Shore Power Connections -- Again

[Stewie12]

The UK 13 amp plugs are good, but not infallible. I have not seen one house plug anywhere that I would say is. They can all suffer from the socket they plug into getting slack and causing heat. If the plug feels hot and the pins are not damaged then change the socket or both.

[timb7734]

I had the beginnings of a fire on the boat plug, in the cockpit of my trawler. Was leaving the boat for dinner, just prior to stepping off I smelled cooking plastic and started looking around. The smoke was the result of a short in the boat plug side, and was cooking inside of a cockpit locker. After examination of the fixture all I could conclude was that the short was caused by long term pressure of the plug in the socket. Miraculously the replacement of the boat socket, though Marinco, same manufacturer, was a completely different design. Since then I have sold that boat and have one with a cable system that is hard wired on the boat side. Further, I highly recommend use of electrical grease on all boat electrical connections.

[MarkI]

80 % Loading:
The US and European standards decided on different ratings standards!!!

The exact same cord, rated 20 amps in the US and not to be used above 16 amps (20% derating) is called 16 amps in Europe, and can be loaded continuously at 16 amps. Same cord, same safe continuous usage, same actaual breaker trip point, but one standard used the nominal breaker trip point and the other uses the safe capacity.

Essentially for any circuit the disconnect point needs to be above the normal operating point or false shut offs would be common. So for a 20 amp breaker in US, 16 amps is a US electrical code defined 16 amps full load circuit. But in Europe they call it by the safe full load value, 16 amps.

So depending what part of the world you are in, both of the below can be true:
(Europe and other countries) I can use at the rated capacity
(US and probably other countries) I need to plan to use no more than 80% of the rated capacity for "continuous loads" as defined the the US NEC (and probably some other countries).

[ronstory]

My observations after installed a Smart Plug, a replacement of a 30A Marinco stainless socket.

The cord that came with the boat had a hot spot on the plug so I replaced with the standard Marinco 30A cord. It had dielectric grease on it and was always dry when I removed it.

Three years later when I installed the smart plug, the cord and socket looked pristine. Thought I was just being paranoid... but 'hey'... it's a boat.

When I removed the socket from the bulkhead, I noted that there was a large burn mark on *back side* socket at the Hot connection. When I removed the wire, there was no indication of any corrosion in the connection, so I added a touch of dielectric grease and installed the new smart plug socket all is good.

So I've now added item to the spring checklist, physically stuff my head in there and make sure the socket looks pristine on *both* sides.

My two cents and YMMV.

[Tudorsailor]

I read about boat fires being caused by poor shore power connections. I understood that this was more likely a US problem with 110v AC rather than 240v.
I then asked the guy who looks after my yacht in Greece if he had seen problems with the ubiquitous twist and lock Hubble type connector. He sent me these photos of the connector on an Oyster!





I have now installed a SmartPlug

TudorSailor

[ronstory]

Yikes! MaineSail has come great photos on:

https://marinehowto.com/shore-power-...tplug-vs-1938/

[a64pilot]

The old Smart Plugs on the boat end that plugs in had a thermal reset circuit breaker, there are several theories as to why it was removed one at least being that it got too expensive.
However I believe but am not sure but that ABYC doesn’t allow an automatic resetting circuit breaker, which makes sense as it could cause a person who was being sloppy and unaware of the auto reset to be electrocuted.

Mine has it and it’s never tripped so far.

So far as corrosion by not keeping the contacts clean being the problem, I wish that was the case but it’s not. I always keep mine coated with Dow Corning silicone grease. The problem is I believe two fold, first the contact area is too small to carry that much current, but the biggest issue is I believe the dock side plug is often corroded and or loose contacts etc so when you plug in, both plugs get burnt.

Anything, and I don’t care what it is from an electric motor to your Diesel or absolutely any device I know of, if you operate it at 75% power or less it’s going to last a lot longer than if your pulling the guts out of it.
The only time that isn’t true is if the manufacturer has already derated it, so that 100% is actually 75% or less, that’s not uncommon at all, and the majority of the motors that have reputations for very long longevity, are seriously derated.

