When to replace lights - Orchid Board

Ross · #1 (**permalink**) 12-20-2007, 04:59 PM

For those pondering when to replace florescent lights (in this case t5 straight 47" tubes) consider this:

I measured FCs with calibrated meter on tubes set up last January and got 800 (or so) FCs. Actually a bit less, like 795.

I just replaced all four tubes and measured (at same point with same meter) and got 1380+ FCs! That should be a signal to replace bulbs more frequently than the manufacturer states. I had less than 6000 hours and they were rated at 10,000 hours. Who knows when they first started dropping off? I plan to check weekly now,

Ocelaris · #2 (**permalink**) 12-20-2007, 09:21 PM

The Manufacturer's rated life of a bulb is 50% of it's inital lumen output. So you can figure that if the bulb was rated at 10,000 hours, you would have 3.5 years at 8 hours a day before it was 50%... They usually give a derating curve for bulb life span on commercial bulbs. I wish I could say I was better at keeping track of when I last replaced the bulbs!

Grandma M · #3 (**permalink**) 12-21-2007, 08:12 AM

Thanks for this info. I think I need to make a chart to record when the bulbs were replaced. Thanks for reminding me.

FinnBar · #4 (**permalink**) 12-21-2007, 10:18 AM

During my fish tank days i used to change the oldest one out of my four tube setup every 3 months. that kept the light levels even all year round

But i'm thinking if you could somehow make an advantage out of a) bulbs weakening and b) replacing them simultaneously at a certain part of their growth cycle. to give them a little boost in the spring for example..?

Ross · #5 (**permalink**) 12-22-2007, 06:08 PM

Good idea. I think your idea of averaging is a better one tho. I might try this, but, it seems the tubes go all at once. I had one out of four that was any good when I read the FCs.

Grandma M · #6 (**permalink**) 12-23-2007, 06:32 AM

[quote=FinnBar;71086]During my fish tank days i used to change the oldest one out of my four tube setup every 3 months. that kept the light levels even all year round

It would take a lot of recording but it sounds like a good idea. My T5 units are made so if one of the 4 bulbs goes out they all go. It's difficult to know which on it is. Replacing one every 3 months and doing it in order, 1st then 2nd....on every unit would help me know which ones were replaced last. I think I will try that.

I have some cart units from Housermanns which require special high intensity bulbs, from Housermanns. I was told they are T12. I took one to my local hydroponics store to see if he could get them for me without my paying the extra shipping cost from Chicago. He said they were not T12 but are T10, which I didn't know were made.

HIS MESSAGE TO ME: I can get a T10 high intensity, full spectrum tube that has a color rendering of 5000 (which is full spectrum), and a lumen output of 3700 per bulb.

He got me 4 bulbs with the condition if they didnt work I could return them. They work great, are a lot cheaper, and a higher intensity. I may try that suggestion on these new ones which were newly replaced.

FinnBar · #7 (**permalink**) 12-27-2007, 06:03 AM

Merry Christmas y'all! i was starting to get some withdrawal symptoms from the board..

i don't know how many setups you run so maybe some kind of calendar keeping track of the tube changes might be in order. however, if my memory serves me right, you can usually spot the weakest tube with the naked eye, especially when it's next to the brightest one 3 times out of 4..

Pippin · #8 (**permalink**) 12-27-2007, 09:37 AM

I measure them once a month, I don't trust my eyes for that and the light meters are pretty cheap in our days

FinnBar · #9 (**permalink**) 12-27-2007, 03:31 PM

Quote:

Originally Posted by FinnBar

you can usually spot the weakest tube with the naked eye, especially when it's next to the brightest one 3 times out of 4..

i can see i was a little vague there

that would apply only if changing one tube out of four every 3 months. otherwise i'd rely on a light meter too..

Ross · #10 (**permalink**) 12-27-2007, 04:17 PM

Quote:

Originally Posted by FinnBar

i can see i was a little vague there

that would apply only if changing one tube out of four every 3 months. otherwise i'd rely on a light meter too..

All this is really cool, but I decided a while ago to just recycle all the bulbs at same time and move old ones to room lighting till they fail. Mine go to the kids who use them to light the front porch area (enclosed). They don't care about lumens, lux or foot-candles - just how bright they are!