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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#41
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As long as the maximum current load does not exceed the current rating of
any of the cables that are used in the extension, it will be safe. There should not be very much loss over a few hundred feet of extension. If there is a loss, you can then change the extensions for ones that are of a larger gauge. I have run extensions of up to 400 feet. These were 10 Amp rated. I had no performance loss in the loads that I was using. The load was about 4 to 5 amps. I am working with 120 VAC at my location. I took a voltage reading, at the outlet, and one across the load. There was a drop of about one or two volts. But, the total voltage at the extension output was still in specs while under the load. The source voltage at the outlet was about 118 VAC. Across the load, if I remember correctly, it was about approximately 116 VAC. In areas that are using 220 VAC, the current is about 1/2 for the same wattage, as when compared to 120 VAC. This would lead to less loss when using an extension cord. Most devices here in North America are rated at 105 to 125 VAC. Some are rated from about 105 to 135 VAC. -- Jerry G. ====== "Ian Stirling" wrote in message ... In uk.d-i-y Sammo wrote: I am in the UK (so mains voltage is about 230V or 240V). I have a reel of main extension cable made of 3-core 1.0 mm^2 wire rated at 10 Amps. So the nominal power rating would be about 2,400 Watts. (Link to tech reference for the cable is below.) It's always going to be safe, as it's got a fuse. Ok... Copper has a resistivity of 0.7*10^-8 ohms/meter. Or, for a 1mm^2 wire, 0.7*10^-2 ohms/meter. Or for 2 wires, 1.4*10^-2 ohms. Or for 60m, 8.4*10^-1 ohms, or .84 ohms. At 10A, 8.4V, or heating by 84W. If at the plug end is 240V, at the socket end will be 232V, which is (232^2/240^2)= .93444444444444444444 So, you lose 7% of the power for a heater, for example. |
#42
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"Watson A.Name - "Watt Sun, the Dark Remover"" wrote in message ... "Mike" wrote in message ... "Watson A.Name - "Watt Sun, the Dark Remover"" wrote in message ... And then when they get tired of doing that, they go out and buy a weed wacker with the gas engine. One question to somebody presumably residing in the western colonies. What's a "weed wacker"? Where are you from? Ever heard of Google? This URL shows a pic of the business end of a weed wacker. Traditionally they use monofilament. There are both electric and gas engine types, but the noisy gasoline engines (and leaf blowers) are sometimes banned from some communities. Hell, if you have any more grass than that the size of a postage stamp here in the UK, we buy a petrol driven "weed wacker", the electric ones, even at 230v are worse than useless! Tim.. |
#43
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In article ,
Peter A Forbes wrote: Why use anything as small as 1mm sq cable??? For 30metres I'd want to see 2.5mm sq at least, if not 4mm sq. If not for the volt drop or lack of, for the mechanical strength and resistance to damage. Dunno where you'd get 4mm flex, but you'd never get it to fit a 13 amp plug. 2.5mm is the limit, and not all plugs will have a cord grip suitable. -- *If a thing is worth doing, wouldn't it have been done already? Dave Plowman London SW To e-mail, change noise into sound. |
#44
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Watson A.Name - "Watt Sun, the Dark Remover" wrote:
wrote in message oups.com... I'm in the U.S. and this gives me a flashback on what I was thinking about trying a few months ago. We have a PBX at work that's on 48V batteries, but the batteries are 9 yrs old and need replacing. They cost a bundle the first logical thought is repair them rather than replace. Lead acids are often repairable. Quick repair, doesnt always work: rinse muck out of cells fill with new acid charge, monitor acid conc and adjust as required This wont fix all cells by any means, but many it will. Those it wont in some cases may only need replacement plates and acid, which can be made much cheaper than buying new batts. No. These cells are 4V each, 12 in all, each is sealed. If youre going to deal with this you'll need a few clues. You will have 2v cells in pairs, 4v lead acid cells dont exist. Well, except for the one cell that's split open because of internal pressure. :-( They must be replaced, not repaired. This is a phone system, where it has to be online during emergencies. Batteries that are working fine, but over 5 years old are considered unacceptable and must be replaced. thats fine if youve got the money, but since they've been there 9 years, and are found dead but still in service, I was guessing you havent. Is it April yet? Also they can often be run happily at 24v, if not in all cases. If yours could, it may be that your present cells would do that as is. This is *not* how you run a battery backup system! The idea is to start out with fully charged batteries, so that when the power fails for a long period, the voltage of the batteries may drop to 40V or less as the cells discharge, keeping the PBX online. If you start at anything less, even 36V, you're not going to have any discharge time before the PBX system crashes. It would be essentially worthless. You misunderstood completely, hopelessly, and idiotically. 48v is a very old standard, and many 48v telecomms systems are now run on 24v. If your equipment were 24v compatible, as some is, you would only need half the number of cells. And if you had no money to replace the battery, odds are you'll have at least 50% of cells still serviceable. Even if its not 24v compatible, you would get better backup performance by removing any dead cells from the chain. Whether you remove them or not you'll run below voltage. What capacity at 48v is it on? The rectifier can put out a hundred amps at 54VDC, to charge the batteries while the PBX is also running. That must be 6 or so kW input. So I would guess that it's 208V at 30A breakers. But with no batteries, the load would be more like 3.6kW. 3=2E6kW @ 50v =3D 72A, so if we take an ultra-vague guess at C/10 charging, that gives us 700ah capacity @48v. Ouch. I thought it would be possible to run a power cable underground to the big UPS we have in our computer room. Problem is that the PBX's rectifier takes 30A max at 120VAC, or about 3.6kW. i've no ida how that fits into this The UPS in the computer room is 150kW, easily capable of handling another 6 or so kW. And the distance between is about 1300 feet or about 400m. I would guess that the UPS output should go into a transformer and come out 480VAC, so the cable losses would be minimized. Then another transf on the PBX end to bring it back to 120VAC. But should I expect to have a max loss of 5% at max current, or what? well how much current are you shifting?? And why cant you power your pbx from whatever power source it uses now? You havent given us nearly enough information. The batteries and rectifier are a "UPS" to protect the PBX against failure of the commercial power. That's what it's being fed from. Why dont you find someone else to discuss this with. I think I came up with 4GA cable, but at 480VAC, I'm guessing that it would have to be special insulated underground cable. standard uk T&E should do that, but shuold be insulation tested to the required v first. Costs around =A312 a 100m reel, depending on copper size. Assuming that it could be pulled 1300 feet. Probably not without damage. You thread it section by section. Regular access points also allow a section can be replaced if it fails. The T&E also includes a spare conductor for backup. Heavily insulated cable would be needed. Probably double jacketed. T&E is double insulated, high v rated and cheap - thats why i suggested it. Someday I'll have to ask one of the electricians that work on our HV stuff. We have 4160VAC underground around campus but that's all specialized switchgear, etc. rf transmission co-ax is rated pretty high... and its concentric. RF transmission coax is typically copper clad steel wire center conductor, which would have much greater I^2R loss than pure copper cable at 50 or 60Hz. That would be unacceptable. obviously it depends what v and i youre running it at, its very much higher v rated than T&E. T&E's probably far more practical. Thanks, but I've never heard of T&E here in the U.S. I don't know what that acronym stands for. twin and earth, its our standard house wiring cable, 2 cores double insulated plus one single, comes in various copper sizes, is very cheap and can be bought at thousands of outlets... here, anyway. I dont know what export would cost. You would need to get some basic concepts sorted out before youre in a position to imlpement anything. NT |
