# T5 vs. T8 electronic ballast question



## [email protected] (Jul 17, 2008)

I searched this forum thread but can't find an answer to this question. I may not have searched long enough. Please forgive me if I'm rehashing old ground. 

After reading spec sheets until I can't tell what manufacturer made what, I don't understand what is special about T5 ballasts? other then the low power factor electric rates in some areas, and the smaller physical size. Before I do something experimental like soldering wires to a T5 lamp as I don't have any T5 sockets - is there an electrical difference I'm missing? 

Also, the spec sheets say a four lamp T5 ballast can be wired for four, three, two, and one lamp. With a T8 and standard electronic ballasts that is over driving. Do T5 lamps over drive or is the ballast detecting the electrical characteristics of the T5 lamps and reacting to programing?

I lucked into a supply of used two lamp electronic ballasts from a building remodeling. Besides replacing the old magnetic ballasts in my basement lights I've been having a good time over driving both standard (nominal) 48 inch T8 and PL-L 40 lamps for my aquariums. A young man I gave a couple ballasts to has used them to really over drive two 24 inch T8 lamps for his 29 gallon tank. No, they don't get overly warm.

T5 seems the next logical step. Or is it?

Please, no guesses based on guesses. I actually have been reading the spec sheets. Fulham's Workhorse ballast and lamp spec sheets are where I started.


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## DiscusIt'sWhats4DinneR (Apr 25, 2008)

t5 ballasts are intended to run t5 bulbs at the wattage they are designed for, in the same way that t8 ballasts are intended to run t8 bulbs.

a t8 ballast for 48 inch tubes is designed to pump 32 watts to each of its four outputs, whereas a t5 ballast would pump say 54 watts to each of it's four outputs. 

this means that you could very well bridge the four outputs of a t8 ballast to run 2 t5 lamps and it would work fine. or even all four outputs into one t5 bulb... but it will get very hot. the more juice you try to throw at a bulb the less efficiently it can use it. the rumor is that t5's dont react as well to overdriving as the t8's do, probably because the t5ho bulbs are already engineered with lighting intensity as a priority over energy efficency.

conversely, you could run the 4 outputs of a t5 ballast to four t8 bulbs, or anything else you might want to test out, maybe connecting two sets of outputs to one bulb.. but this would probably get too hot and just not be practical 


they say that a 4 lamp ballast can be used to run 1,2,3 or 4 bulbs meaning that you could just use one set of output wires to power one or more bulbs, leaving the remaining wires capped off and unused.
but we dont want that, we want to use the ballast to it's full potential.

using two pairs of outputs from the t8 ballast should have no problem firing the t5 bulbs.

here is a good page you might like with a lot of info on odno;
http://www.geocities.com/teeley2/overdrv1.html


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## DiscusIt'sWhats4DinneR (Apr 25, 2008)

i might ask why it is that you want to use t5 bulbs?
i use 4 t8 bulbs overdriven 2x by two sylvania quicktronic 4x32's over a 55 gallon tank and it is tons of light, and a lot to manage. my lighting setup could go on a 75 gallon and still be considered too much.

i really encourage you to find some endcaps...

experiment with the t5's and see what you can come up with, id like to know the result.


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## Left C (Nov 15, 2003)

DiscusIt'sWhats4DinneR said:


> ... the rumor is that t5's dont react as well to overdriving as the t8's do, probably because the t5ho bulbs are already engineered with lighting intensity as a priority over energy efficency. ...


Would you mind going into a bit more detail? I'm planning on doing this. If it is not going to work, I want to stop right now.

I know that Reef Geek and Champion Lighting sell various IceCap OD T5HO kits that use 430 and 660 ballasts that can OD these bulbs by ~ 67%.
http://www.reefgeek.com/lighting/T5_Fluorescent/IceCap/SLR_Retrofit_Kits/
http://www.championlighting.com/home.php?cat=688


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## DiscusIt'sWhats4DinneR (Apr 25, 2008)

Left C,

there is no reason why what you are trying to do wouldnt work.
it will, you still get more power by kicking more watts to the bulbs.

t5 bulbs can be overdriven just fine.

