Pib Posted June 8, 2012 Share Posted June 8, 2012 (edited) Glowing fluorescents when 'off' is invariably a switched neutral. Since it seems the main wiring is the correct way round then the switching needs investigating. Did you buy a neon? If not go and get one, this test is far easier with one than with a meter. With the light off check both incoming connections to your light fitting, if it is correctly wired you should see NO glow on the neon. If the neon glows on one or both of the connections then the switch is in the neutral. A switched neutral is not going to cause a fire or anything similar, it is however a hazard because even with the light switched off the fitting is live and will happily kill you when you are changing the tube. It does really need to be fixed. Installing electronic ballasts may fix the glow, but there is the danger of introducing a more annoying effect whereby the tubes flash at relatively long intervals (possibly once an hour), I've not seen it with full sized tubes, but it's very common with low-energy lamps even if they are correctly wired. I got the neon but am obviously doing something wrong as it doesn't light up when I touch any part of the fixture even with the circuit on (when it clearly does have current) so I must be touching the wrong place. It is not the tester as it works fine when I try it in for example a socket. Where on this am I supposed to put the tester? Or was I supposed to disconnect the whole business and touch the incoming wires? I tried where the wires enter the ballast etc but no luck With the light switched turned on, touch/lay the tester tip against the insulation of each/the two incoming wires that come through the hole in the ceiling...make actual contact with the insulation...the tester tip is actually touching the insulation. From looking at the picture it appears it would be the black wire and the white wire that has the tape connection. And actually for the black wire that is connecting to the ballast you could also just touch the bare connector of the ballast where the the black wire hooks to. The hot wire will cause the tester to light up and for any wire with no voltage on it like the Neutral the tester will not light up. Most of these type testers you just need to hold the grip and touch the bare wire or insulation and it works/lights up when voltage is detected, but there are some that may have a little press switch on the handle end that you need to press down with your finger to make it work. Edited June 8, 2012 by Pib Link to comment Share on other sites More sharing options...
electau Posted June 9, 2012 Share Posted June 9, 2012 The switched line (active) should be connected to the ballast terminal first. The fitting should earthed, this may remove the glowing tube problem, I have never seen this problem outside of Thailand. Most light fittings are not earthed in Thailand. Transposition of the L and Neutral can cause a hazardous condition electrically, as the equipment is still energised when switched "off". Link to comment Share on other sites More sharing options...
electau Posted June 9, 2012 Share Posted June 9, 2012 What will shorten the life of electronic ballasts is over voltage. Never experienced glowing tubes with CFL lamps when switched off. Link to comment Share on other sites More sharing options...
Crossy Posted June 9, 2012 Share Posted June 9, 2012 Never experienced glowing tubes with CFL lamps when switched off. The mode is not a glow, the CFLs give a single flash. The period between flashes is anything from 20 minutes to many hours, often it's not noticed for a long time as invariably it's only visible at night. The UK wiring method of supplying live and neutral to each ceiling rose and then running a dropper to each switch seems to accentuate the problem, particularly with long switch runs and even more-so when two-way switching is involved. Opinion is divided, but the most likely explanation is capacitive coupling between the wires in the switch dropper slowly charging the reservoir capacitor in the CFL until there is sufficient energy to initiate the ignition sequence and give a single, short, flash. This of course discharges the capacitor and nothing further happens until the charge again reaches trigger level. Adding a conventional lamp to the circuit invariably stops the flashing, as does placing a small (0.1uF) X-rated capacitor across the fitting. Link to comment Share on other sites More sharing options...