#45
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wrote in message oups.com... Watson A.Name - "Watt Sun, the Dark Remover" wrote: wrote in message oups.com... I'm in the U.S. and this gives me a flashback on what I was thinking about trying a few months ago. We have a PBX at work that's on 48V batteries, but the batteries are 9 yrs old and need replacing. They cost a bundle the first logical thought is repair them rather than replace. Lead acids are often repairable. Quick repair, doesnt always work: rinse muck out of cells fill with new acid charge, monitor acid conc and adjust as required This wont fix all cells by any means, but many it will. Those it wont in some cases may only need replacement plates and acid, which can be made much cheaper than buying new batts. No. These cells are 4V each, 12 in all, each is sealed. If youre going to deal with this you'll need a few clues. You will have 2v cells in pairs, 4v lead acid cells dont exist. Well, except for the one cell that's split open because of internal pressure. :-( They must be replaced, not repaired. This is a phone system, where it has to be online during emergencies. Batteries that are working fine, but over 5 years old are considered unacceptable and must be replaced. thats fine if youve got the money, but since they've been there 9 years, and are found dead but still in service, I was guessing you havent. Is it April yet? Also they can often be run happily at 24v, if not in all cases. If yours could, it may be that your present cells would do that as is. This is *not* how you run a battery backup system! The idea is to start out with fully charged batteries, so that when the power fails for a long period, the voltage of the batteries may drop to 40V or less as the cells discharge, keeping the PBX online. If you start at anything less, even 36V, you're not going to have any discharge time before the PBX system crashes. It would be essentially worthless. You misunderstood completely, hopelessly, and idiotically. 48v is a I think I'm talking to a tree here. **PLONK** very old standard, and many 48v telecomms systems are now run on 24v. If your equipment were 24v compatible, as some is, you would only need half the number of cells. And if you had no money to replace the battery, odds are you'll have at least 50% of cells still serviceable. Even if its not 24v compatible, you would get better backup performance by removing any dead cells from the chain. Whether you remove them or not you'll run below voltage. What capacity at 48v is it on? The rectifier can put out a hundred amps at 54VDC, to charge the batteries while the PBX is also running. That must be 6 or so kW input. So I would guess that it's 208V at 30A breakers. But with no batteries, the load would be more like 3.6kW. 3.6kW @ 50v = 72A, so if we take an ultra-vague guess at C/10 charging, that gives us 700ah capacity @48v. Ouch. I thought it would be possible to run a power cable underground to the big UPS we have in our computer room. Problem is that the PBX's rectifier takes 30A max at 120VAC, or about 3.6kW. i've no ida how that fits into this The UPS in the computer room is 150kW, easily capable of handling another 6 or so kW. And the distance between is about 1300 feet or about 400m. I would guess that the UPS output should go into a transformer and come out 480VAC, so the cable losses would be minimized. Then another transf on the PBX end to bring it back to 120VAC. But should I expect to have a max loss of 5% at max current, or what? well how much current are you shifting?? And why cant you power your pbx from whatever power source it uses now? You havent given us nearly enough information. The batteries and rectifier are a "UPS" to protect the PBX against failure of the commercial power. That's what it's being fed from. Why dont you find someone else to discuss this with. I think I came up with 4GA cable, but at 480VAC, I'm guessing that it would have to be special insulated underground cable. standard uk T&E should do that, but shuold be insulation tested to the required v first. Costs around £12 a 100m reel, depending on copper size. Assuming that it could be pulled 1300 feet. Probably not without damage. You thread it section by section. Regular access points also allow a section can be replaced if it fails. The T&E also includes a spare conductor for backup. Heavily insulated cable would be needed. Probably double jacketed. T&E is double insulated, high v rated and cheap - thats why i suggested it. Someday I'll have to ask one of the electricians that work on our HV stuff. We have 4160VAC underground around campus but that's all specialized switchgear, etc. rf transmission co-ax is rated pretty high... and its concentric. RF transmission coax is typically copper clad steel wire center conductor, which would have much greater I^2R loss than pure copper cable at 50 or 60Hz. That would be unacceptable. obviously it depends what v and i youre running it at, its very much higher v rated than T&E. T&E's probably far more practical. Thanks, but I've never heard of T&E here in the U.S. I don't know what that acronym stands for. twin and earth, its our standard house wiring cable, 2 cores double insulated plus one single, comes in various copper sizes, is very cheap and can be bought at thousands of outlets... here, anyway. I dont know what export would cost. You would need to get some basic concepts sorted out before youre in a position to imlpement anything. NT |
#46
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Jerry G. wrote:
As long as the maximum current load does not exceed the current rating of any of the cables that are used in the extension, it will be safe. There should not be very much loss over a few hundred feet of extension. If there is a loss, you can then change the extensions for ones that are of a larger gauge. The other issue to beware of is as the length of wire increases, so does it fault loop resistance (i.e. path from line to earth / ground). This will reduce the maximum current that can be passed to earth in the event of a fault, and hence extend the time between the fault occuring and the circuit protective device (fuse, circuit breaker etc) opening to disconnet the power. Obviously if *you* are forming part of this earth fault loop, the sooner the power goes off the better! Out of interest, are US style plugs fitted with fuses? (An extension lead running outside ought to have RCD protection anyway of course, to negate the problem) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#47
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Paul Miller wrote:
The big problem is going to be earth loop impedance, I know it sounds trivial because it will work fine, but you did quote a PSC figure of 120A......must be a TT instalation. Please make sure you have a RCD on this circuit.. If you do the sums for 1mm sq cable that is the PSC you get *without* including the supply impedance - it only gets worse in reality. (not sure what significance the supply being TT would have on PSC mind you) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#48
