Fluorescent Lighting

[MonMotha]

So I need to install a 36" light for a lightbox I'm making (basically a holder for a marquee taken from a dedicated cabinet).  The fluorescent fixture I'm cannabalizing for this purpose (since the whole fixture certainly won't fit in the space I need it to) insists that everything must have the safety ground hooked up or bad things including overheating and low light output could result.  The box is wood, but I could ground the ballast (since that's all that appears grounded anyway) if need be.

I'm curious if this is just a "beware the consequences, do the right thing(tm)" type thing or if there's acctually a need for that earth ground to be hooked up to these fixtures.  Obviously there are plenty of fixtures (under-cabinet for example) that don't require such a thing.  Anyone know enough about fluorescent lights to figure out what they may be referring to?  If it's just a safety issue to catch the metal fixture becoming hot, that's not worth worrying about on a wood enclosure.

[Ken Layton]

If it's a "trigger" start fixture then the tube must be mounted within 1" of a grounded metal frame and the ballast grounded to ensure starting of the tube.

A 36" light fixture for a marquee??? Are you trying to blind everyone??? That's way overkill.

[MonMotha]

Ok, so I guess I'd need to have a metal plate or something running along the bottom of the enclosure so that it would start reliably.  Does it need to actually run the length (to imitate the fixture), or just be in certain areas?

I realize it will be very bright (and I do worry it may end up being too bright), but it's in a somewhat interesting application here.  I'm actually lighting a marquee that is printed on the back of a piece of plexi (about 1/6" thick) from the bottom - that is, I'm shining light into the bottom edge of the plexi.  The printing on the marquee itself is rather opaque and won't let light through.  It looks cool lit from the back nonetheless, but I'd like to be able to read it in the dark.  It's also rather large at almost 4 feet in length (it's about 44" long), hence the use of a big tube - I want fairly even lighting.

Is there an easy way to dim fluorescent lights?  I know you can't use the traditional triac approach taken with conventional incandescent dimmers.

Thanks for the info - While I do lots of computer and digital work, I'm not very familiar with fluorescent lighting.

[Fozzy The Bear]

Is there an easy way to dim fluorescent lights?  I know you can't use the traditional triac approach taken with conventional incandescent dimmers.

Scrap this whole idea about ripping a fitting to pieces and go buy the correct size fitting for your box!!! It's quite clear that you are not an electrician. What you are doing is dangerous, when in fact you actually very clearly, have no idea what you're doing. It's really not something that should be described to you on here.

As for dimming a Flourescent Tube..... you are actually not quite correct about not being able to do it with a triac.  You can in fact do it if you also connect a balast load to the circuit. Say for example a 150Watt incandescent lamp.   BUT! the light output from the Flourescent will be relatively unstable and non linear. Not really what you want.

Best Regards,
Julian (Fozzy The Bear)

[SirPeale]

Jeeze...all that work - dangerous work.  Just fit in a couple F15 fixtures.  Problem solved.

[MonMotha]

The fixture is the correct size, at least in terms of width and length.  The thing is meant to take the 36" tube that I'm using.  The issue is that the channel formed underneath it (where the ballast is mounted and the wires are meant to be run) is far too tall.  My biggest concern is heat from this stuff, actually.  It's a fairly tight space.

You really can spare me the "dude, electricity is dangerous, you're going to kill yourself" lecture.  The EE degree taught me plenty of that, and if I wasn't aware of it beforehand I would be dead by now anyway.  I appreciate your concern and information (including safety info, especially application specific or otherwise non-obvious safety info that I might not be aware of), but the alarmist stuff is unneeded.  The guy who sold me the fixture (and actually saw what I was going to do) was fairly optimistic that this would work fine, but apparently did not take into account the ground plane requirement, hence why I decided to ask - I don't do fluorescent lighting (my work is mostly digital and RF).  The person who sold it to me is, after all, just your average hardware store lackey: a fair bit of experience selling them, but likely very little in actually installing or using them.

The issue with using most stock fixtures is vertical clearance.  In most cases, the problem is dead space underneath things.  My objective was to elimate that dead space: for the "metal plate" I was just going to use the mounting plate for the original fixture.  It may be that I just can't fit a fluorescent in there (especially given heat concerns), and I'll just leave it unlit in that case since it isn't worth moving to more esoteric methods of lighting.

I'm guessing that it's probably easier to just attempt to cram an undercabinet light in there (though even that'll be fun...these lights have lots of extra plastic on them).  It's too bad though - I wanted the more even light.

[SirPeale]

An F15 fixture (undercounter) are dead easy to replace, they're an industry standard.  And once behind a marquee, you'll never notice.

[MonMotha]

I managed to find a 22" T5 undercabinet type fixture that (just barely) will fit in the space needed with no modification.  Unfortunately, I don't believe T5 comes in 36" (or if it does, you can't buy it at your average hardware store), and as a result of it being so much shorter, the lighting is a bit uneven, but concentrated at the center it doesn't look too bad - I'd still like more even though.  At least the shorter stuff is lower power, so there is less of a heat concern.  It's solid state, so no giant ballast, too - definately a plus.