30m long mains extension cable trips fuse - Page 1
Forum section: electronics / beginners

author: vinlove
author_rank: Frequent Contributor
timestamp: February 21, 2022, 09:33:33 pm
content: I have this 30m long mains extension cable. It has 13A fuse in the plug, and is plugged into the mains 230V UK socket in the house, and I use it to connect the Bosch power hose. The Bosch power hose / washer is one of the top model from Bosch, and it is very powerful. As soon as it is switched on, it trips the fuse in the mains extension cable 13A fuse.If the power hose is connected directly to the mains socket in the house without the extension cable, then it is OK. The power washer will run all day without tripping any fuse.So what is it? What causes the extension cable fuse to blow? Would it be the length of the extension cable having excess resistance? Or would it be the extension cable is not thick enough to be able to cope with the current required by the power washer?

author: TimFox
author_rank: Super Contributor
timestamp: February 21, 2022, 09:39:00 pm
content: This sounds like normal behavior of a standard fuse that is marginal for the starting/inrush current of an electric motor.What protects the house outlet that you plug the equipment into? A fuse or circuit breaker?

author: tggzzz
author_rank: Super Contributor
timestamp: February 21, 2022, 09:44:31 pm
content: What is the mean operating power rating of the equipment? Ditto peak startup rating?What is the fuse in the equipment?Excess resistance would reduce the tendency of the fuse to blow.

author: vinlove
author_rank: Frequent Contributor
timestamp: February 21, 2022, 10:03:36 pm
content: The power hose / washer is this one.https://www.amazon.co.uk/Bosch-06008A7D70-Pressure-Washer-AdvancedAquatak/dp/B07MQ9HHS2/ref=sr_1_4?adgrpid=53916679915&gclid=Cj0KCQiAjc2QBhDgARIsAMc3SqTp9jlTGP9TbczLp2K0WYeZ81hdivybSBrgUZr5OfzAsHSlrSd0z8UaAh_gEALw_wcB&hvadid=259101229342&hvdev=c&hvlocphy=1007330&hvnetw=g&hvqmt=e&hvrand=343638132528553728&hvtargid=kwd-489502856392&hydadcr=5309_1829680&keywords=bosch+power+washer&qid=1645480794&sr=8-4It is rated at 2100W and runs on 230V AC mains.The machine has a 13A fuse in the plug. It is fine, no problems.But the 13A fuse in the 30m long extension cable always blows.Tried with a 10m long extension cable, and it is OK.

author: Zero999
author_rank: Super Contributor
timestamp: February 21, 2022, 10:11:23 pm
content: Quote from: vinlove on February 21, 2022, 10:03:36 pmWhat's the crossectional areas of the 30m and 10m cables?If anything the longer cable should be less likely to blow the fuse, because it will limit the current surge.

author: tggzzz
author_rank: Super Contributor
timestamp: February 21, 2022, 10:23:16 pm
content: Are the fuses equivalent?Differences could be slow-blow vs normal, or poor manufacturing.

author: rs20
author_rank: Super Contributor
timestamp: February 21, 2022, 10:24:16 pm
content: Quote from: vinlove on February 21, 2022, 10:03:36 pmYou say "13A fuse" as if all "13A fuses" are identical, but they are not. Have you swapping the fuses in the machine and the extension lead? Just to eliminate the possibility that the fuse currently sitting in the power washer is on the more tolerant side of the bell curve (or indeed, maybe a slow-blow variety of fuse?) (oops tggzzz pipped me, but I'll still post with the concrete suggestion of how to check)Is the area where the extension lead fuse is located (right near your mains powerpoint I presume?) extremely hot for some reason?

author: vinlove
author_rank: Frequent Contributor
timestamp: February 21, 2022, 11:38:30 pm
content: I used to think all 13A fuses are identical. Maybe they are not.Will check them out tomorrow, and update here.Yes, it is a mystery to me. Why the 30m long extension cable keeps blowing its 13A fuse when plugged with the Bosch power washer.With every other devices such as Bosch hedge cutter, work lights (800W), battery chargers, it is fine.The Bosch power washer works OK with the other extension lead which is 10m long (13A fuse in the plug), or when connected directly to the wall socket 230V AC mains in the house on the kitchen wall next to the door to the garden.

