[marque08]

Marque, try googlying t5 24w 6400k and t5 24w 2700k (dont want to post links incase I get into trouble)

The 6400k are veg and then mix in the 2700k bloom I think.

My 2ft T5 has 4 6400k bulbs. I got mine from Greens hydro, they sell the replacement bulbs too.

Cheers mate. It's just I'm struggling to find those easily.

[Anonymiss]

6500K ('daylight') is great for the vegetative phase

Most metal halides are somewhere around 4000K to 4200K; HPS are usually in the region of 2700K to 3000K; and household compact fluorescents tend to be 2700K to 3200K.

I used to mess about with switching tubes from 6500K down to 3000K or so (sometimes in several steps), but running 4000K or 4200K throughout seems to work just as well, and research seems to suggest that it's the best option overall.

@marque08 - Tubes are generally labelled as 8xx, where the 8 is the colour rendition index (80% to 90%) and the xx is a pair of digits representing the colour temperature: 27 for 2700K, 30 for 3000K, 32 for 3200K, 40 for 4,000K, 42 for 4200K, 65 for 6500K.

Don't worry about the rendition index, just make sure the last two digits are what you want.

@Marc - Links are generally OK here

Some sources I've used are Lampshop Online, National Lamps and Components, and TLC Direct

[marque08]

Thanks @Anonymiss. That helps a lot. I've been going quietly mad this afternoon😀

[Anonymiss]

Cheers Missy, post a link on other forum places and it's all...
download.jpg

 
Yep, so I heard

But we're here to have fun, share, and help people - Not to make money and be beholden to advertisers or sponsors.
 

But (little hijack here) have you run T5 start to finish then?

 
Nope - I use T8s (And many years ago T12!)

I know T8 might seem an odd choice these days, but the T5s are either much less efficient (for the HO versions) or they don't produce enough light (the HE variety).

I don't use them overhead though, for three reasons:

Firstly (and mostly) because it's really hard to get enough of them in to produce enough light (those 2' square fittings really need eight lamps, not four), and

Secondly my space is too small anyway - it's only about 35 cm x 45 cm - so they're placed vertically around the perimeter, and

Third there's the temperature vs. ouptut issue, which can have a fairly large effect on brightness - T5s require an ambient temperature of 35°C whereas T8s work best at 25°C, which is much better when the lamps are actually in the growing space.

Attached Files

•  t8-t5-lumen-temperature-curve.png   7.42KB   0 downloads

[marque08]

Yep, so I heard

But we're here to have fun, share, and help people - Not to make money and be beholden to advertisers or sponsors.


Nope - I use T8s (And many years ago T12!)

I know T8 might seem an odd choice these days, but the T5s are either much less efficient (for the HO versions) or they don't produce enough light (the HE variety).

I don't use them overhead though, for three reasons:

Firstly (and mostly) because it's really hard to get enough of them in to produce enough light (those 2' square fittings really need eight lamps, not four), and

Secondly my space is too small anyway - it's only about 35 cm x 45 cm - so they're placed vertically around the perimeter, and

Third there's the temperature vs. ouptut issue, which can have a fairly large effect on brightness - T5s require an ambient temperature of 35°C whereas T8s work best at 25°C, which is much better when the lamps are actually in the growing space.

@ anonymiss sorry to ask again, but would probably take me an hour on Google. Could you explain the temp vs out put in laymans terms please. I had no idea temp effected a tube!! My t5 gets nowhere near 35c so it's not at its potential??

[2scoops]

I got 12 x 2ft= t5 veg bulbs 4500k or summink 24watters each tube or summink like for around a  tenner on fleabay. :0

[Funky]

@marque08 - 35 degrees is the temp of the light, not the growing space.

[Anonymiss]

@ anonymiss sorry to ask again, but would probably take me an hour on Google. Could you explain the temp vs out put in laymans terms please. I had no idea temp effected a tube!! My t5 gets nowhere near 35c so it's not at its potential??

 
Fluorescent lamps are designed to work at specific temperatures (it's all to do with the condensation of mercury vapour) and for T5 tubes this means an ambient temperature of 35°C (the lamp wall should be closer to 38°C, I think) - Values higher or lower than this will affect the ouput (see the graph I posted earlier).

Well-designed fixtures will have carefully calculated and tested thermal properties (air flow, etc.) and will probably keep the tubes at the right temperature under 'normal' conditions, which I imagine means something like 20°C or so.

In my case, I use T8s because I have them inside the grow space and T8s prefer 25°C.

--

From Wikipedia:

"Fluorescent lamp efficacy is dependent on lamp temperature at the coldest part of the lamp. In T8 lamps this is in the center of the tube. In T5 lamps this is at the end of the tube with the text stamped on it. The ideal temperature for a T8 lamp is 25 °C (77 °F) while the T5 lamp is ideally at 35 °C (95 °F)."

eta: Here's another graph showing the same thing (from Chapter 1, Radiation, in The Plant Growth Chamber Handbook)

Attached Files

•  t8-output-v-temperature.jpg   70.33KB   0 downloads

[marque08]

Thanks@anonymiss🤗

[marque08]

@marque08 - 35 degrees is the temp of the light, not the growing space.

Cheers man. I was starting to get even more confused😝