51m0n Posted July 10, 2012 Share Posted July 10, 2012 Always always always test each socket and use an RCD. One of the 3 LED testers. Mine goes beeeeeeeeppppp when it all good, so you wouldnt want to leave it plugged in! Got looked at strangely a few times (esp by guiatrists) and have found issues on a handful of sockets in the last two or three years in pubs of varying states of decrepitude. When it finds a fault jsut before someone plugs their kit in that shuts them the f*** up sharpish! Quote Link to comment Share on other sites More sharing options...
xilddx Posted July 10, 2012 Share Posted July 10, 2012 [quote name='bremen' timestamp='1341932185' post='1726420'] If a fault in the amp made the case live, the current would flow through the earth wire and blow a fuse. If said earth wire was missing, it would attempt to flow through an alternative path, usually the drummer's dick...in which case the RCD would detect the difference between current flowing into Live and out of Neutral and switch the amp off. So the drummer's dick would only be excited for a few milliseconds and be perfectly fine for its usual aprés-gig entertainment. [/quote] Thank you Quote Link to comment Share on other sites More sharing options...
daz Posted July 10, 2012 Share Posted July 10, 2012 RCD's are essential these days, we always use one on the lawnmower and i have one in the mains for my amp n stuff. Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted July 10, 2012 Share Posted July 10, 2012 If you put a cheap one without the beeper Nigel it would work perfectly, Its a shame they dont make one that beeps if a fault occurs instead of the all clear, (Its like that for when we are testing on our own especially when trying to find an unlabelled circuit, saves a lot of walking!) with the sorts of leads we use you never know where a bad connection could be, I guess we would look a bunch of dicks If we tested every socket in every pub for 10 years with one only to find the multi gang lead in our rack cases had no earth all along! Quote Link to comment Share on other sites More sharing options...
bremen Posted July 10, 2012 Share Posted July 10, 2012 [quote name='stingrayPete1977' timestamp='1341935948' post='1726520'] I guess we would look a bunch of dicks If we tested every socket in every pub for 10 years with one only to find the multi gang lead in our rack cases had no earth all along! [/quote] Quite...I once rented a PA that worked fine but had a bit of a residual hum. Turned out the earth and neutral had been reversed in one of the supplied plugblocks, so all the current was flowing through earth. This proved that the venue either had no RCD or it wasn't working. Had the plug on this pugblock then been plugged into a socket with a faulty earth, anything else plugged into that socket would have a low impedance (high current capacity) 240V applied to its chassis and all its audio connectors. And the drummer would have a *very* sore dick. Quote Link to comment Share on other sites More sharing options...
Dood Posted July 10, 2012 Share Posted July 10, 2012 [quote name='bremen' timestamp='1341930803' post='1726390'] I don't understand the reference to the transformer...? [/quote] I wasn't referring to the transformer having a fault, but as you know a transformer will have an impedance (or DC resistance when read with a multimeter) I simply wanted to know if the tester unit was meant to be used without anything plugged in to get a proper result or if the loading of the mains transformer on the circuit (if the amp is switched on of course) would interact with the tester? I mean, for example, you wouldn't try to measure the impedance of a speaker whilst it is connected to another speaker cabinet as the reading would not be true. I wanted to know if the tester simply measured open/short circuits or if it relied on resistance too. If it did, would loading on a mains socket cause the threshold for those readings (and alarm) to change. Make sense? Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted July 10, 2012 Share Posted July 10, 2012 I did a rewire a while ago and the guy had fitted his own extra socket in the garage for the chest freezer, usual novice mistake of cutting the wires too short to reach, although they did reach with the L and N reversed so he did that then swapped them round in the plugtop for the freezer, Genius Quote Link to comment Share on other sites More sharing options...
