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Tingle from metal lamp = dangerous?
On Wed, 27 Apr 2005 20:16:20 UTC, Lars wrote:
I have an old Anglepoise lamp with painted metal arms and painted metal lampshade (Anglepoise model 90). It has a two-core mains lead. I am in the UK so this is all at 230-240 volts. Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. QUESTION: Is my lamp safe to use and could I get a shock from it in its present condition? No. Yes. QUESTION: If my lamp is unsafe then is there a repair I can do? I would guess that the insulation is failing somewhere. Your test with the meter wasn't high voltage and didn't show it up. You need proper equipment to do that test. I would guess that replacing all the wiring would probably do it. It *might* be the lamp holder, but I'd change the wiring first. If you do replace the lampholder, it's probably a special heat resistant one (probably ceramic). -- Bob Eager begin a new life...dump Windows! |
#2
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In article , "Lars"
says... My electrical theory is fair but not great. Can someone please advise me. I have an old Anglepoise lamp with painted metal arms and painted metal lampshade (Anglepoise model 90). It has a two-core mains lead. I am in the UK so this is all at 230-240 volts. Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. That's because you were measuring it at a few volts - you need to measure at a few hundred volts. So the lamp seems ok. But something seems to be wrong! QUESTION: Is my lamp safe to use and could I get a shock from it in its present condition? Probably not very safe - you already had a mild shock from it. QUESTION: If my lamp is unsafe then is there a repair I can do? Find the loose wire or damaged insulation and replace it. |
#3
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Lars wrote:
My electrical theory is fair but not great. Can someone please advise me. I have an old Anglepoise lamp with painted metal arms and painted metal lampshade (Anglepoise model 90). It has a two-core mains lead. I am in the UK so this is all at 230-240 volts. Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. REplace the wiring! |
#4
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"Lars" wrote in message ... Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling' when I touch the base or the stem. The wiring has been checked and renewed several times and it still happens - and Spouse is absolutely thorough about doing a good job mainly to prove me wrong because he can't feel it. I can still feel it. I could also, once upon a time, feel the same thing from a metal electric kettle and nobody else could. The kettle was taken away by the first child to go to university. Over the years we lost all our electric kettles like that which is why we're left with an ancient copper one on the gas hob, it used to be used by Spouse's grandmother on their coal fire. But that's a different story. It's not a shock and it can only be felt with the lightest possible touch - but it's very definitely there and can only be sensed when the lamp is plugged in and the outlet switch is on. The lamp itself doesn't have to be lit. I've never suffered and I doubt that the OT will either. If he were going to he would have done by now. Mary |
#5
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Lars wrote:
My electrical theory is fair but not great. Can someone please advise me. I have an old Anglepoise lamp with painted metal arms and painted metal lampshade (Anglepoise model 90). It has a two-core mains lead. I am in the UK so this is all at 230-240 volts. Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. So the lamp seems ok. But something seems to be wrong! QUESTION: Is my lamp safe to use and could I get a shock from it in its present condition? QUESTION: If my lamp is unsafe then is there a repair I can do? It's probably just capacitive leakage between the live wire and the metal, and is unlikely to be serious, but what is serious is that the metal isn't earthed. The resistance measurements aren't completely reliable, as presumably they were made with a low-voltage source rather than a few hundred volts, but they do suggest there isn't a direct short of wire to metal. You shouldn't have any appliance with exposed metal parts which are not earthed. Such an appliance needs three-core cable and all of the metal parts well earthed. In an anglepoise, in particular, there will be mains wires flexing every time the lamp is moved. Eventually the insulation will crack, and a wire will touch the metal body. You really want a good earth at this point. I would recommend fitting a three-core cable, making sure the plug fuse is correct (almost certainly three amps) rather than the default 13 amp one that came with the plug. Again, particularly with an anglepoise, it would not be safe to assume that all the metalwork is in good electrical contact and that earthing at the cable entry point would provide a good connection at the shade. For maximum safety, I would replace the existing internal wiring. If it's really old, then it may have deteriorated significantly, particularly in the hot area. Probably any paint at the lamp joints will have worn away long since, but I'd consider using star washers on the joints and linking around the 'elbows' of the lamp with wires to solder tags screwed down over the washers. That way, the shade, the part most likely to be touched, should have good earth continuity. Maybe you can go on using it as it is for decades more without incident. Are you feeling lucky...? |
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On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher"
wrote in : "Lars" wrote in message ... Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling' when I touch the base or the stem. The wiring has been checked and renewed several times and it still happens - and Spouse is absolutely thorough about doing a good job mainly to prove me wrong because he can't feel it. I can still feel it. I could also, once upon a time, feel the same thing from a metal electric kettle and nobody else could. The kettle was taken away by the first child to go to university. Over the years we lost all our electric kettles like that which is why we're left with an ancient copper one on the gas hob, it used to be used by Spouse's grandmother on their coal fire. But that's a different story. It's not a shock and it can only be felt with the lightest possible touch - but it's very definitely there and can only be sensed when the lamp is plugged in and the outlet switch is on. The lamp itself doesn't have to be lit. I've never suffered and I doubt that the OT will either. If he were going to he would have done by now. Mary It is a common case, and possibly capacitive coupling between the hot wire and the metal frame (if no isolation problem). The responsible things to do is use a 3 lead mains cable and plug, and connect the ground to the metal frame. Problem solved. ANY other configuration will leave the possiblity of a short between a live wire and the frame, causing the metal to become live. When ground is connected a short will blow the fuse. |
