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F20T10 and F15T12 running in series, on incandescent ballast, on 120V

F20T10 and F15T12 running in series, on incandescent ballast, on 120V

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Upon seeing Dave the Silverliner's 2x F14T12 incandescent ballasted floor lamp, it surprised me that two F14T12 lamps, which add up to an arc voltage of some 84V, were able to reliably start and run on 120V, when a single F30T12, which is around 77V, generally had a difficult time doing the same. I tried a similar setup with an F14T12 and an F15T12 (total arc voltage 87V or so), and indeed, they fired up no problem. So, I tried an F15T12 and an F20T10, and, without too much trouble, they fired up. Arc voltage was 102V! You can see the incandescent ballast barely glowing as a result of seeing only 18V. I guess this works because the arc doesn't have to jump across a single set of cathodes?

How this is wired up isn't too much different from a single-lamp preheat circuit. One pin of one end of one lamp is connected to power, after the ballast of course. Then one pin of the other end of that lamp is connected to one pin of one end of the second lamp. Then one pin of the other end of the second lamp is connected back to power. Then, two starters are connected, one between the remaining two pins of each lamp. However, to my knowledge automatic starters don't work well in a series preheat circuit like this - I believe fixtures with a setup like this had a single manual preheat switch which did both lamps simultaneously. For this setup, I used an automatic starter on one lamp, and manually connected the second lamp for preheating. Then when the first lamp struck, I disconnected preheating from the second lamp.

Note that a higher wattage incandescent bulb had to be used for this setup. While 60 watt bulb works for a single 14, 15, or 20 watt lamp, a 75 watt bulb is required for two lamps.

I next plan on trying this across three, maybe even four, F4T5 lamps.

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Album name:themaritimegirl / Experiments, Projects, & Mods
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Date added:May 29, 2014
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rjluna2
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Robert


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May 29, 2014 at 02:12 PM Author: rjluna2
Sounds like fun

Pretty, please no more Chinese failure.

themaritimegirl
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May 29, 2014 at 03:06 PM Author: themaritimegirl
Haha, I love playing and experimenting with this stuff, learning new things and such.

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sol
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May 29, 2014 at 05:26 PM Author: sol
Two lamps in series each with its own starter works quite well. In Europe, two 18 watt lamps are wired in series just like you describe only with two 120 volt starters and one 36 watt ballast. This works only with 230 volt ballasts however with certain combinations (mainly large tubes with low wattage, such as F15T12 or F14T12) works quite well as discussed above. I would be curious of the results you would get from trying this with two starters instead of just one and a manual preheat on the other lamp.
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May 29, 2014 at 07:51 PM Author: themaritimegirl
I only have the one starter, but if I get another one I'll definitely try it. I imagine it would be very finicky, if not impossible, to strike, because one lamp can strike only if the other lamp is either currently in the preheating phase, or happens to successfully strike at the same time. So if one lamp strikes, and the second lamp's starter opens, but that lamp doesn't strike, it knocks out the already-running first lamp, and the process has to start all over again.

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sol
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May 29, 2014 at 08:10 PM Author: sol
You are right, it is more finicky as both starters have to fire at the right time. However, it does not really add a lot of time to the startup. If, on the other hand, you have a lamp that is hard to start to begin with, you might run into problems. Some North American members here have wired two F20T12 lamps in series (each with a Fs-2 starter) on a single lamp F40 preheat ballast with good results.
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May 29, 2014 at 11:07 PM Author: Medved
There is other problem with starters: In order to close when the lamp does not ignite, they need the balast OCV with no current to be in the peak voltage at least 1.5x the starter's closing voltage. But to not interfere with the running lamp, the arc voltage has to be maximum about 2/3 of that starter's closing voltage. With an optimized starter it means the mains voltage has to be about double in rms voltage than the lamp arc.
Therefore the starters are made with two voltage levels: One for 230Vrms (so >300V peak) single lamp operation (S10,...) with closing voltage about 200..240V, second for 120V (>160V peak) or 230V series operation with closing voltage around 100..130V.

So at 120V it means max about 60..70V (if the system is stretched) for an arc, at 230V the limit is about 120V. So with 120V you may fit just single lamp there, while at 230V you may easily operate two in series.

Here the circuit started as single lamp, as the second was bypassed by the wire, so the starter worked. After ignition the lamp operated well, so it is not necessary for the starter to operate anymore...

No more selfballasted c***

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Jun 07, 2014 at 05:43 AM Author: Seth11
Will the lamps be over driven on a incandescent ballast?

