Pontoon Wiring

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ip485

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Maybe something just slightly different - I decided to get a new mains cable - 50 metres and rated at 36 Amps to hopefully deal with any mooring issues at different places. Much of the time I expect it will be on 16 Amps but we can also hook up to 32 Amps where available and certainly draw the full 32 Amps.

So my question is;

I know on a reel it is possible to generate a reasonable amount of heat. I also know I will have a better idea when I use it - but in the mean time thought it was worth asking the collected wisdom whether the heat is likely to be a problem on 16 Amps, and if anyone has any clever solutions. I appreciate the cable could just be laid out on deck to dissipate as much heat as possible and this might be the simplest / only solution. Obvioulsy the reason for a reel, or some other system, is a way of keeping all that cable a bit tidier when it is not all needed.

Should be ok at the moment for melting the snow!
 
ip485 said:
Maybe something just slightly different - I decided to get a new mains cable - 50 metres and rated at 36 Amps to hopefully deal with any mooring issues at different places. Much of the time I expect it will be on 16 Amps but we can also hook up to 32 Amps where available and certainly draw the full 32 Amps.

So my question is;

I know on a reel it is possible to generate a reasonable amount of heat. I also know I will have a better idea when I use it - but in the mean time thought it was worth asking the collected wisdom whether the heat is likely to be a problem on 16 Amps, and if anyone has any clever solutions. I appreciate the cable could just be laid out on deck to dissipate as much heat as possible and this might be the simplest / only solution. Obvioulsy the reason for a reel, or some other system, is a way of keeping all that cable a bit tidier when it is not all needed.

Should be ok at the moment for melting the snow!
Click to expand...

If you have more than 2 layers of cable on the drum I would guess that 16A will be a problem and would never risk it. The extra layers act as a heated thermal overcoat.

A neat figure "8" of cable need not take up too much deck space. If you are a raggie, then hoist it up out of your way.
 
I keep our shore power cable in a loose coil, just like a rope. Fits into the locker better than if it were kept on some sort of reel. I uncoil enough to get from the boat to the power point: the remaining coil is then hung from the pushpit rail, where air is free to circulate round it. OK, we only ever draw a max of 16 amps (entry MCB limit) but we've never had any problems about the wire heating up. We do carry a 32 amp to 16 amp adapter so we can use a 32 amp supply when it's there but only draw 16 amps or less.
 
13-amp extension leads trip their thermal cutouts when used partly rolled up and drawing less than 13 amps. I've seen an older one without a cutout melted to the bare copper. I definitely wouldn't try drawing 16 amps through a coiled up lead.

I only have the normal 16 amps / 2.5cm2 cable, but I too wanted a long length of it to reach potential power sources far away. However, rather than deal with big unwieldy coils when in a marina berth with its own socket right at the bow, I split the cable into four 10m lengths with male and female plugs at each end. Two of them live in the cockpit locker and suffice for any normal marina situation, using either one or both, but there are two more in a locker below which I can add if I end up on a town quay with one spare socket 40m away. I also have adapters to 13a domestic sockets both ways, so a secondary use for the 10m lengths is as an extension lead by putting the adaptors on each end. I've used this occasionally for tools on deck.

Only thing I would do differently is use 15m rather than 10m, either for all the lengths or just one. I quite often find that a marina socket is only just out of reach of a single 10m length.

Pete
 
From what I remember of my A-level physics in the '50s, the heating is caused by induction when cable is coiled. By uncoiling the wire and laying it out you only have the resistance to cause heat and provided the wire is up to the job the heat resulting should be negligible.
 
I have seen a long cable on a reel, only partly unrolled, start smoking. It was quite fortunate that we were standing beside it chatting. Also endorse the suggestion that a 50m cable would be very cumbersome. We had a 30m cable on a previous boat and that was a bit awkward. I have several shorter lengths now which is fine.
 
Cut it into two. 20m and 30m. you'll find that most of the time you only use one or the other, on the occasion that you need a longer length then just link them together.
 
That's the way I've done mine. My boat is fed with some 10mm fat black 3 phase as used in outdoor event temporary power applications. Annoying if you had to get it all out for a small 10 meter run!

Dougal Tolan said:
When making an extension lead for a welder I bought 50m cable, 2 sockets and 2 plugs. With that I made a 15m and a 35m lead.... gives comfortable lengths for most situations.
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Actually the 50M cable is fine - it isnt that heavy and quite easy to man handle. I do have shorter extensions so I will keep those and use as necessary. Any longer would not be so easy - so that has turned out to be a sensible length.

