Fluorescent Not Starting At Initial Turnons ?

[sligoNoSPAMjoe]

Try it, you may like it.

[George]

Considering where you bought it that would be a good guess.

My buddy really bought into all of the HD marketing. He had an outbuilding built and asked me to help him hang 4, 8' HO strip fixtures. He bought them from "the depot". Three of the fixtures didn't light properly. After troubleshooting and swapping stuff it turned out 3 of the ballasts were bad. We pulled the fixtures to return them. We brought them back and at least the guy was honest. He said they had changed over to some even cheesier supplier and returns were common. I told my buddy he was going to do the job himself if he bought more fixtures from "the depot". He bought 4 better quality fixtures at the local real supply house for less money and they worked the first time we turned them on.

[dpb]

...

For what reason? Makes no sense unless the neutral is bad.

--

[Don Klipstein]

The reason why grounding can make a difference:

If the fixture is grounded, then the "electric field" ("voltage gradient") within a bulb that has voltage across it but is not yet conducting,

is concentrated in one end around one of the filaments. This increased concentration of "electric field" helps the gas in the bulb break down there. Once the breakdown begins, the electric field distribution changes, resulting in concentration of electric field at the tip of the breakdown region - provided the fixture is grounded. This helps the breakdown spread over the length of the tube.

Grounding the fixture helps the breakdown begin, and helps it spread over the tube.

===============================

Should all bulbs in a fixture glow dimly over their entire lengths, then grounding is not the problem. If all or any bulbss in a fixture do not glow at all or only glow with "filament glow", then the problem may be grounding or need to clean the bulbs - and one of these is probably the problem if touching or stroking the bulbs helps them to start.

Keep in mind that temperature colder than the ballast is rated for, bulb/ballast mismatch and use of 34 watt version of F40T12 ("energy saver F40") can make things "crankier".

- Don Klipstein ( [e-mail])

[dpb]

Don Klipstein wrote: ...

Just how does it decide which end???

The bulb isn't tied into the ground, only supply/neutral.

...

[dpb]

OK, I went and read up on these-here new-fangled thingies...I see now; the age of the house and church is apparent when there are no rapid-start fixtures in sight so I'd never actually looked into them for no need to...

Your explanation is sorta' about the mark but not directly to the actual construction/operation as to make any sense but after reading some online detailed discussions I now see what they consist of...

So, ok, grounding is indeed important for newer (current-day) fixtures...

I'll be jiggered, so to speak... :)

--

[clare]

Then you too are one lucky son of a gun, or perhaps you still have the old units with neon starters?????

[clare]

You need to understand how discharge tubes light. Flourescents are gas discharge tubes, and they work something like a xenon strobe - which will not fire untill the "trigger" is energized - and the "trigger" is not inside the tube.. The capacitive coupling of the tube to groud reduces the amount of voltage required to fire the tube,

It is a well known fact among electricians and knowlegeable homeowners that a bad or missing ground can make a flourescent fixture difficult to start - particularly if cool or danp.

[Don Klipstein]

In most 120V North American fixtures, one end of the bulb (or the "low one" of a "series pair") is tied to ground via neutral if the wiring diagram on the ballast is obeyed, even if the fixture is not grounded. In USA, 120V circuits have "neutral" being a/the "grounded conductor". (And the "safety ground" is the "grounding conductor", usually tied to the "grounded conductor" at the breaker box, and "hot" is the "ungrounded conductor" with full 120V with respect to "ground".)

The other end (of the bulb or of a series pair thereof) gets full voltage of the line and any "inductive kicks", or full voltage of a voltage-boosting ballast (such as the 120V-North_America-"traditional" dual-F40 "rapid start magnetic ballast" and North American 120V "trigger start" ballasts).

Grounding the fixture means that until the bulbs start conducting, assuming their surfaces do not conduct along their lengths due to hygroscopic dirt, that the electric field gets concentrated in the gas around the "ungrounded end" electrode, and such concentration of electric field gets the gas in that region of the bulb to "break down".

- Don Klipstein ( [e-mail])

[Bob M.]

No. All are electronic ballasts. The old magnetic ballasts were removed three years ago after I got sick of the buzz. (the upstairs units were original too, ~50 years on them). 6 upstairs controlled via a solid-state relay, 6 in the basement controlled via normal switches. Not a single problem.

[JIMMIE]

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Make sure all the covers are in place for the same reasons Don gave, the grounding is that important. I once left off a reflector because it was a pain to put back on while standing on a ladder and thinking it was unimportant. I wasted a weekend working on my shop lights trying to get them to work. The reflector was part of a ground plane for the lights.

Jimmie

Jimmie