Sheryl Posted June 9, 2012 Author Share Posted June 9, 2012 With the light switched turned on, touch/lay the tester tip against the insulation of each/the two incoming wires that come through the hole in the ceiling...make actual contact with the insulation...the tester tip is actually touching the insulation. From looking at the picture it appears it would be the black wire and the white wire that has the tape connection. And actually for the black wire that is connecting to the ballast you could also just touch the bare connector of the ballast where the the black wire hooks to. The hot wire will cause the tester to light up and for any wire with no voltage on it like the Neutral the tester will not light up. Most of these type testers you just need to hold the grip and touch the bare wire or insulation and it works/lights up when voltage is detected, but there are some that may have a little press switch on the handle end that you need to press down with your finger to make it work. Pib, this is what I have been doing. Nothing lights up. i know how to use the tester and it works fine when I put it for example into a socket. the grey wire is actually slightly exposed where it enters the ballast so I also tried directly touching the uninsulated wire itself, nothing, which leads me to think that the black wire (which loops to the starter rather than going straight into the ballast) is the live one. I can't touch uninsulated black wire without removing it from the ballast as none of it is exposed. Since the tester definitely works and current is definitely there (as the light is on), could it be that the current is lower than what the tester can detect? In any case I am not sure what this test will prove? Since we already know there is current flowing to he light when it is turned off as how else would it glow?? Electau: none of the light fittings are grounded. As mentioned earlier, when the house was wired it was not grounded at all, when I realized this I had a ground installed at the main but all of the outlets, fixtures etc remain ungrounded. As I buy new appliances I've been having them grounded so 2 of the 4 A/Cs and the water pump have their own ground wires, that's it. To ground the fluorescent light fixtures would I think be a huge job. I wonder if this lack of grounding can explain it? To my (electrically illiterate) mind it might fit with the fact that the problem often disappears in the dry season and returns in the rainy (general moisture may be conducive to leaked current?). Suggestion made by others earlier than the seasonal difference is due to people on the grid using less a/c etc in the rainy season doesn't seem at all likely to me given where I live. I'm pretty much the only one on the grid with a/c and certainly the only house using anything like 30 amps (the contractor who built the house had never wired one for more than 5 amps and refused to believe I could possibly need that much!). Link to comment Share on other sites More sharing options...
Sheryl Posted June 9, 2012 Author Share Posted June 9, 2012 Update: After re-reading the instructions I thought that maybe the thing was that I was supposed to be touching both wires simultaneously. So I went back up the ladder and with some manuevering managed to do that. Still nothing (this is touching the insulated wires). Then I got the (as it turns out not so bright) idea of touching the tester to both ballast contact points simultaneously. Doing that immediately shorted out the bulb and tripped the circuit breaker. Flipping the circuit breaker back on immediately produced popping sizzling noises and another trip of the circuit. Removing the blown bulb from the light fitting, it is now possible to turn the circuit back on and the other lights on it seem to be working OK but I am now rather wary of what I may have done. What exactly is that? Can I simply replace the fluorescent bulb or does the whole fitting, ballast and all, now need to be replaced? or might it be worse than that? Is it safe to leave the circuit turned on? (I have it off for the moment) Link to comment Share on other sites More sharing options...
Crossy Posted June 9, 2012 Share Posted June 9, 2012 Oops! Please post a photo of the device you have, then we can tell you how to use it properly. If it is a simple neon screwdriver (30 Baht job) you put one finger on the end cap and touch the other end to the terminal you wish to test. It will not detect through insulation. You need to be reasonably well grounded for it to work, mine glows only dimly when I am stood on my plastic toolbox Meanwhile, shorting the ballast will have fried the tube and probably the starter, replacing them should be sufficient to get things working again. EDIT since you are going shopping, why not get an electronic ballast as well and save a few % on your electricity useage Link to comment Share on other sites More sharing options...
Sheryl Posted June 9, 2012 Author Share Posted June 9, 2012 Crossy, I am sure i know how to use the tester (it was an 80 baht thing) and I have no problem using it in other locations. I am just not showing anything at the fluorescent fixture. (Until I touched both contact points of the ballast at once-- in the split second before things shorted, the tester did indeed light up ). You say it won't show anything thru insulation and indeed it isn't but Pib said to touch the insulation? I have also tried, as described, touching the contact points on the ballast and the exposed wire of the grey line (as some of it is exposed where it enters the ballast). . Did not directly touch an exposed part of the black line as I can't get to it without undoing the ballast. Of course as it now turns out I'm going to have to replace the whole thing so when I do, I'll check the 2 lines. And just to be clear here, I touch them each separately, right? Oh and 2 more ignorant questions: (1) Ho do i tell an electric ballast from non electronic (what do they look like?) and (2) How do I know which line to connect to where when i replace the fixture? Link to comment Share on other sites More sharing options...
Crossy Posted June 9, 2012 Share Posted June 9, 2012 You need to test on the incoming lines to the fixture, one will be on the ballast, the other goes to one of the tube connections. A regular neon needs to actually touch the terminal you are interested in. What are you standing on when you test the fitting? As I said you yourself have to be reasonably well grounded when using the tester as the return path is via the body. As it seems to work properly on an outlet it's likely not getting a good enough earth path. With the switch off, neither of the incoming wires should light the tester, if either of them do, you have a switched neutral. Link to comment Share on other sites More sharing options...
