Author Topic: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp  (Read 4739 times)
slipperypete
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Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « on: January 16, 2012, 10:57:42 PM » Author: slipperypete
Hi all, I was looking at some old ballasts that have a line current. 77 amps and they are rated for 30 and 40 Watt lamps.   Will running 34 Watt lamps ruin these ballasts?  The reason I ask is because I have a case of 34 Watt lamps.
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RyanF40T12
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #1 on: January 17, 2012, 03:38:24 PM » Author: RyanF40T12
I've mistakenly burned out old ballasts that were only made for F40T12 bulbs when running F34T12 bulbs in them. It will overheat the ballast.   
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funkybulb
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #2 on: January 17, 2012, 07:49:32 PM » Author: funkybulb
you can run them in modern F30- F40 ballast. but it will be a lot dimmer and more flickery

but runing F34 lamp on only F40 ballast will overheat. that reason why that tube nickname the ballast smoker.

it best to find F34 ballast design run them at rated current.
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #3 on: January 17, 2012, 08:58:08 PM » Author: Patrick
In theory, shouldn't it be safe to use F34T12 lamps with ballasts made before they existed?  I know there can be issues in practice, particularly with inexpensive "shoplights", and I wouldn't recommend using them with older ballasts, but my understanding was that at the time the 34W lamps were introduced, they were intended to be retrofit lamps for existing fixtures and ballasts.
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Ash
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #4 on: January 18, 2012, 12:47:22 AM » Author: Ash
And they indeed work in there and save power. They overload the ballast somewhat, what the davelopers of the lamps seen as aceptable but later proved to be not-so

Or they just wanted max power saving figure no matter what
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #5 on: January 18, 2012, 01:38:06 AM » Author: Medved
In theory, shouldn't it be safe to use F34T12 lamps with ballasts made before they existed?  I know there can be issues in practice, particularly with inexpensive "shoplights", and I wouldn't recommend using them with older ballasts, but my understanding was that at the time the 34W lamps were introduced, they were intended to be retrofit lamps for existing fixtures and ballasts.

It should be, in the theory, safe and when taking a lot of newly made (really new, not NOS) ballasts of the old type, the ballast failure rate would be practically the same as with F40 (and the same as we see with "unreliable" new ballasts). All "problems" with old ballasts and F34 tubes are, then most of the old ballasts are way past the end of their life (both operating as well as shelf life), so become sensitive to any unusual condition

The problem is, then the "old reliable" ballasts are reliable only, because the weaker pieces were already "filtered out" by the test of the time, so remain only pieces capable to run the F40.

Now many of them are "just on the edge" - they are weaker (because they were so since manufactured, or they weakened over time), but just not as much to die on F40, but as F34 cause a bit higher current (quite big part of ballasting is in wire resistance on 120V ballasts, so the current depend a bit more on the arc voltage, then use to on the 230V series chokes), what mean higher operating temperature, just tipping them over. And many ballasts would die anyway, but the F34 is blamed, because the ballast died when F34 was in there...

So from collector point of view it is safer to not do these changes, the old ballasts pieces just happened to survive long only with the F40 tubes...
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randacnam7321
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #6 on: January 28, 2012, 08:17:56 PM » Author: randacnam7321
F34 lamps work by reducing the potential drop across the lamp.  This increases the lamp current but there is an overall reduction in lamp power as the current increase is proportionally less than the potential decrease.  It is this excess lamp current that is bad for F40 only ballasts.
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #7 on: February 17, 2012, 01:08:13 PM » Author: DieselNut
Craigslist the case of 34 watt junk and get you a case of good F40 tubes!
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slipperypete
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #8 on: February 18, 2012, 02:25:03 AM » Author: slipperypete
Already done.  My dad got me a case of vintage sylvania day light F40T12 tubes from the early 70s
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DieselNut
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #9 on: February 24, 2012, 01:40:19 PM » Author: DieselNut
Awesome!!!!!!!!
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #10 on: March 20, 2012, 10:45:29 AM » Author: don93s
Hi all, I was looking at some old ballasts that have a line current. 77 amps and they are rated for 30 and 40 Watt lamps.   Will running 34 Watt lamps ruin these ballasts?  The reason I ask is because I have a case of 34 Watt lamps.