#7
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"Jan Panteltje" wrote in message news:1114635656.816ed00d683a52da9acef964a66ac677@t eranews... On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher" wrote in : "Lars" wrote in message ... Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling' when I touch the base or the stem. The wiring has been checked and renewed several times and it still happens - and Spouse is absolutely thorough about doing a good job mainly to prove me wrong because he can't feel it. I can still feel it. I could also, once upon a time, feel the same thing from a metal electric kettle and nobody else could. The kettle was taken away by the first child to go to university. Over the years we lost all our electric kettles like that which is why we're left with an ancient copper one on the gas hob, it used to be used by Spouse's grandmother on their coal fire. But that's a different story. It's not a shock and it can only be felt with the lightest possible touch - but it's very definitely there and can only be sensed when the lamp is plugged in and the outlet switch is on. The lamp itself doesn't have to be lit. I've never suffered and I doubt that the OT will either. If he were going to he would have done by now. Mary It is a common case, and possibly capacitive coupling between the hot wire and the metal frame (if no isolation problem). The responsible things to do is use a 3 lead mains cable and plug, and connect the ground to the metal frame. Problem solved. Nope. That's what Spouse said. It now has that (he did it) and there's no change.. Mary |
#8
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"Mary Fisher" wrote in
. net: "Jan Panteltje" wrote in message news:1114635656.816ed00d683a52da9acef964a66ac677@t eranews... On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher" wrote in : "Lars" wrote in message ... Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling' when I touch the base or the stem. The wiring has been checked and renewed several times and it still happens - and Spouse is absolutely thorough about doing a good job mainly to prove me wrong because he can't feel it. I can still feel it. I could also, once upon a time, feel the same thing from a metal electric kettle and nobody else could. The kettle was taken away by the first child to go to university. Over the years we lost all our electric kettles like that which is why we're left with an ancient copper one on the gas hob, it used to be used by Spouse's grandmother on their coal fire. But that's a different story. It's not a shock and it can only be felt with the lightest possible touch - but it's very definitely there and can only be sensed when the lamp is plugged in and the outlet switch is on. The lamp itself doesn't have to be lit. I've never suffered and I doubt that the OT will either. If he were going to he would have done by now. Mary It is a common case, and possibly capacitive coupling between the hot wire and the metal frame (if no isolation problem). The responsible things to do is use a 3 lead mains cable and plug, and connect the ground to the metal frame. Problem solved. Nope. That's what Spouse said. It now has that (he did it) and there's no change.. Then it is probably not being plugged into a properly grounded outlet. At the very least, you should have him install a GFI outlet in the place that the lamp is used. Better is to make sure that the safety ground on the outlet really has a good, low impedence run to the main breaker box. Of course, he may have failed to properly connect the safety ground to the metal parts of your lamp. -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. remove ch100-5 to avoid spam trap |
#9
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Lars wrote:
My electrical theory is fair but not great. Can someone please advise me. I have an old Anglepoise lamp with painted metal arms and painted metal lampshade (Anglepoise model 90). It has a two-core mains lead. I am in the UK so this is all at 230-240 volts. Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. So the lamp seems ok. But something seems to be wrong! QUESTION: Is my lamp safe to use and could I get a shock from it in its present condition? QUESTION: If my lamp is unsafe then is there a repair I can do? There are several potential causes. IMHO, the lampholder would be the prime suspect. Over many years of being baked by the proximity of the lamp below it, the surface can degrade and allow a minute leakage current to flow. This can be made worse by dust/dirt getting into small cracks. A normal multimeter type tester is not a lot of use for testing for leakage - that is why electrical safety testing is done using special testers energised at 250 or 500 v. If it was a three wire cable, this very small leakage current would have a return path. The leakage current would have to increase to a point where the RCD/ELCB tripped, if fitted, or the plugtop fuse blows. That could take many years. No tingle though. With a two wire cable, the leakage current will be able to increase with time until it trips the RCD/ELCD via the person touching the exposed metalwork. The RCD/ELCB should mean that this will probably not be fatal. Without one fitted, the current will rise to a point where it is high enough and flows for long enough to easily be fatal - it is then Russian Roulette as to whether it kills or not. So, basically, you can ignore this and hope that the leakage grows only slowly. If you have an RCD/ELCB, probably no one will die if your hopes prove optimistic. If you don't have one, then you are playing for pretty large stakes.. So, your options a Test the lamp using a proper insulation tester. You may find that the lab tech in the electrical engineering department of a local university will do this for you for the cost of a beer. The lamp may actually be fine as some people are able to detect leakage currents way lower than anything demanded by the rules. Fit an RCD/ELCB at the supply or replace the consumer unit with a split box - if not already fitted. Replace the cable with a three wire one and connect the earth wire to the metalwork. That should stop the tingle. If the insulation iof the lampholder does deteriorate further then all that should happen is the RCD/ELCB will trip. Replace the lampholder in the assembly with a new one. I have managed to fit a standard ceiling lampholder to an Anglepoise in the past. You may be able to get hold of the genuine article. -- HTH Sue |
#10
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Mary Fisher wrote:
