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View Full Version : The eternal mysteries of fluorescent lights



Lynn Kasdorf
11-29-2006, 2:17 PM
I have always struggled with fluorescent lamps over the years. It seems like the y just stop working, then start up again. Sometimes I'll swap in new bulbs to no effect. Bulbs I thought were dead work in another fixture. Lamps flicker sometimes, etc.

After stumling across this site:
http://members.misty.com/don/f-lamp.html#int0

... I may know what is going on. Apparently, on rapid start fixtures (like most of us have) grounding the lamp chassis is important. Not just for safety reasons but for starting reasons!.

Apparently the capacitance between the bulb and the refelctor assists in starting!

I recently obtained some used 4 bulb 2x4' fixtures, and I did the normal frustrating dance of bulb swapping with inconsistant results, trying to find a combination that works. I wire nutted a simple lamp cord with no ground onto the thing and was trying to get it to work with poor results.

After reading the article, I swapped in a grounded cord and shazam! It started working!

Steve Canada
11-29-2006, 2:27 PM
Interesting.

I just installed my shop lighting, but haven't had any flickering issues.

Does anyone have any recommendations on reducing humming? I have 8 DBL 4' fixtures, and 2 hum, although I can't locate which ones.

Frank Snyder
11-29-2006, 2:46 PM
I'd also like to know how to eliminate, or at least reduce, the humming as well. Is it something insode the fixture or ballast which is vibrating?

Lynn Kasdorf
11-29-2006, 3:20 PM
The article discusses hum somewhat. But the real solution is T8 fixtures with electronic ballasts. These run the bulbs at a higher frequency, so there is no hum.

The T8's I have work really well- start instantly even when the ambient temp is really cold.

But- I have (and seem to keep getting) older style fixtures and bulbs for free....

Al Willits
11-29-2006, 3:21 PM
Found this, maybe it'll help


Humming or buzzing in a fluorescent light fixture is usually caused by a ballast that's poorly built or improperly mounted. The hum occurs as electrical current moves through metal plates in the ballast.

With the power off, open the fixture. The ballast is a metal box about 2 by 3 by 10 inches with wires leading to it. Make sure that the mounting screws are tight. If there are vibration-isolation spacers, check them. Compare this bad fixture to any similar quiet fixtures you may have to identify the problem. It may be necessary to replace the ballast. Also check to make sure that the framing of the fixture is not amplifying the sound. You may need to change the mounting.

Al

Bill Arnold
11-29-2006, 3:27 PM
... The T8's I have work really well- start instantly even when the ambient temp is really cold. ...I installed eight 2-lamp 4' T8 fixtures in my existing 16'x24' shop building. I haven't noticed any issue with hum. All eight are on the same switch. One interesting thing about them is that all eight of them come on simultaneously about a second after the switch is flipped. So far, they have operated well at low temperatures -- well, low by South Georgia standards -- down to the upper 30's.

Dustin Bartlett
11-29-2006, 3:30 PM
I'll add something I learned a while ago about the bulbs. If you can, try and get a bulbs with a color temp over 5000K and a CRI (color rendering index) of 90 or higher. The closer these get to 6500K and a CRI of 100 the closer the light is to matching sunlight from an imaging perspective. Makes the colors you see in your shop more accurate and is also a lot easier on the eyes.

Steve Canada
11-29-2006, 4:19 PM
Before we go to far down the lighting brick road, read this post of mine. It's a month or so old, but gets very indepth into choosing bulbs and why.

http://sawmillcreek.org/showthread.php?t=41349

John Gornall
11-29-2006, 4:44 PM
I read the instructions that came with my last bunch of ballasts. It said to leave them on for the first 48 hours to avoid hum - I did - they don't hum.

At work I installed T8's with electronic ballast - more light for less power - start fast - never hum - I'll use these from now on.

I only use "daylight tubes" - I like the color, makes it easier for me to see.

Al Willits
11-29-2006, 5:19 PM
I've just spent a bit over a hour researching lights....add confusion to my learning curve..

