armstrongpiper Posted March 29, 2016 Share Posted March 29, 2016 It is frequently stated that one should always fully unroll the mains hook-up lead when it is in use to prevent overheating. Surely, if the lead is rated at 15amps or more, then if this current is not exceeded the wire will not get hot. The hook-up supply almost invariably has a limiting trip switch set to 15 amps (or fewer), again within the capacity of the wire. I have used site hook-up supplies for 30 years and have never fully unrolled the cable, and have never had any overheating problems. So, what is the basis for the cable unrolling advice? Armstrongpiper Link to comment Share on other sites More sharing options...
pepe63xnotuse Posted March 29, 2016 Share Posted March 29, 2016 I did notice our, loosely coiled, lead get very warm , not long after we had our first van..it was winter,with snow on the ground (so we probably had some additional electric heating running?). I had just gone to rearrange it / stuff it further under the van and it was quite hot to the touch(almost soft!),so I uncoiled it sharpish...and it remained cool after that. Some years on, I mounted our lead(s) onto a cable reel ...but I always unwound them fully. Link to comment Share on other sites More sharing options...
Brock Posted March 29, 2016 Share Posted March 29, 2016 Have a read at this thread http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Coiled-Extension-Leads/25749/ Link to comment Share on other sites More sharing options...
Charles Posted March 29, 2016 Share Posted March 29, 2016 When my 7kw shower is on the 6mm flat cable gets slightly warm. So if it was wound tightly round itself I would imagine it would get hot. Try it for yourself if you've got an electric shower. Link to comment Share on other sites More sharing options...
paulmold Posted March 29, 2016 Share Posted March 29, 2016 http://www.bbc.co.uk/news/uk-wales-north-west-wales-15940837 Link to comment Share on other sites More sharing options...
Will H Posted March 29, 2016 Share Posted March 29, 2016 By habit I would never use any electric cable coiled, regardless of the passing current. I've seen a coil melted solid, the next stage would have been a fire. In one of my past lives I operated an induction heater which is an industrial coil based on the same principal as your coil of M/H cable. There are many modern industries using this process. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 29, 2016 Share Posted March 29, 2016 All the ‘reeled’ extension-cables I’ve owned have had advice on them regarding their maximum amperage fully wound or fully unwound. For example http://www.ebay.co.uk/itm/PIFCO-4WAY-25M-CABLE-EXTENSION-REEL-LEAD-MAINS-SOCKET-HEAVY-DUTY-ELECTRICAL-/141618117397 (I thought everybody was aware of the potential risk in not unwinding the cable...) Link to comment Share on other sites More sharing options...
Dave225 Posted March 29, 2016 Share Posted March 29, 2016 One thing I have noticed, and I always fully unwind it, is that trying to rewind it up again can be a pain as the lead coils itself up into loops which are fun to straighten. However, I also suspect that part of the confusion can be laid at the doors of our EU neighbours who always it seems travel with leads on spools and rarely unwind more than what they need. Their cable is of a lower wattage than ours and seems more flexible. Certainly it is not as rigid as the orange one we use here. I have not heard of any major disasters with what they are doing so I guess it is an 'approved' method. Link to comment Share on other sites More sharing options...
Ninian Posted March 29, 2016 Share Posted March 29, 2016 Hi, Not unrolling the lead fully can cause " Eddy Currents ". Google it's effects. Link to comment Share on other sites More sharing options...
Agaric Posted March 29, 2016 Share Posted March 29, 2016 I you went and bought a copy of this book BS 7671. IET Wiring Regulations, it would soon become very clear how cables are rated under different conditions. All electricians are required to understand and conform to these regulations. All cables are rated as in free air but once you put them in conduit, roll them up, put them under plaster etc. those ratings change because of the dissipation of heat leading to fire. Some cables don't get to the stage of melting when they continually get hot they just disintegrate, I had a case of this occurring in a London office block recently the outer and inner casings just crumbled in your hands. The cable was only 7 years old. Link to comment Share on other sites More sharing options...
Guest pelmetman Posted March 29, 2016 Share Posted March 29, 2016 I coil mine in a bucket, cant say I've ever noticed it get warm, if it did I'd fill the bucket with water :D .......... Link to comment Share on other sites More sharing options...
