LED newbie - distance, power Qs

[JimmyPage]

Starting a C99 in DWC. Have grown under HPS for years.

Got a 465W Lumatek Zeus LED rig (just !) in my 1m x 1m tent.

 

Currently it's about 100cm above the plant and running at 25%, as I was warned in the shop not to try it at 100% as it's too strong.

 

10 days in (pic is from 3 days ago) and all looks great. However I have a slight concern that no roots have yet started to poke through the basket ????

 

Is there a simple rule of thumb about distance, power and %age ?

 

The Lumatek comes with a controller that's 0/25/50/75/100%

 

[MindSoup]

Lumatek should have some PAR maps on their website for you to work from, basic rule of thumb is about 400-600ppfd in veg and 750-1000 in flower. 

 

You can get sensors if you want to get more accurate, either a proper PAR sensor or a lux meter as discussed in this thread. 

 

 

 

[Shumroom]

You could either move the light a wee bit closer to around 75cm,

or move it up to about 130cm and turn it up to 50% depending on how the environment is  

 

How is the air temperature and relative humidity?

 

Atb

 

 

 

[JimmyPage]

No idea about humidity. But in 15+ years of growing I never have had any idea  

 

Temps are 18C - I have a hanging heater strip at the back with a thermostatic control. 

[Shumroom]

Yeah these things didn't used to seem so important with HPS  

 

With LEDs it's fairly vital to get your environment pretty spot on,

otherwise it just seems to lead to problems.

 

I've no recent experience with pure hydro,

used flood and drain system for a couple of runs many moons ago

 

 

 

Folks argue about temperatures,

some say they absolutely must be at least 28C,

but not everyone can achieve this.

 

Also when pushing the temperature up it has a large effect on reducing the humidity.

 

 

Because you're not getting the benefit of under pot heating mats as you have to retain your water temperature,

you'll probably need to get your air temperature up above 24C at least to get happy plants,

depending upon whether they are particularly hardy or not.

 

 

Make the investment of a hygrometer,

ideally one that can store time/temp/humiditity data but at least one that shows minimum and maximum.

 

 

Get your air intake taking nice warm air from a heated room.

 

 

@stu914 has loads of experience with hydro and LEDs,

so do others like @badbillybob sorry tag stopped working mid post  

 

 

Atb

 

 

 

[Notorious B.U.D]

I’m no expert on leds either but my findings so far are that you don’t need to have air temps of 28c and above to grow well with led lighting although you do want to make sure your roots are always at a temp of at least 20c otherwise you’ll run into deficiencies fairly quickly so the use of a heat mat or even a couple of small tube heaters close to the pots should do the job ideally on a thermostat with its probe inserted into the bottom of the pot. Humidity is also important and I’d want it ideally above 60% if possible.

 

Ive also found that you’ll be surprised at how low of a wattage you can get away with in veg especially using a light with good spread over the plants, I’m running my whole propagation tent (90cmL x 60cmW x 60cmH) on just 22w of Par+ Ultra led and I could probably get away with less but it doesn’t turn down any lower 

 

Lots of experimenting to be done mate 

[catweazle1]

I would advise to get a light meter. Migro's Shane has a video on using correcting 3 or 4 versions of chap lux meters. With HID you brought them close enough not to burn, but you don't have that intuitive guide with led and the risk is leaves bleaching if you go too low in height on a high setting. For the sake of about twenty quid you can save that unnecessary empirical learning curve and jump straight out of the blocks... into the next problem.

Edited January 15, 2023 by catweazle1

[JimmyPage]

Thanks for all the tips.

 

My understanding was that anything over 22C nute temp isn't good for roots. I have a nute heater if needed but last time I used it I couldn't get my temps below 23 !

 

I'll try and get some proper PAR readings - seems a common theme.

[catweazle1]

If you are looking for maximum then 28c  leaf temps are the way to go but I ran my plants on led sometimes down to 18c with no issues.

[stu914]

@JimmyPage

 

Is this your first outing in DWC Jim? You need a decent rootball before going into that system which is why you're having issues.

I always start them off by having a same sized solid pot round the mesh one and water by hand....like this...

 

 

Once they get to about here you can take the solid pot off and they should fly...

 

[Thai Stick]

2 hours ago, MindSoup said:

Lumatek should have some PAR maps on their website for you to work from, basic rule of thumb is about 400-600ppfd in veg and 750-1000 in flower. 

 

You can get sensors if you want to get more accurate, either a proper PAR sensor or a lux meter as discussed in this thread. 

 

 

 

 

Interesting that.
Checked with the Photon app and im running 1500ppfd in one of my tents.

 

In my veg room i was testing out a light and im pretty sure something about the spectrum or intensity caused major issues fairly quickly.

[JimmyPage]

49 minutes ago, stu914 said:

Is this your first outing in DWC Jim? You need a decent rootball before going into that system which is why you're having issues.

 

Nope - started in 2007. Have done the same every time. Soak seed. Then pop into a cube. Wait for it to sprout and until we see a root, and then whack it in the basket with pebbles under the light. The only change was from a system circulating nutes to a 1-bucket system.

 

Like I said the plant looks great - to be honest one of the best starters I've had. But with the new lighting I'm keen to spot anything amiss.

 

I could probably do quite a bit better with very little effort. However there are other calls on my time. Also it doesn't do any harm if I ever get busted and it looks a bit shit. (You should see the state of the room. No one will see that and say "What a professional setup". More like "How did he get to the tent without turning sideways ?"  )

 

E2A: Had a bit of a shit year from July. This is the first grow since the Mrs got out of hospital, so maybe not the best time to experiment. However with the price of energy, it would have been a bit much to carry on with HPS.

Edited January 15, 2023 by JimmyPage

[stu914]

@JimmyPage

 

 

LED is certainly the way to go mate but it takes a bit of fiddling around to get it right, lowest setting as near as possible is what I do.

If you have no meter then it's trial and error, you'll soon know if it's too close as the leaves start to bleach, too far and the plant stretches.

Hope your mrs is on the mend, I know only too well what it's like having one that's poorly.

 

[JimmyPage]

So tonight, and 2 roots have just started poking through. Upped the light to 50% and leaves still look good. Will prolly post some pics before the weekend.

[JimmyPage]

So a few weeks on ...

 

Power is now running at 100%. Decided to bring the light down a bit. Played around with a nute heater and timer (6 hours on spread over 24) which seems to be keeping the nute temps around 19C. Air temp swings between 16-22 and is always 20C when I check around 6pm.

 

Here's where we are now. Any comments gratefully received. Stlll not sure about when and how to deal with keeping the height down.