Heat comparison: 400w HPS > 600w HPS > 200w t5 + 200w CFL

Any ideas which run hotter?

I have 200w flouro plus 200w CFL, and wanting to upgrade to a HPS.

I have a 6 ft x 3 ft x 7 ft closet in a shed outside where I am growing, and temps already are hitting 100 degrees inside the grow closet with the t5 and the cfl.

What I am wondering is if the 400w HPS would run at comparable temps or hotter that the same wattage I have now. And what if I jumped to 600w?

The closet is not currently exhausted (todays project), and I already have a 6" inline fan to use for exhaust.

Anyone have ideas approximately how much hotter the HPS will run than what I have?

https://www.rollitup.org/grow-room-design-setup/452892-cmh-who-uses-why.html

400 watt ceramic

After you get exhaust running you could probably get a 400watt HPS, but it is gonna be probably twice as hot as CFL setup. 600watt would be 3 times as hot as current. You basically are going to need an intake and exhaust if you go with HPS.

But if you are experiencing 100F already you should probably just stick with the current setup and ventilate it well

HID bulbs burn considerably hotter than any fluorescent bulb, whether it be a CFL or T5 bulb, and they require a separate ballast to operate. It's hard to really put a number on it, but if you've already got 400W of fluoro's running than it's hard to imagine a 400W HPS raising your temps by anything more than a couple of degrees. If your growing area is already running hot, however, then it's definitely time to get some decent ventilation and you may also want to look into getting a cooled hood for your HID lamp. Moving up to a 600W lamp will perhaps increase temps another couple degrees. If at all possible, try to keep your ballast outside of your grow as they also tend to emit quite a lot of heat.

I do have the ability to place the ballast outside the closet. I also can draw cool(er) air in through a passive duct from a shaded, north facing wall. I had planned on doing a ducted hood to pull air out of the room as well.

I wasn't sure if heat generated by wattage would be the same or not.

I plan on doing the ducting before I purchase any kind of different light than what I have. If anything I was going to replace my 4 bulb t5 with an 8 bulb t5 unit.

I am limited on power as there is only a 12/2 wire running to the outbuilding, and I am SURE I would not be able to sustain the draw of an a/c unit plus a HID light out there. I don't want to rewire the whole damn thing, but I have seen the difference in buds HPS makes over the current setup I haveand I want to grow the best meds I can with whatever I am doing.

400 watt hps is manageable with an air cooled hood and a 300 CFM inline fan. I left one end of my hood open and just drew air out of my tent and into the attic with no issues keeping temps around 75 F.
600 watt hps is almost a whole new ball game (haha well it was for me), i run a 435 CFM inline fan and leave one end of my air cooled reflector open and can keep temps just under 80 F all the time. i run that fan wide open though, and it is loud.
the t5s are bitchin, they always will run cooler than HID lighting.
and Ive heard great things about 125w and 200w CFLs...if you have a good reflector the CFLs are fantastic. ive seen people pull some awesome ganja out of high wattage CFLs

cmh doesn't "throw" the heat as hps does...but it gets really hot...best bulb made...period

yeah i like my 250w cmh - phillips
but i also like my 250w hps eye hortiluk
i run them together spinning and rotating pots

ther is no best bulb for both jobs if i was to pick one bulb setup would be cmh

but nutin in dis world give you rock hard buds like hps


truly the best if you dah one bulb stup and both bulbs would be to

use yo cmh vr veg up to after stretch is over -is best for veg and cuts down on stretch in brgin of flower

use yo hps bulb mid stage of flower - addsmkes themtight and hard to the rock hard buds

then awitch back to yo cmh for the final bulk up stage of flower


but who wants to be bothered wit all dat -i just run both bulbs all the way through
after the third week of flower i throw in my uvb for either an hour or two mid day
it is not needed as much after i added the cmh-cause cmh has sum uvb rays

i spin each pot 1/4 turn every other day
and i rotate the positons under the lights once a week

I can throw my limited experience in, but not what the OP asks for...I am using a Pro-Gro 180 (150w actual) and recently added a 150w CMH. I can tell you that the CMH puts off way more heat than the LED panel does, but the panel has a heatsink and two fans.

Well, I am going to do two things first, put a whirlybird on the roof to get the heat out of the shed itself, then vent the room and re-evaluate the temperatures.

Thank you for all the info everyone. It all helps. And I haven't heard of the CMH bulb yet. That is interesting in itself.

Fortheloveofgreen said:

And I haven't heard of the CMH bulb yet. That is interesting in itself.

Click to expand...

Same here..I am gonna have to research that one.

I would say the 400 watt would be almost twice as hot but with a 6in inline fan exausting you should be ok, but if temps are reaching 100 degrees on the regular, you might have bigger problems

I got the roof vent installed for the shed today. Next is the fresh air vent, and the exhaust fan install.