Older magnetic ballasts

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so I humbly ask-- I have seen so many older fluorescent light fixtures not come on when energized but will light if you turn the switch on and off several times---??????????
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
so I humbly ask-- I have seen so many older fluorescent light fixtures not come on when energized but will light if you turn the switch on and off several times---??????????

I see you're in Missur'a. Is this usually during periods of high humidity? If you can touch the outside of the tube while standing on the ground, they'll kick on too. Something about the high humidity interferes with arc formation, and the capacitive coupling with your body is the "go" button.
 

jumper

Senior Member
I see you're in Missur'a. Is this usually during periods of high humidity? If you can touch the outside of the tube while standing on the ground, they'll kick on too. Something about the high humidity interferes with arc formation, and the capacitive coupling with your body is the "go" button.

Why do I have an intense aversion to using my body to "jump start" HID lighting?:roll:

Is it just me?:-?
 

mxslick

Senior Member
Location
SE Idaho
The new lamps have less mercury and often are hard to start or refuse to start on older ballasts. The green end tubes are the worst, I have had trouble with them even on new electronic ballasts.

Ain't progress wonderful? :roll:
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Why do I have an intense aversion to using my body to "jump start" HID lighting?:roll:

Is it just me?:-?

I didn't realize fluorescent lights were considered "HID" :-?. I had an overhead fixture above a basement work bench in a house I owned for 17 years and this was my usual routine during July and August: turn on switch, place thumb and forefinger across both tubes, light comes on. Never felt so much as a tingle as I was only touching the glass. Probably not much different than the "ball of lightning" where you touch the globe and the pretty arc jumps to the glass where your finger tips rest.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Usually, if touching the tube helps it start, it means the "grounded metal reflector" isn't.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Usually, if touching the tube helps it start, it means the "grounded metal reflector" isn't.

If true, glad I didn't learn that the hard way :grin:! Although there were times when I did touch the reflector under these conditions and still didn't get a tingle. Luck 'o the Irish I guess ;).
 

LEO2854

Esteemed Member
Location
Ma
so I humbly ask-- I have seen so many older fluorescent light fixtures not come on when energized but will light if you turn the switch on and off several times---??????????

Check to see if the fixtures are Grounded that is the usaual problem.
 

stevebea

Senior Member
Location
Southeastern PA
I'm with you on this one Larry.... I have run into this before with lamps that will not start and if I remember correctly it said on the ballast that the grounded reflector had to be within 1/2" of the lamp for proper starting.
 

broadgage

Senior Member
Location
London, England
As many others post, one likely reason for poor starting is the absence of a ground to the reflector.
Another possibility is the wrong lamps fitted.
Here in the UK older type lamps (often T12) start from line voltage after the cathodes are heated by the ballast circuit.
The more modern lamps (often T8) require a higher starting voltage, obtained from a glow starter or an electronic ballast.

A modern lamp in an old fitting may never start, but will sometimes start under favourable conditions, such as repeated turning on/off.
 

a.bisnath

Senior Member
Occupation
Electrical worker
most of the time grounding is the problem ,also even a 2 volt drop below the nomal supply voltage in some instances will not allow the tube to strike.Conducted an experiment with an auto transformer on a 120 volt lamp line voltage was 114 volts measured and lamp would not strike in one shot ,used auto transformer raised voltage to118 volts sure anough it did strike and this was with the lamp ungrounded
 
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