will carry is based on how it is used in the circuit. Breakers will carry their handle rating in open air but are limited to 80% of handle rating due to the heat they generate when enclosed. The same is true for conductors.
The cord set plugs can be affected by corrosion but most often plug burnouts are due to not completely twisting the connection and holding the plug in place with the locking ring. The contact surface is reduced when the plug is not fully engaged, especially the neutral connection.
I’ve replaced multiple 30A plugs over time due to these issues. I just purchased a boat with a 50A cord set and noticed some burning starting on one of the plugs. I changed to a 50 A Smart Plug and have had no problems since.
It’s all about contact surface and being able to lock the plug in place. Smart Plugs do both well. Switch to these new connectors and forget worrying about them burning up. When you hear it snap into place you know you have a good connection.
Also remember to close the receptical cover on your boat to help keep it free of contamination.
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Old 03-02-2020, 04:54 PM   #84
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[QUOTE=Mike3888;852309]Thanks much. I have the old style plugs. we are new to the larger boat seen and I was wondering what I should be looking for when I inspect the plugs. ....The easiest way to check is to put your hand on the plug when you are pulling a heavy load. The plug should feel the same temperature as the surface next to it. A temp gun is also mighty useful, If the plug is 10 degrees warmer than ambient, it is time to fix it. Remember to check both ends of the cord. . Any time you disconnect, you should inspect carefully for any discoloration in either side of the connection. .
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Old 03-02-2020, 05:36 PM   #85
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I agree with your hand test as it will uncover a problem prior to a failure. I noticed the hotter plug by hand before I noticed the beginning of a plug failure. You will see plug failure as a browning or blackening of the yellow plastic along the edges where the blade enter the cord plug.
You will only use smart plug(s)on the boat end of your cord(s) and the boat receptical(s). (Get the SS cover plate). You are not to monkey with the connection at the dock pedestal as this is not part of your boat. Of all the burnt power connections I have seen is always on the boat and not on the dock end which jives with my opinion that most problems are due to operator error. (Failure to fully twist the plug and locking the plug in place with the locking ring) we can see the wear on our dock lines due to the movement of the boat, but don’t check our electrical cords.
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Old 03-02-2020, 05:42 PM   #86
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Don’t overlook the thought that if one is making their own connections inside the connector (Not a factory molded plug), and the screw holding the wire down was not tightened properly, it will gradually become looser and looser as it expands and contracts due to heat created from the load. You will end up with a higher resistance connection meaning more heat where there should be very little. If tightening stranded wire under a screw (in a connector or at the breaker), tighten it down and then physically wiggle the wire back and forth and you can then re-tighten more as the strands move around and settle into place. You will find you may obtain another full turn or more depending on wire size and number of strands.
If you are pulling close to the limit of a 30 amp plug, then a 50a would be a much better choice.
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Old 03-02-2020, 06:24 PM   #87
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Statistically speaking, most boat fires are the result of shore power faults. One observation from the photo, the back of those inlets are supposed to be covered/insulated, you should do that on the replacement, even if it's a Smart Plug, their inlets lack full insulation without an enclosure. If you can see a energized screw, it should be covered.

For some time I've recommended smoke alarms be installed above shore inlets, again statistically speaking it's high risk.

More on shore power overheating here https://stevedmarineconsulting.com/o...11-newsletter/

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Old 03-02-2020, 06:32 PM   #88
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Originally Posted by rhoulio View Post
Don’t overlook the thought that if one is making their own connections inside the connector (Not a factory molded plug), and the screw holding the wire down was not tightened properly, it will gradually become looser and looser as it expands and contracts due to heat created from the load. You will end up with a higher resistance connection meaning more heat where there should be very little. If tightening stranded wire under a screw (in a connector or at the breaker), tighten it down and then physically wiggle the wire back and forth and you can then re-tighten more as the strands move around and settle into place. You will find you may obtain another full turn or more depending on wire size and number of strands.
If you are pulling close to the limit of a 30 amp plug, then a 50a would be a much better choice.
Connecting stranded wire directly under a screw is not recommended. Crimp a ring terminal to the stranded wire then place that under the screw.
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Old 03-02-2020, 06:44 PM   #89
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i would go to the local ace hardware, and buy a new 30 AMP plug to replace the bad one! worked for me...clyde
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Old 03-02-2020, 08:20 PM   #90
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I do not understand why people think that, switching to the so called smart plugs or to 50A plugs should solve their issues or prevent the above damage.
- Do not waist your money on these plugs because the dock side will still be the same 30A.
You can save your boat however, a fire on the dock is pretty much the same. Also, you are still at risk inside your power panel or somewhere else that is not visible on the boat.
- Please, do not replace your 30A connectors and shore power cables to 50A. You need to know that all your wiring inside your boat is still designed for 30A system.
- the best item to add to your boat and to protect it is a current meter for every 30A (or a single gauge with a switch). Boats are designed for 80% continuous draw however, system do get old and the current draw will most likely to go up. Proper maintenance of your systems and proper power management (80% rule) is recommended.
Monitor you current draw to protect your boat.
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Old 03-02-2020, 09:02 PM   #91
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I have seen plenty of burnt shore power plugs at the pedestal end.


