If done properly only the bulbs will get hotter. The ballasts will actually run cooler because they are not drawing full power. I run mine 16 hours a day.

I glad this question was ask...I'd like to put it another way since I'm interested in trying this for my tomato seedlings. If put on a timer could this possibly short out or burn the house down if nobody is home?

Tom

I haven't heard of it yet but an electrical fire is possible with any electric device. Some people have been running these types of lights since before '04' with no problems. I've been running mine for about a year now. I've had a timer quit working but no fires or burned wiring.
I suggest you use push in connections and not wire nuts. Wire nuts are known to fall off and leave exposed wires but if you have a newer home with breakers I wouldn't worry much.
It's also a good idea to use power strips with resets and power switches especially when testing your handy work the first time around.

Update - So far everything is running great!!! They don't seem to get hot at all. Maybe because i hardly ever use our Heater at home so the temps are relatively cool inside (60-65 F) never above that.

I've been running overdriven T8 fixtures for over 6 years with no issues. I typically run them 16 hours per day from December through April.

Occasionally, a ballast will fail and need to be replaced. This is a more common occurrance with the cheap ballasts used in box store fixtures.

sumith2008, you need at least one more fixture over those seedlings! When is your plant out date? Hopefully within 4-6 weeks.

I have a bunch of identical cheap 48" 2-tube T8 shop lights, about 4 years old. Some of them have the ballasts doubled up and some have the stock setup. They don't get very hot even with a 16 hour on cycle. You can put them close to your plants as long as you leave a few inches of space.
I noticed today one fixture is out with a dead ballast. It was one of the stock fixtures, not an overdriven one. It died nicely without any smoke or burning, so I don't worry about fires. But I do make sure I don't overload my electrical circuits.
Bob B.

From the photo it looks like some of your seedlings toward the outside edges aren't getting enough light. Methinks for the cost of converting one regular fixture to an overdriven one you could have bought another regular shoplight and with two shoplights would have had more total light plus had it distributed more evenly over your plants.
The main reason for using overdriven fixtures is if you don't have space to add more regular fixtures, and you do have enough space to add another fixture.

The cost of overdriving depends on the deal you get on the ballast needed. I'll bet I can find a ballast on ebay for half the price of a new fixture.
More light in the same area = stronger plants.

The price of a new shop light fixture in most home centers is around $10. How much would your E-Bay ballast cost including shipping? And then the work of modifying the fixture, and modifying it voids all warranties. And from what I read on various threads your overdriven fixture would use 170% more power but only put out 150% more light.

Well obviously you can't read. I know how much fixtures cost because I've bought plenty. Modifying comes natural for an electronics and electric DIYer. It's a pleasure to spend my extra time doing such hobbies not a chore. Who cares about warranty's when you're getting an HO fixture that would cost at least 5X the price if bought new and why would you need one when they've lasted over a year anyway.
BTW I hate CA and the people in it. Lived there for 29 years and met nothing but thieves, liars, drug addicts and litter bugs. I say let Mexico have the broken down, overrun and useless state with most of the people that live there and their attitudes.

Taz6122, you need to take an anger management class.

Californian you need to quit BSing people. Especially me. I'm not angry, just tired of the BS. Especially that which comes from CA and God knows there's plenty of it.