"Jan Panteltje" wrote in message news:1114635656.816ed00d683a52da9acef964a66ac677@t eranews... On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher" wrote in t: "Lars" wrote in message ... Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. It is a common case, and possibly capacitive coupling between the hot wire and the metal frame (if no isolation problem). The responsible things to do is use a 3 lead mains cable and plug, and connect the ground to the metal frame. Problem solved. Nope. That's what Spouse said. It now has that (he did it) and there's no change.. Following fitting the earth connection, does it tingle even when switched off at the wall socket? If so , it sounds like you are discharging a static charge into the lamp, rather than getting a charge from it. Touching something that is earthed (eg wall radiator) shortly before touching the lamp should prove/disprove this. But don't touch the two at the same time until you have had the lamp professionally tested for safety - I wouldn't have trusted my hublet with anything electrical.. -- Sue |
#11
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"Mary Fisher" wrote in message . net... "Jan Panteltje" wrote in message news:1114635656.816ed00d683a52da9acef964a66ac677@t eranews... On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher" wrote in : "Lars" wrote in message ... Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling' when I touch the base or the stem. The wiring has been checked and renewed several times and it still happens - and Spouse is absolutely thorough about doing a good job mainly to prove me wrong because he can't feel it. I can still feel it. I could also, once upon a time, feel the same thing from a metal electric kettle and nobody else could. The kettle was taken away by the first child to go to university. Over the years we lost all our electric kettles like that which is why we're left with an ancient copper one on the gas hob, it used to be used by Spouse's grandmother on their coal fire. But that's a different story. It's not a shock and it can only be felt with the lightest possible touch - but it's very definitely there and can only be sensed when the lamp is plugged in and the outlet switch is on. The lamp itself doesn't have to be lit. I've never suffered and I doubt that the OT will either. If he were going to he would have done by now. Mary It is a common case, and possibly capacitive coupling between the hot wire and the metal frame (if no isolation problem). The responsible things to do is use a 3 lead mains cable and plug, and connect the ground to the metal frame. Problem solved. Nope. That's what Spouse said. It now has that (he did it) and there's no change.. In that case it may be advisable to check that your 13amp socket has a good earth. |
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On a sunny day (Wed, 27 Apr 2005 22:20:56 +0100) it happened "Mary Fisher"
wrote in : "Jan Panteltje" wrote in message news:1114635656.816ed00d683a52da9acef964a66ac677@ teranews... On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher" wrote in : "Lars" wrote in message ... Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling' when I touch the base or the stem. The wiring has been checked and renewed several times and it still happens - and Spouse is absolutely thorough about doing a good job mainly to prove me wrong because he can't feel it. I can still feel it. I could also, once upon a time, feel the same thing from a metal electric kettle and nobody else could. The kettle was taken away by the first child to go to university. Over the years we lost all our electric kettles like that which is why we're left with an ancient copper one on the gas hob, it used to be used by Spouse's grandmother on their coal fire. But that's a different story. It's not a shock and it can only be felt with the lightest possible touch - but it's very definitely there and can only be sensed when the lamp is plugged in and the outlet switch is on. The lamp itself doesn't have to be lit. I've never suffered and I doubt that the OT will either. If he were going to he would have done by now. Mary It is a common case, and possibly capacitive coupling between the hot wire and the metal frame (if no isolation problem). The responsible things to do is use a 3 lead mains cable and plug, and connect the ground to the metal frame. Problem solved. Nope. That's what Spouse said. It now has that (he did it) and there's no change.. Mary Well, I was in this house once, where they also earthed the stuff, but it then turned out the earth (I had to install some equipment there) was not connected to anything, it was originally connected to water pipes, but somebody had just cut the wire. You (he) can test if earth is there with say a 40 W lightbulb between earth and live. It should light. Then test between live and your lamp frame, it should light too. The only alternative is that you pick up something from the floor (bad wiring conductive carpet), anything goes. |
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Lars wrote:
My electrical theory is fair but not great. Can someone please advise me. I have an old Anglepoise lamp with painted metal arms and painted metal lampshade (Anglepoise model 90). It has a two-core mains lead. I am in the UK so this is all at 230-240 volts. Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. So the lamp seems ok. But something seems to be wrong! QUESTION: Is my lamp safe to use and could I get a shock from it in its present condition? QUESTION: If my lamp is unsafe then is there a repair I can do? Thank you for any info. Lars ----------------- PS: Picture of Anglepoise model 90: The two questions I haven't noticed anyone asking you directly are these: What are you standing or sitting on and/or touching when you feel that tingle? And, what is the "cold end" of the "screwdriver" mains tester connected to when you see it lighting? If you can reasonably feel that your body is well insulated from ground when you feel that tingle, like you are standing on dry carpeting on a wooden floor inside a house, then I'll put my chips in with the folks who say you are probably just feeling a capacitivly coupled ac current flowing between the hot lead in the lamp and the lamp's metal body which is then charging and discharging your body's capacitance. How about trying this? connect a wire to a known ground, get the smallest wattage 240 volt bulb you can find, unplug the lamp and connect that bulb beween the metal lamp body and the grounded wire. Then plug the lamp back in. Does the bulb light, with the lamp either off or on? If it doesn't, then the current flow (in amps) is less than the wattage of the bulb divided by 240. If it does light, you DO have a dangerous condition of deteriorated insulation or some other conductive path within the lamp, STOP and get it fixed. If the test bulb doesn't light, replace it with an ac ammeter set to a range higher than that bulb would draw at 240 volts and then switch to lower ranges until you can measure the "leakage" current. I'm betting you'll find it will be less than a milliampre, and is likely capacitively coupled. While it's nice to hear that all metal bodied lamps ought to have a direct connection from their metal parts to ground through a three wire cord and appropriate plugs and recepticals, that is certainly the exception rather than the rule for household use in the USA. I've got all sorts of metal bodied lamps in my home, all of them purchased new, some as recently as last year, and not one of them came equipped with a three wire cord. In fact, I've installed capacitive "touch switch" multi level dimmers in four of those lamps, using their bodies as the sensing elements. I couldn't do that if we had to ground the lamp bodies. Let us know what you find, Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "As long as there are final exams, there will be prayer in public schools" |