author: WatchfulEye
author_rank: Regular Contributor
timestamp: February 22, 2022, 12:12:30 am
content: This could be due to the resistance of the cable. Increasing the cable resistance can result in an increase in inrush current duration, which can blow fuses or trip breakers. The increased line resistance reduces motor torque, which causes a delay in the motor reaching normal operating speed and normal operating current.Try using an extension cable rated for 32A as this will have larger conductors with lower resistance.

author: vinlove
author_rank: Frequent Contributor
timestamp: February 22, 2022, 10:30:16 am
content: Quote from: WatchfulEye on February 22, 2022, 12:12:30 amyeah this is what I thought, but wasn't sure. The 30m long extension cable is an old one, and was very cheap. It has 4 sockets on the winding base. The wire looks a bit thinner than the other extension cable.

author: MathWizard
author_rank: Super Contributor
timestamp: February 22, 2022, 10:45:48 am
content: I've ran a 125V 15A compressor of an outlet right next to the panel, on a 10A breaker. And it would run, and drop the mains voltage 1V or so. And not trip the breakerAnd on the same breaker, if I move to the next plug along, the voltage drops another 1-2V, and by the next plug, another 1-2V. On the far end of the house, still on same breaker, the AC is down from 118V to about 108V, and the breaker does trip then.So yeah like another guy said is it just an increased duration of in-rush current, at the lower voltage ?All the plugs and wires are new in my home, IDK what good contact resistance for wire nuts, and plugs that u just strip and insert the mains wires into, some day I better measure some resistances...., I'd love to know what current the compressor really uses.

author: nali
author_rank: Frequent Contributor
timestamp: February 22, 2022, 10:59:00 am
content: You say "fuse" and "trips". Is it a fuse or a breaker? If it's a breaker then earth leakage might be your issue, not overcurrent.

author: Zero999
author_rank: Super Contributor
timestamp: February 22, 2022, 11:09:21 am
content: Voltage drop would make sense. Induction motors tend to have a quasi-constant power characteristic. Reducing the voltage, increases the slip, along with the current, which would explain why the breaker is blowing, with the longer extension lead, which would drop more voltage.Using cable with a higher conductor crossectional area (thicker wires) would help. In the UK and Europe the crossectional area is measured in mm2. The minimum size for a 13A flexible cable is 1.25mm2, but you probably need 1.5mm2or 2.5mm2. I doubt you'll be able to go thicker than that because it might not fit a 13A plug.

author: vinlove
author_rank: Frequent Contributor
timestamp: February 22, 2022, 11:17:58 am
content: Quote from: nali on February 22, 2022, 10:59:00 amIt is "fuse". There is no breaker. Sorry. I didn't make it clear.The 13A fuse in the plug of the 30m long cable keeps blowing, and it had to be replaced.It only happens with the Bosch power washer, when it is powered on.

author: CaptDon
author_rank: Super Contributor
timestamp: February 22, 2022, 02:17:25 pm
content: Are the physical sizes of the fuses identical?? Somehow I get the impression the one on the washer unit is an AGC or MDL size and maybe the one on the cord is a GMA or T size?

author: vinlove
author_rank: Frequent Contributor
timestamp: February 22, 2022, 09:27:26 pm
content: Quote from: CaptDon on February 22, 2022, 02:17:25 pmyeah, they are all identical in size. I checked the 13A fuses both in the machine plug and the extension plug, and they are just the same 13A fuses. No difference was noticed.I am wondering also - from the 30m long extension cable, only 10m cable is extended from the base, and the rest of the cable is in wound state. Would wound cable exhibit some peculiar characters in resistance or inductance, causing anomalies?

author: wraper
author_rank: Unknown
timestamp: February 22, 2022, 09:38:43 pm
content: Device may pull more current due to the voltage drop on the cable to keep the same power. But it still would not explain why the fuse in the socket where the extension cord is plugged in does not blow.

