# Why is magnetic ballast not required to be removed when installing LED tubes



## fy lighting (Jul 4, 2011)

LED tubes come in single end power revision and double end power revision. For double end power LED tube. I was told that it is not required to remove the maganetic ballast when installing. And even the starter needn't be removed, either. Why is it so? I am looking forward to your answers. Thank you.


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## kbsparky (Sep 20, 2007)

Do they want the old ballast disconnected or bypassed?


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## fy lighting (Jul 4, 2011)

No, the ballast is still be connected. See the picture attached


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## oliquir (Jan 13, 2011)

they probably put electronics in tube so you can keep ballast, but i would remove it for energy savings


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## fy lighting (Jul 4, 2011)

Yes, the LED tube has built-in driver. The question is how the current can flow in the circuit with a magnetic ballast


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## retiredsparktech (Mar 8, 2011)

According to the print, it shows a simple series-reactance ballast. With the amount of current being passed through the ballast, the losses would very minimal.


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## oliquir (Jan 13, 2011)

i think the ballast connected this way just act as an inductance so it is almost short since current of led is very low compared to fluorescent


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## guest (Feb 21, 2009)

oliquir said:


> they probably put electronics in tube so you can keep ballast, but i would remove it for energy savings


And risk killing a very expensive LED tube replacement. 

If the manufacturer says to leave the ballast in the circuit, they have a reason for it. They are most likely using the inductance of the ballast as part of the driver circuit. 

If the instructions do not specifically say to remove or bypass the ballast, don't do it!


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## fy lighting (Jul 4, 2011)

oliquir said:


> i think the ballast connected this way just act as an inductance so it is almost short since current of led is very low compared to fluorescent


The LED tube is 1.2m T8 tube and the current that is input into the tube is 430mA


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## Electric_Light (Apr 6, 2010)

#1, without adding a current limiting device or a fuse, the full fault current of 277v is available at the sockets. 

#2, the ballast is not 100% efficient and they consume phantom power even if there is no load, so when the luminaire is to be tested in an integrating semi sphere, the electrical input watt with the ballast still in place shall be used, which means reduced luminaire efficacy.

Of course, the testing ambient conditions need to be controlled to actual application and shall be warmed up until lamp temperature is no longer increasing.


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## crosport (Apr 4, 2010)

Sort of defeats the purpose of switching out flourescent tubes with L.E.D. you would think!If ya need a magnetic ballast to work a L.E.D. then that is just plain stupid.


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## oliquir (Jan 13, 2011)

mxslick said:


> And risk killing a very expensive LED tube replacement.
> 
> If the manufacturer says to leave the ballast in the circuit, they have a reason for it. They are most likely using the inductance of the ballast as part of the driver circuit.
> 
> If the instructions do not specifically say to remove or bypass the ballast, don't do it!


i was answering to his post that said it is not required to remove ballast but they dont tell you you need a ballast, that would be crazy for led tube to require a ballast


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## Electric_Light (Apr 6, 2010)

fy lighting said:


> No, the ballast is still be connected. See the picture attached


glow bottle and single series choke type ballast is hardly ever used in commercial lighting in the US. That design is usually limited to portable fixtures and appliances using smaller lamps, such as F15T8 or F20T12. 

The 1200mm 48" lamps in present days DO NOT use glow starters period in the US.


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## fy lighting (Jul 4, 2011)

mxslick said:


> And risk killing a very expensive LED tube replacement.
> 
> If the manufacturer says to leave the ballast in the circuit, they have a reason for it. They are most likely using the inductance of the ballast as part of the driver circuit.
> 
> If the instructions do not specifically say to remove or bypass the ballast, don't do it!


I was told yesterday that it's OK to remove the ballast when installing


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## guest (Feb 21, 2009)

fy lighting said:


> I was told yesterday that it's OK to remove the ballast when installing


Told by whom? Your own post (#3) shows that the ballast is to be left in the circuit. 

If you do it without the manufacturer's specific instructions in writing, you risk:



Premature failure of the LED replacement;
Possible catastrophic failure of same;
Voiding the UL/NRTL listing of the LED assembly;
Voiding the manufacturer's warranty.
Further, if the fixture involved starts a fire you will be held liable for all damages. 

And this by Electric_Light brings up a very valid point:



Electric_Light said:


> #1, without adding a current limiting device or a fuse, _*the full fault current of 277v is available at the sockets.*_


It is not within the scope of your job to assume you know more than the manufacturer and remove the ballast _*unless specifically told to do so in the instructions*_ for the LED replacement lamp.


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## guest (Feb 21, 2009)

oliquir said:


> i was answering to his post that said it is not required to remove ballast but they dont tell you you need a ballast, that would be crazy for led tube to require a ballast


If they don't specifically tell you to remove the ballast then as I said in the post above this one is not your decision to make for the reasons I outlined. 

