General lighting and electric question on fluorescent fixtures

[JLNorthGA]

NOT theatrical fixtures. I have a drop ceiling in my basement. I have drop in troffers (2 x 2 on one side and 2 x 4 on the other). I get a LOT of static on my FM radio when the lights are on. Needless to say, I prefer not to have the static.

Suggestions?

I have even contemplated switching over to LED troffers.

 

[Les]

Maybe you could wrap a few ferrite chokes in there? Need to do a bit more research on which part(s) of the circuit they'd be most effective - if at all - but it might be an interesting project.

 

[DavidNorth]

Funny enough, I was going to assume electronic ballasts and that you should check grounding, mostly because I have seen many household installations done without grounding, and then I found this....

http://www.gelighting.com/LightingW...ectronic-Ballasts-Whitepaper_tcm201-78523.pdf

So, to make sure both the fixture housing and the ballast are well grounded. Maybe even scrape some paint off between the two to verify connections. Twist feed wires and also twist lamp wires. Consider changing to a better electronic ballast or LED.

Do remember that the lamp wires are going to have higher voltage on them than mains so do be careful about what you do with them and do not work on this live.

Interested to know if something you do makes it better or worse.....

David

 

[FMEng]

Electronic ballasts can radiate RF, even though they are not supposed to. Some are better than others. A few years back, there was a GE product that was so bad that it got the FCC's attention. Un-intentional radiators is an area where the FCC severely falls down on the job.

 

[RickR]

Check the grounding of the circuit all the way back to the breaker panel. Be especially alert for the neutral and the ground meeting. It's not supposed to happen but it does. A little know fact; fluorescents should have a ground along the tube (CFLs are weird and small) generally the body of the fixture. If that grounding is weak the arc is unstable and you get increased EMI.

Old magnetic ballasts also create EMI. If you have magnetic ballasts replacing them (and maybe the whole fixture) is a really good idea. Loose sockets (tombstones) or other wiring issues can create problems as you get a little arcing.

 

[JD]

Depends if the noise is forward radiation (Coming from the fixture) or backwards radiation (Noise broadcast from the wiring to the fixture.) In the case of backwards radiation, Les has the answer above. Grab a ferrite choke core off an old computer monitor cable or right out of a scrapped PC supply. (All you want is the little metal ring, no wires.) Loop the Hot and neutral ballast wires in the fixture through it two or three times. This will snub any RF from back-feeding from the ballast to your house wiring. Forward radiation is harder to fix as it would have more to do with a poorly designed or defective fixture. Sadly, there are a ton of those out there! Solid State ballasts usually scream in the RF bandwidths inside, but are suppose to be sufficiently shielded as not to radiate. If it's a transformer based ballast then RF noise would indicate a failing power factor cap inside the ballast can. Replace it.

 

[Dionysus]

In agreeance with much that was said regarding EMI and RFI. Also never forget other factors that are "fun" with things like florescents such as Power Factor and other changes to the electrical system itself (yay for mangled waveforms?).

Efficient fluorescent lights have a 90% PF, which means that they actually cause a phase shift to the electricity. Actually this is one reason why flourescents were commonly used in factories with large inductive loads. Capacitive and Inductive loads have opposite effects that cancel out.
I remember back in the factory many of my family worked in (before it closed down) the Power Factor correcting Capacitor banks. Lots of fun.

Anyways regardless, not everything is approved for it's emission or protection against EMI and RFI (and other forms of interference), and as stated, when things get old this gets worse. Cheap units are far far worse typically as well. And even things that ARE approved by regulatory bodies, do not have full "protection" (shall we say) they just fall within a guideline.

Failing capacitors in florescents or old windings (especially when they start to leak tasty tar) happen often enough, and are going to create a much bigger problem.

Are the flourescents T12, T8, T5? Ive seen a lot of horrible T12 8' HO fixtures create lovely problems and keep working.
Electronic Ballasts, vs not of course are hugely different animals.

Thoughts?