LED vs "BULB"
- Thread starter westpoint
- Start date
Fardsnarp
Well-Known Member
Define "issues". Seriously. You mean ambient air/tent temp?
BigGreenThumb
Active Member
I can confirm as a first time LED user.. I was used to using HID and having to GET RID of heat, whereas now I find myself struggling to keep it . Plants noticeable suffered when my temps and humidity were down and I couldn’t raise them…
Struggling to keep what temp? The standard 68-77? Leds produce less heat so if you don’t have a heat source for your room now(winter) you would struggle. I don’t use leds except for veg. So I’m curious. How does changing the bulb change the needs of what cannabis has evolved to thrive in?
Ok, so it is like I thought. Ppl get confused with air temp and surface temps.
BigGreenThumb
Active Member
actually with LED, the air and surface temp are major factors..
there is a formula and chart that you should follow (look up vapor pressure deficit) when using LED in relation to air temp, leaf temp, and relative humidity…
BigGreenThumb
Active Member
I was VERY close to just switching back to HID, but once I dialed it all in and saw how much things REALLY thrived, I was sold…
the light for my space gives off way more of an even distribution throughout the canopy and all while using less than half the power of an HID.
DoubleAtotheRON
Well-Known Member
~79 in veg ambient. 80 to 85 in flower. You CAN run higher temps with LED, and especially with CO2. Get an IR meter from the hardware store and read your leaf surface temps. Adjust your room/tent to get ~79 degrees leaf surface temperature.
NanoGadget
Well-Known Member
for those not in the know who don't understand higher ambient temps with LED.... it's simple. HID puts out sufficient IR to heat the leaves of the canopy to a temperature above ambient temps. so ambient temps of 75 under HID will result in leaf temps of 80 to 85. LED doesn't put out IR for the most part so ambient temps and leaf surface temps will be much closer together than they would be under HPS.
Great discussion folks, most of you have highlighted the issue with LEDs when you first switch over! When we first started to dive into LEDs in our grows 2-3 years ago, we noticed they weren't doing as well as HPS and HID. I was convinced LEDs would be better and then thought LEDs were a scam. Plants were shorter and had less flower. This is was especially the case during the winter. The issues was highlighted in these previous posts that there wasn't enough radiant heat coming from the light downward to the plants and we were having a VPD issue. HPS leaf temps were about 2-2.5 degrees C warmer than LED, so stomata we're not opening and transpiring at the same rate at the HPS plants. Once we realized that we started only having uniform rooms(all LED no HPS) and let those rooms get a bit warmer to keep up the transpiration rates. Once the plants got use to that they were doing just as well if not better than the HPS. You save 30-40% on electrical and HVAC costs with LED. I would never go back to HPS/HID
King Avitas
Well-Known Member
I run 3 LED lights over a 4x8 table. At 100% power my temps would easily rise to 100⁰f if I let it. Even at 60% they still kick in my AC at 85⁰f every few minutes. But to get the same coverage with HID, I would need 2x 1000w bulbs or 3x 600w bulbs. The power usage would be considerably higher with HID and AC would run continuously.
As I said my room is currently at 85⁰f, but my plants are small so my leaf surface temp is only 79⁰ to 81⁰f about a -5⁰f differential. The key for me is to run humidity at about 65% to keep my VPD at .9 to 1kPa. The plants seem to love it. Btw I am running CO² in a sealed room so my plants can handle higher temps. But this is my room and these same parameters in someone else's room could cook their plants.
The trick is to get your VPD dialed in regardless of what type of light you are running. Best bet is to research the light you want, buy it, install it and test it. Then you know what temps to expect and adjust your humidity according to your plants leaf surface temp. That all said, achieving a leaf surface temp of 79⁰f in the early plant stages might be difficult without CO² because the plants can be considerably cooler than the room temp when they are young and small. As they get bigger and the leaves get darker they will absorb more infra red light and actually have a temp higher than room temp.
It's a balancing act and no two rooms are the same. All I can recommend is playing with your set up and try to dial it in. Hope this helps.
As I said my room is currently at 85⁰f, but my plants are small so my leaf surface temp is only 79⁰ to 81⁰f about a -5⁰f differential. The key for me is to run humidity at about 65% to keep my VPD at .9 to 1kPa. The plants seem to love it. Btw I am running CO² in a sealed room so my plants can handle higher temps. But this is my room and these same parameters in someone else's room could cook their plants.
The trick is to get your VPD dialed in regardless of what type of light you are running. Best bet is to research the light you want, buy it, install it and test it. Then you know what temps to expect and adjust your humidity according to your plants leaf surface temp. That all said, achieving a leaf surface temp of 79⁰f in the early plant stages might be difficult without CO² because the plants can be considerably cooler than the room temp when they are young and small. As they get bigger and the leaves get darker they will absorb more infra red light and actually have a temp higher than room temp.
It's a balancing act and no two rooms are the same. All I can recommend is playing with your set up and try to dial it in. Hope this helps.
I can't like on this forum yet but THIS.
Planning is the key. We've found the LEDs have this VPD issue during our winter seasons so to compensate we have good insulation to keep the rooms warm in the winter and we have fans to push the heat so overall room temps stay up. Keeps the leaf temps around 25-26 C