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OT? Fluorescent Shop Light Mounting Question

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  • OT? Fluorescent Shop Light Mounting Question

    I bought and am installing some inexpensive shop lights. Two tube fluorescents that have an AC cord with standard plug and provision for hanging with chains. I have a ceiling that is only slightly over 8 foot and plan to install them directly on the ceiling (dry wall, aka gypsum board). The instructions state they should be at least 3" from the ceiling with no reason why. I just love that.

    Anyone know why they specify that. Is it some kind of minimum hanging distance for the chains, or is there some non apparent safety concern?
    Paul A.
    SE Texas

    Make it fit.
    You can't win and there IS a penalty for trying!

  • #2
    It's in case the ballasts go POOF and let out the magic smoke and start a fire. You could put a fire proof plate behind them I suppose. I have mounted them directly on the ceiling and never had a problem but I never left the lights on in the shop when I wasn't there. I use incandescent bulbs now.
    It's only ink and paper

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    • #3
      Originally posted by Carld
      It's in case the ballasts go POOF and let out the magic smoke and start a fire. You could put a fire proof plate behind them I suppose. I have mounted them directly on the ceiling and never had a problem but I never left the lights on in the shop when I wasn't there. I use incandescent bulbs now.
      That's exactly right, and they will do just that, usually you can smell them giving up the ghost though, presuming you are around, I never leave them on unattended for any length of time. Saves energy too if you are gone for even 10 minutes.

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      • #4
        I like hanging them, so that I can tilt the reflector away from me. That cuts glare, and puts more light on the machine/workbench/wall of shelves vs having it shining in my eyes as I work.
        1601

        Keep eye on ball.
        Hashim Khan

        Comment


        • #5
          Get rid of excess heat?

          Originally posted by Paul Alciatore
          I bought and am installing some inexpensive shop lights. Two tube fluorescents that have an AC cord with standard plug and provision for hanging with chains. I have a ceiling that is only slightly over 8 foot and plan to install them directly on the ceiling (dry wall, aka gypsum board). The instructions state they should be at least 3" from the ceiling with no reason why. I just love that.

          Anyone know why they specify that. Is it some kind of minimum hanging distance for the chains, or is there some non apparent safety concern?
          Air gap for heat dispersion/dissipation and/or ventilation?

          Comment


          • #6
            I use the 8 foot variety and they can be mounted flush to the ceiling. Lots of light and they last a long time.

            Comment


            • #7
              The airplane maintenance shop I worked in had 8-foot fixtures mounted directly to the wooden trusses. When one of the ballasts failed, it got hot enough to ignite the wood, and that got our attention. We never smelled the stuff oozing out of the ballast and collecting in the fixture.

              There was an airplane on jacks under the fire, so I climbed up into the overhead with a fire extinguisher to put out the small fire and disconnect the fixture.

              Roger
              Any products mentioned in my posts have been endorsed by their manufacturer.

              Comment


              • #8
                Originally posted by Carld
                It's in case the ballasts go POOF and let out the magic smoke and start a fire. You could put a fire proof plate behind them I suppose. I have mounted them directly on the ceiling and never had a problem but I never left the lights on in the shop when I wasn't there. I use incandescent bulbs now.
                The gov'mnt gonna bring that to and end soon enuf. Too bad they want us to use only these energy savings stuff with all the bad juju (mercury, etc)they contain. My only beefs with the florescents is the noise they sometimes put out, the slow time to put out adequate light in my ice cold shop and the strobing I get on my rotaing machinery.

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                • #9
                  Do you actually get strobing on rotating machinery? I know in theory it's possible but without repeating parrot fashion from what they have read, does anyone manage to see a stopped piece of equipment ?

                  The reason I ask is I have tried to reproduce this running variable speed lathes on a bench under a low florry essence light and I can't get it to work.

                  I know about those small lights on record decks that stop the marks so you know you are on 33 and a 1/3 but they are right next to it, not 7 bloody foot away.

                  At the piano company I worked at we had to hand grind small drill and cutters down to less than 0.050" to assist us they bought a powerful lab strobe lamp that could 'stop' the wheel so it made grinding easier. Once we bought a Christian drill grinder this fell into disuse.

                  After I left I had to machines some bearing bores in some deep skeletal motor housings and the view of the boring bar thru the slots was very off putting and hard to see when at speed.

                  I asked to borrow the strobe and was given it, I still have it, set up at 12 "- 15" away, the closest I could get it wasn't sufficient to 'stop' the housing. 6" away worked but it was then in the way of the carriage so I gave up.

