I just changed my recessed 2- 4ft light fixture in my kitchen for a
4-4ft light fixture, actually it is 2 separate light fixtures wired
together with 2 tubes and a ballast for each. When I turn them on, it
is perfect lighting for about 30 minutes and then the flickering
starts. It produces a pretty good light show. Please help.
I have yet to hear of this one before.
However, I would hazard to guess that there is a fair chance the fixture
has an el-cheapo ballast.
Cheap garbage ballasts (sometimes called "residential grade" ballasts)
are more likely to do, instead of the above, the following:
1) Result in less light than is typicaly available from the bulbs -
sometimes as little as half as much as they are rated to typically
2) Wear the bulbs out faster than "normal".
3) In the case of electronic 2-bulb ballasts, sometimes one bulb
intermittently starts dim (and sometimes recovers to full brightness) if
the ballast design is poor.
Other issues to watch for:
Ballast overheating - some cheap fixtures come with chains and need to
have air above the part of the region of the fixture where the ballast is
mounted so that the ballast does not overheat. Ballasts with "Class P"
thermal protection may cut in and out if they overheat. The traditional
type "Class P" thermal protection will usually cut in and out once every
few minutes. If this happens the situation needs to be remedied (fixture
mounted more properly or a ballast gone bad needs to be replaced). I fear
that the thermal protector could only be good for so many cycles and after
that the ballast could catch fire.
I wonder if any more modern ballasts could have a different thermal
protection scheme that dims the bulbs when overheating? The bulbs may
become electrically unstable when dimmed, especially in the
"pseudoparallel" 2-bulb and multi-bulb electronic ballasts.
Bulb-ballast mismatch - such as ballast for T8 bulbs being used with T12
ones. T12 bulbs will be underpowered by T8 ballasts, and possibly
especially with cheaper ballasts could sometimes be unstable with 2-bulb
and multibulb "pseudoparallel" electronic ballasts.
Bulb could be burning out. Look for one end of maybe only one bulb in
the fixture to be severely darkened - for a length almost twice the bulb's
Fluorescent bulbs burning out may put on a light show, especially
4-footers and especially ones run with 2-bulb and multibulb balasts and
especially with electronic ballasts. Usually the failing bulb produces a
light show for only a few hours before completely croaking. The severe
blackening of one end may not occur until after the bulb has done half an
hour to a couple hours of the flashing, flickering, strobing, swirling,
snaking, whatever it does for its "swan song".
More common for dying bulbs 2 feet or shorter is to just go on and off,
or to dim, go out and restart. Ones with starters especially tend to do
that and may do this for days before completely croaking, and wear out the
starter in the process. Because of this, starters should be replaced when
bulbs are replaced. Bad starters can be bad for bulbs, and bad bulbs can
be bad for starters.
And if you see a fluorescent bulb in a fixture with a starter glowing at
just the ends, worse if doing so brighter than a very dim reddish orange
glow, it is advisable to pull either the bulb or the starter to stop this.
The urgency is greater if the glow is either a brighter yellowish orange
or flamelike or orangish-flamelike color, or close to the color of normal
operation or somewhere in between (pinkish or pale orange), or one end
more of a flame-orange and the other more of a slightly orangish pinkish
white to normal color. Allowing this brighter end glow to continue can
severely overheat the ballast, and I know of a fire starting from that
Dim reddish orange end glow in fixtures without starters does not have
such urgency, especially not in fixtures that lack starters.
- Don Klipstein ( email@example.com)
I have almost exactly to same problem as Danny K. I haven't dealt with
fluorescent lighting in decades so I forgot about starters. I haven't
bought the replacement bulb yet It is a new fixture (2 years old) tied
to a much older fixture. Does the new one have a starter? Ballast?
Is the ballast a silver-looking round deal which protrudes from behind
the bulb? I can't get it out, but it does turn. Ides? Any help
appreciated. Q- handy (?) gal
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