Hi, I just put in 18 light fixtures on a 20 amp breaker with 10 gauge wire. I put 23Watt Fluorescent bulbs in each of the fixtures for a total of 414 Watts. The lighting is great the problem is that I hear a hum along the metal conduit that the wire was run in. I don't hear any hum at the bulbs themselves or any hum along the pvc conduit between the fixtures. Any suggestions? Or is this normal? Thanks for any help. GGH
try adding more clamps to the conduit.
Of course, there are no dimmers?
RE
Did you carry a ground wire through out the system, especially to the ballasts?
Using pvc between fixtures is a bit odd. Are the lamps matched to the ballasts?
There are several grades of ballasts. El-cheap-o's do tend to make more noise.
Sorry I should have explained they are regular incandescent fixtures with the compact fluorescents no dimmers so this is "of course" normal? Thanks???
Hi I did use a proper ground through it all. They are just regular fixtures not fluorescent tube set ups. I used the compact fluorescents that go in regular sockets so I think the ballasts are in the bulb itself. I also have 9 lights lined up on a seperate circuit that dont hum and I put two lines of nine lights seperately switched on the 18 I mentioned in the original post that is why I'm curious about the hum on these 18 because even if only 9 are on i get the hum. Thanks for your help. GGH
Are you serious? I would try this since I only have about one clamp per 4 feet?
yes... to make noise something must viberate. eliminate the vibration and no noise.
The Compact Fluorescents probably have a rather low power factor and large harmonic current component, leading to current peaks way in excess of what you might imagine for a 414W load. The current generates a magnetic field around each supply conductor, and this in turn generates a force on the conductors, and can lead to their vibration at the line frequency, or some higher harmonic of it. What I would do is withdraw the condutors from the steel conduit, and wind them into a gental twisted pair before replacing them. (You may need new wires, as this will make them shorter.) This will help keep them close so the magnetic fields from each is cancelled by the other and there's no vibrating force against the conduit, and also help stop them from vibrating against each other. I'm not familiar enough with the NEC to know if it has anything to say on this though.
Hi, Thanks for the help. Now I have tried everything. Twisted wires, extra clamps on conduit (no help), I put in new wire, I put in new breakers and against my better judgement I even changed the conduit to pvc and I still have a damn hummmmmmmmm. Any more suggestions or is this just an aspect of these damn compact fluorescents. GGH
Get out the old stethescope and find out what's humming...
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