This year I would like to use T8 bulbs on four shelves. I plan on hanging Mylar over the two long sides of the unit to capture as much light as possible. I'm hoping that someone with some experience can answer a couple of questions.

1. Will two light fixtures per self containing two bulbs each (total of four T8 bulbs) be enough light for starting the seedlings? Or will I need to utilize three fixtures per shelf (six bulbs in total)? There will be four standard flats per self. I only plan on having the seedlings under light for six weeks. FYI, I typically start the seeds during the first week in April and plant outside around mid-May (I would harden off the plants as usual).

2. Can anyone suggest where to purchase a roll of Mylar that is 48" wide? I'm planning on using Mylar based on the suggestions from this forum. If you have any alternate suggestions I would like to hear them.

Thanks in advance for your help, Pat

2) Go to walmart, target, etc. and purchase mylar emergency blankets from the camping dept. They are approx 53"x84" and cost 1-2 dollars each.

Regards,

Rokal

I think you will have better results with three 2-tube fixtures per shelf. That's what I use, and for larger seedlings I use overdriven fixtures for the light equivalent of 9 tubes per shelf.

The Home Depot Commercial Electric 732-334 ShopLights are 5 inches wide, so three of them will fit between the posts of the 18" x 48" chrome steel wire shelves. The model 732-334 shoplights can use either T8 or T12 bulbs. They have Sunpark SL15 ballasts, which can be rewired to use two of them per fixture, one for each tube. That overdriven configuration puts out 50% more light per tube. The tubes run somewhat warmer, but not hot. The ballasts actually run cooler because they are driving only one bulb instead of two.

You can purchase the extra ballasts separately, but the shipping costs make them cost about as much as a complete fixture. In order to get the extra ballasts, I purchase extra fixtures from our local Home Depot and cannabalize the Sunpark SL15 ballasts from them, which makes the overdriven fixtures cost $8 more than the regularly driven fixtures. I think the brighter light is worth the eight bucks.

But if you go to three fixtures instead of two, you may not need to overdrive your fixtures. Three normally driven fixtures provide about the same light as two overdriven fixtures. But it would take four fixtures to make two overdriven fixtures. Overdriving is only needed when you need more light than you can get from the maximum number of normally driven fixtures.

MM

Just be sure to keep the trays propped up so that the top of the seedlings are within a couple inches of the lights, and move the tray (or the light) frequently as the seedlings grow to keep it that way.