Switching from hps to led

[Guest]

Withnailed. 

Edited April 11, 2022 by fatboy77

[ratdog]

i think it would be useful for those succeeding with all led to give us the ambient temps of the rooms they grow in without heating

 

i would find it very interesting considering some comments recently

[KC]

@greenfingers1987

 

I don't really do conventional grows, I'm a perpetual grower. But let's just say I usually wanted 4oz from a plant which sometimes I didn't get, now I regularily get 6oz. In small pots I expected 2 but now I get about double. I have to add heat in winter but I did with hid too. 

When I first got my new light is shut down my room to change the duct fans so when I started it was like a conventional grow, I think it worked out about 1.4g/watt. I'd never even got 1g/ watt before. Best was about 0.84. 

The weed is better too according to my friends. 

I am getting through more food on the downside as they want watering more often than they used to. 

 

Edit-regarding temps, I only check at floor level really, I'm. Lucky to hit mid 20's most of the year. Summer can hit 32 (lights on and off). I run lights on at night. 

Edited April 11, 2022 by KC
Temps

[GSZZ]

1 hour ago, ratdog said:

i think it would be useful for those succeeding with all led to give us the ambient temps of the rooms they grow in without heating

 

i would find it very interesting considering some comments recently

 

It's not like I haven't been bashing my head against the wall in LED threads about this, and I can feel @fatboy77s frustration from 'ere!
 

LEDs produce a lack of IR, unlike HID, so ambient AIR temps need to be ran a bit higher than they would normally to compensate for this and to increase LEAF SURFACE temps to, ideally, 28c (peak photosynthesis) - how much the AIR needs to be raised by depends on loads of factors like how warm your house is, what way the room faces, your extraction etc. 

 

Light, temp, RH and Co2 are all intrinsically linked together. They all have to move up and down the scale of intensity with each other in balance, which can also complicate things when dialing in an LED room if just one of these factors is out of balance we're in for a bad time.  TBH the biggest mistake most growers are making are retrofitting LEDs into rooms designed and built for HID lighting, a little consideration for the environmental differences at the putting-together stage can save huge headaches and electrical savings later down the line. In HID rooms we were trying to get rid of the humidity and heat, in an LED room we're trying to keep it in - an undersized extraction can and will pay dividends especially an EC Fan that can be controlled in 1% increments. (A little less commonly known tidbit, is that traditional AC fans still consume 100% of the power even when ran at a lower % with a fan controller, unlike an EC fan which will only consume however much power in correlation to the % of the fan speed. 10% speed = 10% power, a 6" EC fan is a little over 90w at full chat... heaters not having to work so much)

 

All these things taken into consideration, its plain to see how many growers make the mistake of bringing their environment and plants out of balance. Usually by increasing the light, but not the co2 or more destructively the temps, and or the RH. 

 

 

Edited April 11, 2022 by GSZZ

[Guest]

@GSZZ rh has been the missing piece of the puzzle for me.  My plants are way happier at 80 than they are at 50.  Didn't matter really with hid

Edited April 11, 2022 by fatboy77

[NezA]

This is where I'm currently at.

 

If you're bombarding your plants with a ridiculous number of photons they need to be metabolising at peak rates, I know people say VPD isn't important but I think with LED's it really is. If you can maximize transpiration, LST won't matter as much it'll still need to be at an acceptable level but you can get away with a couple of degrees less because the additional transpiration makes up for the lack of photosynthetic efficiency at lower LST's. If your VPD is off you'll need higher LST's to compensate for the lack of transpiration. If you get everything dialed then that's what will allow you to push the really big PPFD numbers that Bruce Bugbee talks about. At 1000 PPFD you can afford for some things to be slightly out but not by much.

 

That's the theory anyway, I will be testing it as soon as I can get my room going again looks like an electrical inspection is on the cards for me next... I just want to get another grow on and test this shiny new light!

Edited April 11, 2022 by NezA

[GSZZ]

8 minutes ago, fatboy77 said:

Didn't matter really with hid

 

When you take the plant and environment balance into consideration, it goes to show just how inefficient HID lighting actually is and how much of the power drawn is wasted as heat and IR radiation (40 - 60% of reflected light comes back as IR, also). If we can run such high temps and low RH under HID, how much available light was actually hitting our plants? 

 

Just now, NezA said:

At 1000 PPFD you can afford for some things to be slightly out but not by much.

 

 and its realistically more like 800ppfd in the "average" ambient co2 growers situation , which is about 2 x ambient air co2. In theory it should be 1ppm co2 = 1ppfd of light, but IME its usually 1ppm co2 = 2ppfd of light which I suspect is down to the constant exchange of air not some changing of nature  

 

Just now, NezA said:

I know people say VPD isn't important but I think with LED's it really is. If you can maximize transpiration, LST won't matter as much it'll still need to be at an acceptable level but you can get away with a couple of degrees less because the additional transpiration makes up for the lack of photosynthetic efficiency at lower LST's.

 

The proper understanding of VPD is important. Its commonly misunderstood as being the driving force of transpiration, but rather its the result of transpiration. The only thing that drives transpiration in our plants is light, any other water loss is convection from heat or air movement. 