I got some high temp lights 5700 or 6100k I think from Phillips...they had a blue tinge to them, drove me crazy and brought them back, found some high 4000k ones that the guy at menards said were very white and bright...found out only if the garage was over about 65 degree's...brought them back.
Finally went back to the Sylvania cool white plus for utility and shop usage and at 4100K they ain't to bad, and they work down to 38 degree's, which is what my garage is at when not in use.

It appears I'm missing the boat here and there are lights out there that would work better, brighter, whiter...but not sure which ones to get.

I have a Lowe's/Menard's/Home Depot close so anything they have would be nice, don't mind online ordering, but I'd like to make sure they don't end up pink or some other odd color.

Wandering though any of these stores gets multiple answers and even more confusion.....helpppppp!!!!!

Considering temps and cri numbers have just confused both the store clerks and myself.
Can someone please give me a name and model of a T-12 bulb I should try?

Al...who thought he was well light.....till now...:)

John Gornall
11-29-2006, 5:23 PM
My favourite - Sylvania "Daylight Deluxe"

Robert Mayer
11-29-2006, 5:33 PM
I have been using them for 5 years with no problems. Only issue I have is slapping them with a 12' piece of wood and exploding them all over the shop.

Al Willits
11-29-2006, 5:51 PM
Ok, so if I can find a box of tubes that say "Daylight Deluxe" on them, I'm good to go?

Thanks, makes life a bit easier for the old guy here.

Al

glenn bradley
11-29-2006, 6:34 PM
Yeah, that zero cost factor is what keeps ballast T-12 fixtures in some locations in the shop.

Brad Noble
11-29-2006, 9:12 PM
I have 14 3-bulb 4' T-8 fixtures in my 16 x 24 shop. The difference is my fixtures all have electronic 277 volt ballast in them. I run them on 240 volts. The trick was to get them to work on regular 110V light switches, and three way at that. I have no hum to speak of and they've come on just fine so far and we've had a few days down in the 20's already.

Brad

Roger Myers
11-30-2006, 12:07 AM
Found this, maybe it'll help


Humming or buzzing in a fluorescent light fixture is usually caused by a ballast that's poorly built or improperly mounted. The hum occurs as electrical current moves through metal plates in the ballast.

With the power off, open the fixture. The ballast is a metal box about 2 by 3 by 10 inches with wires leading to it. Make sure that the mounting screws are tight. If there are vibration-isolation spacers, check them. Compare this bad fixture to any similar quiet fixtures you may have to identify the problem. It may be necessary to replace the ballast. Also check to make sure that the framing of the fixture is not amplifying the sound. You may need to change the mounting.

Al

Not quite as black and white as that... older fixtures (T-12) generally have magnetic ballasts as opposed to electronic ballasts... magnetic ballasts will gnerally have some degree of hum, anywhere from barely noticeable to downright aggravating...this will have to do with the construction of the ballast, how well the laminations inside were vacuum impregnated and so on... To silence them is challenging. Newer electronic ballasts rarely have noticeable hum, are more energy efficient, and generally start well at low temps... the good news is you can retrofit old T-12 fixtures with new T-8 electronic ballasts...change the tubes to T-8 tubes, and save energy, have better light, and quieter fixtures.
Roger

Al Willits
11-30-2006, 1:53 PM
Thanks Roger, I posted that in hopes it might help.

Several have mentioned go to the T-8 bulb and changing ballast, seems some of the shop lights I just bought say will work with both T-8 and T-12 bulbs.
Gonna assume that maybe the new ballasts will work for both, but the older T-12 units won't work with T-8 bulbs?

Al

Roger Myers
11-30-2006, 2:39 PM
Unless the ballast specifically lists T-8 lamps, then you shouldn't assume they will work... and certainly not optimum for the bulb.

Al Willits
12-01-2006, 9:59 AM
Roger, Below is what they say on the box.
After looking at several they offer, looks like some will and some won't.
Nice option for those of us (me) that bought T-12 bulbs and may want to switch over.
Al


48" x 7.5"
Professional quality
Ideal for work areas, garages, utility rooms, basements and recreation rooms
Not recommended for use with timmers, photo cells and motion control deivces
Minimum starting tempeture is -20 degrees F
Uses two T32 T12 or T32 T8 bulbs, sold separately
Dry locations only
Two year limited warranty