#14
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On Wed, 27 Apr 2005 21:36:00 +0000 (UTC), bz
wrote: "Mary Fisher" wrote in .net: "Jan Panteltje" wrote in message news:1114635656.816ed00d683a52da9acef964a66ac677@t eranews... On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher" wrote in : "Lars" wrote in message ... Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling' when I touch the base or the stem. The wiring has been checked and renewed several times and it still happens - and Spouse is absolutely thorough about doing a good job mainly to prove me wrong because he can't feel it. I can still feel it. I could also, once upon a time, feel the same thing from a metal electric kettle and nobody else could. The kettle was taken away by the first child to go to university. Over the years we lost all our electric kettles like that which is why we're left with an ancient copper one on the gas hob, it used to be used by Spouse's grandmother on their coal fire. But that's a different story. It's not a shock and it can only be felt with the lightest possible touch - but it's very definitely there and can only be sensed when the lamp is plugged in and the outlet switch is on. The lamp itself doesn't have to be lit. I've never suffered and I doubt that the OT will either. If he were going to he would have done by now. Mary It is a common case, and possibly capacitive coupling between the hot wire and the metal frame (if no isolation problem). The responsible things to do is use a 3 lead mains cable and plug, and connect the ground to the metal frame. Problem solved. Nope. That's what Spouse said. It now has that (he did it) and there's no change.. Then it is probably not being plugged into a properly grounded outlet. At the very least, you should have him install a GFI outlet in the place that the lamp is used. Better is to make sure that the safety ground on the outlet really has a good, low impedence run to the main breaker box. Of course, he may have failed to properly connect the safety ground to the metal parts of your lamp. For "ground" read "earth" For "outlet" read "socket" For "GFI" read "RCD" .... in the UK :-) I would agree with others that for an "Anglepoise" type lamp you would ideally have a piece of braiding solidly linking each leg, but if you have an earthed connection to the lampholder, and shielded "flex" through the lamp you should be OK. An alternative would be to use a say, 12 or 24V lamp and a proper isolating transformer. -- Frank Erskine |
#15
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Use a Megohmmeter (Insulation tester) between the wiring and the metal
on the lamp. Some Air Conditioning contractors (Like Me) use them to test compressor motors. An electrician may have one also. If that tests OK, then it is probably capacitive coupling and not a problem. Stretch |
#16
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I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. Many appliences ground the outside of metal appliance, which means it should be in electrical contact with your neutral pin. Which means THAT resistance should have been LOW (zero). This is a measure to prevent shock, in case something inside the appliance should contact that outer case (which would then blow your fuse instead of making the case "hot", and leave it as a safety hazard in case you should grab it in one hand, and something else that goes to ground in the other). If you can follow the grounded pin inside your lamp, you should see that it ends SOMEWHERE. Probably it goes to the metal screw fitting of the bulb. If you really want to make your lamp safer, you can run a wire from that to the metal arms somewhere. Then you can't ever shock yourself by grabbing it. Caution--- it's only safe to do this if your 2-pole plug is polarized so it can't be put into the wall, in reverse. I have no idea what UK plugs look like, so you'll have to tell me if this is true. From your description it sounds as though it is. SBH |
#17
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"Lars" wrote in message ... My electrical theory is fair but not great. Can someone please advise me. I have an old Anglepoise lamp with painted metal arms and painted metal lampshade (Anglepoise model 90). It has a two-core mains lead. I am in the UK so this is all at 230-240 volts. Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. So the lamp seems ok. But something seems to be wrong! QUESTION: Is my lamp safe to use and could I get a shock from it in its present condition? QUESTION: If my lamp is unsafe then is there a repair I can do? Thank you for any info. Lars Its not safe... how good your meter is and how good you are using are open to question..but the tingle is proof positive you have some degree of short or current leak in the lamp wiring to the lamp base metal. Rewire it. Phil Scott ----------------- PS: Picture of Anglepoise model 90: http://www.anglepoise.com/timeline/model_90.jpg |
#18
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"Sbharris[atsign]ix.netcom.com" wrote in message oups.com... I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. Many appliences ground the outside of metal appliance, which means it should be in electrical contact with your neutral pin. Which means THAT resistance should have been LOW (zero). This is a measure to prevent shock, in case something inside the appliance should contact that outer case (which would then blow your fuse instead of making the case "hot", and leave it as a safety hazard in case you should grab it in one hand, and something else that goes to ground in the other). If you can follow the grounded pin inside your lamp, you should see that it ends SOMEWHERE. Probably it goes to the metal screw fitting of the bulb. If you really want to make your lamp safer, you can run a wire from that to the metal arms somewhere. Then you can't ever shock yourself by grabbing it. Caution--- it's only safe to do this if your 2-pole plug is polarized so it can't be put into the wall, in reverse. I have no idea what UK plugs look like, so you'll have to tell me if this is true. From your description it sounds as though it is. SBH Hi, We don't have 2 pin in the uk for 99.9% of appliances. We have a fused 3 pin plug, earths must always be used as earths, neutrals as neutrals as far as appliances are concerned... |
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On Wed, 27 Apr 2005 21:16:20 +0100, Lars wrote:
QUESTION: Is my lamp safe to use and could I get a shock from it in its present condition? Certainly not safe. It sounds like the insulation is breaking down under mains voltage. QUESTION: If my lamp is unsafe then is there a repair I can do? Get the wiring replaced and the bulb holder inspected. sponix |
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On Wed, 27 Apr 2005 21:51:24 +0100, Joe wrote:
You shouldn't have any appliance with exposed metal parts which are not earthed. Such an appliance needs three-core cable and all of the metal parts well earthed. In an anglepoise, in particular, there will be mains wires flexing every time the lamp is moved. Eventually the insulation will crack, and a wire will touch the metal body. You really want a good earth at this point. If it's the sort of anglepoise lamp I'm thinking of it will be double insulated. Whilst it would be sensible to earth the thing, it will need 'cross bonding' across the hinged joints. |
#21
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"Frank Erskine" wrote in message The responsible things to do is use a 3 lead mains cable and plug, and connect the ground to the metal frame. Problem solved. Nope. That's what Spouse said. It now has that (he did it) and there's no change.. Then it is probably not being plugged into a properly grounded outlet. It is. The house was completely re-wired some time ago. And no other appliance demonstrates the same response. At the very least, you should have him install a GFI outlet in the place that the lamp is used. Better is to make sure that the safety ground on the outlet really has a good, low impedence run to the main breaker box. It's not worth it, it's no problem, it usually isn't touched at all (being on a properly functioning and wired etc. time switch) and even if it is it's not an unpleasant experience, certainly not a dangerous one. Of course, he may have failed to properly connect the safety ground to the metal parts of your lamp. Phftttttttttt! For "ground" read "earth" I do. For "outlet" read "socket" O pefer outlet, having been taught that by an English electrician 53 years ago. He was amused that I wanted to know what everything was. For "GFI" read "RCD" er- yes. Thanks :-) I would agree with others that for an "Anglepoise" type lamp you would ideally have a piece of braiding solidly linking each leg, but if you have an earthed connection to the lampholder, and shielded "flex" through the lamp you should be OK. An alternative would be to use a say, 12 or 24V lamp and a proper isolating transformer. There's no alternative for my (non-anglepoise) lamp except a modern reproduction which we don't want. I only mentioned it so that the OP didn't think his lamp was unique! Mary -- Frank Erskine |
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According to Lars :
It has a two-core mains lead. Does it have an earth (ground) prong too? Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. If you get a continuous tingle, then it's _highly_ unlikely to be a capacitive/inductive/static leak (as others have suggested). Last time I touched a device and got a minor tingle, repeating that test while holding on to something grounded was something I'm not going to repeat. That hurt! Dumb me. At least we're only 120V... You say "old", and the picture shows that the wiring in the lamp is being moved whenever you adjust the lamp. Possibly abraded and the conductors may now be intermittently contacting the frame. I recommend removing the wiring and inspecting both it and the lamp socket as others have suggested. The socket may need cleaning. If you see worn spots in the wiring, replace it. If you don't see any obvious worn spots, now you really worry about the fixture. Measuring resistance won't be particularly reliable, fancy equipment or not, because if you have a bare spot on the wiring in the arms, the slightest bit of movement may break/make the connection. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
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Lars wrote:
My experience is the same as yours in that I have many 2-core only appliances with metal bodies which seem designed specifically to be 2-core. Often their label refers to "double insulated" - whatever that may be. In double insulated equipment the basic protection is afforded by the first layer of insulation. If the basic protection fails then supplementary protection is provided by a second layer of insulation preventing contact with live parts. You *know* it makes sense to get all portable electrical equipment tested regularly and properly using a purpose-designed Portable Appliance Tester. -- Sue |
#24
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"James Salisbury" wrote in message ... "Sbharris[atsign]ix.netcom.com" wrote in message oups.com... I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. Many appliences ground the outside of metal appliance, which means it should be in electrical contact with your neutral pin. No, No, No. Modern appliances with exposed metal parts will be connected to Earth. This means it should be in contact with the EARTH pin. NEVER connect exposed metal parts to neutral. It may appear that the neutral wire has no voltage but this is not so. If a short is placed between earth and neutral the RCD in your consumer unit will trip. If it doesn't there is an earth fault. Get it seen to. Roger |
#25
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Roger R wrote:
"James Salisbury" wrote in message ... "Sbharris[atsign]ix.netcom.com" wrote in message groups.com... I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. Many appliences ground the outside of metal appliance, which means it should be in electrical contact with your neutral pin. No, No, No. Modern appliances with exposed metal parts will be connected to Earth. This means it should be in contact with the EARTH pin. NEVER connect exposed metal parts to neutral. It may appear that the neutral wire has no voltage but this is not so. If a short is placed between earth and neutral the RCD in your consumer unit will trip. If it doesn't there is an earth fault. Get it seen to. This may help: http://www.tlc-direct.co.uk/Book/5.6.1.htm -- Sue |
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"Lars" wrote in message ... My electrical theory is fair but not great. Can someone please advise me. I have an old Anglepoise lamp with painted metal arms and painted metal lampshade (Anglepoise model 90). It has a two-core mains lead. I am in the UK so this is all at 230-240 volts. Today I touched the outside of the lampshade and got a sort of vey mild tingle feeling which felt "odd". When I used a mains tester screwdriver on the exposed metal (at the joint of the lampshade and support arm) then it glowed as if the metal of the Anglepoise lamp was live. I'd strip it down and check it thoroughly, and if you're still not happy, destroy and dispose of it safely. Better still, pass it on to trading standards in case it has a design flaw. I must point out though that it is rare for UK approved double insulated appliances to fail and present a shock hazard. If you find a design fault which could have contributed to the case becoming live, be sure to report it to trading standards so it can be investigated. Is it a constant tingling feeling or a momentary minor jolt? It's very common to get static discharges to metal appliances, but there's also an odd gentle 'vibrating' or 'buzzing' sensation which can sometimes be felt touching the metalwork of double insulated appliances. These are perfectly harmless phenomena. Dave |