                  Point being if a very powerful strobe, made for the job, can't do this close up what chance does a florry essence stand ceiling mounted and feet away ?

                  .
                  .

                  Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                  • #10
                    Originally posted by winchman
                    The airplane maintenance shop I worked in had 8-foot fixtures mounted directly to the wooden trusses. When one of the ballasts failed, it got hot enough to ignite the wood, and that got our attention. We never smelled the stuff oozing out of the ballast and collecting in the fixture.

                    There was an airplane on jacks under the fire, so I climbed up into the overhead with a fire extinguisher to put out the small fire and disconnect the fixture.

                    Roger
                    Aircraft maintenance shops don't have 8' ceilings, that is probably why you didn't smell it as they have a unmistakable odor when they get hot and start melting down.

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                    • #11
                      John, the phosphor decay is long enough that it VERY unlikely to
                      ever get a strobe effect to stop rotation visually.
                      ...lew...

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                      • #12
                        Originally posted by Lew Hartswick
                        John, the phosphor decay is long enough that it VERY unlikely to
                        ever get a strobe effect to stop rotation visually.
                        ...lew...
                        Not entirely true....... But WAY true enough to count....

                        If you look closely, you will see that the moving item is blurred and obviously moving, but there is a green stop-motion image that does slow, stop, reverse etc depending on RPM and number of visible features.

                        ARC lights stop motion, fluorescents are arc lights with phosphors that decay slowly as mentioned, and are not the same thiing.

                        Strobing effect of fluorescents is an old wives tale.
                        1601

                        Keep eye on ball.
                        Hashim Khan

                        Comment


                        • #13
                          Yea it depends on how much of the mercury emission lines and which
                          ones leak through the phosphor coating . The singly ionized line at
                          5460.74 would be the greenish one and I don't know if the arc
                          produces enough double ionized one at 6149.5 to make a visible
                          image of "orangish" or not.
                          ...lew...

                          Comment


                          • #14
                            Well, just for fun I hung one temporairly overnight and let it run to see how hot it would get. It is warm by the ballast, but certainly not hot. So I suspect it will be fine in normal operation. I don't plan to leave them on unattended so that should be OK too. And there is the dry wall between them and any wood so I think it will be fairly safe.

                            On the strobe thing, this will depend on two things. First, the older ballasts operate at 60 Hertz so they will show a more apparent strobe effect as it is easier to see it at lower frequencies. Some of the modern ballasts use higher frequencies which make the strobe effect harder to see. It can still be there, but it is harder to see due to the second factor below.

                            The second thing is the persistance of the phosphors used in the tubes. They are excited by the radiation from the gas in the tube, which is very intermittant as well as invisible. When the phosphors recieve this radiation, they radiate visible light. But this radiation can be for a short or longer time depending on their persistence. If it is short enough, you will see the flicker, but if it is longer you will not because the next burst of radiation from the gas will come before it has a chance to die down. Different brands and types of tubes can/will show different amounts of flicker; if they show any at all.

                            CRTs used in TVs have relatively short persistence phosphors to better show the motion so the flicker is easy to see. Just wave your hand in front of a TV and see the individual fingers frozen in multiple positions. Other CRTs, like some used in scopes, have longer persistence to show very short events by keeping them on screen for longer times. This is all before modern displays of course. But persistance is a factor there also in spite of the fact that few manufacturers ever mention it.

                            To see a maximum flicker effect, as in the phonograph strobes, they use gas discharge lighting such as neon bulbs. I have one in a turntable that I still use. Photo flash tubes are even shorter persistence and can freeze even fast motion. I believe they can be as short as 10 micro seconds or perhaps even less.

                            It has always amused me to hear people who talk about how fluorescent bulb flicker irritates them, but they can sit and watch TV for hours on end and never complain. I work with one such person and he has read about the fluorescent flicker so it bothers him. He is a informercial script writer and has a TV in his office along with all incandescant lighting. I haven't the heart to tell him that the average CRT style TV is 1000% worse.
                            Paul A.
                            SE Texas

                            Make it fit.
                            You can't win and there IS a penalty for trying!

                            Comment


                            • #15
                              As a former tv newsphotographer with a fire/police scanner in my car I won't be screwing any flourescent fixtures to my ceiling. Heard at least 1 - 2 calls a week due to defective ballast in a metro area of about 350,000. Almost as common as "meat on the stove" calls. I have the 4 footers and they are hung from the ceiling.
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