Shore Power Connections -- Again

[ttex]

One of the wires was loose on my outlet plug breaker in my panel. The breaker did not trip at all but the wood around the panel and the wire in question was so hot I almost **** myself at how close I was getting to utter disaster.

This was right when I bought the boat and I was going over everything. I didn't notice this until about day three. I inked my undies.

[noelex 77]

I would also suggest derating any AC and for that matter DC connection in a marine environment. Derating by more than 80% is much easier with 240v rather than a 110v system.

Unfortunately, it only takes a very small amount of corrosion to reduce the current carrying capacity of these plugs.

The smart plug looks considerably better than the more common Marinco connections, but there is a lot to be said for one of cheaper high current connections. A cheaper connection encourages frequent replacement that combined with sensible derating keeps everything safe.

[ArmyDaveNY]

Originally Posted by Dockhead

I got rid of the odious Marinco twist plug my boat came with, some years ago.

This is really dangerous I knew someone who lost a boat because of a fire which apparently started at the shore power inlet. Once fiberglass starts to burn, it's pretty hard to put out.

Excellent post and thanks for sharing this.

Below I have posted a link to an excellent and very easy to read discussion of why the smart plug is so vastly superior to the old Marinco three pronged plug.

In summation, the Marinco style plug was invented in 1938 for a quick and TEMPORARY source of power at construction sites until they could get hooked up to the grid. They were NEVER intended for marine applications.

S/V Illusion is correct that proper maintenance will go a long ways towards reducing the potential for fire, but the design has inherent weaknesses. The principal weakness is that there is a very small total contact area of approximately 6.6 mm (square) through which the power is transmitted. The smart plug has somewhere around 190 square mm of contact area! This drastically reduces the resistance, and thus the heat.

Additionally, smart plug due to its design is a far more secure connection, reducing movement. It is also far better sealed, reducing corrosion. It still should be inspected though.

Per BOATUS, roughly 55% of all boat fires can be attributed to electrical issues. The actual number may be higher but the cause of the fire can't be determined in a fair percentage of fires. Of the 55% of known electrical fires, roughly 54% are caused by shore power issues.

If one uses shore power, replacing the old style connection with a smart plug is one of the best things to do to enhance safety.

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

[carstenb]

Well Dockhead - we have solved this problem.. We have not been on shore power since june 2016. We live exclusively on our solar.

just an aside for all of you

[Dockhead]

I believe Noelex and Seaworthylass do it the same way.

But, different ships, different long splices. I have no solar, and like shore power for electric heat, when shore power is available.

Originally Posted by carstenb

Well Dockhead - we have solved this problem.. We have not been on shore power since june 2016. We live exclusively on our solar.

just an aside for all of you

[ArmyDaveNY]

Originally Posted by carstenb

Well Dockhead - we have solved this problem.. We have not been on shore power since june 2016. We live exclusively on our solar.

I've done something similar although I still have my shore power cords. I now only use shore power when I absolutely need it, and I NEVER leave it unattended when I am away from the boat for anything other than a short period.

I also spray the ends with anti-corrosion spray such as that from CRC every time I put the cord away. I also seal the ends in a bag, Finally, I ordered a smart plug that I will, in theory, install this spring.

While I don't need shore power very often, there are times when it is useful. In particular, it is useful when working on some projects.

[ArmyDaveNY]

Originally Posted by Dockhead

The "80% Rule"? I never heard of such a thing. I always assumed that the ratings were for continuous use, and were calculated conservatively. If what you say is true, it's a totally different situation. And would explain a lot of my experiences, so you may have made a significant contribution to my education
/

The 80% rule is a real thing, and when it comes to shore power, many electricians recommend only 70% especially when using the old Marinco connection. I was on the phone with Marinco a while ago and they said the same thing about the 80% rule.

I have been told that the ratings are for peak draw, and not continuous power. I guess in some ways that is similar to the ratings on generators. Even engines will have issues when run at 100% constantly.

[rslifkin]

Originally Posted by Pelagic

IF I was doing frequent day sails from a dock, I would simply disconnect cable lugs from engine room box and leave cable ashore.

This is exactly why so many boats use external connectors unless they've got a nice retracting hardwired setup. In my case, if I'm going out for the day, my power cords stay on the dock. If I'm traveling, then I take the cords with me.