flyfisher Posted July 10, 2012 Share Posted July 10, 2012 [quote name='silddx' timestamp='1341930382' post='1726384'] There are different types of RCD. Some fitted to the supply, some are plug adapters you plug your kit into, after plugging the adapter into the wall supply which protect you from your own gear, or prtect the gear itself. They won't stop you getting a shock but they minimise the effects of the shock.[b] They are not a substitute for correct fuses.[/b] [/quote] Fuses really only protect the wiring. They limit the maximum current and thus prevent overheating and, possibly, a fire. An incorrect fuse might be dangerous as far as the building safety is concerned, but I'd suggest it makes little difference to any shock hazard. An RCD (as most will know, but maybe not all) works by detecting an imbalance between the current flowing in the Live and Neutral conductors. In proper operation, all the current flowing down the live conduction will return via the neutral conductor (OK, not quite accurate with AC, but a good enough analogy for this discussion). Thus, if the neutral current does not equal the live current it means that some current is going somewhere else. Usually it will be "leaking" to earth somewhere because of a fault of some description. That fault might be your finger on the live conductor, or your lips on a microphone. Either way, it shouldn't be happening and the RCD will detect the problem and trip. An RCD might not prevent you getting a shock in the technical sense (because it cannot trip until there is a fault current) but it will trip so quickly and at such a low current (usually below 30mA) that you're unlikely to feel anything and even if you do it will be be well below the fatal curve of time/current for the vast majority of people. The bottom line is that I don't really care if the pub I'm playing in has the correct fuses or not, I'm still going to use an RCD to protect me from a shock - whether the fuseboard has the correct fuse or a nut&bolt in the consumer unit! Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted July 10, 2012 Share Posted July 10, 2012 [quote name='dood' timestamp='1341937120' post='1726552'] I wasn't referring to the transformer having a fault, but as you know a transformer will have an impedance (or DC resistance when read with a multimeter) I simply wanted to know if the tester unit was meant to be used without anything plugged in to get a proper result or if the loading of the mains transformer on the circuit (if the amp is switched on of course) would interact with the tester? I mean, for example, you wouldn't try to measure the impedance of a speaker whilst it is connected to another speaker cabinet as the reading would not be true. I wanted to know if the tester simply measured open/short circuits or if it relied on resistance too. If it did, would loading on a mains socket cause the threshold for those readings (and alarm) to change. Make sense? [/quote] If its all OK it would read OK, if not then it would be prudent to start at the beggining and work your way back with everything else unplugged, 99% of the time it would be the wall socket or the extension reel feeding the stage area at fault. With other faulty gear plugged in you might get all sorts of variable readings, If the earth light only comes on bright when the drummers dick touches anything connected to it then its probably a bad earth coming good via his penis As much as we poke fun at drummers they can be hard to find. Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted July 10, 2012 Share Posted July 10, 2012 (edited) I know what your saying Flyfisher but fuses are still the basis for Automatic Disconection of Supply that essentially the entire regs book is based on, all the calculations are based upon the [u]fuse[/u] values, The probelm is in most cases those values are hard to meet especially once your on the end of 3 50M ext reels! If we could be certain that the values were being met fuses would be OK as we cant RCD is the best bet in most cases. ie a socket circuit in a pub correctly wired on a 32A fuse or circuit breaker with a good earth loop test result will still blow in 0.4 of a second in the event of a short circuit, its not practicle or possible to know this and does not allow for faults occuring to the cables at a later date so only an RCD will do really. Edited July 10, 2012 by stingrayPete1977 Quote Link to comment Share on other sites More sharing options...
oggiesnr Posted July 10, 2012 Share Posted July 10, 2012 Once roadied at a venue where the three phase had kept blowing so the fuses had been replaced with sections of nails. The lighting guy was up a ladder focussing a genie when it went pear shaped and he got blown twety foot back to earth! Steve Quote Link to comment Share on other sites More sharing options...
bassace Posted July 10, 2012 Share Posted July 10, 2012 Ah, The Man Who Failed to Earth. Quote Link to comment Share on other sites More sharing options...
Oopsdabassist Posted July 10, 2012 Share Posted July 10, 2012 Nice call, will be investing in one I think, checked RS, Cat No changed. http://uk.rs-online.com/web/cpd/0203748/?searchTerm=203-748 for any who are interested. Quote Link to comment Share on other sites More sharing options...
lurksalot Posted July 10, 2012 Share Posted July 10, 2012 Our guitarist makes and tinkers with his own amps and ALWAYS uses an RCD . Mainly because me made him as he blew the main RCD at the community centre reheasal room one night , and the door to the consumer unit was locked. the flower arrangers at the other end of the building were not amused. Quote Link to comment Share on other sites More sharing options...