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Dave Plowman (News) wrote:
Dunno where you'd get 4mm flex, RS for one, see stock no. 250-1410. but you'd never get it to fit a 13 amp plug. 2.5mm is the limit, and not all plugs will have a cord grip suitable. Actually 1.25 mm^2 is the limit - in the sense that it's the largest size that BS 1363 requires a plug to accept. Nevertheless _most_ plugs will accept 1.5 mm^2 without too much difficulty and _some_ will accept 2.5 mm^2. -- Andy |
#49
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In article ,
Andy Wade wrote: Dunno where you'd get 4mm flex, RS for one, see stock no. 250-1410. but you'd never get it to fit a 13 amp plug. 2.5mm is the limit, and not all plugs will have a cord grip suitable. Actually 1.25 mm^2 is the limit - in the sense that it's the largest size that BS 1363 requires a plug to accept. Nevertheless _most_ plugs will accept 1.5 mm^2 without too much difficulty and _some_ will accept 2.5 mm^2. Right. Didn't know chapter and verse. Our location sparks use 2.5mm TRS for most uses - and as many things may have to plug into a house supply at some point, use 13 amp adaptor leads to feed theirs. Think the 13 amp plugs they use are Duraplugs -- *A chicken crossing the road is poultry in motion.* Dave Plowman London SW To e-mail, change noise into sound. |
#50
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"John Rumm" wrote in message ... Jerry G. wrote: As long as the maximum current load does not exceed the current rating of any of the cables that are used in the extension, it will be safe. There should not be very much loss over a few hundred feet of extension. If there is a loss, you can then change the extensions for ones that are of a larger gauge. The other issue to beware of is as the length of wire increases, so does it fault loop resistance (i.e. path from line to earth / ground). This will reduce the maximum current that can be passed to earth in the event of a fault, and hence extend the time between the fault occuring and the circuit protective device (fuse, circuit breaker etc) opening to disconnet the power. Obviously if *you* are forming part of this earth fault loop, the sooner the power goes off the better! Out of interest, are US style plugs fitted with fuses? (An extension lead running outside ought to have RCD protection anyway of course, to negate the problem) I just got thru working with some equipment that we inherited that had the fuse in the plug. In this case, the luser that had replaced the fuse used 32V auto fuses instead of the proper 125V or 250V rating. I'm glad I caught that problem. But fuses in plugs are rare, usually the only thing between the breaker panel and the equipment is the 15A breaker built into the power strip. -- Cheers, John. |
#51
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"Andy Wade" wrote in message ... Dave Plowman (News) wrote: Dunno where you'd get 4mm flex, RS for one, see stock no. 250-1410. but you'd never get it to fit a 13 amp plug. 2.5mm is the limit, and not all plugs will have a cord grip suitable. Actually 1.25 mm^2 is the limit - in the sense that it's the largest size that BS 1363 requires a plug to accept. Nevertheless _most_ plugs will accept 1.5 mm^2 without too much difficulty and _some_ will accept 2.5 mm^2. I don't know about the UK, but in the U.S. most decent plugs come with three large headed screws that have a square washer under them, with one edge of the washer hanging over the edge of the brass pin, so it retains the copper wire. So if you can unscrew the screw 3/16" (5mm) and get the copper strands in there and screw it down, then it would hold almost that big a conductor. Of course getting it all thru the hole in the cord grip is another matter.. -- Andy |
#52
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**PLONK**
good, itll save me the temptation to reply in future |
#53
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On Sun, 13 Feb 2005 17:49:42 UTC, "Watson A.Name - \"Watt Sun, the Dark
Remover\"" wrote: I don't know about the UK, but in the U.S. most decent plugs come with three large headed screws that have a square washer under them, with one edge of the washer hanging over the edge of the brass pin, so it retains the copper wire. So if you can unscrew the screw 3/16" (5mm) and get the copper strands in there and screw it down, then it would hold almost that big a conductor. Of course getting it all thru the hole in the cord grip is another matter.. Some earlier plugs were like that. These days, there is a hole in the end of the pin, and a grubscrew into a threaded hole at right angles that clamps the wire. Remember the wire is thinner over here. And of course, nearly all of our plugs have fuses in them. A 15A breaker is not too good at protecting a 5A flexible cable to an appliance. -- Bob Eager begin a new life...dump Windows! |
#54
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In message , "Watson A.Name - \"Watt
Sun, the Dark Remover\"" writes "raden" wrote in message ... In message , "Watson A.Name - \"Watt Sun, the Dark Remover\"" writes T&E's probably far more practical. Thanks, but I've never heard of T&E here in the U.S. I don't know what that acronym stands for. Twin and earth ... colonials ! Yeah, we call it ground here stateside. And it's Romex. And it's AC line in every schematic I've seen from the American mfgrs the likes of HP, Tek, etc., not "mains". Mains are those wires up on top of the power pole. Separated by a common language, as they say -- geoff |
#55
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John Rumm wrote:
(not sure what significance the supply being TT would have on PSC mind you) A terminogical inexactitude, to a degree. The earthing derangements will make naff-all difference to the PSC for an L-N fault, but will clearly affect the current which'll flow for an L-to-E (or, since the distinction is crucial here, actually an L-to-protective-conductor) fault. It's precisely becuase the impedance of a local earth rod can't be expected to be low enough to get a hefty enough fault current to flow that UK regs [note trimming of followups :-] require a 100mA RCD on all TT installs. As you know anyway ;-) |
#56
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Spehro Pefhany wrote:
SNIP Is that what you'd call a "Strimmer"? Best regards, Spehro Pefhany Yep! |
#57
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John Rumm wrote:
SNIP Out of interest, are US style plugs fitted with fuses? (An extension lead running outside ought to have RCD protection anyway of course, to negate the problem) _FUSE?_ 1/2 of their plugs don't even have an earth!! |
#58
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Andrew Chesters wrote:
_FUSE?_ 1/2 of their plugs don't even have an earth!! Aye - and their stores [sic] will happily sell you an adaptor to let you plug those weird-ass 3pin plugs with that pinko-liberal ground pin into an honest red-blooded real man's 2-pin outlet... |
#59
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"Andrew Chesters" wrote in message ... John Rumm wrote: SNIP Out of interest, are US style plugs fitted with fuses? (An extension lead running outside ought to have RCD protection anyway of course, to negate the problem) _FUSE?_ 1/2 of their plugs don't even have an earth!! Yeah, but everything's gone cordless nowadays, even the weed wackers. So who cares? ;-) I think the appliances that have a plug with only two prongs have to be double insulated, and meet stringent leakage specs. I got one for you. I checked the fuse panel of a really old bldg (well for the U.S., anyway..) - almost 100 yrs - and it had the ground fused(!) Now _that's_weird. |
