Fluorescent Lighting Harmonics
Fluorescent Lighting Harmonics
(OP)
Hello,
Our company is in the process of installing lighting circuitry for an office building. The electrical engineer has circuited these lights with a seperate neutral for every lighting circuit. The fluorescent lights are 120 volt, 3-lamp T-8, electronic ballasts, approximately 80 fixtures. Many of these fixtures are dual switched and have two seperate circuits feeding them. This is the first time I have ever seen this type installation.
Will this wiring method reduce the amount of harmonics in this system?
Thank you, Andy
Our company is in the process of installing lighting circuitry for an office building. The electrical engineer has circuited these lights with a seperate neutral for every lighting circuit. The fluorescent lights are 120 volt, 3-lamp T-8, electronic ballasts, approximately 80 fixtures. Many of these fixtures are dual switched and have two seperate circuits feeding them. This is the first time I have ever seen this type installation.
Will this wiring method reduce the amount of harmonics in this system?
Thank you, Andy






RE: Fluorescent Lighting Harmonics
Mike
RE: Fluorescent Lighting Harmonics
As for separate neutrals, they don't reduce harmonics. The concern is that 3rd harmonic current adds in common neutrals. If there is enough 3rd harmonic current, the neutral can overheat. Running separate neutrals (or some people use oversized common neutrals) eliminates this possible problem.
It is my opinion that running separate neutrals is an unnecessary cost for typical fluorescent lighting. I am not aware of any reported cases of excessive harmonic current in lighting branch circuit neutrals. Separate neutrals also increase voltage drop in your circuits.
RE: Fluorescent Lighting Harmonics
RE: Fluorescent Lighting Harmonics
It may be time well spent discussing harmonic performance with a few fixture/ballast reps. It seems like there has been significant advances in the last decade, considering that losses from harmonics in discharge lighting has been made a priority at the regulatory level.
It would probably be worthwhile writing a performance spec, and specifying field verification before project turnover.
RE: Fluorescent Lighting Harmonics
RE: Fluorescent Lighting Harmonics
http://www.gelighting.com/na/downloads/ballast.pdf
for fluorescent fixtures ballast parameters. THD varies from below 10% to below 32% (which is high).