TimR Posted July 10, 2012 Share Posted July 10, 2012 I made the comment about the transformer. The RCD will only detect an imbalance in the current flowing between live and neutral on the mains side of the transformer in the amp. If the earth is missing then the case voltage can 'float' up to the transformer secondary voltage. When you earth this through another amp you get a shock. Because this current is isolated from the mains current by the transformer it will NOT trip the RCD. It's painful usually you get a spike on the lips or a tingling in your fingers, but it's not usually enough to be fatal. Quote Link to comment Share on other sites More sharing options...
flyfisher Posted July 10, 2012 Share Posted July 10, 2012 [quote name='stingrayPete1977' timestamp='1341937720' post='1726573'] I know what your saying Flyfisher but fuses are still the basis for Automatic Disconection of Supply that essentially the entire regs book is based on, all the calculations are based upon the [u]fuse[/u] values, The probelm is in most cases those values are hard to meet especially once your on the end of 3 50M ext reels! If we could be certain that the values were being met fuses would be OK as we cant RCD is the best bet in most cases. ie a socket circuit in a pub correctly wired on a 32A fuse or circuit breaker with a good earth loop test result will still blow in 0.4 of a second in the event of a short circuit, its not practicle or possible to know this and does not allow for faults occuring to the cables at a later date so only an RCD will do really. [/quote] But fuses are pretty crude devices. I can't remember the specs off the top of my head but they need very high currents to actually blow. Even a 13A fuse will pass 20A or more for a relatively long time - certainly long enough to see you depart this world. And, as you rightly say, it's even worse when the fault occurs a long way away from the fuse itself. I once got a graphic demonstration of this when I drilled through a wall and into the cable to a socket. When I had recovered from the bang I noticed that the 8mm drill bit had been burned right through. But the 30A fuse in the consumer unit [u]did not blow[/u], presumably because the drill bit 'blew' first. Even your less extreme example of a 32A fuse that stays intact for 0.4 seconds will will cause extreme harm if your're on the end of it! I'd far rather be on the end of an RCD-protected circuit where the current will be limited to about 30mA for about 30mS. Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted July 10, 2012 Share Posted July 10, 2012 Over time the regs will just keep moving towards RCD in all cases unfortunatley the dog and duck are keen to keep using the old Wylex fuse board that was installed when the Beatles were on the bill. We are a bit exposed to this in our musical world which most folk will not realise, as someone who tinkers with old cars when Im not playing bass most of the tools have become either class 2 (no earth required) or even just battery operated (or air), most of our kit uses a good old earth making it an area where its still leaving us open to earth faults where a lot of other pass times or even careers are not, kitchen staff are probably the other main ones off the top of my head where earthed class 1 gear is still the main type of kit used. Quote Link to comment Share on other sites More sharing options...
xilddx Posted July 10, 2012 Share Posted July 10, 2012 Plenty of useful stuff about RCDs etc in here [b] Electrical safety at places of entertainment.[/b] [b] Overview[/b] This guidance contains advice on preventing electrical danger at places of entertainment, how the law is applied to this area and on the role of the enforcing and licensing authorities. It is intended primarily for the managers of places of entertainment and for people who provide facilities for entertainers. The guidance will also be of use to technicians and technical managers http://www.hse.gov.uk/pubns/priced/gs50.pdf Quote Link to comment Share on other sites More sharing options...
flyfisher Posted July 10, 2012 Share Posted July 10, 2012 [quote name='lurksalot' timestamp='1341938970' post='1726612'] Our guitarist makes and tinkers with his own amps and ALWAYS uses an RCD . [/quote] Anyone 'tinkering' inside equipment needs to be even more careful because an RCD won't always offer any protection. For example, any current leaking to ground AFTER a mains transformer will NOT result in a Live-Neutral imbalance and an RCD on the mains side WILL NOT trip. Most of the time, this is not a big deal because A) you can't normally touch any wiring inside an amp and most amps use low voltages on the secondary side of the mains transformer. BUT, valve amps use high voltages and if you come into contact with them, then the RCD will happily keep providing mains current to the amp because it cannot 'see' anything on the other side of the mains transformer. The other instance when an RCD can offer no protection is if you inadvertantly find yourself connected between the live and neutral conductors. If all the live current flows through you and back down the Neutral conductor, the RCD will not trip and will happily pass enough current to fry you into the next world. This is not to scaremonger, but just to remind people that they don't suddenly become immortal just because their gear is plugged into an RCD. Quote Link to comment Share on other sites More sharing options...