author: Ian.M
author_rank: Super Contributor
timestamp: February 22, 2022, 10:25:38 pm
content: British ring main wiring! The BS1363 plugs have max. 13A fuses but the ring main feeding the sockets is typically fused (nowadays with a breaker) at 32A. Its also possible to have radial circuits fused (breakered) at 16A feeding BS1363 sockets, but they are far less common. However both are rated for more than a BS1362 13A fuse, which is *supposed* to provide discrimination such that the distribution panel fuse doesn't blow if an appliance shorts out. Nowadays with circuit breakers in the panel, discrimination is much less reliable and near non-existant on 16A circuits, though admittedly its much less of a PITA to reset a breaker rather than having to replace a fuse cartridge or rewire a fuse.

author: Monkeh
author_rank: Super Contributor
timestamp: February 22, 2022, 10:35:39 pm
content: Quote from: CaptDon on February 22, 2022, 02:17:25 pmErr, no, they're going to be the same.Quote from: wraper on February 22, 2022, 09:38:43 pmBecause there is no fuse in the socket?

author: WatchfulEye
author_rank: Regular Contributor
timestamp: February 23, 2022, 01:22:08 am
content: Quote from: wraper on February 22, 2022, 09:38:43 pmThere is quite a wide tolerance on fuses. See the attached specification for BS1362 fuses.It is likely that the one fuse that has survived multiple overloads is towards the lower sensitivity end of the population. I suppose that there is always the possibility of a counterfeit fuse, but by the sounds of things the fuse came with the appliance, so this may be less likely than a fuse bought off amazon or alix.

author: wraper
author_rank: Unknown
timestamp: February 23, 2022, 09:31:38 am
content: Quote from: Monkeh on February 22, 2022, 10:35:39 pmSeems my memory failed me as I recalled UK sockets were fused too.

author: nali
author_rank: Frequent Contributor
timestamp: February 23, 2022, 09:39:11 am
content: No fuse in the socket, but it's still a bit strange as there will be two fuses inline - one in the equipment's plug and one in the extension lead's plug.I'm wondering if it's a heat conduction thing? The fuse is right at the threshold of its I2t rating but the equipment's plug has more substantial contacts sinking just enough of that heat away that it doesn't blow on the startup surge.

author: Ian.M
author_rank: Super Contributor
timestamp: February 23, 2022, 09:43:30 am
content: Quote from: wraper on February 23, 2022, 09:31:38 amSome are:https://www.tlc-direct.co.uk/Products/MKK2737.htmlThat's a triple socket, that for the purposes of the UK wiring regulations, counts as a single socket because its fused. They used to be popular in hotels etc. to limit disruption due to *IDIOTS*!

author: Terry Bites
author_rank: Super Contributor
timestamp: February 23, 2022, 09:59:32 am
content: Shoving 10A down a 30m lead is asking for trouble. A 13A socket can't necessarily provide 13A safely, see makers advice.Run your washer from a dedcicated RCD/ MBC outlet.Most extension leads are crap

author: Zero999
author_rank: Super Contributor
timestamp: February 23, 2022, 11:10:49 am
content: Quote from: nali on February 23, 2022, 09:39:11 amAnother possibility is the temperature. If the extension lead is plugged in to an indoor socket, it will be much warmer, than the plug on the pressure washer outside.Quote from: vinlove on February 22, 2022, 09:27:26 pmTo answer the question: no. There won't be a significant difference in inductance, because both the live and neutral wires are in parallel, so the fields generated by the current will cancel. The resistance won't change, as long as the temperature rise isn't big enough to significantly affect it. The reason why it's considered a bad idea to use an extension lead, without fully unwinding it is because the heat can't escape as easily and there's an increased risk of the cable overheating. The temperature rise won't affect the resistance much, but it can be enough to melt the insulation, cause a short circuit and fire.

author: Kleinstein
author_rank: Super Contributor
timestamp: February 23, 2022, 11:28:42 am
content: Induction motors may draw more current when the voltage drops. As an additional effect the motor may not even start proper. Especially compressors have this problem with a long extension cord.