NO MORE ELECTRONIC BALLASTS!!!!!!!!!!!!

MAGNETIC BALLASTS FOR EVER!!!!!!!!!!!!!!!

SAY NO TO BULB AND MAGNETIC BALLAST BANS!!!!!

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Jun 07, 2014 at 08:30 AM Author: migette1
This idea was used in UK in the 50s 60s see my comments on Seths example.

Interested in the history of electric lighting and incandescent in particular and neon glow lamps.

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Jun 07, 2014 at 11:01 AM Author: themaritimegirl
Seth: Lamp current varies depending on the wattage of incandescent bulb you use, so it's always possible to get it right.

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Jun 11, 2014 at 08:57 PM Author: ultralume
Trent, did the bulbs start without a choke? I thought fluorescent lamps would not start from 120v without a choke ,.... Interesting !
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Jun 11, 2014 at 09:03 PM Author: themaritimegirl
Nope, no choke. While it does indeed help to have an inductive kick, it's not required. As long as the lamps are near something that's grounded or that otherwise provides a capacitive coupling (in the case of a setup like this I lay my free hand on the lamp to aid in starting), it will work just fine. In the case of lamps with the lowest arc voltage, like the F14T12 or F4T5, the preheating alone is usually all that's required to start. I plan on building an F14T12 fixture based on an incandescent ballast.

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Jun 11, 2014 at 09:26 PM Author: funkybulb
I have use two starters FS2 on series 2 x 20 watt lamps on single high power factor autotransformer ballast. It will blink in tandem
And when one lamp starts it will drive lamp at
25 watts until the other lamps starts and both lamps even out at 430 mA

This how they do this in EU 240 volr circuit
There enough OCV to drive both F20 lamps

No LED gadgets, spins too slowly.  Gotta  love preheat and MV. let the lights keep my meter spinning.

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Jun 11, 2014 at 11:13 PM Author: Medved
What helps a bit is to have the ballasting resistor on the Neutral side. Then during preheat the electrodes are at the line potential, so towards the shield there is quite significant voltage forming a bit of ionisation before the starter switch opens.

No more selfballasted c***

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Jun 13, 2014 at 03:59 PM Author: BG101
With our 240V circuits we use series starters for 4-22 watt tubes (these are for 120V single circuits as well) and once one lamp strikes, if the other fails to light the first will also go out and both repeat the starting cycle. Also (with the series 4-8W circuits anyway) the running lamp will be noticeably overdriven during preheat of the other lamp, or if the starter gets stuck at tube EOL.

The only problem with series circuits as I see it is that when one lamp fails the other, even if new, could also be harmed by the failing tube, either due to excessive restarts or rectifying lamps. Probably better with electronic starters although rectification is still possible.

The twin 40W rapidstart ballasts I have (presumably also the 30W, 20W and 13W versions which I know existed) will run the lamps into the ground and can run for ages with one rectifying lamp, so best to replace both lamps at the same time and use the working lamp somewhere else if it's still got some life in it. Mine ran a pair of tubes from new and one got dropped not long after, breaking one of the electrodes. It worked OK but both tubes flickered unless the damaged tube was put in the correct way round (and in the earthy side I think) and it aged fast probably due to cold starting.


BG

Say NO to DICTATORSHIP in the form of bulb/tube/ballast bans !!

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Jun 13, 2014 at 09:15 PM Author: themaritimegirl
Medved, I didn't know that! I'll have to try that out. By shield, do you mean cathode shields?

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Jun 15, 2014 at 02:12 AM Author: Medved
No, I mean the grounded metalwork of the fixture around the lamp, so the reflector,... It then act as an external electrode aiding the ignition.

No more selfballasted c***

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Jun 19, 2014 at 02:03 AM Author: vytautas_lamps
I once tried to turn on a two f40t12 lamps on f80t12 ballast with one switch and other actual FS4 starter. when I shorted the "manual" starter (the switch) the real starter on the other lamp turned the lamp on and when I turned of the manual "STARTER" (the switch) the other lamp turned on also. they was working fine, with no complain the reason why I put one fs 4 starter and switch, is because the f40 lamps will flash and not turn on on the fs2 starter, so I had to use one manual switch and for the other lamp fs4 starter. I hope you will understand my explanation on how to turn two f40 lamps on f80 balast (f96 t12)

New lighting technologies is a pity fest everywhere you look. From LEDs that last only for two months, to a never-ending global starvation of t8 fluorescent tubes.
We shall reinforce ourselves with good old full mercury t12s and HIDs made to surpass one's life, and give them all the middle finger ;

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