I have under-cabinet fluorescent lights. Two
light fixures in parallel, wired to one single pole switch.
Each light fixture consists of 2 13W tubes, driven
by a "ballast". (So, the total rig consists of 1 switch,
2 ballasts, and 4 fluorescent tubes).
Today, 3 out of the 4 tubes went dark. Long story
short, all is well after I replaced only *one* tube. That
one bad tube had caused both tubes in 1 fixture to
go dark, *and* one tube in the neighboring fixture. (?!)
Anybody know what's going on?
To be honest, I don't have a clue as to how flourescent lights work.
However, I always replace all the tubes in any fixture that fails. To
do otherwise seems like a total waste of time.
In regards to the second fixture, I would think that there is something
coincidental going on. Assuming a good parallel connection, it strikes
me as an impossibility that the one fixture could effect the other one
(except for a short circuit situation).
There is a remote possibility, I suppose, that if the voltage is
marginal, the power factor of the failing fixture's ballast could be
dragging the power down on the other fixture. That seems kind of far
Do you have an evaporative (swamp) cooler by the way?
Have you tried removing the tube again to see if you can reproduce the
all the lamps are near the end of their life. all have the same number
of hours, and same number of off and ons. most likely all tubes are
darkened at their ends.
always replace all lamps in a mixture.
bottom line you will be needing more lamps soon........
I have about 25 fluroscent fixtures here. bulbs act flakey, replacing
one bad one often gets the other lamp working temporariliy.
after all asuming they were new and all installed at the same time
their end of life should be similiar.
the other fixture is likely a fluke........
big question are bulbs ends dark?
My experience is that replacing a bad tube usually
fixes the problem but that is with shop lighting
fixtures. The other fixture may be a fluke but
the problem is likely to be some kind of
interference from the first fixture.
In any case, replacing tubes in small under
counter fixtures is often/usually a waste of
money. The tubes often cost more than a fixture
with tubes and the fixtures seem to suffer from
heat exhaustion. I suppose it is due to the
production numbers (high numbers lower costs) but
the little tubes are very costly compared to
regular 4 foot tubes.
First, to restate the problem. I have 2 FSC3024 undercab lighting
modules. Each module consists of 2 8W T5 flourescents and a
single (complex) electronic ballast. These 2 FSC3024's are
wired in parallel and run back to a single pole switch. One T5
tube went down, and brought down the other tube in the same 3024 module
and one (?) of the tubes in the other module. When I changed the one
bad tube, everything lit up. Everything ran ok for 1 yr before this
happened. The switch is a
Lightoleer MSP600NDW, one of those fancy-pants
switches (non-dimmer) which is controlled by a "master" over an
ASCII bus, and which can be manually overridden. When 3 out of
4 tubes were dark I bypassed the switch, hardwiring to "hot". No
change, i.e. 3 out of 4 tubes still dark.
The wiring isn't exactly rocket science, but anyway I checked the
voltage to each ballast and it reads 119.6vac from hot to neutral, both
when the fault is showing and when everything is lit up.
I was hoping someone had encountered this before.
My only theory is that the electronic ballasts are of a lousy design,
and that they "crosstalk" to each other, i.e. they put out some kind of
noise spikes, especially when the load on the ballast drops below 16W.
Has anyone seen this type of behavior before. Have you had trouble
with FSC electronic ballasts?
Chris Friesen wrote:
To find out what is happening you need to see if the problem is repeatable.
Put the "bad" tube in and out several times to see if the three others
always fail to light when it is in. It is common for two tubes on a common
ballast to go out when one tube fails or is removed. I strongly suspect that
the other two tubes going out was caused by something other than the one bad
tube. Poor grounding of the metal reflector can cause some rapid-start tubes
to not light.
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