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Thread: T12 AND T8 ballast? Or does it have to be one or the other?

  1. #1

    Default T12 AND T8 ballast? Or does it have to be one or the other?

    Hi! I'm really confused about some light fixtures I have. I bought the cheap shop lights Walmart sells. I didn't really pay any attention to what the box said, put T12 bulbs in, and threw the boxes away.

    Then I got to thinking that maybe the fixtures had T8 ballasts, so I looked up the model number, and found this: http://www.lightsofamerica.com/Products/8045E.aspx

    The product description says it can operate either T8 or T12 bulbs. Is it possible that for $10 you could buy a light with a ballast that is well suited for both types? I figured it was actually designed for T12 but T8 still works (with more rapid loss of bulb life).

    I'd rather run T8's, but only if the fixture was truly designed for that!

    Do some ballasts work well for both T8 and T12?

    Thanks!

    Ted

  2. #2

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    It was designed to operate T8 well because the power rating is about 32 watts/bulb. It operates T12 at substantially less than than the bulb rating of 40 watts. Your reference doesn't specify whether the fixture uses instant or rapid start ballasts. You should know that most, if not all, T12 bulbs are NOT designed for use with instant start ballasts. That doesn't stop ballast manufacturers from making instant start ballasts for T12 bulbs, but using instant start ballasts voids T12 warranties, not that I would worry.

  3. #3

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    So these lights will operate either bulb type, but the T8's much more efficiently, right?

    This brings up an interesting question. I don't know how if these fixtures have instant or rapid start ballasts, but they do say they have "cold start" ballasts.

    I ran T12 bulbs in these fixtures for a while, but put T8 bulbs in to see if they would work. They worked well for several days, but then a couple of the fixtures quit working. I checked to make sure the bulbs were seated properly and still they didn't work. However, when I unplugged the fixtures, and plugged them back in they started working again. This happened a number of times, though sometimes I have to unplug several times before they will kick on again. I put T12 bulbs back in, and they consistently worked fine. Strange! Maybe this has something to do with the instant/rapid start ballast issue?

  4. #4
    Flashaholic jhellwig's Avatar
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    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Quote Originally Posted by aruzinsky View Post
    It was designed to operate T8 well because the power rating is about 32 watts/bulb. It operates T12 at substantially less than than the bulb rating of 40 watts.
    4' T12 bulbs are rated for 34watts. Energy saving and all that bs.

    Fullam (I think it the name) is one manyfacture of ballast that have a wide range of bulbs that they can operate. The basicly give you a maximum wattage that the ballast can handle.

  5. #5

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Quote Originally Posted by jhellwig View Post
    4' T12 bulbs are rated for 34watts. Energy saving and all that bs.

    Fullam (I think it the name) is one manyfacture of ballast that have a wide range of bulbs that they can operate. The basicly give you a maximum wattage that the ballast can handle.
    No, SOME T12 bulbs are rated for 34watts; most typically 4 ft. T12 bulbs are 40 watts. See http://en.wikipedia.org/wiki/Fluorescent_lamp_formats .

  6. #6

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Quote Originally Posted by Paperdesk View Post
    So these lights will operate either bulb type, but the T8's much more efficiently, right?
    If the ballasts are instant start, it is rumored that the average life of the T12 bulb will be shorter than advertised and there is a safety issue because the ends of failed T12 bulbs will become very hot. T12 bulbss are usually less efficient than T8s for other reasons.

    Quote Originally Posted by Paperdesk View Post
    This brings up an interesting question. I don't know how if these fixtures have instant or rapid start ballasts, but they do say they have "cold start" ballasts.
    You should be able to see whether the lights come on instantly or not.

    Quote Originally Posted by Paperdesk View Post
    I ran T12 bulbs in these fixtures for a while, but put T8 bulbs in to see if they would work. They worked well for several days, but then a couple of the fixtures quit working. I checked to make sure the bulbs were seated properly and still they didn't work. However, when I unplugged the fixtures, and plugged them back in they started working again. This happened a number of times, though sometimes I have to unplug several times before they will kick on again. I put T12 bulbs back in, and they consistently worked fine. Strange! Maybe this has something to do with the instant/rapid start ballast issue?
    I doubt it. I have used American Fluorescent 234SLESW Shoplights (instant on) without problems. Sometimes they are on sale at Menards for around $10-$15.

