T8 lamp run by a T12 magnetic ballast

[Ravenvalor]

Hello,

Will a T8 lamp run properly on a T12 magnetic ballast? If not, why?

Thank You,

 

[kbsparky]

It might work for awhile, but experience has shown me the bulbs get burned out much faster that way ....

 

[Dennis Alwon]

There are many ballast out there that will run both T12 and T8-- check the ballast specs.

 

[LarryFine]

I've seen it done once or twice, although I don't remember whether it was T-8 tubes on a T-12 ballast or vice versa, but it didn't work for even a moment, and it wasn't pretty. I remember the tube being instantly damaged.

 

[hillbilly1]

Just had a customer last week call and said he had a fixture that was acting weird and he already replaced the lamps. When I got there, I found he had relamped it with T-8's. The fixture had two 2 lamp T12 magnetic ballasts, in which both were toasty. His lamp supplier had told him they did not make the T12 lamps anymore, and the T8 lamps would work fine in the old fixtures. Went down to the orange box and bought him a case of T12's. Changed the two toasted ballast to one four lamp T8, as eventually he will have to replace all of the ballasts.

 

[flatlander]

place a sticker on that fixture. " T-8 only"

 

[LEO2854]

Hello,

Will a T8 lamp run properly on a T12 magnetic ballast? If not, why?

Thank You,

It will work but the ballast and lamps will not live as long:roll:

 

[Ravenvalor]

I Wonder Why?

I Wonder Why?

I am trying to figure out why they are not compatible. Besides size are the lamps made differently? What is the difference between a T8 and a T12 lamp besides the size?

Thank You,

 

[Dennis Alwon]

I found this on the net so...

Since ballasts limit current flow in the circuit, an improper (t12) ballast would cause more current to flow through the t8 lamp than the lamp is rated to handle.

 

[hillbilly1]

There are many ballast out there that will run both T12 and T8-- check the ballast specs.

I think the newer electronic ballasts may, but I have not seen a magnetic ballast labeled as such yet.

 

[Ravenvalor]

My Theory of Electricity must be skewed.

My Theory of Electricity must be skewed.

I found this on the net so..."Since ballasts limit current flow in the circuit, an improper (t12) ballast would cause more current to flow through the t8 lamp than the lamp is rated to handle".

Is my thinking wrong?

1) I think of current as the amount of watts being pulled by a lamp. How can a lamp pull more watts than it is designed to pull?

2) Is something forcing wattage into it?

2.1) Does voltage have anything to do with it?

3) Is the output voltage of a t12 ballast higher than the output voltage of a t8 ballast?

4) What principle does the electronic ballast that feeds both t12 and t8 lamps operate under?

Thank You,

 

[flatlander]

I think the newer electronic ballasts may, but I have not seen a magnetic ballast labeled as such yet.

I don't think you'll find a ballst like that. THey don't want you to use T-12's as they are phased out.

 

[wireguru]

Is my thinking wrong?

1) I think of current as the amount of watts being pulled by a lamp. How can a lamp pull more watts than it is designed to pull?

2) Is something forcing wattage into it?

2.1) Does voltage have anything to do with it?

3) Is the output voltage of a t12 ballast higher than the output voltage of a t8 ballast?

4) What principle does the electronic ballast that feeds both t12 and t8 lamps operate under?

Thank You,

think of the arc in the tube as a short (or very low resistance) the ballast limits the current flow to keep the lamp operating at its rated wattage.

 

[steve66]

Is my thinking wrong?

1) I think of current as the amount of watts being pulled by a lamp. How can a lamp pull more watts than it is designed to pull?

That may work for simple incandescent lamps, where the voltage is always 120 volts.

But you should be thinking of watts as the product of voltage x current.

For fluorescent lamps, the lamps are designed to handle a certain amount of voltage and current. That gives them a wattage rating. The ballast regulates the current that flows into the fixture by adjusting the voltage it applies across the lamp.

So T12 lamps are normally designed to run at about 40 watts. You can get high power factor ballasts that might run them 10% over that, at 44 watts. You can also get Low power factor ballasts that might only run them at 34 watts.

T8 lamps are made to run at about 32 watts. Again, ballasts can be selected to run them a little higher, or quite a bit lower.

So when you connect a T8 lamp into a T12 fixture, you will probably overdrive it.

Also, fluorescent lamps have different starting methods - preheat, instant start, rapid start, programmed start, etc. The difference in starting between a T12 and a T8 might be the first think to kill a lamp when you plug it in.

 

[Ravenvalor]

That may work for simple incandescent lamps, where the voltage is always 120 volts.

But you should be thinking of watts as the product of voltage x current.

For fluorescent lamps, the lamps are designed to handle a certain amount of voltage and current. That gives them a wattage rating. The ballast regulates the current that flows into the fixture by adjusting the voltage it applies across the lamp.

So T12 lamps are normally designed to run at about 40 watts. You can get high power factor ballasts that might run them 10% over that, at 44 watts. You can also get Low power factor ballasts that might only run them at 34 watts.

T8 lamps are made to run at about 32 watts. Again, ballasts can be selected to run them a little higher, or quite a bit lower.

So when you connect a T8 lamp into a T12 fixture, you will probably overdrive it.

Also, fluorescent lamps have different starting methods - preheat, instant start, rapid start, programmed start, etc. The difference in starting between a T12 and a T8 might be the first think to kill a lamp when you plug it in.

Hey thanks,

If I can find a f34t12 magnetic rapid start ballast do you think that I can effectively operate a 4' t8 lamp on it?

I appreciate the time you have spent explaining this to me.

J.

 

[HotConductor]

I'm pretty sure that Workhorse ballasts operate T8 & T12's. I do alot of service work and I carry three or four or each WH ballast because they cover over a hundred different lamp combinations of linear, cf, u-bends, dulux, you name it type fluorescents.

 

[Ravenvalor]

I'm pretty sure that Workhorse ballasts operate T8 & T12's. I do alot of service work and I carry three or four or each WH ballast because they cover over a hundred different lamp combinations of linear, cf, u-bends, dulux, you name it type fluorescents.

Very interesting, I have never heard of the term work horse ballast. Can you recommend a model? I am using a magnetic ballast that is rated for 40 and 34 watt fluorescent t12 lamps. Do you think it would run a f32t8 lamp?

 

[LEO2854]

Very interesting, I have never heard of the term work horse ballast. Can you recommend a model? I am using a magnetic ballast that is rated for 40 and 34 watt fluorescent t12 lamps. Do you think it would run a f32t8 lamp?

Here's a link for work horseBallast..http://www.prolighting.com/woba.htm...ts&?mt=Exact&gclid=CLyp9Oi_zqQCFdR65QodzRYIjA

 

[Ravenvalor]

Here's a link for work horseBallast..http://www.prolighting.com/woba.htm...ts&?mt=Exact&gclid=CLyp9Oi_zqQCFdR65QodzRYIjA

I looked at the website, I will give them a call tomorrow. They will probably give me the number to the manufacturer tech support and hopefully I will learn something.

Thank You,

 

[jeremysterling]

I'm pretty sure that Workhorse ballasts operate T8 & T12's. I do alot of service work and I carry three or four or each WH ballast because they cover over a hundred different lamp combinations of linear, cf, u-bends, dulux, you name it type fluorescents.

I carry three "Workhorse 5" ballasts on my truck. I like them for display lighting fixtures like anthony or such. The only drawback to the Workhorse ballast is that they are typically single voltage.