jsmalone1
Member
- Location
- southwest Missouri
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---??????????
Older magnetic ballasts
- Thread starter jsmalone1
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Maybe the repeated pulses help break down the Mercury vapor so it conducts.
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
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
- Location
- 3 Hr 2 Min from Winged Horses
Why do I have an intense aversion to using my body to "jump start" HID lighting?:roll:
Is it just me?:-?
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
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
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
.
Check to see if the fixtures are Grounded that is the usaual problem.
Heres a link for more info ground fluorescent fixtures.:grin:http://members.misty.com/don/f-lamp.html#wgf
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.
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.
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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