Why is there so much variation of color in fluorescent tubes of one temp, for example 4100k?
Some appear purple, some appear yellow and they're all marked with the same part # and came out of the same box. All ballasts are the same type and the lamps are recommended for that particular ballast.
I don't know what to try next. Has anybody else had this problem?

Cheap tubes. Ask for manuf. tolerance levels of different bulbs. Many corporations demand the bulbs are the same color and will not accept them if they vary noticeably.

high pressure sodium is yellowish, mecury jobs are greenish, metal halide is a tad blue, there's warm white, cool white, all sorts of colors.

doctor's offices want a true skin color, so there is a particular flour. that they like, meat coolers like their meat red looking...

i get the same sort of Q's, drives me nuts


somewhere, there should be a chart as to what visible spectrum is addressed..

I just went through this with some lights in a schools biology lab. The answer of cheap lamps is the most probable cause. I used the Granger catalog to help explain the problem. The catalog shows the Color Rendering Index (CRI) and it shows the lamps are rated from 0-100 with 100 being the sun or incandescent lamps. The lamps in the 41k range vari from 62 to 86. Still lamps from the same box should all look the same so its back to the cheap lamps as the cause for your problem.

Dave T.

As with any flourescent or hid lamp, let them run for a few hours they will even out.

Actually, the problem, believe it or not was mixing different brands. There were GE and Sylvania, both 4100k but still had differences. We went with GE because there were more of them and everybody is happy now.By the way, they didn't come from the same carton as I stated earlier. As we randomly removed each of the ninety fixtures from their cartons, we noticed that some came pre lamped and some didn't. The ones that didn't, got 3500k lamps. That is when the color difference first became apparent.So after three rounds of lamping and re lamping, the nightmare is over and I learned something useful. Thanks for your replies.

Don'tKnow,

I've been following your question and responses. My first impression was they were different Manufacturers. A very common thing that they look different. Thanks for telling us the end of the story so we're not left wondering.


Bill

Here is a Link to some information concerning Fluorescent Lamps, Ballasts, and Fixtures. Nothing specifically on why different brands look different though.
http://www.repairfaq.org/REPAIR/F_flamp.html


Bill

Thank you for posting this. Lots of good info there. I printed out all 22 pages and put it in a binder.
I have a new adventure now. I only had 30 minutes to check it out so I'll do an update after work tomorrow. There are sixteen 2x4's on two circuits with two sets of 3 way switches. When I turned one breaker off, two fixtures turned off, the rest were mostly off. When I turned the second circuit off, everything was off. Then I turned the first circuit back on and left the second one off and most of the fixtures were mostly off. I turned both breakers on and turned the 3 way switches on and off one at a time and the results were bizarre, unpredictable and not consistent.
Anyway, my mission, should I decide to accept it, is to add six more fixtures. Seems simple enough but this is the same group of criminologists who were unhappy with the different colors.
The new fixtures have electronic ballasts, the existing ones don't.
The whips look longer than six feet and the only one I had time to look at didn't have a ground wire so I'm assuming none of them do. I didn't notice if the flex was steel or aluminum.
This should be lots of fun.

Thanks for yet another informative link Bill. I shoot much of these to my on-line customers, nothing like an informed one!

dontknow-
post us back on your lighting snafu there...

Well I don't know everything yet and I haven't seen everything yet, but here's a new "first".
From a 120/240 single phase, 3 wire panel, circuits one and three sharing the neutral, circuit one feeding the inside lamps, and circuit three feeding the outer ones. Maybe I'm not understanding something correctly but it seems like that arrangement could be hazardous if something should happen to the neutral.
What I've done so far is put everything on one circuit and recommend electronic ballasts for the ten existing fixtures so that everything will be the same as the five fixtures I am adding.
Then there will be a total of fifteen fixtures,each with four 32 watt lamps for a total of 1920 watts times 1.25 equals 2400, divided by 120v gives me 20. The wire is #12 THHN and I pulled ground wires into the flex whips which were all steel and 8-9' in length.
Did I handle this properly? What would anybody have done differently in this situation?

Don'tknow;
without gettin' the good book out, i believe you must size per ballast, not element.
( probably because people can change an element)
then you should use the 80% rule for totals as applied to circuits.
yes, a shared noodle can have it's drawbacks, not that it's a violation. There is the consideration of the electronic ballasts vs. regular ones, i think they create more harmonics....

Don'tknow,

If you're putting things on 1 circuit I would check with the owner/tenant to be sure that's OK. The arrangement they had with 2 circuits supplying would allow them to only turn on 1/2 the lamps if they wanted to thereby saving $$$.

Bill

Most of the time that's true. Not always though. We recently completed a historical renovation of a county courthouse. As part of the renovation the flourescent lighting was demo'd and hid wall washers were installed. All of the 250w metal halide lamps were from the same manufacturer and the same type. The color differences were huge! Most were a nice white light....but many, probably %10-%15, were yellow. Very noticeable when they were mixed in the same room.

We rearranged the lamps so that the rooms were color matched then replaced the ones that we could not get to come out even.

All in all, a major hassle. Quality of materials seems to worse and worse as time goes on.....the obvious result when the job always goes to the low bid. Means we have to use low bid materials or not get the job.