315 CMH heat management
- Thread starter turbobuzz
- Start date
Lordhooha
Well-Known Member
I’d stick with the Phillips personally.
OrgrO
Well-Known Member
Heat management with a 315W CMH, like other lamps, will depend a lot on ambient temperature around your tent, open or air cooled fixtures and the volume and temperature of replacement fresh air entering your grow tent or closet.
When you grew in your closet before what wattage's were used? If you used 300-400watts of whatever light source before then you should be able to handle 315w CMH.
I just made the switch in my 10’ X 3.5’ X 6.5’H flower cabinet from three 400w HPS to three 315w CMH. The HPS had to be air cooled to maintain temperature control. I was hoping to get by with open hoods to take full advantage of the CMH spectrum but couldn’t control temps. I had to place the CMHs in the air cooled hoods.
It’s not the best situation but I’m thinking three CMHs behind glass were still a better spectrum and PAR then the three HPSs in the same air cooled fixtures.
Word of WARNING! After my brief experience with open fixture CMHs I never work in the flower cabinet without a wide brim hat, UV glasses and a long sleeve shirt. CMH will give you a “sun burn” if your under the lights too long. The glass in air cooled hoods will block most UVB and but still pass about 75% of the UVA from what I understand.
Second WARNING! If moving plants from under t-5s to open CMH fixtures start with lights high at first and lower over time. Acclimate them slowly. The UV will seriously damage or even kill your plants besides increasing your chances of cancer and growing tumors in the future.
When you grew in your closet before what wattage's were used? If you used 300-400watts of whatever light source before then you should be able to handle 315w CMH.
I just made the switch in my 10’ X 3.5’ X 6.5’H flower cabinet from three 400w HPS to three 315w CMH. The HPS had to be air cooled to maintain temperature control. I was hoping to get by with open hoods to take full advantage of the CMH spectrum but couldn’t control temps. I had to place the CMHs in the air cooled hoods.
It’s not the best situation but I’m thinking three CMHs behind glass were still a better spectrum and PAR then the three HPSs in the same air cooled fixtures.
Word of WARNING! After my brief experience with open fixture CMHs I never work in the flower cabinet without a wide brim hat, UV glasses and a long sleeve shirt. CMH will give you a “sun burn” if your under the lights too long. The glass in air cooled hoods will block most UVB and but still pass about 75% of the UVA from what I understand.
Second WARNING! If moving plants from under t-5s to open CMH fixtures start with lights high at first and lower over time. Acclimate them slowly. The UV will seriously damage or even kill your plants besides increasing your chances of cancer and growing tumors in the future.
Kingrow1
Well-Known Member
Now im not sure but i thought there was minimal uv risk from the new cmh's?
Correct me here please but aint no way im buying no light that gives me sun burn, aint no hat and glasses you want its factor 50 and slip slop slap.
I use bare bulb, dont see the difference, mainly get your thermometer out of the light as extraction removes heat wether air cooled or bare bulb, it dosent however remove light radiation
Lordhooha
Well-Known Member
They do have a bit of the ole uv but it’s part of the appeal of cmh.Now im not sure but i thought there was minimal uv risk from the new cmh's?
Correct me here please but aint no way im buying no light that gives me sun burn, aint no hat and glasses you want its factor 50 and slip slop slap.
I use bare bulb, dont see the difference, mainly get your thermometer out of the light as extraction removes heat wether air cooled or bare bulb, it dosent however remove light radiation
Kingrow1
Well-Known Member
This was the first flaw of the old cmh, cancer dosent sell lights well.
They went away and sorted this plus added an extra uv screen (optional on the first models) so i was assured no real protection was needed for growers.
I dont look at my hps or stand too close to the bulb but find it safe and non lethal to an average dude such as myself, i wouldnt change that just so i could run cmh.
Not bashing just discussing
Lordhooha
Well-Known Member
People have been adding much stronger uv lights to supplement in their grows. With cmh they provide the uv that gets the plants extra frosty. Trichromes are their own natural sunblock. I mean I’m not sitting in my room during lights on most time so I’m not concerned. I’ve been in my rooms anyhow with the light on just wear my glasses to protect the eyes. I’d imagine it’s no worse than a tanning booth never experienced a tanning booth just speculating.This was the first flaw of the old cmh, cancer dosent sell lights well.
They went away and sorted this plus added an extra uv screen (optional on the first models) so i was assured no real protection was needed for growers.
I dont look at my hps or stand too close to the bulb but find it safe and non lethal to an average dude such as myself, i wouldnt change that just so i could run cmh.
Not bashing just discussing
Kingrow1
Well-Known Member
Sounds not so great but i suppose the uv is minimal to humans, probably a little overhyped.
Lordhooha
Well-Known Member
I know it can damage your eyes but I would imagine the effect as far as skin is concerned is no worse than being outside on a sunny day all day.
Dynamo626
Well-Known Member
Bam! Well said sir. Was reading the thread the entire time wondering why no one has mentioned this about ambient air temps in the room the tent is in. If the tent is in a small bedroom regardless of the kind of light ambient temps will rise so then will the grow space. Also noticed a pic of a fan in the tent. Inline fan moters produce heat also. If your worried about heat keep your inline fan outside your tent.
blowincherrypie
Well-Known Member
R ppl really getting almost 2 gpw? Might have to dust the ol' 315 off for the winter lol
Lordhooha
Well-Known Member
I’ve seen some pretty stellar grows looking on the web. It’s why I got a de630 to see what I can get.
Nellyitis
Member
I find that intresting, As Im in aus, temperatures around 35-40 celcius during day, inside temperature 25~, in my 3x3 tent 315w cmh open fixture, with 170cfm i was seeing temperatures of 35~ degrees in there.
couldnt contain the heat no matter how many extra fans i added, ended up having to buy a air cooled fixture.
Kingrow1
Well-Known Member
Nellyitis
Member
Well yeah, i can only have so much exhaust before it sounds like a rocket ship from my spare room.Fans dont cool they only move heat....
but still regardless, tried higher cfm still issues, had to get an air cooled hood to control the temps.
gwheels
Well-Known Member
I have a point and read thermometer. My canopy height is around 73 and the other thing i used showed 80.There are exact sciences on reading air temps, easy google. Under the light is hot because of light radiation not air temps.
Extraction fans are simple. Carbon scrubber in tent with a 4 inch duct going to your exhaust fan out of the tent (if you have the room) and a fan controller. I use a veriac transformer to dial it in just right but a regular controller will get you started cheaper.
The veriac removes the fan howl caused by the cheap controller which uses voltage interruption to work. A veriac transformer changes the voltage going in.
I run 2 tents totalling 10 square feet with a 4 inch fan at 50% currently. 73 degrees canopy height in both tents (one fan with a T pipe pulling 2 carbon scrubbers)
Your scrubber will decrease your tent humidity when compared to ambient air by about 3 to 6%. It matters if you cant get it past 30. The girls tend to suffer.