#60
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On Sun, 13 Feb 2005 12:22:02 -0800, "Watson A.Name - \"Watt Sun, the Dark
Remover\"" wrote: I got one for you. I checked the fuse panel of a really old bldg (well for the U.S., anyway..) - almost 100 yrs - and it had the ground fused(!) Now _that's_weird. Was it 3-wire DC originally?? Peter -- Peter & Rita Forbes Email: Web: http://www.oldengine.org/members/diesel |
#61
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Andrew Chesters wrote:
John Rumm wrote: SNIP Out of interest, are US style plugs fitted with fuses? (An extension lead running outside ought to have RCD protection anyway of course, to negate the problem) _FUSE?_ 1/2 of their plugs don't even have an earth!! The standard 120V receptical has the two parallel blades polarized. The "neutral" blade is wider than the "hot one", so even a proper two-blade plug gives some protection to exposed components, like the shell on thraded lamps. However there are still many table lamps with equal size blades which can be inserted either way. Many small appliances and tools are "double insulated", and these do not require a ground, (earth), wire plug. Years ago, as a broacast radio engineer, I had to set up remote locations. If the "hum level" was too high the standard proceedure was to reverse the plug on the amplifer. Almost all the new equpment has three-prong grounded plugs. -- Virg Wall, P.E. |
#62
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VWWall wrote:
Andrew Chesters wrote: John Rumm wrote: SNIP Out of interest, are US style plugs fitted with fuses? (An extension lead running outside ought to have RCD protection anyway of course, to negate the problem) _FUSE?_ 1/2 of their plugs don't even have an earth!! The standard 120V receptical has the two parallel blades polarized. The "neutral" blade is wider than the "hot one", so even a proper two-blade plug gives some protection to exposed components, like the shell on thraded lamps. However there are still many table lamps with equal size blades which can be inserted either way. Many small appliances and tools are "double insulated", and these do not require a ground, (earth), wire plug. Years ago, as a broacast radio engineer, I had to set up remote locations. If the "hum level" was too high the standard proceedure was to reverse the plug on the amplifer. Almost all the new equpment has three-prong grounded plugs. I have to concede that my knowlege of colonial wiring pracice is somewhat out of date. My family was part of the UK "Brain Drain", a period of history where engineers (my father, not me) from here got _1st class_ berths on liners taking them to the new world! |
#63
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John Rumm wrote:
Jerry G. wrote: As long as the maximum current load does not exceed the current rating of any of the cables that are used in the extension, it will be safe. There should not be very much loss over a few hundred feet of extension. If there is a loss, you can then change the extensions for ones that are of a larger gauge. The other issue to beware of is as the length of wire increases, so does it fault loop resistance (i.e. path from line to earth / ground). This will reduce the maximum current that can be passed to earth in the event of a fault, and hence extend the time between the fault occuring and the circuit protective device (fuse, circuit breaker etc) opening to disconnet the power. Obviously if *you* are forming part of this earth fault loop, the sooner the power goes off the better! I doubt that a *you* of any value would survive if it were to pass the fusing current of the plug-top fuse! -- Graham W http://www.gcw.org.uk/ PGM-FI page updated, Graphics Tutorial WIMBORNE http://www.wessex-astro-society.freeserve.co.uk/ Wessex Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps Change 'news' to 'sewn' in my Reply address to avoid my spam filter. |
#64
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Stefek Zaba wrote:
(not sure what significance the supply being TT would have on PSC mind you) A terminogical inexactitude, to a degree. The earthing derangements will make naff-all difference to the PSC for an L-N fault, but will clearly affect the current which'll flow for an L-to-E (or, since the distinction is crucial here, actually an L-to-protective-conductor) I guess I was kind of hinting (gently) that the term PSC implies a L-N short, rather than L-E. Hence the fact that it is TT (from an earthing arrangement point of view) will make no difference, although to be fair the likelihood of a TT setup being out "in the sticks" a long way from a substation is greater, and hence _may_ have a higher supply impedance as well. fault. It's precisely becuase the impedance of a local earth rod can't be expected to be low enough to get a hefty enough fault current to flow that UK regs [note trimming of followups :-] require a 100mA RCD on all TT installs. As you know anyway ;-) ;-) (yes painfully... having just spent a fortune on a big pile of CUs and RCDs ready for the great CU replacement party....) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#65
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Graham W wrote:
disconnet the power. Obviously if *you* are forming part of this earth fault loop, the sooner the power goes off the better! I doubt that a *you* of any value would survive if it were to pass the fusing current of the plug-top fuse! Depends on if you are in serise or parallel with it! -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#66
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Jerry G. wrote:
As long as the maximum current load does not exceed the current rating of any of the cables that are used in the extension, it will be safe. There should not be very much loss over a few hundred feet of extension. If there is a loss, you can then change the extensions for ones that are of a larger gauge. I have run extensions of up to 400 feet. These were 10 Amp rated. I had no performance loss in the loads that I was using. The load was about 4 to 5 amps. I am working with 120 VAC at my location. I took a voltage reading, at the outlet, and one across the load. There was a drop of about one or two volts. A ~ 2 volt drop at 4 amps means ~ 1/2 ohms. You had 800 feet of wire - 400 out and 400 back. That means your extension cord wire had to be rated at (1000/800) * 1/2 = .625 ohms per 1000 feet. Your extension cords had to be made from #6 or #8, given those numbers. That is highly unlikely. A typical heavy duty extension cord 100 feet long would most likely use #14 wire. #14 wire is rated at 3.1 ohms per 1000 feet. At 800 feet, if the 4 amp load was running, there would be a drop of about 9.9 volts. If #12 wire (rated at 2 ohms per 1000 feet) were used in the cords, the drop would be about 6.4 volts. The ohms per 1000 feet numbers come from table 9 in the National Electrical Code. There has to be an error in this, somewhere. Ed But, the total voltage at the extension output was still in specs while under the load. The source voltage at the outlet was about 118 VAC. Across the load, if I remember correctly, it was about approximately 116 VAC. In areas that are using 220 VAC, the current is about 1/2 for the same wattage, as when compared to 120 VAC. This would lead to less loss when using an extension cord. Most devices here in North America are rated at 105 to 125 VAC. Some are rated from about 105 to 135 VAC. |
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Jerry G. wrote:
