Plants are always 2-3 temps below ambient temps, as they are mostly made of water and water does not heat fast or like air
So a living tissue will always be lower than the actual heat you feel
Under LEDs I do think they are even lower at leaf temp as leds just don’t cause so much ambient heat
Anyway plants love high temps when rh is right, it’s really all a matter of transpiration, high temps high humidity, low temps low humidity is the gold rule
1 Like
I run with xxxl magnum reflectors, and i would buy 400w cmh bulbs if they still made them
But the fact is, they do run hot even at 400w
I love them, but they are not known for running cool… this benefits leaf Temps, but not my living temps
1 Like
Still sad they stopped making the 400w ceramic metal halide, mogul style…
I know there’s various options, but that was my jam
1 Like
We have a shop here that still has some of those in stock for cheappp
But a 400 hps is so much better, everytime I think about running MH or CMH I find myself putting hps in the socket 
3 Likes
I bought these a month ago, Im so impressed with how they are growing under the 6700K CFL, I figured I need to try the same with HIDs and see if they are comparable in that spectrum
2 Likes
If you go with the de cmh there are a few hps bulbs out there for the fixtures.
3 Likes
You can always changes sockets, but the ballast of the 315 or the 630 is different so that’s kinda limiting.
I’m gonna try the 6K MH in my winter veg, I wanna see if the extra sun spectrum grow them like the comfort of the CFL
1 Like
More than this with led, almost certainly.
They are, it’s a fact. It’s because there’s little to no IR from the leds, which is more of a “directed” heat (it directly heats objects).
We really need to observe the plant’s temperature, that’s the more important temp., not the air. And under leds, the optimal values of air temp and air rh are just different than with hid.
Companies that actually do some testing (with their leds) have been saying for years to have your (ambient air) temp. in the mid to high 80’s. That’s because, on average, they know your actual plant temps are going to be significantly lower than that, due to lack of IR mostly.
I don’t think it’s as simple as high temps high humidity. From experience. There are interactive vpd charts where you can enter/take into account the actual plant temps (most people do not) and enter that number as a “leaf temperature offset” and it significantly changes the results as far as recommending “ideal” air temp and air rh targets. The guys who make the Pulse room sensor/monitor have one, with quite thorough details/explanations. In the end, I dropped my rh even lower than it recommended, I think, and my results have been much better under led. Several things change transpiration, rh is a good one to use. I use pretty high ambient air temps and pretty low rh (along with what are pretty high ppfd numbers) to get the transpiration and ‘growth’ results I want.
(I hesitate to give numbers because the trolmaster 3-in-1 / temp/rh sensor is not precise nor very accurate).
I think we’re agreeing on most of this… Sorry for the rambling. I spent too much time agonizing over this whole vpd thing a couple years ago. Hah.
Eg. of Pulse’s simple vpd calculator, don’t take as gospel, I don’t:
Their more comprehensive “chart maker” and guides, again - not a bible really:
Edit: readability.
2 Likes
As the others are saying.
CMH is a great spectrum too. I only know a bit about the 315w, not the DE or anything.
ONE of these is has the same/similar par output as a 315 cmh, at ~225 watts:
HLG 225
Not great coverage though, says 3x3 for flower. It’s the same led board as I mentioned above (qb96 elite v2). You could put your own fixture together easily for less I’d say, with better coverage. I’d help.
Orgro and Soil2coco did lots of testing, back in the day: QB96ELITE V2 ***No BS, information only*** | Grasscity Forums - The #1 Marijuana Community Online. I used to use these boards and built quite a few fixtures with them.
Hope things work out for you.
1 Like
@Nitt I would like to add, you said plant’s temperature, I would say it might help people to say it’s the leaf temperature we can measure, typically I’ve seen people use an infrared thermometer (laser) but there’s also a new vpd thermometer product, and you can use that on the leaf surface. (No personal experience here, just adding on from what I’ve read)
Another complaint, a bit trivial, but relevant:
Bulb blew, no idea how long
Could’ve been my fault, sometimes bulbs blow on their own, but i was also running my washing machine nearby. I don’t know when it happened but hey, no longer running the washing machine while lights on, just in case. It shakes a lot, even on thick rubber anti vibration pads.