I replaced my ammeters with the new digital Blue Sea ammeters. One feature they have is alarms, if I pull 25 amps the alarm goes off. There most be some delay built into the meters as a short duration surge like the AC starting doesn’t trip the alarm.
Below the shown menu is also Hz alarms, both low and high

[darylat8750]

Originally Posted by tarian

A poor response , thousands of boat fires every year, were is your link, and a breakdown of what caused them , facts makes sense your post does not
fires can be caused by gas, petrol, oil, diesel , electrical. dropping of a cigarette
what are the % of fires caused by thermal heating as you as the OP have told us that you worry about this but what is your fear based on ,
Or is it I read it somewhere or heard it somewhere like most rumours and that silly article reads like a poor magazine article from Hello

The author of the article you referred to goes by MaineSail on this forum. He is a well respected professional marine technician and backs up his opinion with research and often pictures.

[sdj]

Originally Posted by S/V Illusion

There problems can be easily prevented simply by using any of the myriad copper coating greases on the market.

I have heard this too, so I tested it. ANY grease I have ever tested, including coppercoat, had a very high resistance and provided NO help at all with regards to conductivity. Aside for keeping moisture out, I can't see how using grease to fix conductivity problems would be useful.

Loose terminals are the biggest problem. Without proper service, and after damage by misuse, spring terminals inside female connectors are dangerous to use and will cause the problems mentioned.

[a64pilot]

The whole idea of grease is to prevent oxidization of the terminals and therefore a high resistance connection.
First widespread mandated use of a grease type coating I know of was for aluminum wiring I believe in the 70’s?
Aluminum was causing fires, first it would oxidize, that would cause heat, as it heated and cooled it eventually loosened connections causing overheats and fires, or that is how I remember it anyway, it’s been a long time since I took that test.
Just an example
https://www.homedepot.com/p/Ideal-NO...-026/202276208

[Dockhead]

Originally Posted by Tudorsailor

I read about boat fires being caused by poor shore power connections. I understood that this was more likely a US problem with 110v AC rather than 240v.
I then asked the guy who looks after my yacht in Greece if he had seen problems with the ubiquitous twist and lock Hubble type connector. He sent me these photos of the connector on an Oyster!





I have now installed a SmartPlug

TudorSailor

Yep, that's what Marinco connections DO. I wasted a lot of money back in the day replacing them with the same crap, only to do it again two or three years later . They should be outlawed.

[Dockhead]

Originally Posted by sdj

. . . Loose terminals are the biggest problem. Without proper service, and after damage by misuse, spring terminals inside female connectors are dangerous to use and will cause the problems mentioned.

Indeed. As was mentioned, one of the many flaws of the Marinco connectors is that the springs in the sockets are weak and get bent from the twisting action. This is simply a design flaw. You can make them last a little longer by bending them back, but the right thing to do with a Marinco connector is put it directly into the trash where it belongs.

[CharlieJ]

Dockhead #14:
You are absolutely correct. A burned shore power plug occurs because of high resistance at the plug/inlet interface which becomes a very inefficient heating device. The trip point of the upstream (pedestal) circuit breaker will not be exceeded unless there is a short circuit between phase (line) and ground or an overload condition. The high resistance contact that causes a burned shore power plug is neither a short circuit nor an overload.

[joycemango]

I'd like to go with a smartplug but gave some basic and naive questions .... When I look at the female connector side it does not resemble the outlet on our boat (C&C41 we bought 2 months ago.) Does this mean we need to purchase some sort of adapter kit in addition to the smartplug? How do most sailboaters with older boats use these? Also, we need to get an adapter to go from 50 amps to 30 ... We have a pedestal with a 30 and a 50 and need to bring in two 30s. What would be best and most cost effective with a smartplug?

Thanks!
Joy

[Auspicious]

Originally Posted by joycemango

I'd like to go with a smartplug but gave some basic and naive questions .... When I look at the female connector side it does not resemble the outlet on our boat (C&C41 we bought 2 months ago.) Does this mean we need to purchase some sort of adapter kit in addition to the smartplug? How do most sailboaters with older boats use these? Also, we need to get an adapter to go from 50 amps to 30 ... We have a pedestal with a 30 and a 50 and need to bring in two 30s. What would be best and most cost effective with a smartplug?

Hello Joy. You replace the boat outlet as well as the plug on the cord.
https://www.defender.com/product.jsp...039&id=3472922