As long as the maximum current load does not exceed the current rating of any of the cables that are used in the extension, it will be safe. There should not be very much loss over a few hundred feet of extension. If there is a loss, you can then change the extensions for ones that are of a larger gauge. On 13 Feb 2005, John Rumm wrote: The other issue to beware of is as the length of wire increases, so does it fault loop resistance (i.e. path from line to earth / ground). This will reduce the maximum current that can be passed to earth in the event of a fault, and hence extend the time between the fault occuring and the circuit protective device (fuse, circuit breaker etc) opening to disconnet the power. Obviously if *you* are forming part of this earth fault loop, the sooner the power goes off the better! Out of interest, are US style plugs fitted with fuses? (An extension lead running outside ought to have RCD protection anyway of course, to negate the problem) I am the original poster with two 30m extension cables. You refer to RCD protection. I have got a plug-in RCD device but I know nothing about earth fault loops. It is similar to the one in this illustration. http://www.argos.co.uk/wcsstore/argo...IFN104773M.JPG Where should my RCD device be plugged in to best avoid the problem of earth fault loops: (1) At the mains supply end where the first extension goes into the mains socket. (2) In the middle of the two 30m extensions. (3) At the far end of the two extensions where the appliciance I am using is plugged in? |
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In uk.d-i-y Sammo wrote:
On 12 Feb 2005, Andrew Chesters wrote: Others have discussed the current & voltage side of your post. However, something else to concider is where you are doing this. At 30-60m my guess is that you would be outdoors? If so, you should be using an earth leakage circuit breaker (RCD)to supply your extensions. This could be installed in your CU, built in to the supply socket or a plugtop type. CU? Consumer Unit. The box where the electricity comes into the house, which contains RCD/breakers/fuses for the individual circuits. |
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Sammo wrote:
On 12 Feb 2005, Andrew Chesters wrote: Others have discussed the current & voltage side of your post. However, something else to concider is where you are doing this. At 30-60m my guess is that you would be outdoors? If so, you should be using an earth leakage circuit breaker (RCD)to supply your extensions. This could be installed in your CU, built in to the supply socket or a plugtop type. CU? = Consumer unit. The RCD should protect the whole of the "outdoor" section. Earth Loop Fault Current = the current that would flow in the event of a live to earth fault. This current is calculated from the earth loop impedance (measured or calculated) including suppliers cable. This value is then compared with standard graphs for various protective devices (fuse, circuit breakers) to ascertain the disconnect time. If this does not meet the requirements, additional methods of protection are required. This could be changing to a faster breaker, and/or adding earth leakage protection. |
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Darcy B wrote:
What is earth fault loop impedance? It is the sum total of the resistances af all the wiring in the path to earth or ground. It is significant because should a major fault occur (like a wire falls inside an appliance and shorts to the casework, or you cut through an extension lead), the earth fault loop impedance will place a limit on the maximum current that can flow to earth. Ideally this fault current wants to be large, so that it causes the protective device (fuse / breaker) to open quickly. We have regulations in the UK that require a circuit with socket outlets to disconnect in under 0.4 secs in these situations. The fault loop impedance is also dictated by the impedance of the earth provided at the supply where it comes into the house. In the UK there are three common ways the power company can provide the supply - with two of them (known as TN-C and TN-C-S (aka PME)) the supplier provides a good earth (i.e. typically well under 1 ohm) which when used with suitable fusing and circuit breakers should result in good disconnection times in most cases. However if you add long circuits with undersized earth conductors (i.e. big extension lead for example!), then the impedance creeps up and lowers the fault current that could lead to much greater electrocution risk. The third type of supply common over here does not supply an earth at all (this is typical for power fed via overhead wires - typically into rural locations), and relies on a local earth rod that is staked into the ground. These tend to give much higher resistance earths and hence you can no longer rely on them to allow enough fault current to flow, so the whole installation must be protected by additional Residual Current Device circuit breakers (RCDs) to detect any leakage from the circuit and cut off the power that way. (RCDs are also mandatory here for all socket circuits that may potentialy feed portable equipment that could be used outside). There is some more info he http://www.tlc-direct.co.uk/Book/5.1.1.htm -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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Sammo wrote:
I am the original poster with two 30m extension cables. You refer to RCD protection. I have got a plug-in RCD device but I know nothing about earth fault loops. It is similar to the one in this illustration. http://www.argos.co.uk/wcsstore/argo...IFN104773M.JPG See my reply elsewhere in this thread for a fuller description of earth fault loop impedance. Also see here for more background: http://www.tlc-direct.co.uk/Book/5.1.1.htm Where should my RCD device be plugged in to best avoid the problem of earth fault loops: (1) At the mains supply end where the first extension goes into the mains socket. Yes (2) In the middle of the two 30m extensions. No - but better than 3 (3) At the far end of the two extensions where the appliciance I am using is plugged in? no - but better than not at all! Having the RCD at the start of the cable will mean the whole cable is protected by it. So should you accidentally do the "hedge trimmer through the extension lead" exercise, the RCD hopefully will cut off power to the lead, rather than leaving live exposed conductors flopping about in the wet grass under your ladder! -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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cable is not that expensive, it's copper after all.I can see in an invoice
that I paid 28 cents a meter for a 3G1.5 mm^2 A05VV-U cable.A 2.5 mm^2 conductor, single core, which we generally use to connect washing machines, costs 9 cents a meter .Or 6 mm^2, for ranges, 22 cents a meter.Why don't you ask an electrician to construct you an extra heavy duty extension cable, with industrial-grade plugs?I did in college, when doing my Practicum, for a high-temperature oven, three-phase, 25A, which plug tended to overheat.Cost was negligent. -- Tzortzakakis Dimitri?s major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr ? "Peter A Forbes" ?????? ??? ?????? ... On Sat, 12 Feb 2005 10:51:00 -0800, "Watson A.Name - \"Watt Sun, the Dark Remover\"" wrote: "Bob Eager" wrote in message ... On Sat, 12 Feb 2005 12:46:19 UTC, Ian Stirling wrote: Or for 60m, 8.4*10^-1 ohms, or .84 ohms. Plus the resistance on the two connections. Not sure whether the earth fault loop impedance is still OK... Yeah, true. You 220VAC and 240VAC guys think you got it bad, we have four times as much of a problem here in 120VAC land. ;-) Those poor souls that put a hundred feet or so of 18GA (about 1mm sq) extension cord on their weed wackers soon find that not only does it run slow, but the motor overheats. So we have extension cords that are 16 or 14 gauge, and can handle the extra current. But people are too cheap to pay double for the heavy duty extension cord, so they end up eating their money up in burned out motors. And then when they get tired of doing that, they go out and buy a weed wacker with the gas engine. This is on the end of a long pole, so the engine is right up next to their face, so they go deaf from all the engine noise. And they put the weed wacker in the garage, where the gas from the tank runs out and catches on fire! -- Bob Eager Why use anything as small as 1mm sq cable??? For 30metres I'd want to see 2.5mm sq at least, if not 4mm sq. If not for the volt drop or lack of, for the mechanical strength and resistance to damage. Peter -- Peter & Rita Forbes Email: Web: http://www.oldengine.org/members/diesel |
