T5 Ballast question

[maestro]

If you were to run 39 watt tubes off a 54 watt ballast what would happen?

would the bulbs be 39 watt still or be overdriven to 54?

thanks

[Entropy]

Depends on the ballast. What ballast are you planning on using?

[maestro]

They will just be totally standard t5 electronic ballasts not icecap or anything.

The reason I ask is that on my old tank I use to run 39 watt tubes off a 54 watt ballast (I didnt know it was 54 watt at the time, it was 2nd hand) the bulbs ran fine. I now want to add 2 more t5's to my tank and wondered whether it was worth getting the higher rated ballast if it made them produce more light?

[Entropy]

I don't think it will add anything noticable. Most good ballasts will not overdrive bulbs as much as it would seem. A 54w ballast for instace will not drive a 39watt bulb to 54w levels. I would just get a T5 ballast for the bulb combo you intend to run. They are only $35 or so from most online retailers.