Ive done several hours of testing and I think my DIY heatsinks will be fine.
Here are the results from the initial testing with the fixture just sitting, leaned up against my workbench with no fan. Ambient at the time was 72 F/22C. These are the highest readings taken from several places on the face of the strips. The heatsinks measured anywhere from 2C to 10C deg cooler depending on where I measured it.
150W = 37C / 97F
175w = 40C / 104F
200w = 43C / 108F
250w = 48C / 118F
I didn’t actually test it, but it looks like I could run at the max recommended wattage (48wx6=288w total) and probably be right at the max temp even with no fan.
Oh, I should note that I had a silly idea while I was assembling the frame. I have several left over sticks of that small ¾”x3/4” U channel that I used to build the frame. It occurred to me that I could try a redneck heatsink mod by bolting a piece of that on the back side using the solstrip mounting bolts and some more heatsink paste. They don’t really add all that many sq inches of cooling area, and they are probably not that efficient, but what the heck – I had the stuff on hand and it wasn’t much trouble to add. You can sort of see the details in the pics I posted above.
Ok, with the fan and fixture mounted and the fan on low, I am good to go with a large margin of safety as far as temps. It ran this morning for several hours at 42 watts/strip = 250 watts total and the highest temp on any of the strips was 33C / 91F. At 200 watts total, it drops to 27C / 81F. I was pleased that even the ends of the strips that are not directly under the fan were only running about 1 deg warmer.
That’s with an internal temp of 24C / 75F – which is down from my old average of 27C-29C 81F-85Fwith the CFL lights on. I also had to turn off the small in-line fan I have that was blowing outside cool air into the tent. The main exhaust fan is still pulling outside air in, but its no longer being forced in.
One other note – I would recommend that folks use larger wire than I did for the power run between the driver and the fixture. I used 16ga and I have a little over one full volt drop between the driver and the solstrips at 250 watts. I have extra wire in the run now (about 10 ft total) because I may want to relocate the driver later. But that’s still more drop than I Like. At roughly 10 amps total draw, that’s 10 watts being lost as heat in the wiring. That’s a lot. Once I have everything where its going to stay, I plan to go up to 12 ga for the main run.
Over all, Im very pleased with how this is working out.
Oh, here is a shot of the power readings with both pots at minimum.