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Sammo wrote:
Jerry G. wrote: As long as the maximum current load does not exceed the current rating of any of the cables that are used in the extension, it will be safe. There should not be very much loss over a few hundred feet of extension. If there is a loss, you can then change the extensions for ones that are of a larger gauge. On 13 Feb 2005, John Rumm wrote: The other issue to beware of is as the length of wire increases, so does it fault loop resistance (i.e. path from line to earth / ground). This will reduce the maximum current that can be passed to earth in the event of a fault, and hence extend the time between the fault occuring and the circuit protective device (fuse, circuit breaker etc) opening to disconnet the power. Obviously if *you* are forming part of this earth fault loop, the sooner the power goes off the better! Out of interest, are US style plugs fitted with fuses? (An extension lead running outside ought to have RCD protection anyway of course, to negate the problem) I am the original poster with two 30m extension cables. You refer to RCD protection. I have got a plug-in RCD device but I know nothing about earth fault loops. It is similar to the one in this illustration. http://www.argos.co.uk/wcsstore/argo...IFN104773M.JPG Where should my RCD device be plugged in to best avoid the problem of earth fault loops: (1) At the mains supply end where the first extension goes into the mains socket. (2) In the middle of the two 30m extensions. (3) At the far end of the two extensions where the appliciance I am using is plugged in? You can draw the same current through any length of wire, asd long as it isn't coiled up, because the heat per unit length does not vary with the length, and that is what causes temp rise. Which is why cable is rated in amps, not watts. Nor yet amp-meters. The v drop on even quite extended lengths of extsnion cable is not likely to be an issue. |
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"John Rumm" wrote
| Depends on if you are in serise or parallel with it! I *still* get confused with blue being live because it's a 'brighter' colour than brown in cables; WTF did cerise come into it? Will Channel 5 be giving us Colin & Justin's How Not To Write Wiring Regulations in the near future... Owain (This posting may contain UK-specific cultural references.) |
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"Sammo" wrote
| However, if the cable has resistence then presumably current capacity | (ignoring voltage) gets reduced. I am thinking of W = I^2 * R. No, because that resistance - and hence the heating effect - is spread along the length of the cable. If 1m of cable is rated for 10A then 100m of cable will also be rated for 10A. You will probably need a thicker cable to reduce the voltage drop, but that is not the same as the current-carrying capacity of the cable. | I have got a plug-in RCD device but I know nothing about earth fault | loops. It is similar to the one in this illustration. | http://www.argos.co.uk/wcsstore/argo...IFN104773M.JPG | Where should my RCD device be plugged in to best avoid the problem of | earth fault loops: | (1) At the mains supply end where the first extension goes into the | mains socket. Here, because the RCD protection must be applied to the whole extension flex, because it is in effect a portable appliance. | (2) In the middle of the two 30m extensions. No, because that would leave the first flex (or more specifically - someone handling it) unprotected. | (3) At the far end of the two extensions where the appliciance I am | using is plugged in? No, same reason. If you were wiring a *permanent circuit* then RCD protection could usually be applied at the load end, because fixed wiring does not need such a high standard of protection. Note, however, that using an RCD plug on only one extension lead raises the possibility that someone might plug the extension leads togther the wrong way round, with the result that the first flex would be unprotected. The way round this is to have an RCD plug on both leads -- this will do no harm, but either or both may trip in the event of a fault -- or use an RCD socket. The point remains -- why are you contemplating using 60m extension cables? Owain |
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"Dimitrios Tzortzakakis" wrote in message ... cable is not that expensive, it's copper after all.I can see in an invoice that I paid 28 cents a meter for a 3G1.5 mm^2 A05VV-U cable.A 2.5 mm^2 conductor, single core, which we generally use to connect washing machines, costs 9 cents a meter .Or 6 mm^2, for ranges, 22 cents a meter.Why don't you ask an electrician to construct you an extra heavy duty extension cable, with industrial-grade plugs?I did in college, when doing my Practicum, for a high-temperature oven, three-phase, 25A, which plug tended to overheat.Cost was negligent. Negligent! Hah-hah-hah-hah! -- Tzortzakakis Dimitri?s major in electrical engineering, freelance electrician |
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On 14 Feb 2005, Owain wrote:
| (1) At the mains supply end where the first extension goes into | the mains socket. Here, because the RCD protection must be applied to the whole extension flex, because it is in effect a portable appliance. | (2) In the middle of the two 30m extensions. No, because that would leave the first flex (or more specifically - someone handling it) unprotected. | (3) At the far end of the two extensions where the appliciance | I am using is plugged in? No, same reason. If you were wiring a *permanent circuit* then RCD protection could usually be applied at the load end, because fixed wiring does not need such a high standard of protection. Note, however, that using an RCD plug on only one extension lead raises the possibility that someone might plug the extension leads togther the wrong way round, with the result that the first flex would be unprotected. The way round this is to have an RCD plug on both leads -- this will do no harm, but either or both may trip in the event of a fault -- or use an RCD socket. The point remains -- why are you contemplating using 60m extension cables? I live in a flat and my car is kept in a garage in a block which is in the yard. The garages do not have power and sometimes I might need to use a power drill, electric light, soldering iron, charge a run-down battery, etc. This is the layout: I'm on the third storey and my cable flex would be slung along the building for about 30 metres and be supported once where it goes out of my flat and supported again (at about the same height) where it leaves the building 30m later. The next 15 metres of cable would be a sort of descent to my garage roof. The last 5 metres or so takes the power to where I want it. (I am using 30m + 30m because those are the lengths on my two extension reels). In this scenario, I don't really need to protect the cable from accidental cutting or damage anywhere along its length as it runs along the building or in the air away from any likely harm. For my *own* protection as a user of an applicance at the far end of the cable it seems that it might be better to put an RCD close to whatever appliance I am using. Is this correct? OTOH maybe a domestic RCD is so sensitive that it is likely to work perfectly well at the mains end even when I am chiefly looking to protect me at the far end? |