[GordMay]

Originally Posted by Dockhead

The "80% Rule"? I never heard of such a thing...
... Right off the bat: https://www.electriciansforums.net/t...80-rule.35406/

80% Rule:
When the load continues for more than 3 hours (definition of ‘continuous’ load), under normal operation, the total load on any overcurrent device in the panelboard should not exceed 80% of the overcurrent device rating per NEC Section 384-16(d), unless, the assembly, including the overcurrent device, is listed for continuous duty at 100% of its rating.
“Sizing a Circuit Breaker” explains it.
➥ https://www.ecmweb.com/basics/sizing...e-olyticsmodal

[Dockhead]

Originally Posted by GordMay

80% Rule:
When the load continues for more than 3 hours (definition of ‘continuous’ load), under normal operation, the total load on any overcurrent device in the panelboard should not exceed 80% of the overcurrent device rating per NEC Section 384-16(d), unless, the assembly, including the overcurrent device, is listed for continuous duty at 100% of its rating.
“Sizing a Circuit Breaker” explains it.
➥ https://www.ecmweb.com/basics/sizing...e-olyticsmodal

OK, thanks. But does that apply just to circuit breakers, or to the whole circuit?

[GordMay]

Originally Posted by Dockhead

OK, thanks. But does that apply just to circuit breakers, or to the whole circuit?

Yes & no, sort of ...
OCPDs (breaker & fuses) are sized for 125 percent of continuous current, which means that they are expected to carry continuously 80 percent of rated current.
Since the ampacity of the conductors is matched to OCPD rating, they end up derated to 80%, without further adjustment from the appropriate conductor sizing tables.
There are 100% rated circuit breakers (uncommon), which may require the use of conductors rated 90°C, but sized according to the 75°C ampacity rules.

[SaltyMetals]

A most interesting discussion. I think that many of the fires in connectors are possibly because someone allowed the connector to drop in the sea while the cable was being fed out or brought in. Hence corrosion and then overheating of the connection.
I am fortunate on my boat Jeanneau 43ds that the inboard end of the cable has a connector inside a locker and then there is the usual circuit breaker. The cable feeds out from the locker through a pre-designed slot which does not harm the cable. On my previous bout i had to cut a slot on the edge of the locker but this was still covered by the lid when closed.
Dockhead; I am sure you know a lot more than me on this matter but if you hv a concern about the UK 13A plugs why not reduce the fuse inside the plug? Alternatively, reduce the size of the unit (heater?) that is drawing so much current? You know these plugs as well as me so one of the precautions after a few months is to tighten the three screws inside the plug because the heating and cooling of the connection allows the pressure of the connector to reduce. Not that brass and copper suffer much creep but the effect is much the same.
andrew
"Genial Bee"

[tarian]

Originally Posted by ArmyDaveNY

Excellent post and thanks for sharing this.

Below I have posted a link to an excellent and very easy to read discussion of why the smart plug is so vastly superior to the old Marinco three pronged plug.

In summation, the Marinco style plug was invented in 1938 for a quick and TEMPORARY source of power at construction sites until they could get hooked up to the grid. They were NEVER intended for marine applications.

S/V Illusion is correct that proper maintenance will go a long ways towards reducing the potential for fire, but the design has inherent weaknesses. The principal weakness is that there is a very small total contact area of approximately 6.6 mm (square) through which the power is transmitted. The smart plug has somewhere around 190 square mm of contact area! This drastically reduces the resistance, and thus the heat.

Additionally, smart plug due to its design is a far more secure connection, reducing movement. It is also far better sealed, reducing corrosion. It still should be inspected though.

Per BOATUS, roughly 55% of all boat fires can be attributed to electrical issues. The actual number may be higher but the cause of the fire can't be determined in a fair percentage of fires. Of the 55% of known electrical fires, roughly 54% are caused by shore power issues.

If one uses shore power, replacing the old style connection with a smart plug is one of the best things to do to enhance safety.

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

Your article is scaremongering , if I tied my boat with frayed warps I would expect them to break in high winds , if I did all the things you should not due with my electrical connections I might get a fire , and it is a might , but if I check my wires my connections and ensure that everything is safe then the potential of a fire are zero , this is as usual something being invented for the sake of it , proper maintenance and do as it says will ensure happy sailing,
Also the wiring of the boat needs to be looked at, highly unlikely that a modern boat form a reputable brand have wired it to blow up , the problem comes when owners start to fiddle with their boat and do it wrong
Articles like this are to drive traffic to there website and to the manufacture of the product, no matter what they tell you.
As soon as a website says I do not make anything from this Worry!!!!