Sheryl Posted June 9, 2012 Author Share Posted June 9, 2012 I'm standing on a ladder. It's a metal ladder and I was wearing rubber flip flops, would that be a problem? In any case I think we already know there is current when the switch is off, don't we? As how else could it glow? (and it glows brightly enough to wake me up!) . So if I follow you corrcetly this means the lines are reversed at the switch, yes? When I instakll the new fixture how do I know which line to connect to where? Link to comment Share on other sites More sharing options...
Crossy Posted June 9, 2012 Share Posted June 9, 2012 If you actually buy a complete new fixture there are only two wires to connect, it does not matter which way round they go although one polarity may reduce the glow somewhat (worth experimenting with). Unfortunately it is not as simple as reversing the wires at the switch, we need to determine where the polarity reversal is happening, you may have both live and neutral in the switch box, but equally you may not. Without actually seeing how the lights have been wired (there are several standard connection schemes and being Thailand it could be less than standard) it's impossible to detail simple checks that the layman (woman) can perform safely. It may be that all your lights are reversed, in which case swapping the live and associated neutral in the distribution board would likely solve the problem (of course then the wires would be the wrong colour), but I hesitate to suggest further power-on testing as I really don't want anyone to get fried. I think the time has come for power-off testing. You have a meter, do you have a long wire that you can use as a wander-lead to verify where each wire in the circuit goes? EDIT By the way, an electronic ballast will be more expensive, will probably say 'electronic ballast' on it, will likely have six connections (4 for the tube) and will not have a starter. Last time I was in HomePro they had kits of circular tube and electronic ballast, 500 Baht or so IIRC. Link to comment Share on other sites More sharing options...
Sheryl Posted June 9, 2012 Author Share Posted June 9, 2012 If you actually buy a complete new fixture there are only two wires to connect, it does not matter which way round they go although one polarity may reduce the glow somewhat (worth experimenting with). Thanks, that's reassurring. It will require a trip to the provincial town so won't do it till tomorrow. Unfortunately it is not as simple as reversing the wires at the switch, we need to determine where the polarity reversal is happening, you may have both live and neutral in the switch box, but equally you may not. Without actually seeing how the lights have been wired (there are several standard connection schemes and being Thailand it could be less than standard) it's impossible to detail simple checks that the layman (woman) can perform safely. It may be that all your lights are reversed, in which case swapping the live and associated neutral in the distribution board would likely solve the problem (of course then the wires would be the wrong colour), but I hesitate to suggest further power-on testing as I really don't want anyone to get fried. I think the time has come for power-off testing. You have a meter, do you have a long wire that you can use as a wander-lead to verify where each wire in the circuit goes? This sounds way beyond what I can safely undertake myself (or would have the nerve to). I've been living with this nuisance for many years, is there any danger to leaving it as is for now until such a time as I can get a competent electrician to come out here (which i need to do anyhow to get the SPD on a circuit)? EDIT By the way, an electronic ballast will be more expensive, will probably say 'electronic ballast' on it, will likely have six connections (4 for the tube) and will not have a starter. Last time I was in HomePro they had kits of circular tube and electronic ballast, 500 Baht or so IIRC. I'm 200km from the nearest HomePro so will have to see what's i the provincial town (Home Mart and Tesco). Anyhow if there will be only 2 wires and it doesn't matter which I connect to what, I suppose I can't go too wrong... Thanks! Link to comment Share on other sites More sharing options...
Crossy Posted June 9, 2012 Share Posted June 9, 2012 There is no immediate danger from having a switched neutral, except to someone working on your electrics who does not know. Please, switch off your incoming breaker before connecting up your new light fitting. Link to comment Share on other sites More sharing options...
Sheryl Posted June 9, 2012 Author Share Posted June 9, 2012 Please, switch off your incoming breaker before connecting up your new light fitting. You can be sure I will. At both the insulator and the MCB. I absolutely hate (and fear) having to do this stuff. the only thing worse is letting the local "chang" come in and do it. That has been known to lead to electrical fires in a matter of hours... Link to comment Share on other sites More sharing options...
