No appliance (that I can think of) manufactured in the last few years should be damaged by a 500V insulation tester because the safety standards for products demand that they can withstand far higher voltages. This is often used as an excuse for not properly PAT testing a PC for example, but they have to be made to EN60950 which requires them to withstand IIRC 3000V flash testing. Greg
No, you should temporarily short live and neutral and megger between these and earth, that way you test the insulation from live conductors to earth (which is where the leak will be), without stressing the electronics. Greg
You've clearly got an earth fault in the dryer, in my experience it's almost certainly the motor as these are made to such crap standards these days that the insulation from windings to frame breaks down after a year or two. The chances of an economic repair are minimal I'm afraid, it's certainly not worth replacing a motor. Greg
On or around 8 Dec 2006 03:06:21 -0800, "Greg" enlightened us thusly:
interesting info.
bloody electrickery gremlins, obviously. The socket that powers up our telly complex (TV, video, dvd, skybox and an old amp for better stereo) failed impressively yesterday night, taking out the circuit fuse as it did so. testing today reveals no fault (as expected) in any of the boxes and no power at the socket in question even with the fuse replaced. Of course, there's no way of knowing where the wire to the offending socket runs.
Mind, it looks like the fault that was causing the skybox case to be live (proabbly about 80V-worth) is not present with it plugged into a different source. Beats me, as none of the kit has earth connections anyway.
Lee_D uttered summat worrerz funny about:
Well, so far so good... 5p got stuck betwen the filter and the bit the filter sits in so basically the filter was getting blown past. I've cleaned it all out and thus far it's behaved. Not counting my chickens just yet , normally goes around the end of sending an.....
;-)
Lee D
Do a search on UK d-i-y. Look for a thread called 'that tingling feeling' (or similar) It's within the last few days.
It's not a fault. it's caused by high value resistors between live and _chassis_ in the device. This is for RF suppression. Because of the high value of these resistors, the current flow is well below anything that can give you a shock, however if you have several such boxes, with all their chassis couples together ( think aerial co-axial outer sheath) then you can often feel this as a tingle.
Julian.
On or around Sat, 09 Dec 2006 19:08:24 GMT, "Julian" enlightened us thusly:
this was a fair ol' tingle.
Mind you, it *seems* to have stopped now the whole lot is plugged into a different socket after the one it was in decided to blow up (per other post)
I don't see why that would make a difference, since none of the equipment is earthed (how do you get away with that, I wonder, I thought metal-case stuff had to be earthed?) and indeed if it was earthed a) it'd not bite and b) it'd probably improve the screening.
That was a question raised too. ie it's OK for your freeview box to give you a tingle if you touch (say) the metal aerial plug and a damp brick wall, but would you be happy to get a tingle when you take an electric instant shower?
I couldn't answer the other bits because it's beyond my understanding. (Well I sort of understand but wouldn't fancy trying to explain!)
Julian.
Not if it's double insulated. Such kit will have the double insulated symbol on the rating plate (two squares one inside the other). Double insulation means that none of the mains conductive parts are exposed inside the case, they are fully insulated.
A tingle isn't anything like a bite. Direct contact with the mains HURTS.
But would bring in the possibilties of earth loops and in the case of TV type kit an earthed connection pointing skywards.
With a blown socket I want to know why it blew and why it's no longer working. There is a possibilty that the ring main is now no longer a ring and is now effectively two spurs. The 32A capacity of a ring relies on any point on the ring being fed by two 2.5mm^2 cables. There is real risk of overloading one of the now single cables that won't be caught by the circuit protective device (32A MCB or 30A fuse).
Have you discovered what the problem was ?
"A bit less Range Rover in the garage" Rich
I would strongly advise you to get your ring main fixed, it could be in a very dangerous state.
The aerial socket of most TVs will show a large voltage if measured by a high resistance meter, this is perfectly normal and will be coupled to your other equipment through the aerial leads. It's not harmful but can be felt as a tingle. Greg
Not necessarily, if it's 'class one equipment' yes it does, but if it's 'class two equipment' then any exposed metal parts are 'extraneous conductive parts' which do not have to be earthed. Instead they are separated from live parts by double or reinforced insulation, the failure of which is concdered to be two faults, and the basic principle behind product safety is that it must remain safe only in the presence of a single fault.
As has also been mentioned, it's quite allowable for there to be a leakage path from live parts to exposed conductive parts, so long as the leakage current is small and the chances of it increasing are minimal, in the wiring regs it's called touch current. Greg
On or around Sun, 10 Dec 2006 14:05:10 +0000 (GMT), "Dave Liquorice" enlightened us thusly:
it's not a ring, it's a spur with 2 sockets on it on a 15A wire fuse. This house is not up to modern standards... I'll be investigating it, since I'd rather have it working; trouble is there's no (easy) way of knowing where the wire runs are.
See above. Mind you, 2.5mm² is capable of carrying 30A quite easily IIRC.
The trouble is that a 30A fuse won't blow in a reasonable time until the current is MUCH higher than 30A, that's why you have to match fuse to cable. A 30A fuse will not protect a 2.5mm cable so you have a serious risk of fire if a ring is open. Greg
Can't find my OSG just at the minute but 27A surface clipped with conductor temperature of 70C springs to mind. Note that will derate quit= e quickly in walls or under insulation.
Yep a 30A fuse will carry 30A pretty much indefinately. Double it to 60A= and it might go in under an hour. Fuses are very slow with small overloads they need serious currents to pop (BANG in the case of the 30A= one) in a short time.
I've had a long running battle in my workshop with my old, but very nice, Desoutter 5/8" chuck engineer's drill - it's metal bodied, earthed etc but when it's turned on, the capacitive surge trips the RCD - had it checked out by a professional sparky, he reckons it's good & safe, just that the starting load is such that something makes the RCD trip on start. The fix is to lock the trigger on, walk up to the RCD & force it on for two seconds while the old drill winds up, then it's sweet.
The whole concept of holding a safety switch from tripping has always bothered me, though. But it's such a good, solid, slow drill (the type that if the drill bit stalls, you start spinning instead) that I'm not likely to change it.
Karen
You shouldn't be able to hold an RCD on, nor should you with an MCB, they have a mechanism to prevent it, nor should it trip with a surge. I can only assume it's very old and would suggest replacing it as a matter of urgency, if a modern one still trips there may indeed be a fault with the machine regardless of what you've been told, but as a last resort a time delayed 'S' type should help. Greg
On or around 11 Dec 2006 03:12:20 -0800, "Greg" enlightened us thusly:
yeah, but it's on a 15A fuse. I'm aware of the behaviour of fuses...
It demonstrably did protect the circuit by blowing the fuse. Problem now is access to the thing and working out where the cable run goes.
On or around Mon, 11 Dec 2006 13:41:19 +0000 (GMT), "Dave Liquorice" enlightened us thusly:
I once inadvertently did a test on a 5A plug fuse - it'll run a 3KW load for about 5 minutes...
On or around 11 Dec 2006 00:40:16 -0800, "Greg" enlightened us thusly:
FFS, read what I type.
It's a spur on a 15A fuse, with 2 sockets on it. As far as I know, anyway. The wiring in this house predates ring mains, again AFAIK. The 2 sockets on this spur are only used for low power applications, I doubt the total load with everything switched on is as much as 500W.
And no, I'm not about to have it all re-wired at huge expense, but I will try and trace the fault - at the moment, the fuse is out of the fuse-box so the circuit is dead anyway, and the telly-complex is being supplied by an extension lead from a different socket.
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