Quote Originally Posted by Vancefish
Good question and one that is on my mind too. I'm about to buy two cool tubes and was thinking about running in series. What issues would the second light have? Yours is more then just 2. Do you have any issues with the heat on later lights in the series?
I have 6 lights total, 3 per fan. 2 rows of 600w HPS-400w MH-600w HPS each. And yes, the cooling effect is drastically reduced by the time the airflow gets to the 3rd light in the row. For now, its ok, because the daytime high where I live is about 30 degrees on avg. this time of year, and my cooling air comes from outside. Summer, however, will be a different story. I have my photoperiod from 10 pm to 10 am already so as to avoid a problem come summer, but I have a suspicion that it may not be enough. I'm already looking into a/c for the summer. The reflectors I'm using are not airtight, so if you put your hands around the fixture where the lens meets the body of the reflector at the first light you can really feel the air exiting long before it reaches the next lamp, notwithstanding the natural heating the air would undergo anyway by passing through multiple lights. I imagine they are all the same to some extent. I'm not sure anyone would be willing to pay what it would cost to make them all airtight to maximize airflow at the end, given that the air is going to be heated anyway by the subsequent lights, so the improvement will be at the margins. This is my first grow, so any heat issues will come up in about 3-4 months. I have been worried about it since I started though. I also have a 750cfm exhaust fan on a thermostat set at 78 degrees, and it hasn't come on yet. Again, winter of course. The good thing is that all that air leaking out of my lights is just more fresh air for the babies!