By Code all equipment is to be installed in accordance with the manufacturer's instructions, and_* if it is not stated to remove the ballast then you do not remove the ballast*_!

Why is this so difficult for you and the OP to understand?


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## fy lighting (Jul 4, 2011)

Hi folks, I found a schematic diagram of fluorescent tube lights. Attach here for reference for electrical fans like me

Finally I figure out why the current can flow through the ballast. I thought the ballast was some type of transformer before. Actually it is just a wire wrapped around a magnetic stick. Naturally the current can flow through it.:thumbup:


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## fy lighting (Jul 4, 2011)

Electric_Light said:


> #2, the ballast is not 100% efficient and they consume phantom power even if there is no load,......


Hi Electric_light, could you explain what is phanton power.I found a definition is: Usually power is supplied by a circuit and sigal is transmitted in another circuit. But in sound system (microphone), the power is supplied by signal circuit, which means there is only one circuit which not only supplies power but also transmit signal. Does the phantom power in your comment mean this. If so, where is the signal. Thank you


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## piperunner (Aug 22, 2009)

fy lighting said:


> Hi folks, I found a schematic diagram of fluorescent tube lights. Attach here for reference for electrical fans like me
> 
> Finally I figure out why the current can flow through the ballast. I thought the ballast was some type of transformer before. Actually it is just a wire wrapped around a magnetic stick. Naturally the current can flow through it.:thumbup:



Well a ballast is a auto transformer !

Its also high voltage on its output do what the factorys says but a ballast is not just a wire wrapped around a chunk of iron .

That coil inside has taps which actually gives you more voltage than the incoming ac voltage and its inductance that makes that happen .


Its also a choke which will smooth out the ac wave in that circuit before it goes into the led power supply .


Yes its has inductance which smooths out the ac coming into the circuit that feeds the led,s 


A led is a diode every diode has a loss it will drop voltage meaning each led if you add all them up the leds in that lamp lots of volts dropped to operate that lamp 

.

They use the auto transformer meaning ballast to give back whats used and also to smooth out the incoming ac signal or ac wave because the led,s run on dc power .

Funny but you can hook up 120 leds on 120 volt ac directly but you must control the current in the circuit or they will blow out !

Most leds run on 2 volts or less and they drop .78 volts to operate so think loss of volts we need more volts to make hundreds of leds in one string work .

With out the ballast they would be dim!


But dont listen to me iam just on a EGO TRIP !


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## Electric_Light (Apr 6, 2010)

Electric_Light said:


> glow bottle and single series choke type ballast is hardly ever used in commercial lighting in the US. That design is usually limited to portable fixtures and appliances using smaller lamps, such as F15T8 or F20T12.
> 
> The 1200mm 48" lamps in present days DO NOT use glow starters period in the US.





fy lighting said:


> Hi folks, I found a schematic diagram of fluorescent tube lights. Attach here for reference for electrical fans like me
> 
> Finally I figure out why the current can flow through the ballast. I thought the ballast was some type of transformer before. Actually it is just a wire wrapped around a magnetic stick. Naturally the current can flow through it.:thumbup:


As I mentioned in my post I quoted above, that type of ballast is NOT used in the US for 4' (1200mm) or longer tubes. Even if it was, it has a considerably power dissipation, which reduces system efficacy.


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## zwodubber (Feb 24, 2011)

The LED tubes I'm used to seeing have their own driver (transformer).

Development stage


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## fy lighting (Jul 4, 2011)

Yes, the LED tubes you showed is the type with external driver. Another common type is with internal driver. The driver is built in the aluminum heat shink. The latter may be more convenient for installation because you don't have to find place to hold the driver like the LED tube you showed


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## Electric_Light (Apr 6, 2010)

#1) in the US, we don't use series choke ballast.

#2) Rapid start magnetic ballast in the US is not a simple series choke. It has a series capacitor that is meant to provide regulation and power factor correction when it is used with correct lamps. 

If the ballast was to be bypassed, though 305v (277 + 10% ) is not enough to instantly start a F32T8 lamp, surge voltage can strike the lamp. So, with that said, if F40T12 or F32T8 lamps were accidentally installed, surge voltage causes to strike and short across the 277v feeder, the lamp ends can get very hot and crack the lamp.

Fault current from Poco's 1,000kVA 480/277v transformer feeding the building is beyond comparison to 277v stepped up from a 120v outlet through a 500VA step-up transformer in the R&D lab. In the lab, the lamp will flash and pop the breaker feeding the outlet or the voltage drops enough to cause the arc to quench on its won, but give it 30,000A when the fluorescent lamp starts or something shorts internally in a LED tube. Even if the "breaker size" is comparable, a lot more can happen during that time.

When the ends crack, glass tube separates from the sockets and fall down, which will definitely shatter all over the place and may cause property damage and/or injury depending on what was under it at the time.

of course, nothing will happen as long as something doesn't cause the lamp to ionize (i.e. static electricity or surge)


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