Pib Posted June 9, 2012 Share Posted June 9, 2012 (edited) Sheryl, Sounds like you have a tester that is just not sensitive enough to sense voltage through insulation; only with live contact. The first one I bought was like that...it only cost about 50 baht...it said it would detect voltage through insulation but it wouldn't for me to well. I them went and bought another model (made by Solo) which packaging seemed to indicate it would be a better/more sensitive tester...it cost around 75 baht...and all I need to do is put the tester tip on the insulation and it will light up if there is 70 or more AC volts. Its specs says it can detect voltage down to 1.2V DC. It's so sensitive that the approx 1.5VAC I normally have on my neutral wire can be detected by the tester when touching a neutral bare terminal...I need to have my finger touching the tester metal top for it to detect such a low voltage...the tester's neon light will glow slightly...remove my finger and the test neon bulb glow goes away. But with the tester next to insulation carrying 220V or touching a bare terminal it lights up with or without my finger touching the end cap...when I do touch the end cap it just glows brighter. Different models out there of different quality/sensitivity. You may want to abort further testing of the light fixture based on the results/sparks. Pib Edited June 9, 2012 by Pib Link to comment Share on other sites More sharing options...
Pib Posted June 9, 2012 Share Posted June 9, 2012 Sheryl, As FYI, yesterday afternoon using an old ballast and starter (removed when I replaced it with an electronic ballast), power cord, and new 32W circular light, I hooked it up on the tile floor and then simulated the light switch being in the Neutral and Hot lines. First the Neutral line; then the Hot line. Either way I got no slight glow when either the Hot or Neutral line was removed to simulate a light switch being turned off to break the connection. And I also tried putting the ballast in the Hot line and Neutral line...once again made no difference...I did not get a slight glow when either the Hot or Neutral line was removed to simulated a light switch. But those results were at my house/on my circuits. As suggested before and as a test you may also want to try putting an electronic ballast on one light...which ever light glows the most when turned off. It may solve your problem...an electronic ballast will cost around 200 baht...even if it don't solve you problem you will know you at least tried that approach and you will also then have an instant on light versus once that flicker/blinkers during startup. Good luck. Pib Link to comment Share on other sites More sharing options...
Sheryl Posted June 10, 2012 Author Share Posted June 10, 2012 It doesn't glow initially after being turned off, not at all. The glow starts several hours later in the middle of the night. I'm going shopping soon for a new fixture if they have electronic ballasts will get. Link to comment Share on other sites More sharing options...
Pib Posted June 10, 2012 Share Posted June 10, 2012 You don't need a whole new fixture to convert to an electronic ballast. You just remove the current standard ballast and starter, and replace with the electronic ballast. Link to comment Share on other sites More sharing options...
Sheryl Posted June 10, 2012 Author Share Posted June 10, 2012 OK, baffled again. I bought the new ballast (got electric). After removing the old one and before hooking up the new, I tested to verify which wire was live. They both seem to be, i.e. both the black and the grey wire coming down from the roof are carrying current. Both light up the tester. I'm pretty sure that is not supposed to be the case. <deleted>? Could it be that when I blew out the old ballast I also caused a short in the wire up in the roof? Or other explanation? Please advise. For now I stopped with installing the new ballast and turned off the circuit involved. Link to comment Share on other sites More sharing options...
Crossy Posted June 10, 2012 Share Posted June 10, 2012 Do you have a regular light bulb you can connect to test the circuit? I suspect what you are seeing is caused by capacitive coupling (which may be what's causing the glowing). Use your meter to measure between black and grey, should be 220V that goes on and off with the switch. If that is ok (or a regular bulb behaves as expected) I doubt you have a problem other than (maybe) a switched neutral. I cannot imagine that you've caused anything nasty by your shorting the old ballast other than maybe killing your switch. Link to comment Share on other sites More sharing options...
Sheryl Posted June 10, 2012 Author Share Posted June 10, 2012 No idea how I would do this, Crossy. I have lamps with regular bulbs but not a stand alone bulb fixture that I could attach.A Anyhow I am reassured that you think there is no danger in hooking this up, I was really nonplussed when the "neutral" line lit up. . Will do so tomorrow when there's enough light to see by. Thanks! Link to comment Share on other sites More sharing options...
Sheryl Posted June 10, 2012 Author Share Posted June 10, 2012 P.S. Forgot to mention, the tester lighting up on contact with both black and grey wires is with the switch in the "off" position... Link to comment Share on other sites More sharing options...