TimR Posted July 10, 2012 Share Posted July 10, 2012 (edited) [quote name='dood' timestamp='1341937120' post='1726552'] I wasn't referring to the transformer having a fault, but as you know a transformer will have an impedance (or DC resistance when read with a multimeter) I simply wanted to know if the tester unit was meant to be used without anything plugged in to get a proper result or if the loading of the mains transformer on the circuit (if the amp is switched on of course) would interact with the tester? I mean, for example, you wouldn't try to measure the impedance of a speaker whilst it is connected to another speaker cabinet as the reading would not be true. I wanted to know if the tester simply measured open/short circuits or if it relied on resistance too. If it did, would loading on a mains socket cause the threshold for those readings (and alarm) to change. Make sense? [/quote] Yes. The transformer comment was separate to my answer. But the first part stands. Test BEFORE you plug any of your kit in. So it's a bad idea to have it permanently connected with the rest of your kit. Edited July 10, 2012 by TimR Quote Link to comment Share on other sites More sharing options...
flyfisher Posted July 10, 2012 Share Posted July 10, 2012 [quote name='stingrayPete1977' timestamp='1341941409' post='1726683'] Over time the regs will just keep moving towards RCD in all cases unfortunatley the dog and duck are keen to keep using the old Wylex fuse board that was installed when the Beatles were on the bill. [/quote] Nicely put, but you're absolutely right. Thank goodness for plug-in RCDs. Quote Link to comment Share on other sites More sharing options...
stingrayPete1977 Posted July 10, 2012 Share Posted July 10, 2012 [quote name='TimR' timestamp='1341941774' post='1726705'] Yes. The transformer comment was separate to my answer. But the first part stands. Test BEFORE you plug any of your kit in. So it's a bad idea to have it permanently connected with the rest of your kit. [/quote] In the rack case plugged in is a great place to keep it to save losing it though IMO, plug it in before you start to make sure then pop it back in the rack power point once your done wont hurt anything. Quote Link to comment Share on other sites More sharing options...
TimR Posted July 10, 2012 Share Posted July 10, 2012 [quote name='flyfisher' timestamp='1341941696' post='1726700'] Anyone 'tinkering' inside equipment needs to be even more careful because an RCD won't always offer any protection. For example, any current leaking to ground AFTER a mains transformer will NOT result in a Live-Neutral imbalance and an RCD on the mains side WILL NOT trip. Most of the time, this is not a big deal because A) you can't normally touch any wiring inside an amp and most amps use low voltages on the secondary side of the mains transformer. BUT, valve amps use high voltages and if you come into contact with them, then the RCD will happily keep providing mains current to the amp because it cannot 'see' anything on the other side of the mains transformer. [/quote] See my earlier comment about missing earths and transformers. Quote Link to comment Share on other sites More sharing options...
xilddx Posted July 10, 2012 Share Posted July 10, 2012 [quote name='silddx' timestamp='1341941473' post='1726688'] Plenty of useful stuff about RCDs etc in here [b] Electrical safety at places of entertainment.[/b] [b] Overview[/b] This guidance contains advice on preventing electrical danger at places of entertainment, how the law is applied to this area and on the role of the enforcing and licensing authorities. It is intended primarily for the managers of places of entertainment and for people who provide facilities for entertainers. The guidance will also be of use to technicians and technical managers [url="http://www.hse.gov.uk/pubns/priced/gs50.pdf"]http://www.hse.gov.u...priced/gs50.pdf[/url] [/quote] Thanks Nigel, that's very useful and interesting. An indispensable guide. Cheers. Quote Link to comment Share on other sites More sharing options...
Norris Posted July 10, 2012 Share Posted July 10, 2012 [quote name='silddx' timestamp='1341943266' post='1726763'] Thanks Nigel, that's very useful and interesting. An indispensable guide. Cheers. [/quote] You ARE appreciated - thanks Quote Link to comment Share on other sites More sharing options...
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