I've run 34w lamps on 30/40w ballast with no problem. There should theoretically be enough tolerance for the lower lamp voltage as it under-drives a regular 40w and fully drives a 30w. A 34w falls right in between. I would still check to make sure ballast doesn't get hotter than normal which would be no hotter than running a 30w since a 30w would run hotter than 40w. I'll have to do an experiment with all three lamp types and make some measurements since I haven't tried that in years.
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #11 on: March 20, 2012, 09:48:28 PM » Author: arcblue
I agree with DieselNut - ditch the 34w lamps. I've tried several times to use and like 34 watt T12 lamps. But I always get rid of them and go back to 40 watt lamps. I got rid of my last pair of Watt-Misers last weekend. There is just no good reason to use these lamps, unless you have a particularly rare lamp or colour temperature not available in 40w (i.e. Lite White, though those lamps aren't THAT exciting after all). Or maybe you dig the cool striations Smiley If the goal is to save energy, use T8 32w lamps, or simply reduce the overall number of T12 lamps you use in a room. You could take a 4-lamp T12 troffer and remove two lamps + ballast, add a specular reflector and one pair of SPX41 lamps and it'd look brighter than four 34w cool whites and save more energy.

I find the krypton energy savers (34w 4', 60w 8', 25-28w T8 and 95w, 8' T12 HO) the sorriest lamps, they are always noticeably dimmer than their full-wattage counterparts, have poorer colour, and always striate on a cold start, and using lamps in a basement or garage (or worse yet, outside) is a joke because they will never warm up and will striate forever.
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #12 on: March 21, 2012, 12:45:54 AM » Author: Medved
... it under-drives a regular 40w and fully drives a 30w. A 34w falls right in between.

You can not count in that way.
With discharges the lamp voltage is always dictated by the lamp (but it depend on the lamp component temperature, so with some time constant on the current), the current by the ballast (but the ballast current usually is a bit dependent on the lamp voltage).
The F40 have nominal arc voltage 105V at 0.43A, the F30 about the same 105V at 0.32A (if I remember well), but the F34 (it is designed as a retrofit lamp instead of F40) is about 92V/0.43A.
So F40T12W ballast deliver 0.43A (BF=1, 50/60Hz) into the 105V lamps (F40, F30; and feed them both by 40W), while it may become slightly more when the load voltage fall, so my guess would be 0.44A into 93V F34. So the ballast operate at slightly higher current than with the F40, what may run it slightly hotter.

However I do not believe this could ever make any significant difference compare to e.g. mains voltage fluctuations. My guess would be, then if some ballast died with F34 lamp, it was about to die anyway and it would do so with the F40 as well. If some ballast is so sensitive, in my eyes it is at the first place very poorly designed.
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don93s
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #13 on: March 21, 2012, 10:21:02 AM » Author: don93s
I just tested a 30w vs 34w lamp on a NPF RS 30/40w ballast.
Results:

30w lamp voltage: 88v
    lamp current: 345ma

34w lamp voltage: 87v
    lamp current: 348ma

In conclusion, it seems that both lamps are virtually identical as far as the ballast
can see. These were just random lamps so there could be further variation with other lamps.
The 34w lamp was somewhat more stubborn at starting initially though.



... it under-drives a regular 40w and fully drives a 30w. A 34w falls right in between.

You can not count in that way.
With discharges the lamp voltage is always dictated by the lamp (but it depend on the lamp component temperature, so with some time constant on the current), the current by the ballast (but the ballast current usually is a bit dependent on the lamp voltage).
The F40 have nominal arc voltage 105V at 0.43A, the F30 about the same 105V at 0.32A (if I remember well), but the F34 (it is designed as a retrofit lamp instead of F40) is about 92V/0.43A.
So F40T12W ballast deliver 0.43A (BF=1, 50/60Hz) into the 105V lamps (F40, F30; and feed them both by 40W), while it may become slightly more when the load voltage fall, so my guess would be 0.44A into 93V F34. So the ballast operate at slightly higher current than with the F40, what may run it slightly hotter.

However I do not believe this could ever make any significant difference compare to e.g. mains voltage fluctuations. My guess would be, then if some ballast died with F34 lamp, it was about to die anyway and it would do so with the F40 as well. If some ballast is so sensitive, in my eyes it is at the first place very poorly designed.
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slipperypete
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Re: Using 34 watt t 12 bulbs in ballast that uses 30 watt and 40 watt lamp « Reply #14 on: August 02, 2012, 10:59:08 PM » Author: slipperypete
Thank-you for posting those results Don. I have a case of 34 watters that I got at work, so  even though I prefer 40 Watt lamps. I plan to use up all my 34 Watt lamps first. Save the best for last.
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