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#53410 - 06/23/05 11:14 PM Fluorescent lights  
AdamsAtoms  Offline
Member
Joined: Mar 2005
Posts: 24
Kennedale,t.x.,76060
Is it true that T8 fluorescent bulbs have more light output than a T12 of the same wattage? Also I was told that if one T8 bulb burns out then the others will stay on as compared to a T12 where if one bulb burns out then they all go out. Wouldnt this depend on the type of ballast that you are using?


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#53411 - 06/24/05 04:31 AM Re: Fluorescent lights  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
We are currently involved with replacing about 5000 ballasts in a warehouse.

The originals fixtures where 2 lamp 8' high output T-12s, we convert them to 4 lamp 4' T-8s and the light output is much higher.

As far as the ballasts you need T-8 ballasts for T-8 lamps.

Also available are 4' T-5 high output lamps which with 4 of them can replace a 400 watt HID fixture.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#53412 - 06/24/05 07:28 AM Re: Fluorescent lights  
dmattox  Offline
Member
Joined: Oct 2004
Posts: 265
Anaheim, CA
When T8s fail, usually only that bulb will go bad, if you see 2 T8s out, its almost always a bad ballast.

T12s on the other hand can have a single lamp go out or both lamps. I think it depends on how the lamp fails internally. Also, if you remove a T12 from a 2 lamp ballast, it will shut off the other light, a T8 ballast will power a single lamp with no problem.

I think you are correct that this is more to do with electronic vs magnetic ballasts.


#53413 - 06/25/05 01:33 PM Re: Fluorescent lights  
William Runkle  Offline
Member
Joined: Feb 2003
Posts: 27
Dowagiac, Michigan U.S.A.
T8 4 bulb 2 by 4 troffer luminaire becomes a lot lighter than the T12 so light if installed in suspended ceiling and it is not fasten properly you could push the whole luminaire out of the ceiling grid. The ballast only requires 1 not 2 and they weigh one fourth of ther T12 ballast. Never checked lumens but heard from customers it is alot brighter.


William Runkle

#53414 - 06/25/05 01:36 PM Re: Fluorescent lights  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Quote
I think you are correct that this is more to do with electronic vs magnetic ballasts.


I have never seen a magnetic ballast for a T-8.

Is there such a thing?


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#53415 - 06/25/05 08:21 PM Re: Fluorescent lights  
bucketman  Offline
Member
Joined: Oct 2004
Posts: 72
vancouver WA, USA.
Hay what does the (T) stand for in T5 T8 and T12


#53416 - 06/25/05 08:24 PM Re: Fluorescent lights  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
T = Tube or Tubular.

FYI the numbers represent 8ths of an inch.

A T-5 is 5/8" in diameter, a T-8 is 8/8" or 1" in diameter.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#53417 - 06/25/05 09:36 PM Re: Fluorescent lights  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
The "eighths of an inch diameter" thing goes back to the early days of lamps and radio tubes, and lives on to this day. Even LEDs are commonly specified this way (T1-3/4 is a common package).

The number of eighths in the diameter is also the basis of the NEMA motor frame designations, AFAIK. For example, a 56 frame motor was originally 56/8ths " in diameter, or 7". As motors have improved, they have gotten a bit smaller, but the numbers still provide a rough idea of size.


#53418 - 06/25/05 11:04 PM Re: Fluorescent lights  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Thanks NJ, I did not know that. [Linked Image]

[This message has been edited by iwire (edited 06-25-2005).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#53419 - 06/25/05 11:42 PM Re: Fluorescent lights  
dmattox  Offline
Member
Joined: Oct 2004
Posts: 265
Anaheim, CA
Sorry iwire, I meant that I think its the way the ballast operate, not a difference between the lamps.


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