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Forum Index : Electronics : Removed the caps from my fluro lights.
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5031 |
Ok, I dont know if this was the right thing to do, but I removed the capacitors from a couple of my fluro lights and its dropped the current draw 27%. To start the story, this afternoon I connected up the shed lights to my solar power plant ( 2 80W panels, couple of batteries, controller and 600watt modified square wave inverter ). Turned the lights on and they all worked fine, but I could hear that the inverter was working hard. Closer inspection showed it was drawing 41 amps from the batteries ( 12V set up ). That seamed a bit much I thought. Now I remember when I was a kid of about 12 ( flash back thing happening here, stay with me ) the fluro in the bathroom blew up one night, big bang and lots of smoke. The electrician visited and took out a thing called a capacitor, a black chared mess. He said the fluro light didn't need it, and it was only there to make the fluro draw more power. Now since then I've also heard the cap is there to phase correct, as the fluro is an inductive load a cap is needed to balance the phase loading and keep the power authority happy. Anyway, back to the present. I tested one light circuit, consisting of 2 fluro lights fittings, 3 tubes ( 2 in one and 1 in the other ). When switched on it drew 15 amps from the battery bank. I climbed up on me ladder and took the capacitors out of both fluro fittings. 
They are connected straight across the 240vac mains. Now when I turned the lights on the power draw had dropped to 11 amps, about 73% of the draw with the caps in place. Now this raises a few questions. Is this power saving because I'm using a modified square wave inverter and the caps draw excess current on the abrupt square rise? Would the same gain be achieved if I used a sine wave inverter, or power from my normal grid supply? Is this capacitor needed at all, can they safely be left out for any fluro light, either on a cheap inverter or connected to the grid. Needless to say, I'll be taking out the rest of the caps in the shed lights tomorrow. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Hi Glenn, Yes,, dunno what the end result was ,,but back 20 years or more ago we half-techo's guys allways cut the cap's out of the fluro's they started just the same ,dunno.. magic ,,I guess. Bruce Bushboy |
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| thefinis Regular Member  Joined: 23/08/2006 Location: United StatesPosts: 53 |
For 25% savings in power draw sounds like a great idea. Seems odd to me that they would draw that much extra current just for running. They must be cycling at some point on the wave. Any less light from the fluros with the caps out or can you tell? Wonder if they will start in cold weather without the caps? Finis Texas born and bred |
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| dwyer Guru Joined: 19/09/2005 Location: AustraliaPosts: 573 |
Hi Glenn I wonder if you take the capacitors out and turn off for awhile then if you turn the fluro light back on and find it won't work so therefore got replace capacitors back on again to get this fluro light running ??? 
Dwyer the bushman |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5031 |
I've had a good look around the internet and it looks like taking the cap out of circuit is a good idea, especially if you have a modified square wave inverter! Its only there to provide some phase correction to keep the power authority happy, and not needed for the normal operation of the fluro light. On a square wave inverter it will have a big effect on the current draw, and life, of the inverter. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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herbnz Senior Member  Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Hi Glen Yea you have the right answer. On a sine wave inverter the cap will reduce current but not power strange ha I will not try to explain. on the mod wave the steep front on the wave appears as high frequency and the cap acts as a short curcuit nearly Herb |
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| herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Just a thought the above is ok if the cap is across the supply however there are fittings designed for use around rotating machines called lead lag that has cap connected in series with one leg. be careful these. aherb |
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| petanque don Senior Member Joined: 02/08/2006 Location: AustraliaPosts: 212 |
I think the capacitor makes the power meter read correctly if too many people start getting discount power eventually the power company will get grumpy. 
The flouro without the capacitor introduces some artefact it is still using the same power but the meter reads low. |
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Chris Senior Member Joined: 12/09/2005 Location: AustraliaPosts: 146 |
Ewww put the capacitor back in Glenn! Fluro's themselves alter the power factor alot. The capacitor across the fluro's is designed to counter this. The reason why it looks like your drawing less power is because your meter cant read how much reactive power you are taking, only the active power. This is one of the ways to get free electricity from your power company, but if they catch you, they will install a power factor metre, and charge you an arm and a leg for the difference in power factor! |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5031 |
Hi Chris I did some more testing a couple of weeks ago and there was only a power saving with the modified squarewave inverter, and no saving if I used sinewave power ( mains AC ). I was measuring the DC current to the inverter, so it was giving a true power reading of the effect of removing the caps. Like herbnz mentions above, the leading sharp rise of the squarewave into the capacitor was drawing the extra current. I also tested this with some fluros that were in the house ( not run from the cheap inverter ). If I removed the caps and used a AC ampmeter, there was little change in current used, infact some fluros actually drew more current with the caps removed. So I've left the shed lights cap-less, these run of the modified squareware inverter, and the house lights keep their caps as these run of the mains AC. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Chris Senior Member Joined: 12/09/2005 Location: AustraliaPosts: 146 |
If you take the caps away, then the fluro's will provide a phase shift causing the current and voltage to be out of phase. Thus making it look like there is either less or more power being taken then there actaully is. The idea of the cap's is to counter act inductive loads, which is what a fluro effectively appears as. So in theory you should leave the caps on all fluro's otherwise the voltage/current will be out of phase, which can screw up lots of other devices. Those new energy efficient bulbs, the CCFL's had and i think still have problems with power factor. They infact look like they draw so little, but they are actaully drawing quiet a bit more because of the power factor. Im not to sure if they have fixed it yet, or if it was only the crappy brands but yeh. 
What you did sounds okay, since your still running the ones on the mains AC with caps and hte cap less ones on the square wave inverter, but dont be fooled, they are still drawing hte same amount of power, the cap wont make it draw anymore or anyless, it will just change the way the power appears. If what ive said makes sense, which it all probably doesnt  |
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