Quote Originally Posted by TheGreenFog
I do have a couple things to ask/add about piping in a/c air thru your cool tubes...
When you consider that the surface temp of an HPS tube in free airspace is going to be at least 200C (~400F), I don't think it'll make much difference to the room air temp if you pipe ambient air at 30C (~80F) or air cooled by aircon at 10C (~50F) through the cooltubes.

Even if the ambient air you pump through the cooltubes is relatively warm compared to that cooled by an aircon unit, it's not going to pick up THAT much more heat if cooled first.

I'd reserve any feed from a ducted aircon system to be put on the plants instead of being used to cool the lights, bearing in mind that there has to be an air exit from the op or return path to the a/c unit if you pipe in cooled air from a central a/c system.