http://www.aboutlightingcontrols.org/ed ... -bay.shtml
Sorry I copied the title instead of the link in the first post. lol
This came about because in a post on another forum someone suggested the following to me which I looked at and thought, that is wrong and went about doing some research
T12 normal output puts out about 87.5 lumens per watt.
While T5 High output puts out about 103 lumens per watt.
So while being true that T5 is much more efficient, it certainly wouldn't be doubled. More specifically, after a few calculations I've determined that 1.8wpg of T5 equals 2.34wpg of T12, and about 2.2wpg of T8. Not a significant change by any means, but T5 is definitely stronger, thats for sure. I think the effieciency of T5 over other flourescents has been greatly exaggeratted over the years. Although it is partly true, not to the extent of what it has been told.
So on lumens per watt after a little research by me.
I can see from looking on most websites that T12 at best is about 85 and typically between 60 and 85. T8 are about
90. T5 are about 100-110 and T5HO are about the same as T8.
This is lumens per watt remember and not lumens per inch!!!!. T5 are the most efficient of the options but you don't get the lumens per inch there. however 2 T5s equal in W to a single T5HO will give more total lumens.
The interesting point though is we all accept that tubes 'decline in output' through their life.
This article is trying to explain why tall buildings should go fluoro instead of their old MH units. The MH beats the T5HO to a pulp in output terms when brand new but this article is explaining the 'mean' lumens which is the average through its life. It is fit for our purpose too as this statement taken from the page states:
An MH will have lost 35% of its output at 40% of it's life whereas a T5HO will have lost 5-6%.
At 40% of life the following figures are given as the lumens still being emitted as a percentage of the original output:
MH (probe start) 65%
MH (pulse start) 78-86%
T5HO (Programmed start) 95%
T8 (Instant Start) 95%
This suggest we could feasibly use any fluorescent tubes on electronic programmed ballasts for much longer than the life we currently give them without a worry!!!
For example 20000 hours x 40% = 8000 hours. That is 1000 days @ 8hours a day. so after 3 years we have only lost 5%!!!
What would be interesting would be to see figures for tubes on magnetic ballasts to see their decline. Anothere thing that could be interesting would be to see at what point we actually need to change when we are using electronic ballasts. We can see at 40% we are fine but just how much longer can they go before they reac 90%, 85%, 80% etc?
AC