Simple way is to put in a new tube. If you don't see much difference with the old ones, then you don't need to change the old ones.

dcarch

I know you need to replace the tubes every saeson to start the vegetables
Not necessarily, but probably. Post exactly what ballast or shoplight you have and the exact make and model of tube. Then we'll let you know whether you need to throw it away. A 20% light decrease would not be noticeable to your eyes but is significant to a plant. You'd be able to see the difference side by side with a new tube but not to the extent that you'd throw your hands up in horror.

The light output of all plant lights decreases the longer they are run, also each time they are switched. Historically, as in 20 years ago, every single light lost so much light that it was more cost effective to buy new bulbs or tubes every 6 months than to run old lamps putting out less light. This is no longer true.

Modern triphosphor fluorescents (but not the $1 tubes from China) running on electronic ballasts lose about 5% of their output even after 20,000 hours operation, so run them to failure which will be several years even running every day. Cheaper tubes, specialist tubes (wide spectrum, plant spectrum, actinics, etc.), compact fluorescents (the more compact, the worse), and anything on a magnetic ballast still loses a lot of light and should be replaced frequently.

The best pulse start metal halides on exactly the right electronic ballast lose about 10% of their light output. Again, not worth throwing them away every 6 months. Probe start (ie. anything that doesn't say pulse start) bulbs and most bulbs on magnetic ballasts still lose enough light to need frequent replacement, and many metal halide systems still sold today are so horrible that you absolutely need to replace them every 6 months.

HPS bulbs still lose something like 20% of their output relatively quickly. You should probably replace them every few thousand hours, but check exact specs on any bulb and ballast you have since I haven't looked at the latest data in detail.

Lights which have been stored in sensible conditions will keep for years without problems. Excessive temperature variations can cause them to degrade.

Ushio T8 triphosphor lamps last 30,000 hours+ with 90% maintained lumens. They are intended to do this to keep the mercury out of our landfills, and to reduce landfill waste, and save costs on relamping. This lamp will run THREE TO FOUR YEARS CONTINUOUSLY before it needs replacing. Only replace it if it looks obviously dim. Older T12's had poor lumen maintenance, but new lamp technology improvements are designed to keep the mercury out of the landfill. Also, if run on electronic ballast, pulse start halide WILL RUN FOR 30,000 HOURS CONTINUOUS, but probably need to be replaced every 2 years max, ONLY IF RUN CONTINUOUSLY FOR THAT PERIOD OF TIME. Please invest in a 30$ light meter that will reassure you ur lamps are ok, use rapid start T8 ballast and electronic pulse start ballast to keep ur lamps at their peak for the maximum possible hours. Paul Mozarowski.

The Phillips alto T8 high lumen output lamp has a 36,000 hour lifetime which means it WILL RUN CONTINUOUSLY FOR 4 - 5 YEARS.
It has 97% lumen maintenance at the end of it's life, and is rated at 3100 lumens at 40% of its lifespan. I recommend purchase of Phillips alto high performance t8. You only have to replace it once it is dead, which (God forbid) means it may last longer than you do, depending on how old you are now. If you only used it 2 months a year, then one lamp will last for 24-30 YEARS! and still provide 97% of its lumen output until just before it dies. Since I am 51 now, the lamps I buy today will still be shining the day I die. And if I outlive the lamps, this will be cause for celebration. I will celebrate by buying a new case of lamps. They only cost
2$ per lamp in case of 25 from businesslights.com. They have only a tiny bit of mercury in them, to keep landfill waste down. It is irresponsible to use any other lamp if it does not have similar performance. Paul Mozarowski.

Here is a link that might be useful: Link to Phillips alto website.

Paul,
What do you think of this light:

54W 6500K 85 CRI T5 HO Fluorescent Lamp

I saw it on the businesslights.com website and wondered if it was low mercury - it does not say low mercury. I use 2 - 2 tube shop lights now for small hydroponic veggie garden and wondered if these lights would work. I happen to like the results I have been getting from the fluorescent lights so have not switched to other types.

Also a question - my shoplights can be used with T10 or T8 lamps - are the T5 Fluorescent Twist and Lock Lampholders used in the T10 shop lights to make them adaptable for T5 lamps?? Thanks for any help you can provide.

DL

Here is a link that might be useful: 54W 6500K 85 CRI T5 HO

Hi, I checked the TCP site, beautiful lamps. I would suggest 5000K. You can look at the spectral output yourself and compare what all of the different K looks like. Both the 5000 and 6500 have almost the same amount of blue and red, but 5000 has a bit more red than blue, and 6500 a bit more blue than red. The photosynthesis action spectrum shows that the plant is really most efficient at the red part of the spectrum, but I imagine you like blue to keep the plants short and stocky. I really think if it were me I would grow with the 5000K. I am currently using
a mix of 830 and 850 because I happen to have them in stock, but if I didn't have any 830s I'd be using all 850's. The 5000K has plenty of blue to keep the plants short and bushy, and plenty of red to capture the "red bonus points" - red photons in the optimum range for peak of photosynthesis.
cut and paste the following into your browser
http://nsdl.lon-capa.org/res/msu/botonl/b_online/e24/10.htm

I haven't tried the t5 lampholders, it is possible they will retrofit onto a t8 fixture, but your main problem is: where do I get a t5 ballast? If you're able to find a supply of reasonable t5 ballast let me know. I've spoken in person to businesslights.com, there is someone there who'll answer the phone in a bored voice, and will answer your questions. I would ask him about the lampholder question, and ask him when they will finally start to stock the t5 ballast.
He mainly likes selling the whole t5 fixture, because it's what is in demand right now.

Paul Mozarowski.

Here is a link that might be useful: T5 tcp website, otherwise go to www.tcpi.com/

The T5 won't retrofit to a T8, the electrical characteristics are completely different and obviously the pins are different too. Add in the fact that the "four foot" tube is actually only 46" and you see the issues. I have seen devices which will allow a T5 tube to be used in a T8 fitting but frankly there is no point. Another interesting difference about the T5 tubes is that they are optimised to run at a higher temperature. T8s operate best at 77F, T5s at 95F. That's generally a good thing when used as a plant light but think carefully if you plan to use them in a cold basement without enclosing them to keep the temperature up. Fluorescent tubes will only run about 90% of nominal output if you operate them 15F away from their design temperature.

The spectrum on almost all T5 tubes is a basic triphosphor. The relative amounts of the red and blue phosphors are simply changed to provide the different colour temperatures. You will see a lot of fanciful descriptions of T5 tubes but I have yet to see one which is significantly different. There are "purple" T5s available now. I haven't been able to get a solid answer on the spectrum they produce but I'm fairly sure they are just standard triphosphors with most of the green taken out. This is not the same spectrum as the various T8/T12 plant lights such as the GroLux and the GE equivalent.

T5 plant lights in the US are very expensive, unnecessarily expensive. Look on eBay and check out commercial lighting stores because they are widely used as office lighting, there is nothing fundamentally expensive about these lights, they are just being marked up as a premium product. One good thing about T5s is that they are still essentially all the same, even eBay sources will be giving you the same quality electronic ballast and top notch tubes. Prices in Europe are barely higher than for quality T8 equipment and to be perfectly honest, when something costs more in the US than it does in the UK, you guys are getting ripped off ;)