  7. #7

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    If it is designed for either T8 or T12, using either wont affect the ballast but as others said if the fixture lights the tubes instantly its hard on the T12s. I also think the fixture will underdrive T12s by driving 40w rated lamps at 32w, so they will be slightly dimmer than the T8s in this fixture.

  8. #8
    Flashaholic jhellwig's Avatar
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    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    No, MOST t12 4 foot bulbs are rated for 34 watts. When the bulbs originaly came out they were 40 watt. When the first wave of energy regulation came out in the day they went to 34 watt. Yes you can still buy 40 watt bulbs but they are the more specialized bulbs and bulbs aimed at the every day consumer that only comprehends bigger numbers and shiney packaging. If you buy the cheap normal warm white or cool white bulbs they will be 34 watt. Go to an electical supply house and the very big majority of bulbs they have are gonna be the lower wattage ones.

    If you buy "shop light" bulbs they are rated for 25 watt.

  9. #9

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Very interesting! My lights come on right away, so I guess they're instant start. Still seems strange that some fixtures will run the T12 bulbs but not the T8 bulbs, and others that were bought at the same time and are the same model, will run the T8's just fine. Interestingly enough, I found a T10 bulb in with my other bulbs, I don't even know where that one came from!

    I'll think for now I'll run T8 bulbs in as many of the fixtures as I can, and run T12 in those that won't power the T12's.

    Ted

  10. #10

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Quote Originally Posted by Paperdesk View Post
    Very interesting! My lights come on right away, so I guess they're instant start. Still seems strange that some fixtures will run the T12 bulbs but not the T8 bulbs, and others that were bought at the same time and are the same model, will run the T8's just fine. Interestingly enough, I found a T10 bulb in with my other bulbs, I don't even know where that one came from!

    I'll think for now I'll run T8 bulbs in as many of the fixtures as I can, and run T12 in those that won't power the T12's.

    Ted
    What are the wattage ratings written on your T12 bulbs?

  11. #11

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Quote Originally Posted by jhellwig View Post
    No, MOST t12 4 foot bulbs are rated for 34 watts. When the bulbs originaly came out they were 40 watt. When the first wave of energy regulation came out in the day they went to 34 watt. Yes you can still buy 40 watt bulbs but they are the more specialized bulbs and bulbs aimed at the every day consumer that only comprehends bigger numbers and shiney packaging. If you buy the cheap normal warm white or cool white bulbs they will be 34 watt. Go to an electical supply house and the very big majority of bulbs they have are gonna be the lower wattage ones.

    If you buy "shop light" bulbs they are rated for 25 watt.
    And, where, besides Iowa (population 3,007,856 ), is this "energy regulation?" Look at the 40 watt T12 bulbs advertised by Menards in Illinois (population 12,910,409) Chicago area:

    In fact, I have never seen less than a 40 watt 4' T12 advertised here.

  12. #12

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    My T12 bulbs all say 40 watt. I just bought a bunch more from Walmart and they also say 40 watt. Maybe in CA or other states they only sell 34 watt or something? I'm in WA.

  13. #13

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Quote Originally Posted by Paperdesk View Post
    My T12 bulbs all say 40 watt. I just bought a bunch more from Walmart and they also say 40 watt. Maybe in CA or other states they only sell 34 watt or something? I'm in WA.
    From http://groups.google.com/group/sci.e...e47d683c4b0585 ,

    there is a USA Federal Law, Energy Policy ACT (EPACT) and 40 watt, 48 inch, T12 are legal provided

    1. The output is at least 75 lumens per watt.

    2. The color rendering index (CRI) is at least 82.

  14. #14
    Flashaholic jhellwig's Avatar
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    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Shiney consumer oriented packaging special purpouse blaa blaa blaa excuse me for being an electrician for and not doing much residential never seen a 40 watt outside of stuff from 1955 yada yada yada or whatever junk the homeowner bought from menards flippity floopity floop changed out a mind numbing amount of bulbs and ballast in industrial and commercial facilities and never run across 40 watt bulbs.............