author: Monkeh
author_rank: Super Contributor
timestamp: February 23, 2022, 12:33:03 pm
content: Quote from: Terry Bites on February 23, 2022, 09:59:32 amThen it's not BS1363 compliant and can't be on the market. Stop buying garbage from the poundshop.Quote from: vinlove on February 22, 2022, 09:27:26 pmDon't do that. If you don't need the 30m, just don't use it.

author: vinlove
author_rank: Frequent Contributor
timestamp: February 23, 2022, 05:15:37 pm
content: Quote from: Ian.M on February 22, 2022, 10:25:38 pmyes, I seem seeing it nowwith some parts to delve into more. The most wall mains sockets in UK residential properties are rated at 32A I think especially for the electric cookers, storage heaters and even washing machines. So they will never blow fuses. They don't even have fuses. They can trip the breaker when installed with the breakers.

author: bingo600
author_rank: Super Contributor
timestamp: February 23, 2022, 06:09:25 pm
content: I have a 25m rool/spool of 230v extension cable.When using with high power utils (1000+ Watt) - I always make sure to unrool all of it.Was once told about possible inductive kickback, if not doing that.I'm no EE or Electrician , but i can run my devices wo. fuse blowing (10A).I think 1800W is the max i have loaded it with.

author: vinlove
author_rank: Frequent Contributor
timestamp: February 23, 2022, 11:23:08 pm
content: Quote from: bingo600 on February 23, 2022, 06:09:25 pmYes, I was suspicious of this effect of the rolled cable inductance play up when used with high current device pulling lots of currents through it.I was not sure how it affects, and why in theory.

author: themadhippy
author_rank: Super Contributor
timestamp: February 24, 2022, 12:26:10 am
content: QuoteRing finals are slowly going out of favor with A2 (4mm cable and 32A breaker )and A3 (2.5mm 20A) becoming more popular.A3 especially so for low demand areas like bedroom and living area sockets ,and keeping the ring for kitchens with its higher demand also no need to buy a drum of 4mm.QuoteA standard BS1363 double socket to is only designed for maximum load of 20A

author: Zero999
author_rank: Super Contributor
timestamp: February 24, 2022, 10:54:26 am
content: Quote from: vinlove on February 23, 2022, 11:23:08 pmThe cable should be unwound before using, especially to the full rating, but I repeat:it's got nothing to do with the inductance. As I said before,the currents in the neighbouring conductors flow in opposite directions, thus causing the magnetic fields to cancel each other out. Even if you put the live through one extension lead and the neutral through another (don't do this, it's a bad idea, it's just a thought experiment), so the fields don't cancel, the inductance would have a similar effect at 50 to 60Hz, as the resistance of the cable: a couple of mH inductance will have an impedance of just under an Ohm, similar to the DC resistance. The reason for this is because there's no magnetic core. This is why all transformers and inductors designed to work at mains frequencies have magnetic cores. Also note that inductance doesn't result an any power dissipation.The reason for unwinding the cable ispurely thermal. A tightly wound coil concentrates the power dissipated due to I2R losses in the cable, into a small space. The cable in the middle of the coil, doesn't have air circulating around it to provide convective cooling and any radiated heat is absorbed by a neighbouring turns, causing them to heat up more. When the cable is unwound, the heat can escape more easily due to better air circulation and the heat is able to radiate out into space more easily.The bottom line is, a tightly coiled cable will heat much more, than an unwound cable, given everything else (current, length, conductor size) being equal. The temperature rating of the insulation will be exceeded, if it's not designed to work at full power, when coiled up, which is the case for all extension leads made.Suppose the total resistance of the cable is 1 Ohm* and the current is 12A, P = I2R, so that's a power dissipation of 144W, more than an old school 60W light bulb and a bit more than a slow cooker. Imagine the difference in temperature rise, when that heat is concentrated in a small area, compared to spread out over a large one.*Based on 60m (the total length of the live + neutral in a 30m run) of 1.25mm2cable rounded up, given it's specified at 20oC and the cable will get heat up.http://www.farnell.com/datasheets/1805062.pdf