George Collings Posted March 29, 2016 Share Posted March 29, 2016 I am not a sparky but my understanding is that it would take many times more turns before eddy current were the problem. As our electrician contributor has just said its the lack of ventilation when coiled that stops heat from dispersing that needs to be avoided. The black wire favoured on the continent is I believe rubber covered as it stays d flexible at sub zero C temperatures where the UK PVC covered stuff gets to stiff to handle. It might be that the black rubber is better at conducting heat away. Link to comment Share on other sites More sharing options...
malc d Posted March 29, 2016 Share Posted March 29, 2016 Dave225 - 2016-03-29 7:15 PM One thing I have noticed, and I always fully unwind it, is that trying to rewind it up again can be a pain as the lead coils itself up into loops which are fun to straighten. . I used to have that problem when winding around hand and elbow - but it doesn't happen if you wind it onto a 'spool'. ;-) Link to comment Share on other sites More sharing options...
daviddwight Posted March 29, 2016 Share Posted March 29, 2016 If winding cable or rope into a coil by hand it needs to be twisted with each loop.. Rope and cable has a natural twist and this is why it will twist into loops on its own and create tangles therefore you need to counteract this twist. We get a good chuckle watching people trying to get the cable between the EHU and the van as it is in a lovely tangle. Link to comment Share on other sites More sharing options...
George Collings Posted March 29, 2016 Share Posted March 29, 2016 I learnt to coil rope on hand and elbow boating when a child and have done it for the HU cable for almost twenty years of motorcaravanning. The the knack is in alway starting at the same point and securing the loop in two places( A couple of Velcro straps intended to strap pumps to the bike) To unwind start at the HU and walk away back to the van unwinding as you go keeping a grip on the coil. Plug in van and tuck unused part under van ready to pick up hopefully still dry. Back to the HU and plug in. I wrap a rag around the cable to clean/dry it as its rewound it after unplugging, with a bit of luck the unused part is intact but sometimes the whole reel has to be done. A coil on a drum is rigid but the elbow hand coil is relatively flexible that makes for easier stowage. Pet hate is leads that come away from the HU at an angle as a trip hazard rather than drop straight to ground. If I am not careful I will turn into a safety elf. Link to comment Share on other sites More sharing options...
Brambles Posted March 29, 2016 Share Posted March 29, 2016 Will H - 2016-03-29 6:35 PM By habit I would never use any electric cable coiled, regardless of the passing current. I've seen a coil melted solid, the next stage would have been a fire. In one of my past lives I operated an induction heater which is an industrial coil based on the same principal as your coil of M/H cable. There are many modern industries using this process. No, because remember at any given moment in time the current flowing in one conductor (say Brown wire) is equal but opposite direction to the current in the other conductor (say blue wire) so the balance is 0. Therefore there will be no magnetic field generated. There is in effect zero inductance. To have an induction effect you would have to separate the two conductors and coil separately. All you need to worry about with the lead is the resistance and heating effect from the current flowing. When you coil the cable then you are concentrating the heat and restricting air cooling of the cable. Link to comment Share on other sites More sharing options...
Brambles Posted March 29, 2016 Share Posted March 29, 2016 Ninian - 2016-03-29 7:17 PM Hi, Not unrolling the lead fully can cause " Eddy Currents ". Google it's effects. Sorry but Eddie currents are not generated in your cable coil. Similar to my last reply in one conductor inside the cable takes current in one direction whilst the other conductor is taking current in the opposite direction and cancel out. Also Eddie currents are currents that flow within a metal round in a loop within the metal. Think of a larger flat metal plate and currents are induced within the metal plate and cause the plate to heat up. This is how induction cookers and saucepan work. Link to comment Share on other sites More sharing options...
Will H Posted March 30, 2016 Share Posted March 30, 2016 Brambles, thank you for that I assumed it to be the same. The industrial process was brazing metal parts together, and very effective it was. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted March 30, 2016 Share Posted March 30, 2016 armstrongpiper - 2016-03-29 4:18 PM It is frequently stated that one should always fully unroll the mains hook-up lead when it is in use to prevent overheating... Armstrongpiper Isn’t this a matter of semantics? I have a 25metre and a 10metre EHU cable and both are the ‘orange’ cable type with three 2.5mm cores. Neither cable is on a reel or spool, so when I connect to an EHU the question of “fully unrolling” the cable does not come up. If an EHU is, say, 9 metres from my motorhome my 10m cable will be fully uncoiled. If an EHU is, say, 5 metres from my motorhome my 10m cable won’t need to be fully uncoiled and I’ll (usually) position the ‘spare’ loosely coiled section of the cable out of harm’s way beneath the motorhome. If an EHU cable is ‘coiled’ (ie. not on a reel) there’s no technical reason to straighten it out: if it’s on a reel or spool there is a potential risk of the cable overheating unless it is fully unreeled/unspooled. I also have a 45m cable with three 1.5mm cores. This is on a reel and I use it at home not in my motohome. There is a warning on the reel that the maximum 240V wattage with the cable fully wound on the reel is 720W (3A) or 3120W (13A) when the cable is fully unwound. As I use this cable for mains-powered garden equipment that has relatively low current demand I don’t unreel the cable more than necessary. If I was using the cable to provide power to a 3kW heater, I’d fully unreel it. Our Continental cousins are accustomed to needing ultra-long cables to connect to EHUs and, because 1.5mm core-size (and rubberised cable) is the norm abroad, they can get a lot of cable on a relatively small-diameter reel. Fully unreeling 40+ metres of cable is a pain and it’s common to see a ‘Continental’ motorcaravan connected to an EHU with most of the cable’s length still on the reel. In such instances I’ve never known if the motorcaravanner was oblivious to the risk of overheating, or was aware of it and knew that he/she would not be operating high enough wattage equipment for fully unreeling the cable to matter. This earlier forum thread may be of interest: http://forums.outandaboutlive.co.uk/forums/Motorhomes/Motorhome-Matters/Hook-up-cable/31606/ Link to comment Share on other sites More sharing options...