T8 bulbs only get about 50% brighter when 2x the watts are being pushed to them. doubling the power only gives a 50% increase. the gains in lighting intensity start to get smaller as you crank up the power more and more and you end up with gaining more of an increase in heat than light output.
i think that most t8 bulbs are marketed with energy efficiency in mind as a priority over the lighting intensity, the bulbs can use and handle much more power than what is specified. there is a principle of diminishing returns in effect with these overdriven bulbs, meaning the more power you give the bulbs the less efficiently they can use it.

i once read something where somebody had used a lux meter tested a variety of overdriven bulb scenarios using a number of different sizes, types and even ages of bulbs. there were charts and graphs and the author concluded that t8 bulbs have the most potential for gains in lighting intensity than the all the other bulbs. i do not have a link to this, but i still might be able to find it.

the t5 HO bulbs are already designed with high output in mind, long life and energy efficiency are not the main priority of the design of these bulbs. they are "factory overdriven" bulbs, if that makes sense. so cranking 108 watts to a 48" t5 (which would be doubling the amount of power a 54w t5 is advertised to run at) probably will not yield a 50 percent increase in light, they might only be around 30 percent brighter, although i have never tested or tried this myself.


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## DiscusIt'sWhats4DinneR (Apr 25, 2008)

http://www.plantedtank.net/forums/lighting/21257-odno-measurements-power-consumption-vs-light.html

shalu says:
"I am going out on a limb here, but this implies one thing: overdriving the HO T5 bulbs will also have decreasing efficiency, for example, those 54w 48" T5 bulbs, because they are factory OD to the max efficiency already. Probably because they get really hot. I read some reef folks suggest that extra cooling gets you more light from hot bulbs in general."

i would get some air circulating under the bulbs, crank up the watts and see where it lands. there is still some light that can be gained.


this is what i was referring to, i was looking all over google when i realized it was right here, as a sticky


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## Left C (Nov 15, 2003)

That's great! Thank you.

I freaked out last night and ordered a Sunlight Supply twin bulb READY FIT® T5 FIXTURE with TEK II reflectors even though I already have a 3 bulb IceCap retrofit kit with a 660 ballast. :hihi: 
READY FIT® T5 FIXTURE - http://www.sunlightsupply.com/produ...E89A50EE8C1838BC6592E95807A34&c=34&kys=&pgi=1

Here is the place that I ordered it from. It is a bit cheaper. http://www.carolinareefs.com/index.php?main_page=product_info&cPath=1_4&products_id=22


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## lauraleellbp (Feb 3, 2008)

Have you guys checked out this place jeff found? http://www.horticulturesource.com/index.php/cPath/21?osCsid=8abb28fdd0646e223f40ce64364bd474


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## Left C (Nov 15, 2003)

I saw that. There's some good prices on some of the plant bulbs and fixtures.

Here's the Aquaflora bulbs: http://www.horticulturesource.com/i...age/1?osCsid=f35f309e87111e1f423d16b829b49c2a

To get 2 of the Aquaflora bulbs shipped to me is $60. That is much more than we are paying in our group buy. I'm glad that they are finally entering the country.


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## lauraleellbp (Feb 3, 2008)

Yeah, that place has some of the best deals I've seen on high end retrofits, too. :thumbsup:


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## Left C (Nov 15, 2003)

I just went through checkout to compare prices on the Ready Fit kit with 2 Midday bulbs that I ordered yesterday from CarolinaReefs.com and this place.

There's not much difference in prices. Both places have good prices.

Here's the prices of 1 Ready Fit kit and 2 Midday bulbs shipped to my house:

CarolinaReefs.com - $163.37
horticulturesource.com - $166.60


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## SpeedEuphoria (Aug 5, 2008)

Just a note as I've been looking around at ballasts recently. I noticed that the T5 ballasts mostly have a 1.0 ballast factor while the T8 normal is .88 but can be as low as .77 to as high as 1.15(GE ballast).

Meaning that the T5 ballast drives the lights at the said voltage while most T8's feed lower voltage than you think.


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## Left C (Nov 15, 2003)

Left C said:


> That's great! Thank you.
> 
> I freaked out last night and ordered a Sunlight Supply twin bulb READY FIT® T5 FIXTURE with TEK II reflectors even though I already have a 3 bulb IceCap retrofit kit with a 660 ballast. :hihi:
> READY FIT® T5 FIXTURE - http://www.sunlightsupply.com/produ...E89A50EE8C1838BC6592E95807A34&c=34&kys=&pgi=1
> ...


I was able to cancel my order with Carolina Reefs. I'm glad too. I'm going back to my original plan with the OD IceCap kit..


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