Today I got a grow light setup installed in the garage. I used two GE Ecolux T12 tubes, and a 4Ft 2-light shop light fixture. It is barely wide enough for the trays, and I may have to add a second fixture. The shelf is wide enough to set the trays lengthwise, so by setting three 2-light fixtures (6 tubes), I could have 4 to 5 trays in there. Each tube is 40W, so that would suck 240W. We will see how the single fixture works with those spindly beans first, if they survive, then I may go for a 6-tube setup. For now I use a timer, and will keep the lights on during the day, but with a 6-light fixture, I would use a light sensor to turn the lights off when daylight is strong enough.
This is my first grow light setup, and it is exciting!
Looking online in the "medicinal" industry, I see numbers between 1500 and 3000 lumens/sqft for indoor only plants. In this setup, the starts are next to a South facing window, and get a boost in lumen and spectrum a few hours every day.
A seedling tray is 1.4sqft, and therefore needs between 2000 and 4000 lumens.
Each fluorescent tube is 1900 lumens. The growing setup must have between 1 and 2 tubes per tray. The current setup is on the low side. A setup with 3 fixtures, 6 tubes, for 4 trays, would be adequate.
If the current setup gives satisfying results, then I will install a 6-tube setup with 4 trays.