If the 3 pin 16 amp cable leading into your boat is in good condtion , your socket is tight and waterproof and good condition and it follows the usual protocol of RCD to Fused plugs the chance of an electrical fire are nil
How many camper vans have you heard go up in flames due to electrical fires form this type of input.

You aslo proclaim that 55% of boat fires are electrical , but have not given boat numbers 5 boats burning in a year and 3 are electrical makes 60% + but 3 boat in the 100.000 in the US say is not really an issue , the use of percentage again is to direct fear and make people panic to go and buy a product they do not need the lack of true stats makes it a poor article

From all those boat fires which 55% are electrical I can bet my bottom ass that the electrical fault was poor wiring and battery management , i.e exploding batteries , cable not tight on the battery , poor connections etc, to say thermal conduction causes fire is extremely rare I wonder if any one can tell us with facts that it has happened

I suppose when you get older your fear levels and panic stress levels go up and the ability to think through the problem goes

I have also noted that the pictures used are from an extremely old 3 pin single phase who uses them now , no were in Europe does , the design has changed and is much more robust, a VERY poor article indeed

[Dockhead]

Well, thousands of boat fires occur every year. Statistics available on the USCG site. I don't think it's scare mongering at all to point out the dangers.

I used the Marinco plugs for decades. Never had a fire, thank god, but burned up a bunch of those Marinco connectors. In my opinion they are pure junk.

The European blue plugs are vastly superior, but the SmartPlug seems even that much better still.

Originally Posted by tarian

Your article is scaremongering , if I tied my boat with frayed warps I would expect them to break in high winds , if I did all the things you should not due with my electrical connections I might get a fire , and it is a might , but if I check my wires my connections and ensure that everything is safe then the potential of a fire are zero , this is as usual something being invented for the sake of it , proper maintenance and do as it says will ensure happy sailing,
Also the wiring of the boat needs to be looked at, highly unlikely that a modern boat form a reputable brand have wired it to blow up , the problem comes when owners start to fiddle with their boat and do it wrong
Articles like this are to drive traffic to there website and to the manufacture of the product, no matter what they tell you.
As soon as a website says I do not make anything from this Worry!!!!

If the 3 pin 16 amp cable leading into your boat is in good condtion , your socket is tight and waterproof and good condition and it follows the usual protocol of RCD to Fused plugs the chance of an electrical fire are nil
How many camper vans have you heard go up in flames due to electrical fires form this type of input.

You aslo proclaim that 55% of boat fires are electrical , but have not given boat numbers 5 boats burning in a year and 3 are electrical makes 60% + but 3 boat in the 100.000 in the US say is not really an issue , the use of percentage again is to direct fear and make people panic to go and buy a product they do not need the lack of true stats makes it a poor article

From all those boat fires which 55% are electrical I can bet my bottom ass that the electrical fault was poor wiring and battery management , i.e exploding batteries , cable not tight on the battery , poor connections etc, to say thermal conduction causes fire is extremely rare I wonder if any one can tell us with facts that it has happened

I suppose when you get older your fear levels and panic stress levels go up and the ability to think through the problem goes

[Dockhead]

Thanks for that. Yes, derating the device obviously would help, but I don't want to! The 2000 watt fan heater is a treasure in the middle of the winter.

What would be great would be plugs and sockets with thermal fuses, but I've never seen such.

Yes, svIllusion's point about maintenance is useful.

Originally Posted by SaltyMetals

A most interesting discussion. I think that many of the fires in connectors are possibly because someone allowed the connector to drop in the sea while the cable was being fed out or brought in. Hence corrosion and then overheating of the connection.
I am fortunate on my boat Jeanneau 43ds that the inboard end of the cable has a connector inside a locker and then there is the usual circuit breaker. The cable feeds out from the locker through a pre-designed slot which does not harm the cable. On my previous bout i had to cut a slot on the edge of the locker but this was still covered by the lid when closed.
Dockhead; I am sure you know a lot more than me on this matter but if you hv a concern about the UK 13A plugs why not reduce the fuse inside the plug? Alternatively, reduce the size of the unit (heater?) that is drawing so much current? You know these plugs as well as me so one of the precautions after a few months is to tighten the three screws inside the plug because the heating and cooling of the connection allows the pressure of the connector to reduce. Not that brass and copper suffer much creep but the effect is much the same.
andrew
"Genial Bee"