Pib Posted June 10, 2012 Share Posted June 10, 2012 Try using your voltmeter in AC Volts Function set to measure at least 250VAC. Press the black/negative multimeter lead against a metal portion of the light fixture and then use the red/positve multipmeter to measure the AC voltage coming in on the two wires that come through the ceiling into your light fixture. The measurement/wire that gives you around 220V is your hot wire; the measurement that gives you something substantially less is your neutral wire...it wouldn't surprise me for you to see approx 20V on your neutral lead. Link to comment Share on other sites More sharing options...
Sheryl Posted June 11, 2012 Author Share Posted June 11, 2012 I'm not getting anywhere near 220. The black line shows no more than 50 and also shows it in both ON and OFF switch positions. The grey line is less, about 10-15 when the switch is in the OFF position and nothing at all when the switch is in the ON position. Clearly the black is the"live" tho I don't know why it is showing lower voltage than expected? Nor why its voltage is the same with switch off, or why the neutral carries a small charge when the switch is off (and only when the switch is off). ??? Anyhow I went ahead and hooked up the new ballast, light is working fine, won't know until tonight if any difference in glow. Link to comment Share on other sites More sharing options...
Crossy Posted June 11, 2012 Share Posted June 11, 2012 OK, you have a low impedance meter and are measuring to an imperfect ground, so you'll get much lower readings than you would expect. However, from what you have described you most definitely have a switched neutral, hopefully your new ballast will not glow or flash. In a perfect world you should get the circuit sorted as it does pose a hazard, but TiT and good luck getting your local Chang to understand. Link to comment Share on other sites More sharing options...
Pib Posted June 11, 2012 Share Posted June 11, 2012 Ditto to what Crossy said. I probably shouldn't have said you would see 220V as it would depend on how much of a grounding effect you got on the fixture which will depend on the material it's mounted to to and other factors. On my fixtures and my mother-in-laws fixtures I did get pretty close to 220V. But the key to this method is you will get a significantly higher voltage on the hot line than the neutral line for line identification purposes. And as Crossy said it sure looks like your light switch is wired into the Neutral line, which could be easy or hard to correct depending on how the drops for the light switches were installed. That is, did they just drop one line from the ceiling, like the Neutral wire, down to the switch and then the neutral line goes back up to the ceiling to continue its run with the hot wire to the fixture....or, if they dropped both the hot and neutral lines down to the switch then it should be easy to just switch the light switch from the neutral line to the hot line. Good luck...wishing you no glow tonight with the light turned off. And I assume the light does come on almost instantly now with the electronic ballast. Link to comment Share on other sites More sharing options...
Sheryl Posted June 11, 2012 Author Share Posted June 11, 2012 Yes, the light comes on immediately with the electric ballast, big improvement over the other kind. Will see tonight re the glow. Link to comment Share on other sites More sharing options...
Sheryl Posted June 12, 2012 Author Share Posted June 12, 2012 Well, it still glows. Anyhow I think we've wound up this thread, the take-home being (1) I need to get the SPD onto a circuit and (2) my fluorescent lights are wired in reverse, which is why they glow at night, it is not dangerous and would be fairly complicated to fix. Many, many thanks to Crossy, Pib and others who helped me on this. I have learned a lot! Link to comment Share on other sites More sharing options...
bankruatsteve Posted June 12, 2012 Share Posted June 12, 2012 As any Thai could have told you in the first place: you have ghosts. Link to comment Share on other sites More sharing options...
electau Posted June 12, 2012 Share Posted June 12, 2012 (edited) Correct circuit connections and polarity tests. On TT circuits if the line and neutral are looped to each switch position, double pole switches may be used. Where the line and neutral are looped from light point to light point there is a line and switched line at the switch single pole switches are used. Single pole switches are used on all MEN systems. There may be a small voltage to earth on TT systems on the neutral conductor, this is normal. Correct polarity is L to N 220V nominal. N to earth 0V. L to E 220V. The glowing tube is not a safety issue, the incorrect polarity is. A switch or protective device must always switch the line or active conductor. Non compliant or no earthing, poor circuit protection and coordination, incorrect circuit connections and incorrect polarity are common defects in Thai electrical installations. Edited June 12, 2012 by electau Link to comment Share on other sites More sharing options...
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