blackrose Posted January 12, 2022 Author Report Share Posted January 12, 2022 On 10/01/2022 at 20:58, ptolemy lane said: Have a look on your back deck there should be three of them 2amp ones on the seat 🙂 Thanks Tol, much appreciated. Didn't see them until this morning. Link to comment Share on other sites More sharing options...
IanD Posted January 12, 2022 Report Share Posted January 12, 2022 (edited) On 10/01/2022 at 19:26, Tacet said: Apologies if I was unclear. That's about it. It doesn't really contribute much by saying you can run a 150amp gadget via a nominal 5amp plug when there is a transformer involved. I don't know how much a welder draws via the mains but my 140amp welder has yet to break its 13amp (nominal) fuse Standard fuses take a long time to blow even at well above rated current: https://www.pat-testing-training.net/articles/fuse-operation-characteristics.php The grey shaded area shows the minimum and maximum currents at which the fuse will blow -- so for 10 seconds a 13A fuse will carry at least 25A without blowing, and is guaranteed to blow at less than 55A. It will carry 21A forever. Relying on fuses to limit operating current (as opposed to fault currents) is a *bad* idea... Edited January 12, 2022 by IanD Link to comment Share on other sites More sharing options...
cuthound Posted January 12, 2022 Report Share Posted January 12, 2022 1 hour ago, IanD said: Standard fuses take a long time to blow even at well above rated current: https://www.pat-testing-training.net/articles/fuse-operation-characteristics.php The grey shaded area shows the minimum and maximum currents at which the fuse will blow -- so for 10 seconds a 13A fuse will carry at least 25A without blowing, and is guaranteed to blow at less than 55A. It will carry 21A forever. Relying on fuses to limit operating current (as opposed to fault currents) is a *bad* idea... Indeed, and miniature circuit breakers perform even worse than fuses. As a rough rule of thumb, encapsulated fuses take over twice their rated current to blow reasonably quickly and miniature circuit breakers 3-5 times their rated current. Link to comment Share on other sites More sharing options...
David Schweizer Posted January 12, 2022 Report Share Posted January 12, 2022 I have used 2amp round pin plugs on the boat for decades, with no adverse effect, admittedly most of the appliances have been low consumption items, the only higher consumption unit being a 12v fridge which was hard wired into it's own dedicated circuit. 1 Link to comment Share on other sites More sharing options...
Tacet Posted January 13, 2022 Report Share Posted January 13, 2022 On 12/01/2022 at 12:41, IanD said: Standard fuses take a long time to blow even at well above rated current: https://www.pat-testing-training.net/articles/fuse-operation-characteristics.php The grey shaded area shows the minimum and maximum currents at which the fuse will blow -- so for 10 seconds a 13A fuse will carry at least 25A without blowing, and is guaranteed to blow at less than 55A. It will carry 21A forever. Should not the 13a fuse shown blow (at the 10 second scale) on more, not less, than 55a? Link to comment Share on other sites More sharing options...
IanD Posted January 13, 2022 Report Share Posted January 13, 2022 (edited) 2 hours ago, Tacet said: Should not the 13a fuse shown blow (at the 10 second scale) on more, not less, than 55a? No. The current at which the fuse blows after 10 seconds is between 25A and 55A, varying from one fuse to another. Below 25A, no fuse will blow within 10s. Above 55A, all fuses will blow within 10s. In between 25A and 55A the fuse might or might not blow within 10s. Edited January 13, 2022 by IanD Link to comment Share on other sites More sharing options...
Tacet Posted January 14, 2022 Report Share Posted January 14, 2022 On 12/01/2022 at 12:41, IanD said: ... 10 seconds a 13A fuse will carry at least 25A without blowing, and is guaranteed to blow at less than 55A. It will carry 21A forever. 13 hours ago, Tacet said: Should not the 13a fuse shown blow (at the 10 second scale) on more, not less, than 55a? 10 hours ago, IanD said: No. The current at which the fuse blows after 10 seconds is between 25A and 55A, varying from one fuse to another. Below 25A, no fuse will blow within 10s. Above 55A, all fuses will blow within 10s. In between 25A and 55A the fuse might or might not blow within 10s. You say No - but seem to mean Yes. You are saying that a fuse is both certain to blow at less than 55A and yet may not blow at all between 25A and 55A - all in the 10s timeframe. Between 25A and 55A is definitely less than 55A, of that I am sure In the graph provided, it is only more than 55A at which the fuse is certain to blow within 10s. Link to comment Share on other sites More sharing options...