#27
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"Dave D" wrote in message ... Is it a constant tingling feeling or a momentary minor jolt? It's very common to get static discharges to metal appliances, but there's also an odd gentle 'vibrating' or 'buzzing' sensation which can sometimes be felt touching the metalwork of double insulated appliances. These are perfectly harmless phenomena. Ah! Thank you :-) That's exactly the effect from my art deco lamp but everyone else seems to think it needs seeing to. It has been seen to. Mary Dave |
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Sbharris[atsign]ix.netcom.com wrote:
I unplugged the lamp and tested the resistence between the live pin on the mains plug and some exposed metal on the lamp. I got no resistence reading at all (i.e. it must have been a very high resistence). I then tested the neutral pin in the same way and got the same high resistence result. Many appliences ground the outside of metal appliance, which means it should be in electrical contact with your neutral pin. Which means THAT resistance should have been LOW (zero). This is a measure to prevent shock, in case something inside the appliance should contact that outer case (which would then blow your fuse instead of making the case "hot", and leave it as a safety hazard in case you should grab it in one hand, and something else that goes to ground in the other). If you can follow the grounded pin inside your lamp, you should see that it ends SOMEWHERE. Probably it goes to the metal screw fitting of the bulb. If you really want to make your lamp safer, you can run a wire from that to the metal arms somewhere. Then you can't ever shock yourself by grabbing it. Caution--- it's only safe to do this if your 2-pole plug is polarized so it can't be put into the wall, in reverse. I have no idea what UK plugs look like, so you'll have to tell me if this is true. From your description it sounds as though it is. SBH 1.Please look up UK plugs (British Standard BS1363) on the web, or any more reliable reference. 2.Please imagine, or establish using diagrams, what would happen if the neutral in the flex. broke or became disconnected in the plug, if connected as you recommended. 3.Genuine Anglepoise lampholders were not Edison screw fitting. |
#29
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No, No, No. Modern appliances with exposed metal parts will be
connected to Earth. We're not talking about a modern appliance, is the problem. We're talking about how to make an antique a little safer. This means it should be in contact with the EARTH pin. NEVER connect exposed metal parts to neutral. You can if you like. It will trip your RCD (residual current device), if you have one, but not everybody does. These thingsa are called GFI (ground fault interruptor) devices in the US. But if you don't have one of these in your house, or on the circuit in question, then it does no damage for neutral to touch ground in the lamp or whatever. And it may make the lamp safer. It may appear that the neutral wire has no voltage but this is not so. That depends. Actually, it is so, UNLESS you have an RCD/GFI, which places a small voltage between neutral and ground as they exit the RCD device. After all, the ground and neutral are connected together in the service panel, so there's no difference between them unless the RCD, connected after the panel, puts it there. The purpose of this small voltage is so the RCD can detect a ground-neutral "fault" (one where the neural wire has touched the gound inside your lamp or other appliance) and trip when that happens. The reason RCDs do this is because having the neutral touch ground makes the major feature of the RCD (the ability to tell if more current is flowing in the hot wire than in the neutral, signaling an extra path to ground which may be you being electrocuted) inoperative. So the RCD is designed to shut off the power if its sensing function (which requires a separate neutral and ground path as they exit the device) is compromised and it becomes "blind" and unable to perform its function. But again, if you don't have an RCD in the first place, none of this applies. YOU don't care if the ground touches neural in your old lamp UNLESS you have an RCD/GFI to trip in the first place. If a short is placed between earth and neutral the RCD in your consumer unit will trip. Yes, but again, if you don't have an RCD, it won't. So you don't care. If you don't have an RCD it's better to have a grounded device outer casing, at least, rather than have one that floats. The latter is a shock hazard if internally it should touch the wrong wire and become hot. But if the casing is connected to neutral at least, then you have a chance that a hot wire contacting it will trip your fusebox, which is a poor man's GFI. All this assumes, of course, that you have only 2 wire plugs, which are polarized. These still exist many places in the US. I was assuming that this antique lamp had this design, but it doesn't sound like it. If not, then obviously the 3rd (ground/earth) wire must be followed to make sure it contacts the lamp casing instead. If it doesn't there is an earth fault. Get it seen to. You say, if a short between earth and neutral doesn't make your RCD trip then there is an Earth fault??? Sorry, that doesn't make sense. If it doesn't, then it means your RCD isn't working. Anyway, this guy sounds like he has an old lamp with a polarized 2 pin plug, and no ground pin. The lamp is apparently designed with a floating casing, so that neigher hot or neutral connect to the metal arms of the lamp. Do I have the correct impression? SBH |
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That depends. Actually, it is so, UNLESS you have an RCD/GFI, which places a small voltage between neutral and ground as they exit the RCD device. After all, the ground and neutral are connected together in the service panel, so there's no difference between them unless the RCD, connected SBH Sorry, you don't know much about UK mains distribution do you ?. The neutral wire in the UK is connected to ground only at the sub station under normal situations and nowhere else. Therefore it can be at a different potential to true ground. You really should not begiving advice in a UK ng about a electrical system which you clearly have no first hand experience of. Dave -- For what we are about to balls up may common sense prevent us doing it again in the future!! |
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On Fri, 29 Apr 2005, Dave Stanton wrote:
