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My mistake?

Posted by vmckague Chamois, Mo. Zone 5 (My Page) on
Sun, Feb 11, 07 at 13:17

New to the group and have a question about shop lights. I have been starting seeds under shop lights for about 4 years and remember reading that the bulbs should be replaced every few years. Can't remember how many. OK here's what I did I went to the local Wal Mart and bought replacement bulbs but not looking close enough I ended up buying and installing 25 watt instead of 40 like were in the fixtures. Can I get by with this or should I just count this up to a learning curve and eat my losses and buy new 40 watt, as I threw the old ones out already, or leave the 25's in? I can't seem to tell any difference by just looking at them but maybe the plants can. Any thoughts? Thanks in advance

Follow-Up Postings:

RE: My mistake?

I wasn't aware that 25 watt bulbs were even available for shop lights. What size are your shop lights? My 48-inch shop lights accept either 40W T12s or 32W T8s.


RE: My mistake?

  • Posted by vmckague Chamois, Mo. Zone 5 (My Page) on
    Mon, Feb 12, 07 at 6:01

I didn't realize they came in 25 watt either and that is why I didn't pay any attention when buying them. I didn't notice until I had thrown my old ones away. My light are regular old 48 inch shop lights and I guess that's what I get for buying the cheapest bulbs. Oh well lesson learned.

RE: My mistake?

Fluorescent tubes used to lose brightness after a few thousand hours, some of them eventually becoming only half as bright as they started out. For this reason, plant growers used to replace them, say every 2,000 hours. The half light is significant to plants but not so noticeable to humans.

Quality modern tubes lose only about 5% of their brightness over a lifetime of 20,000 hours or more and can be kept until they fail. When shopping, look for a tube that says something like lumen maintenance 95%. They aren't expensive, but the very cheapest tubes won't have this performance and will need replacing after a couple of thousand hours.

Your 25W tubes are really not suitable for plant lights, they have a little over half the light output of a good new 40W tube. Bearing in mind the lumen maintenance they may actually be nearly as bright as the tubes you were replacing but if you go out and buy a new 40W tube I think you will notice a big difference. The 25W tubes are intended to save energy while producing (with a modern electronic ballast) the same light levels you would have got from a 40W tube about 15 years ago, hence suitable for direct replacement in existing fittings.

Depending on what you are growing, you might be able to keep the 25W tubes, but for most annual and vegetable seeds they will not be bright enough to give good results.

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