IanD Posted January 14, 2022 Report Share Posted January 14, 2022 5 minutes ago, Tacet said: You say No - but seem to mean Yes. You are saying that a fuse is both certain to blow at less than 55A and yet may not blow at all between 25A and 55A - all in the 10s timeframe. Between 25A and 55A is definitely less than 55A, of that I am sure In the graph provided, it is only more than 55A at which the fuse is certain to blow within 10s. I think we're arguing about different interpretations of what was written, not disagreeing on the facts... 😉 You said: "Should not the 13a fuse shown blow (at the 10 second scale) on more, not less, than 55A?" Yes it will definitely blow within 10s above 55A -- but it might also blow above 25A. It will definitely not blow within 10s below 25A -- but it might also not blow below 55A. 25A to 55A is a region of uncertainly, where we don't know if it will blow within 10s or not. Agreed? Link to comment Share on other sites More sharing options...
Hudds Lad Posted January 17, 2022 Report Share Posted January 17, 2022 Just for fun, a side by side size comparison of 15a, 5a & 2a (plus they were rattling round in my drawer whilst I looked for something) 1 Link to comment Share on other sites More sharing options...
GUMPY Posted January 17, 2022 Report Share Posted January 17, 2022 Just found these three plugs whilst having a clear out. They are between 60 and 65 years old as they were on my childhood model railway😎 Link to comment Share on other sites More sharing options...
Balloon Posted January 17, 2022 Report Share Posted January 17, 2022 What is the purpose of these plugs? I have sockets for them on my boat next to my mains sockets…I’ve never seen them in use anywhere else. Link to comment Share on other sites More sharing options...
springy Posted January 17, 2022 Report Share Posted January 17, 2022 Originally designed and rated for single phase 240V A.C. however commonly used on boats for 12v (or 24V if appropriate). Beware there are some who advocate using the neutral and earth pins for the conductors rather than live and neutral on the grounds that you must create a 12V "appliance" with a 240V compatible plug to make use of the socket and if someone unknowingly plugged that "appliance" in to a 240V socket it shouldn't go pop. Personally I'd ensure clear labelling on both plugs and sockets. 5A and 2A AC ratings are common, mostly unfused, they are an old UK standard and quite solidly built (or at least old ones are). springy Link to comment Share on other sites More sharing options...
Ronaldo47 Posted January 17, 2022 Report Share Posted January 17, 2022 (edited) I have met the 2A and 5A ones on hire boats used for the 12V supply for things like the TV. On land, the 5A ones are often found used in hotel rooms for mains-voltage standard lamps which are controlled via wall switches. Edited January 17, 2022 by Ronaldo47 typos Link to comment Share on other sites More sharing options...
GUMPY Posted January 18, 2022 Report Share Posted January 18, 2022 I have a set of four 2amp sockets in the loft on a fused spur from the lighting circuit, this feeds three security lights and the loft light. It was originally 13amp sockets without the fused spur (done by the previous owner) so I changed it to meet current regs. Link to comment Share on other sites More sharing options...
blackrose Posted January 18, 2022 Author Report Share Posted January 18, 2022 15 hours ago, Loddon said: Just found these three plugs whilst having a clear out. They are between 60 and 65 years old as they were on my childhood model railway😎 Blimey, and I thought I was a hoarder! 😂 Link to comment Share on other sites More sharing options...
GUMPY Posted January 18, 2022 Report Share Posted January 18, 2022 14 minutes ago, blackrose said: Blimey, and I thought I was a hoarder! 😂 There was a time at Berko when I had two lockups, reduced that to one which filled the workshop mezzanine and a shed when I moved to Ringstead. Back to the equivalent of one lock up now hopefully by the end of February I will have got rid of much of it. I still have a full set of Whitworth/BSF spanners and I haven't owned a boat with an engine that needs them for 20years but you never know when I might need them😉 Link to comment Share on other sites More sharing options...
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