 

An extraction strategy should be based around maintaining balance between the plant and its environment, using VPD as tool to achieving that, rather than using it to maintain hard environmental set points.

Edited April 11, 2022 by GSZZ

[NezA]

Exactly @GSZZ the plant is trying to maintain a comfortable environment for itself as much as we are trying to provide one, but it has limitations when we push past those limitations is when we start to see issues. With LEDs we shouldn't be extracting more than the bare minimum to maintain Co2 levels except when humidity or temps exceed the comfortable level for our plants. It wasn't until I started paying attention to my VPD that I noticed it's just another way the plants can let us know something is up.

Edited April 11, 2022 by NezA

[GSZZ]

Just now, NezA said:

the plant is trying to maintain a comfortable environment for itself as much as we are trying to provide one

 

and that is the key, a plant has evolved incredible abilities to change itself and its immediate environment to accommodate itself, because it can't get up and walk off! These very same mechanisms can be used to our advantage  

 

Just now, NezA said:

I noticed it's just another way the plants can let us know something is up.

 

It is only when we correlate everything together the picture becomes clearer. The more ways we can listen or visualise what our plants are telling us, the better cannabis we can grow. Data logging and visualisation are invaluable tools.

[Herbal Kint]

25 minutes ago, NezA said:

Exactly @GSZZ the plant is trying to maintain a comfortable environment for itself as much as we are trying to provide one, but it has limitations when we push past those limitations is when we start to see issues. With LEDs we shouldn't be extracting more than the bare minimum to maintain Co2 levels except when humidity or temps exceed the comfortable level for our plants. It wasn't until I started paying attention to my VPD that I noticed it's just another way the plants can let us know something is up.

So what's range of humidity and Temps we should be aiming for?

And plant needs less co2 provided via air exchange with leds??

Edited April 11, 2022 by Herbal Kint

[NezA]

Just now, Herbal Kint said:

And plant needs less co2 provided via air exchange with leds??

 

No if anything the plant needs more Co2 but in order to maintain appropriate Co2 levels the air exchange required is negligible compared to what we're used to with HIDs

 

Just now, Herbal Kint said:

So what's range of humidity and Temps we should be aiming for?

 

It varies depending on the stage of life the plant is at and what your leaf surface temps are. I have a thread in the environment section that covers VPD and has some good information, it's primarily about using inkbirds to maintain it automatically for you but there some useful charts and media in there.

 

Please bear in mind I'm not saying anything definitively at the moment I need to test this for myself I'm purely theory crafting and connecting dots but from what I've looked at so far all the evidence points to being able to run lower temps if VPD is spot on. @GSZZ is better placed to comment but his numbers are more in line with what I would be expecting to be running myself.

[Herbal Kint]

 

I remember @scraglor gave some good info bout co2,you still here?

 

I saw 1000w leds that are rated to use with co2,if that's not commercial trick it would still say they could use extra co2.

[NezA]

So here is the math as I understand it. The minimum air exchange required, is that you need to vent the entire air volume of your grow every 3 mins this will keep the Co2 at the same level as the atmosphere wherever your intake is from.

 

So first calculate the air volume of your grow space in cubic meters, for example a standard 1m x 1m x 2m tent = 2m3 of air volume

 

Fans are rated in m3/h (cubic metres per hour)

 

2m3 / 3 = 0.66 m3/m X 60 mins = 39 m3/h. That's what the extraction fan is required to move in order to keep Co2 levels where they need to be.

 

For example a 4" rvk moves 184 m3/h, so you can dial a 4" fan right back with a controller and still move enough air to adequately ventilate a 1m2 grow tent. The added bonus is now you are venting less heat and the heat generated by the LED has more time to heat your air because less air is being vented. This will also keep humidity higher which in turn makes the plants happier.

 

This is why I think the extra heat thing with LEDs is a red herring.

Edited April 12, 2022 by NezA
Typo

[grooving]

I run 3x 375W Scope V1s and I need to keep my tent and room it’s in at 28ºC or more and I have also recently copied GSZZ’s method of attaching fans to the ceiling to blow the warmth from the LEDs back to the leaves.  My extraction was designed for HID lighting and is maybe too massive for my set up now-will downsize in the next couple of years which will also save my back coz lifting my huge fan and filter into place on my own is a right mission.  I struggled with temps when I first started using LED and only because of this place that I realised my error.  My rH is around 40% at week 3 flower and I can never raise it above that despite running humidifiers-plants seem happy enough but would love to have more ability to vary my humidity.

 

 

 

 

 

[inceywinceyspider]

@groovingI can see your leaves look similar to how mine did before I raised the rh, get it past 60 and the difference is amazing.

 

I used a "swamp cooler" to raise rh, using a duct fan to suck the hot air from the top of the room and blow it into a tub of water at the bottom, I use a small tube heater under the tub to warm the water up a bit (it could do with being warmer still ime) Both the fan and heater are plugged into an ihc200. I'm not sure if it's as good at humidifying as a shop bought humidifier but no white dust, no ro water, no hefty electricity use and moves the hot air to where i want it to be.