StuartO Posted March 30, 2016 Share Posted March 30, 2016 Derek Uzzell - 2016-03-30 9:34 AM ....Our Continental cousins are accustomed to needing ultra-long cables to connect to EHUs and, because 1.5mm core-size (and rubberised cable) is the norm abroad, they can get a lot of cable on a relatively small-diameter reel. Fully unreeling 40+ metres of cable is a pain and it’s common to see a ‘Continental’ motorcaravan connected to an EHU with most of the cable’s length still on the reel. In such instances I’ve never known if the motorcaravanner was oblivious to the risk of overheating, or was aware of it and knew that he/she would not be operating high enough wattage equipment for fully unreeling the cable to matter..... I suspect that they are accustomed to the low amperage supplies on Continental camp site hook ups and few if any of them will ever run heaters, water heaters or even electric kettles, as we Brits do. There can be no doubt that using a British 16 amp camp site supply to run high power equipment, as we Brits often do, will risk over-heating the hook up cable if it is left partly coiled up. Link to comment Share on other sites More sharing options...
colin Posted March 30, 2016 Share Posted March 30, 2016 Derek Uzzell - 2016-03-30 9:34 AM armstrongpiper - 2016-03-29 4:18 PM It is frequently stated that one should always fully unroll the mains hook-up lead when it is in use to prevent overheating... Armstrongpiper I also have a 45m cable with three 1.5mm cores. This is on a reel and I use it at home not in my motohome. There is a warning on the reel that the maximum 240V wattage with the cable fully wound on the reel is 720W (3A) or 3120W (13A) when the cable is fully unwound. As I use this cable for mains-powered garden equipment that has relatively low current demand I don’t unreel the cable more than necessary. If I was using the cable to provide power to a 3kW heater, I’d fully unreel it. I have in front of me a 9m 13amp extension reel. It has a warning note, "Max.current fully wound 6amp(1440W)", gf brother borrowed this pulled out about 1m of cable and ran a 2KW electric fire,it got fairly hot Link to comment Share on other sites More sharing options...
Harvey Posted March 30, 2016 Share Posted March 30, 2016 I have been using this method for some time. (demo'd on U-tube). it works well. does not need a reel and when stored it can be screwed up, folded, hung as required. I have seen better demo's than this one but it shows how to:--- Harvey Link to comment Share on other sites More sharing options...
Keithl Posted March 30, 2016 Share Posted March 30, 2016 This is the 'Over and Under' method that I have used for years... Starts at 2 minutes in. Note how first loop goes 'over' and then next loop goes 'under' each time. The beauty is when you unwind it by letting loops fall off the coil it is not get twisted like conventional coiling. Keith. Link to comment Share on other sites More sharing options...
armstrongpiper Posted March 30, 2016 Author Share Posted March 30, 2016 OK, some interesting views expressed, and thankyou. I think there's a bit of the 'Urban Myth' exaggeration involved, but no doubt it is preferable to have some ventilation around the cable especially if the current flowing is 'highish'. Armstrongpiper Link to comment Share on other sites More sharing options...
Wirralian Posted March 30, 2016 Share Posted March 30, 2016 malc d - 2016-03-29 8:27 PM Dave225 - 2016-03-29 7:15 PM One thing I have noticed, and I always fully unwind it, is that trying to rewind it up again can be a pain as the lead coils itself up into loops which are fun to straighten. .[/i have just yesterday wound up my 25 m cable after several months of it laying in the winter sun in Spain and noticed how easily it coiled up compared to when I am in the UK.QUOTE] I used to have that problem when winding around hand and elbow - but it doesn't happen if you wind it onto a 'spool'. ;-) Link to comment Share on other sites More sharing options...
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