I believe that using a better plug than the standard 30A twist lock is a huge help...just switching plugs doesn't really change much except usually a better connection...if you don't change the shoreside plug or wire of CBs...just changing a plug doesn't induce more dangers. The real advantage is the total upgrade to a 50A 125/250V capable boat.
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Old 03-03-2020, 06:22 AM   #92
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Connecting stranded wire directly under a screw is not recommended. Crimp a ring terminal to the stranded wire then place that under the screw.
The hull inlet fittings from Marinco, Hubble, and Smart plug ALL use a screw compression connection. This type of connection is standard. These connections are acceptable for use on boats provided the screw does not bear directly on the stranded conductor. Generally this is achieved by having the screw bear on a plate, or in the case of Smart Plugs the screw has a rotating end cap fitting so that as the connection is torqued, the cap does not spin as you torque the screw.
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Old 03-03-2020, 06:42 AM   #93
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Of all the burnt power connections I have seen is always on the boat and not on the dock end which jives with my opinion that most problems are due to operator error. (Failure to fully twist the plug and locking the plug in place with the locking ring) we can see the wear on our dock lines due to the movement of the boat, but don’t check our electrical cords.
Actually the dock end of the cord is much more likely to burn first. At the boat end the cord can be locked in with the locking ring so the connection is watertight, and there is no movement in the connection as the boat moves in the slip. At the dock end end of the cord, the receptacle is not provided with a threaded ring to lock into. (We are full time cruisers and are in +/- 30 marina slips per year. On the entire east coast I have only come across 3 marinas with power post receptacles to which we can lock the dock end of the cord into the power post.) Since they cannot be locked in they are open to the weather and there is a lot of salt in the air along the coast. so corrosion builds. When boats leave a slip the receptacle cover is often left open and the receptacle is exposed to salt air. More corrosion builds on the connections inside the receptacle. since the cord cannot be locked in, the electrical connection moves as the boat movers. The cord come s loose and there will be arcing inside the connection. Arc burns add resistance=heat.

Anytime you come to a marina look at the power post receptacle before you plug in. If there is evidence of burns or damage, do not plug into that receptacle. It has already been damaged. If you pull a heavy load through that receptacle you are likely to burn your own cord.
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Old 03-03-2020, 06:43 AM   #94
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The simple precaution of chopping off a foot or so of cable and remounting the plug after each time its dropped/dunked in sea water would be a big help.
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Old 03-03-2020, 06:51 AM   #95
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[QUOTE=Steve DAntonio;852414]Statistically speaking, most boat fires are the result of shore power faults. One observation from the photo, the back of those inlets are supposed to be covered/insulated, you should do that on the replacement, even if it's a Smart Plug, their inlets lack full insulation without an enclosure. If you can see a energized screw, it should be covered.

Steve as designed the hull inlet connectors produced today from Hubble, Marinco and Smart plug do not have any exposed electrical connections where someone might accidentally contact it and get a shock. I suppose you could stick your fingers into the recessed set screws if you tried though.

What I see in that picture though is that the boat wiring is not supported and the weight of the hull cable wiring is hanging on the wire connections of the hull inlet. The wire should be secured and supported independently of the hull inlet.
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Old 03-03-2020, 08:29 AM   #96
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Does anyone use Boeshield T9 as a water repellent- anti corrosion spray on their shore power cables? Any suggestions on what might be a superior product? Thanks Cliff
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Old 03-03-2020, 08:47 AM   #97
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I use CRC 656. I also use it when I plug into a transient slip ( about 30-40 times per year) The trouble is that if you plug your cord into a corroded receptacle the resistance in the connection creates heat which can damage your cord.

The attached pictures are from June in Hampton VA. It is a brand new Smart Plug cord set. It was a warm day 95 degrees, and we were drawing 24 amps consistently. The power post got up to 120 degrees, so I pulled the cord out an checked the pin temperature. 190 degrees! And some minor discoloration of the plastic in my new cord.

So it appears from this that the internal temperature of a cord running 25 degrees above ambient is about 70 degrees .
Attached Thumbnails
IMG_6357.jpg   IMG_6371.jpg  
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Old 03-03-2020, 09:55 AM   #98
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If the setup is not foolproof...then what IS the acceptable continuous rating...as corrosion, looseness,etc could do the same at many different amp draws...why not limit them to 15A as safe?
Thirty amps means 30 amps to me. That is conservative and prudent for 10 wire. Your breaker will protect the wire from anything over.

I agree that the problem is loose connection or corrosion.
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Old 03-03-2020, 10:28 AM   #99
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Actually had a fire in the shore power connection a few years ago, but did not save the pictures. I was leaving the boat headed for dinner out when I smelled smoke, and found smoke billowing out of a cockpit locker where the shore power connection was. Long story short, disconnected there and reconnected to bow alternate plug, and went to replace the male boat end plug because of melted and scorched connections. Found that over time, the downward pressure of the weight of the plug, combined with the twisting leverage from connecting, these forces had put a hot and a ground in proximity to short out. Dock breaker did not trip, boat breaker did not trip either. Surprise!! When I procured a replacement Marinco plug it was redesigned to eliminate that from happening on the new product. I then replaced the alternate plug on the bow as well. The boat was originally built in 2008, do not know when the design was changed, but replaced that boat with a 2019 model and the new boat had the newer design.
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Old 03-03-2020, 10:37 AM   #100
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Originally Posted by Steve DAntonio View Post
Statistically speaking, most boat fires are the result of shore power faults. One observation from the photo, the back of those inlets are supposed to be covered/insulated, you should do that on the replacement, even if it's a Smart Plug, their inlets lack full insulation without an enclosure. If you can see a energized screw, it should be covered.

For some time I've recommended smoke alarms be installed above shore inlets, again statistically speaking it's high risk.

More on shore power overheating here https://stevedmarineconsulting.com/o...11-newsletter/

(In Taiwan)
Thanks for the input Steve. As oft mentioned in this thread, the wiring setup behind this or any vessel connection bears close scrutiny, beyond just adding a smart plug arrangement.
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