Okay sweet, thank you! I haven't got the money for a cool tube but will a fan blowing in line with the light cool it down?
A fan blowing on the light may move some of the heat away from the fixture, but that won't do anything to increase the extraction rate of the hot air being pulled out of your grow space. Fans do not cool air. Fans move air. Air in motion removes heat from your body faster than air not in motion; combine that with water evaporating from your skin and you
feel a "cooling effect."
Those lights generate quite a bit of heat; what is your temperature outside of the grow space (are you using passive air intake or active air intake?) What are you temperatures inside the space with the lights off? What are your temperatures in the space with the lights on?
What is the size of your space and what are you using for extraction fans?
One thing you can do, if you have the lights and the grow space but haven't germinated yet; you can try some dry runs with the light. Let the light run for an 18 hour cycle and monitor the temps at various times of the day. Spring's coming and summer will be here soon; so take into consideration the potential increase in temperature in your area. Remember, there's usually a pretty good temperature shift at dusk and into the evening, if you find your space gets pretty hot in summer months; you can try to run your lights on more in the evening than in the day to help with the cooling effect.
Some great points made by these other fellas; a good test is the "back of your hand" test, where you put the back of your hand at the top level of the plants and hold it there for a few seconds. If it's uncomfortably warm, it's too warm for the plants. If you want to experiment with how much of a difference it makes, stick your hand under it at 12 inches and test it, then start raising it in 2 inch increments. Should be able to correlate real quick how much is too much. HPS/MH can burn seedlings if you're not careful, that's why it's better to keep them raised up higher than you normally would in veg/bloom. If you spend some time with your seedlings, you'll start to see how they react to different light distances (less stretch, more stretch.)
Just my "My 2 cents" Great information everyone!