But led doesn’t blow like this, lol
2 Likes
I run my grow on a very very tight budget because as everybody knows, inflation and other prices are not good lately. I’ve got a decent amount of bulbs to run as needed from when I was using them for various purposes and setups, veg etc, so I don’t need to buy bulbs right away. But leds don’t demand a random or ongoing cost like this as far as I’m aware, only dying diodes or end of life (five years) etc
Anybody with failing parts on led lights, please add here, just want to see the pros and cons of both
2 Likes
I’m a huge fan of the natural warmth, light penetration, light spread of HID lighting by the way, I think I said this before but I’m definitely a fan of this
But it’s got clear drawbacks unfortunately, on my end
I’ve got plenty of sunk cost on these quality products, so I’m able to enjoy the positives
But replacement or future cost, or suggesting it to other people, it’s just not cheap to get a quality reflector or bulb sometimes, even if you can get the ballast and tent etc
2 Likes
I still think about and sometimes miss my old 1000-watt MH and HPS lights.
Those higher temps and the light intensity of an HID can really drive growth if kept within reason.
Yes, I even used the single ended versions. Started with old-school 400-watt and 430-Hortilux enhanced. Upped to 1000-watts along the way.
But eventually came over to LED and must admit, there’s no going back. I’m friends with my LEDs now.
Using Mars-Hydro FC series LEDs in most spaces now.
Agreed that getting temps right was a little bit of an adjustment. They also seem a little needier with cal-mag under the LEDs to me, which I typically don’t tend to use as my water more than compensates usually.
Just recently dropped the MH in my nursery/Veg space. It was a beast. Also used the enclosed reflector with active ventilation.
When I stopped with MH for veg-room, I splurged a little on an ACInfinity Ion-frame EVO4.
As far as the new LED for the nursery.veg space, the EVO4 more than matches the old 1000-watt MH, it and the FC-6500/4800s are much cooler and friendlier to my electric-bill.
2 Likes
Have you considered mounting the fan outside the tent and running hose?
1 Like
my indoor rooms run on controllers that will distribute the heat as needed. The 110cfm exhaust from above the HL 600 Bspec , vents out of the tent , across the lung room ceiling and half way down the wall in the flower room. Helps maintain humidity numbers in the flower room and keeps a stable 20F during lights out.
Flower room exhausts to the lung room with a 6" ac infiity the lung room exhausts to outside with a 450cfm exhaust fan and Can150 carbon filter.
When the fans are running the way things are programed, veg tent stays at a stable 78F
The flower room is set for 78C high temp and it rarely gets that hot in there. The flower room also has passive intake along the one wall.
The entire grow space has negative pressure at all times.
It’s not a perfect system but it works very well in my climate.
usually I shut down my indoor from mid June to October so I am not running rooms during the hot part of summer. Got a late start on the bud room this run so it is finishing further into summer than I had hoped. Still is gets very cool here at night so i always run the flower room at night.
5 Likes
Oh wow it sounds like like you’ve got it dialed in pretty tight. I’m jealous
Personally setting up my tent this weekend. Just a single 2 x 4 but I’ve got that 6 inch AC infinity exhaust fan with the controller 69 and some other accessories. It’s definitely gonna be interesting this winter as It’s in my garage.
Looking forward to the challenge though. So far, I have some reptile ceramic heating coils that I might play around with this winter and 2x4 heat pad, not sure yet we’ll see how much heat the lights put out… i could probably use the heat from the fan during the winter as well, but the thing is so huge for 6 foot tent in 2x4.
3 Likes
my rooms are in a unheated but very well insulated shop/garage with a concrete floor.
I layed down vapor barrier plastic, then layed 2x4’s flat on the floor with rigid insulation panels in between so the 2x4’s are spaced about 16inches apart or so. Then I laid down 3/8" plywood for the floor and covered that with roll out vinyl floor material, silicon sealing all the edges.
That keeps the floor from getting cold in my very cold and long winter months. We get -15 to -30C and colder sometimes so is why HID lighting still has it’s place here.
To add heat when needed I use these NOMA 110V portable baseboard units that have built in thermostats. I find they work very well and are relatively inexpensive.
1 Like