EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: Delta on September 10, 2016, 06:33:34 pm
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I had a problem with a circuit tripping first its 30mA RCD (earth leakage detection*), and then its B16 MCB (overload / short circuit detection*), which I eventually traced to a 1990s vintage 5ft fluoro strip light, fitted with an F65W/35 tube.
On opening the fitting, I found a 5uF capacitor connected directly across the (240V) supply. This capacitor did show some continuity to earth at around 300k \$\Omega\$ (measured using my Fluke 115 DMM - which I know is not the correct instrument for this task), and although measuring at exactly 5uF still, I reckon it must have serious leakage at 50Hz/240V, as it was tripping a 16 amp breaker.
Anyway - I don't have a replacement capacitor, and I plan to replace the fitting completely with a LED setup in the near future - is there any harm in running this fitting without the cap? (Other than a worse PF, but for 65W, meh...)
*just added that as I know different countries have different terms for these things...
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I think I have run the FL lamp in our bathroom for years like that. Still I got fed up with changing the lamp every few years so I converted it to an electronic ballast several years ago.
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No issue at all, just the current through the switch will be higher, and there will be slightly more arcing at every turn on and turn off. Not enough to worry about though.
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Thanks guys! :-+
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It shouldn't cause any problems, other than higher energy consumption, due to increased I2R losses in the cable, so why not insulated the case of the capacitor from the lamp fitting and thus earth? That way there will be no earth leakage to trip the RCD.
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It shouldn't cause any problems, other than higher energy consumption, due to increased I2R losses in the cable, so why not insulated the case of the capacitor from the lamp fitting and thus earth? That way there will be no earth leakage to trip the RCD.
I did consider that, but given that it sometimes it was tripping the 16 amp breaker instead of the RCD, I thought there might also be some serious internal leakage in it too (ie from L to N terminals). Secondly, whilst I've done many a bodge with extra low voltage low energy stuff, I don't like taking any chances with mains powered gear.
PS. I think the initial fault and my testing has caused the contacts in the timeswitch that controls the light to weld themselves together.... (And yes, it is a heavy duty 16A type, intended for immersion heaters...) :palm: