More Light!

[timbert]

I'm currently running 2 x 20w tubes in my 20g and am looking at increasing the wattage. I've noticed that the hagen twin tube ballasts are the same price for the 20w, 30w and 40w units.

Would it be possible to get a higher rated unit (ie 40w) for use with 20w tubes. If possible this would allow me to transfer the unit to a larger aquarium in the future for use with larger tubes. Does anyone have any experience with trying this or will it just blow the tubes?

Also with 4 tubes installed in a hood i'm envisaging heat problems. Has anyone tried using PC exhaust fans hooked up to a transformer to vent the hot air from the hood?

 

[Great Lakes]

If I understand you correctly, you are considering hooking a ballast rated for larger tubes up to your 20w tubes.

This does work really well. It is called overdriving

Before continuing, a disclaimer is in order. Overdriving flourescent lights can cause excessive heat. By excessive, I do not mean prohibitive, just excess in regards to a standard small tube fixture. So prudence in how much you wish to overdrive tham is in order. You will have more heat simply by nature of the higher wattage. This will however be the case, relative to your plastic light hood/cover, no matter what higher light route you choose.

That being said, overdriving is remarkably simple to do.
All you need is the correct size electronic ballast for your application, and follow the wiring diagram provided with it to wire up your flourescent lamps. Only in your application, you are using smaller bulbs than the ballasts are rated for.

Say you gaet a ballast rated for a range of 2x80w, 3x60w, or 4x40w.
Most ballasts are now rated thusly. IT will allow you to hook up 2,3, or 4 bubs.

So if you were to hook this up to a pair of 20w bulbs, in theory you will be overdriving 4x's. A ballast rated for 160w will be sanding that same energy to a pair of 20w bulbs. Now, you will not have the full 80w per bulb because tests have shown that trying to put that much energy into a lower rated bulb causes enough inefficiency to lower the cabability of the ballast by roughly 75%. But that still means 60w!!!.

I used this very approach for over a year with complete success and suffered no bad experiences.
With the ballasts I was using, I was 3x overdriving 40w tubes. The light output was phenominal. I also used the real aluminum duct tape and applied it to the top of my bulbs to form an on bulb reflector. I also had this set up in a home made canopy, so heat never became an issue.

From a bargain perspective, this is a frugal mans dream. The ballasts are readily available at any home improvement store for 10 to 20 dollars. Try just using one of the smaller ballasts at first to just give your lights a nice kick. A little boost can make a big difference at times.

GL