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Sammo wrote:
On 14 Feb 2005, Owain wrote: | (1) At the mains supply end where the first extension goes into | the mains socket. Here, because the RCD protection must be applied to the whole extension flex, because it is in effect a portable appliance. | (2) In the middle of the two 30m extensions. No, because that would leave the first flex (or more specifically - someone handling it) unprotected. | (3) At the far end of the two extensions where the appliciance | I am using is plugged in? No, same reason. If you were wiring a *permanent circuit* then RCD protection could usually be applied at the load end, because fixed wiring does not need such a high standard of protection. Note, however, that using an RCD plug on only one extension lead raises the possibility that someone might plug the extension leads togther the wrong way round, with the result that the first flex would be unprotected. The way round this is to have an RCD plug on both leads -- this will do no harm, but either or both may trip in the event of a fault -- or use an RCD socket. The point remains -- why are you contemplating using 60m extension cables? I live in a flat and my car is kept in a garage in a block which is in the yard. The garages do not have power and sometimes I might need to use a power drill, electric light, soldering iron, charge a run-down battery, etc. This is the layout: I'm on the third storey and my cable flex would be slung along the building for about 30 metres and be supported once where it goes out of my flat and supported again (at about the same height) where it leaves the building 30m later. The next 15 metres of cable would be a sort of descent to my garage roof. The last 5 metres or so takes the power to where I want it. (I am using 30m + 30m because those are the lengths on my two extension reels). In this scenario, I don't really need to protect the cable from accidental cutting or damage anywhere along its length as it runs along the building or in the air away from any likely harm. For my *own* protection as a user of an applicance at the far end of the cable it seems that it might be better to put an RCD close to whatever appliance I am using. Is this correct? OTOH maybe a domestic RCD is so sensitive that it is likely to work perfectly well at the mains end even when I am chiefly looking to protect me at the far end? Basically, the gizmo senses when the current being shoved up the live wire is greater than what comes back down the neutral wire. If it is greater, then the difference, instead of coming back down the wire, is going somewhere else - like through /you/. If it finds a difference it cuts off the power, very quickly. So its sensitivitity will be the same no matter where you put it - as the same current should be going up the live and back the neutral - where ever you measure it. Putting it in the wall socket ensures that the insulation of the whole length of leads as well as the load is being monitored. which give the most protection. Plugging it in after the leads means that the unit doesn't monitor for faults in the leads themselves, only in the load. The only thing you gain from plugging it in at the load end is if you have a piece of hardware that is prone to tripping rcds on switch-on. Having it near the load makes it easier to reset the thing if it trips and saves the hike back upstairs. But you would only plug it in there for that sort of reason. Always use the test button each time you set this up. They are remarkably sensitive devices that have to sense a difference of a few hundredth's of an ampere in a load of many amperes. For the cost, as I think another op may have said, why not fit two - one at each end? Particularly if you are lying on fairly damp ground under a car, clutching a mains lamp in your hand.. I have a main one protecting the sockets for the whole house (excepting a ring main that only feeds my fridges and freezers - where each socket has an rcd), but still use an additional plug-in one when doing anything that makes me nervous. -- Sue |
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"Sammo" wrote
| The point remains -- why are you contemplating using 60m | extension cables? | I live in a flat and my car is kept in a garage in a block which is | in the yard. The garages do not have power and sometimes I might | need to use a power drill, electric light, soldering iron, charge a | run-down battery, etc. [f/u set to uk.d-i-y as getting off-topic for other groups and definately on-topic for this group; subject line changed] Ah-ha! "How do I get electricity to my garage" is the real question you should have asked. This has been discussed before -- google for threads about garages without mains power. Suggestions usually include a battery (recharged in the house, possibly on a trolley for portability) with an inverter, or a small generator. Photovoltaic (solar) panels are sometimes viable for keeping a car battery topped up. Especially as you have a 'block' of garages, it might be financially viable to have a new public supply laid on to the block, as the cost can be divided between all the garages, if other owners agree. Power to a garage is useful, especially if remote from the house, and the cost of the supply would probably be recouped in sale value. That might not be the case for a new supply for one garage. A proper fixed supply will also allow garages to be fitted with mains-powered alarms, which might help persuade your neighbours to agree with the scheme. | This is the layout: | I'm on the third storey and my cable flex would be slung along the | building for about 30 metres and be supported once where it goes | out of my flat and supported again (at about the same height) where | it leaves the building 30m later. PLEASE STOP RIGHT NOW. What you are proposing is wholly unacceptable. Ordinary flex and cable is not designed for being self-supporting over this distance. The flex will be under considerable mechanical strain at the supports. Have you considered what happens when 30m of cable comes loose and whips through the air? Extension lead flex is also not designed for permanent exterior installation and is not completely waterproof or resistant to abrasion and uv light. What you are proposing doing is fixed wiring and should be done according to the regs for a permanent installation -- designed, installed, and inspected and tested in full compliance with the IEE Wiring Regulations. As I surmise you will also be running this supply across other people's property -- even if only the freeholder's -- you will need legal permission from them to do this. | The next 15 metres of cable would be a sort of descent to my garage | roof. There are strict regulations over the height of suspended cables -- they have recently been increased following, I think, the death of a BT engineer. | The last 5 metres or so takes the power to where I want it. | (I am using 30m + 30m because those are the lengths on my | two extension reels). And you are going to waterproof the connection between the two extension reels how? | In this scenario, I don't really need to protect the cable from | accidental cutting or damage anywhere along its length as it runs | along the building or in the air away from any likely harm. On a domestic installation "protection by placing out of reach" is not allowed as a means of protecting either cables or humans. There are serious public liability issues with what you are proposing. If anyone is hurt or killed -- even as a result of their own actions eg vandalising the flex -- you will have to justify your actions in a coroner's court, and possibly face a charge of manslaughter. | For my *own* protection as a user of an applicance at the far end of | the cable it seems that it might be better to put an RCD close to | whatever appliance I am using. Is this correct? | OTOH maybe a domestic RCD is so sensitive that it is likely to work | perfectly well at the mains end even when I am chiefly looking to | protect me at the far end? I'm not going to say *anything* which could possibly encourage you to consider what you are proposing any further. It frightens me :-) Owain |
