T8 bulbs in T12 fixture - Electrician Talk - Professional Electrical Contractors Forum

Hotlegs · 10-13-2011, 05:03 PM

I'm no lighting expert so I wanted some input on what I came across in an office building. I get there and the owner tells me he relamped the fluorescent light fixtures that had burned out bulbs.

He had replaced burned out T12's with T8's and they were all working. The ballast specifically stated they were for T12's. So I told him he screwed up and he asked me why then were the T8's working, and I didn't have an answer. So what would have happened leaving the T8's on a T12 ballast?

Mr Rewire · 10-13-2011, 06:06 PM

Quote:

Originally Posted by Hotlegs

I'm no lighting expert so I wanted some input on what I came across in an office building. I get there and the owner tells me he relamped the fluorescent light fixtures that had burned out bulbs.

He had replaced burned out T12's with T8's and they were all working. The ballast specifically stated they were for T12's. So I told him he screwed up and he asked me why then were the T8's working, and I didn't have an answer. So what would have happened leaving the T8's on a T12 ballast?

How long ago was it that he called because he will be calling soon. I have gotten calls like this and they usually dont burn long.

B4T · 10-13-2011, 06:21 PM

Had a call last week about 4' lamps flickering.. the maintenance guy got them mixed up..

This is going to be a constant problem for years to come.. BUT.. a money maker for us..

Hotlegs · 10-13-2011, 10:14 PM

Quote:

Originally Posted by Mr Rewire

How long ago was it that he called because he will be calling soon. I have gotten calls like this and they usually dont burn long.

Well I made sure I replaced them all with the proper T12's so they were only in there a few hours. I remeber the T8's were very hot when removing them.

**frenchelectrican** · 10-14-2011, 12:27 AM

Because with 4 foot 32 w T8 bulbs in 40 watt T12 ballast will overdrive them a bit and the amprage will be somehow higher and majorty of the T12 ballast I ran into are wired for rapid start which the electrodes always stay warm all the time.

It is a common item when someone get mixed up and not realized that they still have old T12 ballast in there.

So the soluation is either relamp with proper lamps or reballast to T8 ( which I always try to upsell it due they can save little more electrique right there and more quiet as well )

Merci.
Marc

noarcflash · 10-19-2011, 04:40 AM

The T8 ballast in a 2x4 fixture, they don't last more than 3 or 4 years. It's cheaper running the old T12 ballast forever, than the small amount of energy savings.

**Dennis Alwon** · 10-19-2011, 06:28 AM

I am pretty sure I have seen ballast that will do T-8 or T-12 tubes. Not sure if they are junk but they are out there

mattdolan16 · 10-19-2011, 09:19 AM

Quote:

Originally Posted by Hotlegs

I'm no lighting expert so I wanted some input on what I came across in an office building. I get there and the owner tells me he relamped the fluorescent light fixtures that had burned out bulbs.

He had replaced burned out T12's with T8's and they were all working. The ballast specifically stated they were for T12's. So I told him he screwed up and he asked me why then were the T8's working, and I didn't have an answer. So what would have happened leaving the T8's on a T12 ballast?

The
Lights will burn out. Try putting a t12 in. T8 ballast. Won't work.

Fredman · 10-19-2011, 09:25 AM

I just replaced several T-8's that were installed less than 3 months ago in t-12 fixtures. Go maintenance guy, go!!

Cletis · 10-19-2011, 09:33 AM

My personal opinion would be to put in extra efficient instant start ballast with some high efficiency t-8's. It seems to be the best bang for the buck, bulb life, and energy savings...

noarcflash · 11-02-2011, 10:23 PM

today I saw an 8' fixture. 96"
1) T8 bulb
1) T12 bulb
Both lamps were working !
I was curious, so I pulled the ballast cover. It was a T8 ballast.

But it was firing both lamps. no problems. The T8 was obviously brighter than the T12.

Then I had to explain to the maintenance personel to differences.

DEelectrician88 · 11-02-2011, 10:46 PM

Quote:

Originally Posted by noarcflash

The T8 ballast in a 2x4 fixture, they don't last more than 3 or 4 years. It's cheaper running the old T12 ballast forever, than the small amount of energy savings.

Better get me while u still can. I saw a memo at our local supply house the other day that said they were gonna stop making certain t-12 an a few t-8 lamps next july due to some new government efficiency laws.

dthurmond · 11-06-2011, 11:51 AM

My supplier says if you use the wrong bulbs t12 in t8 it voids their warranty on the ballast. Not sure how they would know if the wrong bulbs were used though.
I had this exact problem last week in a kitchen. They would light up but had a very bad flicker. Maint had even put in a new fixture.

Scott Paullin · 12-17-2011, 05:37 PM

Quote:

Originally Posted by Mr Rewire

How long ago was it that he called because he will be calling soon. I have gotten calls like this and they usually dont burn long.

You can expect the T-8 lamps to burn about a week or a little longer

BLohman · 12-29-2011, 10:11 AM

For what it's worth, I just replaced the ballast in a 96" T12-60W single pin 2-lamp fixture. The new ballast, though rated/labeled for T12's, was small like a 4' T8 ballast would be - not like a huge and heavy 96" ballast is typically. Anyhow...works fine. I left the T12's in it, but after reading this am tempted to see how it does on single pin T8's. Totally appeared to be an electronic ballast.

FYI... T12 AND Incandescent lamps are all going to cease being manufactured shortly, as stated earlier in the feed.

Stickshaker · 12-15-2012, 10:31 AM

You can overdrive a ballast with a 4 tube ballast running 2 tubes and they will run a loooong time while giving 1.7 times the light.