That depends. Actually, it is so, UNLESS you have an RCD/GFI, which places a small voltage between neutral and ground as they exit the RCD device. After all, the ground and neutral are connected together in the service panel, so there's no difference between them unless the RCD, connected SBH Sorry, you don't know much about UK mains distribution do you ?. The neutral wire in the UK is connected to ground only at the sub station under normal situations and nowhere else. Therefore it can be at a different potential to true ground. Actually, in a TN-C-S supply, which is pretty common nowadays, they are connected together in the service head (grey box with big fuse in it belonging to the electricity co. next to the customers' meter). -- Alistair Riddell - BOFH Microsoft - because god hates us |
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On Fri, 29 Apr 2005 05:24:28 UTC, Dave Stanton wrote:
The neutral wire in the UK is connected to ground only at the sub station under normal situations and nowhere else. Therefore it can be at a different potential to true ground. I agre with your comment about him not knowing much about UK mains. But in a PME (TN-C-S) situation, neutral and earth are connected together much closer than that - at the cutout (incoming cable connection). -- Bob Eager |
#33
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"Sbharris[atsign]ix.netcom.com" wrote in
ups.com: an RCD/GFI, which places a small voltage between neutral and ground as they exit the RCD device. After all, the ground and neutral are connected together in the service panel, so there's no difference between them unless the RCD, connected after the panel, puts it there. You are so wrong!!!!! The purpose of this small voltage is so the RCD can detect a ground-neutral "fault" (one where the neural wire has touched the gound inside your lamp or other appliance) and trip when that happens. The reason RCDs do this is because having the neutral touch ground makes the major feature of the RCD (the ability to tell if more current is flowing in the hot wire than in the neutral, signaling an extra path to ground which may be you being electrocuted) inoperative. So the RCD is designed to shut off the power if its sensing function (which requires a separate neutral and ground path as they exit the device) is compromised and it becomes "blind" and unable to perform its function. But again, if you don't have an RCD in the first place, none of this applies. YOU don't care if the ground touches neural in your old lamp UNLESS you have an RCD/GFI to trip in the first place. The GFI does not work that way. The ones I have seen use a small toroidial transformer to sample the current flow in the hot and neutral lines. (Some also sample the safety ground and trip if there is any flow there). The circuit is a balanced bridge as long and the current in the hot line is equal to the current in the neutral line, the GFI does not trip. If there is an imbalance, it implies that some current is flowing through something OTHER than the designed load and that current is going to a different neutral or to earth ground. You can still get electrocuted if you have one lamp that has the hot shorted to the frame and you touch that and another device that has neutral connected to the frame. If both were on the same GFI protected circuit, you would NOT trip the GFI. NEVER connect the neutral to the frame of any device because you defeat the GFI when you do this. Frame always connects to safety ground. Your advices would also make the device deadly if it is ever used in an older house with two wire plugs and someone plugs it in backwards. Never connect neutral to the frame. -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. remove ch100-5 to avoid spam trap |
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In article ,
Dave Stanton wrote: You really should not begiving advice in a UK ng about a electrical system which you clearly have no first hand experience of. The article was posted to several newsgroups, only one of which is uk-specific. It's quite likely that readers won't notice that. -- Richard |
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bz wrote:
"Sbharris[atsign]ix.netcom.com" wrote in ups.com: an RCD/GFI, which places a small voltage between neutral and ground as they exit the RCD device. After all, the ground and neutral are connected together in the service panel, so there's no difference between them unless the RCD, connected after the panel, puts it there. You are so wrong!!!!! The purpose of this small voltage is so the RCD can detect a ground-neutral "fault" (one where the neural wire has touched the gound inside your lamp or other appliance) and trip when that happens. The reason RCDs do this is because having the neutral touch ground makes the major feature of the RCD (the ability to tell if more current is flowing in the hot wire than in the neutral, signaling an extra path to ground which may be you being electrocuted) inoperative. So the RCD is designed to shut off the power if its sensing function (which requires a separate neutral and ground path as they exit the device) is compromised and it becomes "blind" and unable to perform its function. But again, if you don't have an RCD in the first place, none of this applies. YOU don't care if the ground touches neural in your old lamp UNLESS you have an RCD/GFI to trip in the first place. The GFI does not work that way. A GFCI works, in part, as you describe below. In addition, it detects a ground/neutral short as described at the following url: http://www.codecheck.com/gfci_principal.htm I believe that function is what the poster was referring to. Ed The ones I have seen use a small toroidial transformer to sample the current flow in the hot and neutral lines. (Some also sample the safety ground and trip if there is any flow there). The circuit is a balanced bridge as long and the current in the hot line is equal to the current in the neutral line, the GFI does not trip. If there is an imbalance, it implies that some current is flowing through something OTHER than the designed load and that current is going to a different neutral or to earth ground. You can still get electrocuted if you have one lamp that has the hot shorted to the frame and you touch that and another device that has neutral connected to the frame. If both were on the same GFI protected circuit, you would NOT trip the GFI. NEVER connect the neutral to the frame of any device because you defeat the GFI when you do this. Frame always connects to safety ground. Your advices would also make the device deadly if it is ever used in an older house with two wire plugs and someone plugs it in backwards. Never connect neutral to the frame. |
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On Fri, 29 Apr 2005 07:41:59 +0000, Bob Eager wrote:
On Fri, 29 Apr 2005 05:24:28 UTC, Dave Stanton wrote: The neutral wire in the UK is connected to ground only at the sub station under normal situations and nowhere else. Therefore it can be at a different potential to true ground. I agre with your comment about him not knowing much about UK mains. But in a PME (TN-C-S) situation, neutral and earth are connected together much closer than that - at the cutout (incoming cable connection). Yes I know I was'nt 100% correct, but did'nt want to cloud what is becoming quite a serious case of incorrect and dangerous info. Dave -- For what we are about to balls up may common sense prevent us doing it again in the future!! |
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Lars wrote:
On Wed 27 Apr 2005 23:35:40, Jeff Wisnia wrote: The two questions I haven't noticed anyone asking you directly are these: What are you standing or sitting on and/or touching when you feel that tingle? I am standing on a carpet on the third floor of a building. The carpet is 80% wool and presumably the 20% is polyester. And, what is the "cold end" of the "screwdriver" mains tester connected to when you see it lighting? I myself am touching the "cold end" of the screwdriver mains tester with my finger. If you can reasonably feel that your body is well insulated from ground when you feel that tingle, like you are standing on dry carpeting on a wooden floor inside a house, then I'll put my chips in with the folks who say you are probably just feeling a capacitivly coupled ac current flowing between the hot lead in the lamp and the lamp's metal body which is then charging and discharging your body's capacitance. How about trying this? connect a wire to a known ground, get the smallest wattage 240 volt bulb you can find, unplug the lamp and connect that bulb beween the metal lamp body and the grounded wire. Then plug the lamp back in. Does the bulb light, with the lamp either off or on? If it doesn't, then the current flow (in amps) is less than the wattage of the bulb divided by 240. If it does light, you DO have a dangerous condition of deteriorated insulation or some other conductive path within the lamp, STOP and get it fixed. If the test bulb doesn't light, replace it with an ac ammeter set to a range higher than that bulb would draw at 240 volts and then switch to lower ranges until you can measure the "leakage" current. I'm betting you'll find it will be less than a milliampre, and is likely capacitively coupled. Could I not use an ammeter inthe first place rather than a test bulb given that a fully-lit 100 W bulb would have a current flow of approx 0.4 A (= 100 watts/240 volts). The reason I suggested using a small bulb rather than a meter is this. Just in case you DO have a dead short between the "hot" side of your 240 volt supply and the metal body of the lamp, then connecting that grounded wire I suggested directly to the lamp body through an ammeter would cause one heck of a lot more current than the 0.4 A you mention, possibly enough to damage the meter before the fuse or breaker opened, unless the meter was set to something like a 400 amp range. Capiche? While it's nice to hear that all metal bodied lamps ought to have a direct connection from their metal parts to ground through a three wire cord and appropriate plugs and recepticals, that is certainly the exception rather than the rule for household use in the USA. I've got all sorts of metal bodied lamps in my home, all of them purchased new, some as recently as last year, and not one of them came equipped with a three wire cord. My experience is the same as yours in that I have many 2-core only appliances with metal bodies which seem designed specifically to be 2-core. Often their label refers to "double insulated" - whatever that may be. And I've recently read that common consumer "pop-up" toasters don't have three wire cords and grounded cases because people often stick tableware in them trying to remove a stuck piece of bread. If those metal implements shorted a toaster element to a grounded case, the element could burn out. They rely instead on the presence of GFCI protected outlets to keep foolish people from electrocuting themselves while doing that. GFCIs have been required by code for kitchen outlets in the US for many years now. In fact, I've installed capacitive "touch switch" multi level dimmers in four of those lamps, using their bodies as the sensing elements. I couldn't do that if we had to ground the lamp bodies. Let us know what you find, Jeff |
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According to Jeff Wisnia :
The reason I suggested using a small bulb rather than a meter is this. Just in case you DO have a dead short between the "hot" side of your 240 volt supply and the metal body of the lamp, then connecting that grounded wire I suggested directly to the lamp body through an ammeter would cause one heck of a lot more current than the 0.4 A you mention, possibly enough to damage the meter before the fuse or breaker opened, unless the meter was set to something like a 400 amp range. Capiche? The meter would probably _still_ explode. I saw the result of someone mistaking a 100A DC ammeter for an AC voltmeter, and sticking the probes in a 120V socket. Not pretty. Yup, the breaker tripped. But the meter innards had vaporized, and the industrial grade receptacle was destroyed. Shouldn't put an ammeter across anything that could even remotely have line potential across it unless there's some sort of limiter (ie: lightbulb) in the way. Intermittent short = kaboom! And I've recently read that common consumer "pop-up" toasters don't have three wire cords and grounded cases because people often stick tableware in them trying to remove a stuck piece of bread. If those metal implements shorted a toaster element to a grounded case, the element could burn out. True, but more importantly, if the toaster is grounded, and you stick a knife into it to clear out a piece of bread, where's your other hand? On the toaster! - Toasted user, not toasted bread. -- Chris Lewis, Una confibula non set est It's not just anyone who gets a Starship Cruiser class named after them. |
#39
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What's in a name? Ahem, I called it a "service panel," and you two call
it a "service head," or a "cutout." But it's the same place in the system. The laws of physics don't differ in the UK, and I would hope good electrical wiring practices (practises?) therefore don't differ much either. Nothing you've said so far convinces me otherwise. SBH |
#40
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A GFCI works, in part, as you describe below.
In addition, it detects a ground/neutral short as described at the following url: http://www.codecheck.com/gfci_=ADprincipal.htm I believe that function is what the poster was referring to. Correct. Modern GFI's really have two parts. The main one keeps you from killing yourself, by cutting off current when you have a hot to ground current. The active SECOND part (a second toroid) allows the device to detect ground-neutral faults, so it can trip then, when its sensing function has been compromised. SBH |
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