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Sammo wrote:
On 15 Feb 2005, Owain wrote: "Sammo" wrote | The point remains -- why are you contemplating using 60m | extension cables? | I live in a flat and my car is kept in a garage in a block | which is in the yard. The garages do not have power and | sometimes I might need to use a power drill, electric light, | soldering iron, charge a run-down battery, etc. [f/u set to uk.d-i-y as getting off-topic for other groups and definately on-topic for this group; subject line changed] Ah-ha! "How do I get electricity to my garage" is the real question you should have asked. Yes I want power in my garage but only on a temporary basis such as those occassions when I ned to charge my car battery or use power tools, etc as I described. This has been discussed before -- google for threads about garages without mains power. Suggestions usually include a battery (recharged in the house, possibly on a trolley for portability) with an inverter, or a small generator. Photovoltaic (solar) panels are sometimes viable for keeping a car battery topped up. Especially as you have a 'block' of garages, it might be financially viable to have a new public supply laid on to the block, as the cost can be divided between all the garages, if other owners agree. Power to a garage is useful, especially if remote from the house, and the cost of the supply would probably be recouped in sale value. That might not be the case for a new supply for one garage. A proper fixed supply will also allow garages to be fitted with mains-powered alarms, which might help persuade your neighbours to agree with the scheme. You talk a lot of sense but my neighbours do not. They are not DIY or car enthusiasts and have no ineterst in laying on power to the garage block. :-( | This is the layout: | I'm on the third storey and my cable flex would be slung along | the building for about 30 metres and be supported once where it | goes out of my flat and supported again (at about the same | height) where it leaves the building 30m later. PLEASE STOP RIGHT NOW. What you are proposing is wholly unacceptable. Ordinary flex and cable is not designed for being self-supporting over this distance. The flex will be under considerable mechanical strain at the supports. Have you considered what happens when 30m of cable comes loose and whips through the air? Extension lead flex is also not designed for permanent exterior installation and is not completely waterproof or resistant to abrasion and uv light. What you are proposing doing is fixed wiring and should be done according to the regs for a permanent installation -- designed, installed, and inspected and tested in full compliance with the IEE Wiring Regulations. I was thinking of this arrangement purely on a temporary basis. So far I have laid the wire on the ground but as it can get damp and/or dirty then I figured it might be better to suspend it in the air. Furthermore other might trip on it (even though it is a red colour) and it seesm better not to inconvenience them. As I surmise you will also be running this supply across other people's property -- even if only the freeholder's -- you will need legal permission from them to do this. This is unlikely to be an issue as we have a 999 year lease and the freeholder is an overseas trust fund. This means that we maintain the flats through our own management company and it holds a lease for the common parts. | The next 15 metres of cable would be a sort of descent to my | garage roof. There are strict regulations over the height of suspended cables -- they have recently been increased following, I think, the death of a BT engineer. | The last 5 metres or so takes the power to where I want it. | (I am using 30m + 30m because those are the lengths on my | two extension reels). And you are going to waterproof the connection between the two extension reels how? No need as I will be using the two extensions in much the same way as someone might use them for powering a mains hedge trimmer. | In this scenario, I don't really need to protect the cable from | accidental cutting or damage anywhere along its length as it | runs along the building or in the air away from any likely | harm. On a domestic installation "protection by placing out of reach" is not allowed as a means of protecting either cables or humans. There are serious public liability issues with what you are proposing. If anyone is hurt or killed -- even as a result of their own actions eg vandalising the flex -- you will have to justify your actions in a coroner's court, and possibly face a charge of manslaughter. | For my *own* protection as a user of an applicance at the far | end of the cable it seems that it might be better to put an RCD | close to whatever appliance I am using. Is this correct? | OTOH maybe a domestic RCD is so sensitive that it is likely to | work perfectly well at the mains end even when I am chiefly | looking to protect me at the far end? I'm not going to say *anything* which could possibly encourage you to consider what you are proposing any further. It frightens me :-) Heh! :-) I must admit to doing much the same when I was living in a London flat - for very similar sorts of reasons and only to rig up and put away each time I used it. It obviously depends on your physical arrangements as to whether it is totally reckless or not quite totally so. What I did, however, was to take some polypropylene cord and tied figure of eight knots on the bight every foot or so, with the loop big enough to pass the plug through. You have guessed the rest - one end of the cord was tied to the window frame and the other to the garage and the power cable just ran down through the loops. That way, the weight of the cable was taken by loops in the tensioned cord - particularly important at the ends, where otherwise the cable would have had to be tied around something. Where I had to do a change in direction to avoid the cable rubbing against anything, I just took a piece of cord from the main cord and tied it off, to a tree branch, IIRC - and then tensioned the cords to get the run I wanted.. I don't know your layout and can only advise that doing things like this is inherently high risk - but, if you are going to do it anyway, this might help reduce that risk a little. If it goes wrong, as you have been clearly told - you will be wishing that you just bought an inverter or a small genny (IIRC, B&Q do a perfectly good one for under 100GBP) - I have one and it has paid for itself time and time again. They weren't available at anything like that price when I played silly games with cables. If you do think about leaving the cord(s) (but not the cable) in place - with a pull through extra cord so that you can pull the cable down as and when you need it, be aware that man-made cords can be very affected by sunlight, by relatively modest sudden shock loads, by abrasion, by pressure at points of sharp change in direction, by the knots and by a whole lot more. So you need to select the cord carefully with a very high factor of safety and inspect it often. Also note that birds will sit on it and do what birds do to whatever is underneath - so routing it over a neighbour's patio is not a good idea - unless you live in London*. -- Sue * Where few flat-dwellers even know the names of their neighbours and then only because of arguments about noise, parking spaces, children, curtains, etc - you might as well add the birds' efforts... |
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