    On another note I just read through the ge light bulb catalog and see that they still make 75 watt 8' bi-pin bulbs.......


    Can I go ahead and say that those cheap shoplites use cheap ballasts that don't last long anyways so don't lose any sleep over what bulbs you put in them or is anyone going to object to that observation?
    Last edited by jhellwig; 03-23-2011 at 08:19 PM.

  15. #15
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    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Take apart the fixture and see if it has 1 or 2 little boxes with wires coming out tucked in the ends between the lamp sockets. If so, it's likely based on the "resi-tronic" ballast which are pretty terrible. They are nothing more than just a bunch of capacitors) and are known to burn lamps out rather quickly (sometimes within as little as 2 months). If you pay close attention, you'll notice that one end of the tube gets blackened rather quickly.

    I've experimented with running T8 tubes on T12 ballasts in the past and its pretty picky. My best result was with an old Robertson S40B Preheat ballast (the type requiring a starter). Most residential rapid-start ballast I tried don't fully light the tube up with the exception of a single lamp Advanced Mark III although that one blackened the tube ends rather quickly.

    Keep in mind not all T12 ballast will act nicely with T8 tubes. Some old GE-Magnatek-Universal ballast do not like anything other than true 40 watt tubes. Even the 34 watt "energy saver" tubes will case them to overheat and eventually burn out.

  16. #16

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    You can easily upgrade the ballasts in some cheap T12 shoplight fixtures. I replaced old magnetic ballasts with this instant start ballast, http://ballastwise.com/item.asp?PID=3&FID=14&level=1 . I have been using one fixture in my kitchen without problem for over 6 months where it is turned on/off about 20 times per day. (turning on/off frequently is supposed to be hard on bulb life)

    Also, you should be aware that overdriving fluorescent bulbs is a common practice among those who grow plants under fluorescent light. Here is a link on overdriving:

    http://reocities.com/heartland/pines/7557/overdrv1.html

  17. #17

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    Quote Originally Posted by yuandrew View Post
    Take apart the fixture and see if it has 1 or 2 little boxes with wires coming out tucked in the ends between the lamp sockets. If so, it's likely based on the "resi-tronic" ballast which are pretty terrible. They are nothing more than just a bunch of capacitors) and are known to burn lamps out rather quickly (sometimes within as little as 2 months). If you pay close attention, you'll notice that one end of the tube gets blackened rather quickly.

    I've experimented with running T8 tubes on T12 ballasts in the past and its pretty picky. My best result was with an old Robertson S40B Preheat ballast (the type requiring a starter). Most residential rapid-start ballast I tried don't fully light the tube up with the exception of a single lamp Advanced Mark III although that one blackened the tube ends rather quickly.

    Keep in mind not all T12 ballast will act nicely with T8 tubes. Some old GE-Magnatek-Universal ballast do not like anything other than true 40 watt tubes. Even the 34 watt "energy saver" tubes will case them to overheat and eventually burn out.
    I am under the impression that more people run T12 on T8 electronic ballasts instead of vice versa. I have done this also with overdiving.

  18. #18

    Default Re: T12 AND T8 ballast? Or does it have to be one or the other?

    T12s are designed for 0.43A. T8s are 0.27A. When they're in operating state, T8s have higher voltage (this is different from open circuit voltage, which is the ignition voltage).

    T8 ballasts usually allow the use of 2 to 4' lamps and they do so by being a current source and voltage changes accordingly.
    So, when you operate T12s in a T8 fixture, they'll run at lower power than T8s. The other way around, it may malfunction(flash or not start) or the ballast can burn out from operating at higher power than it was designed for.

    If you slap in cheap 34W T12 bulbs you will get crappy light as they are 60 CRI. Good T8s have CRI of 85 as do premium T12s, but the latter costs more, so you might as well just get T8.

    Get GE Sunshine T8 they have at Lowe's if you want "cool" 5000K or Philips Soft White T8 if you want warmer 3000K.

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