I dont like joining extensions with an adapter - I have done that before on a 32A connection and the joining connector melted (everything else was fine). Also I dont like the idea of a join anywhere rain etc could get into the connection.

Strangely I always thought it was induction, but it would seem not from the internet.

Thank you all, I think the best solution is for the spare cable to be laid out as suggested earlier.

I am pleased to have a long cable having visited so many places where you are nose too, so in my case thats 20m of cable gone with the gap to the pontoon, then whatever the length to a conenction point that is actually working! My thinking with that length is I should be fine pretty much anywhere there is some power around! Maybe 30m or even 40m would have been ok for most occasions but it was more to cope with any eventuality.
 
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Is the cable core size 4mm2 which rates at ~ 32 amps or 6mm2 which rates at ~ 42 amps (two cable cores together).

These will have a Volt drop of 5.7 or 3.8 mV/A/m, so for 50m cable at 32 amps 18v for 4mm2 or 12v for 6mm2. Assuming again 32 amps the cable power loss will be ~0.6 kW or ~0.5kW of a total power transmission of 7.6 kW.

This is purely the resistive loss. As correctly mentioned heat generation of a coil of cable is caused by inductive impedance, for which the maths to assess the heat generation get very complex. Rolling out the cable eliminates this.
Inductive impedance is not a function of the CSA nor coil length, so the heat generation will be similar and likely to cause overheating above 8 amps, although a thicker cable would disperse the heat better. Simplest way to avoid this is to always trail out an entire coil.

For an adaptable 16a and 32a then a short tail with a 16a Socket and 32a Plug allows simple connection. I would suggest not ever creating a Darwin prize winning dual 16a plug bridal lead to obtain 32a, this is lethal for several reasons, not all of which are obvious - exposed pins of non connected plug; risk of immersion of same; risk of inadvertent cross phase (415v) full short circuit when plugging in the second plug - this would likely blow up in your hand before the protective MCB operated.
 
ip485 said:
See here;

https://uk.answers.yahoo.com/question/index?qid=20100520125802AAs2Ufo

which suggests that it isnt inductive impedance and else where. I thought it was.

Yes, had that discussion about using two 16A and have no intention of doing so - but there are more places with 32A these days which is useful as we can easily draw more than 16A.
Click to expand...
Except the Inductive part does not work at 90 degrees and does increases the overall R, in turn significantly increasing the I2R loss. The poster admits his answer is not a full one, and he fails to mention the phase shift created in an inductive circuit, and its affect on the overall impedance (total resistance). For me its too long ago to remember the precise maths here.

I standby my statement the heating is not purely resistive, but is in large part also inductive, indeed if what the Yahoo entry states were correct then induction heaters would not work.
 
superheat6k said:
Except the Inductive part does not work at 90 degrees and does increases the overall R, in turn significantly increasing the I2R loss. The poster admits his answer is not a full one, and he fails to mention the phase shift created in an inductive circuit, and its affect on the overall impedance (total resistance). For me its too long ago to remember the precise maths here.

I standby my statement the heating is not purely resistive, but is in large part also inductive, indeed if what the Yahoo entry states were correct then induction heaters would not work.
Click to expand...

Induction heaters (cookers) work by forming a transformer where the secondary coil is actually a piece of copper ali or steel which forms a shorted turn which gets hot from resistive heating from the induced power. The heating coils them selves do not get hot (barely noticeable)
Back to a coiled cable. You have essentially two coils (active and neutral) with current going in opposite directions at any given instant so any magnetic field generated at any instant by one wire is cancelled by the field generated by the other wire. In close proximity and twisted together. As inductance is a function of a magnetic field rising then collapsing inducing current into the original wire I can't see any way that inductance can be significant regardless of whether the cable is coiled or not. Of course I may be wrong. olewill
 
Normally I do not use heavy load ( only topping up batteries over night) , with the exception of a 2000 W ceramic heater to keep the Admiral happy in spring and autumn.

I am using 2.5 mm2 PUR orange cables with the blue CE 16 A connectors:
a) Standard length 10 m, just right for my place in the marina, but too short in most other cases
b) Extension 1 is 9 m, which is ok in the "most other cases"
c) Extension 2 is 15 m, which is needed sometimes
d) 50 m 1.5 mm2 on reel, which Comes out only 1-2- times per year ( not used for heavy loads )
In addition I Keep 2 short adapter cables with CE socket and a set of of "local" plugs, which are assembled when needed.
 
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