how often to replace T5s

[VickiC]

Hi,
I'm now using T5s as supplemental lighting in my greenhouse only on overcast days. Can someone please tell me after how many hours they should be replaced?
Vicki

[LinhT]

Usually, they should be changed after a year. However, if you're only turning them on on certain days, perhaps they will last longer. The best way to know when bulbs need replacement is by measuring the light output with a reliable light meter.

I can't say this enough. My light meter was one of the best investments I've made pertaining to my orchid hobby.

[Ross]

Tracy is correct. Trust a good light meter. When I install the new tubes, I tape a paper to the fixture with the foot-candle reading at a certain distance. About a year later I take a reading and if the output has dropped, I change the tubes. Usually it has, so I'm pretty-much changing all the tubes out at 1 year. Mine run 7 days a week all year (various hours, though.)

[VickiC]

Thanks Tracy and Ross!
Vicki

[BioWheel]

I change mine when the ends of the tubes start getting black (darker).

[boytjie]

I'm with Tracy and Ross: once a year. One thing you might want to bear in mind is to be careful that you don't burn your plants after you change the bulbs. The light will suddenly be quite a bit stronger. It might be a good idea to move the more light-sensitive 'chids a few inches lower for a week or two and give them time to adjust. Just watch the leaves for any signs of red or purple streaks.

[camille1585]

Once a year is fine if you're leaving them on a long time, like 10-12 hours a day. That's what I do with the aquarium lights. My orchid lights are only on a few hours a day (only when I'm home) so once a year is probably a waste of my money. A light meter is probably the only way to know, but I can't afford one. The terrarium shop where I get mine recommended every 1,5-2 years for about 4 hours daily use, which is what I'm going to do. They aren't T5, but power compact florescent tubes.

[Oscarman]

Great advice - can anyone recommend a good light meter?

[Ross]

Originally Posted by Oscarman

Great advice - can anyone recommend a good light meter?

The one I use is Buy Light Meters Lux & Foot Candle l 5 Year Warranty l Sper Scientific It's a bit pricey, but it's self calibrating (calibrates the zero point every time you turn it on, so it eliminates drift due to battery strength, etc.) so I can depend on accurate readings (both lux and foot-candles).

[VickiC]

Thanks again, Tracy and Ross. Thanks also to you...BioWheel, Stephen, Camille, Dave.
Vicki