Gen 3 Grow Light Water Cooling Tube Construction & Test
I finished a test lamp using a 4 ft long water cooling tube made from 1" square architectural aluminum tubing with sharp corners. One one end of the tube has a pair of Citizen CLU 048 COB's with cheap plastic holders, the other end has a pair of warm white 100 watt flood light COBs. I'm gonna take some Tc measurements off the citizen and floodlight COBs and the 50 watt drivers as well. One of the citizen Cobs and one of the drivers is using a silicone thermal pad to facilitate thermal transfer, one driver is mounted the regular way and I'm gonna see how much the cooling tube can cool the drivers as well.
An end view with the floodlight COBs and silicone thermal pad material
I held the upside down mounted drivers on tight with nylon wire ties and used a silicone pad under one driver and the other two used medium quality silicone thermal paste. One driver is mounted the usual way and no effort was made to thermally bond it with the cooling tube.
I'll but some black tape on the drivers and tube to take infrared thermal readings and I use it to with the K type thermocouple too. I drilled a hole in the plastic Citizen COB holder over the negative contact to get some Tc readings and I'll get some off the floodlights as well
Using WAGO connectors makes the job a snap and since I'm gonna take the test lamp apart, after I confirm that the cooling tube is up to the job of cooling both floodlight and Citizen COBs, it will make that easy too.
Tomorrow after I feed the girls I'm gonna wet test the lamp on the bench and take some thermal readings after she warms up a bit. If it cools the CBs the way I want, then I'm gonna rebuild my big water cooled rig using the new 6' long design. I've built 3 x 4 ft long 1" square cooling tubes and the test lamp is one of the tubes, I'm gonna expand the grow with another 3 x cooling tube 4 ft long water cooled lamp using leftover drivers and floodlight COBs. There's unused space in the grow room, capacity in the lamp cooling system and spare COBs and Drivers laying about. For now there's going to be a sativa dominate (Moby Dick) going in the space, but something high in CBD would be nice if I could get something stabilised or even a clone. I'll have a 4' x 2' 750 watt water cooled lamp made with 3 cooling bars and a cob spacing of around 11", over a 3' x 5' area. I might add 80 to 100 watts of 4000K LED strips to this light as well.
Gen 3 Test Grow Light Water Cooling Tube Test Results
The results of the wet bench test confirm that I can use these tubes to build my water cooled grow lights, Tc temps in the mid forties for both the Citizen and floodlight COBs using either thermal paste or silicone thermal pads between the COBs and the cooling tube. The coolant temp was 26 degrees celsius, the ambient temp was 25 degrees and the lamp drew 182 watts at the plug, because 3 of the drivers only draw 44 watts each and were an ebay scam (i got a refund). The upside down mounted drivers that were cooled by the cooling tube ran 15 C cooler than the one that was mounted right side up, so the enclosed drivers on the final lamps will be mounted upside down and will be cooled by the tubes too.
You can use 1" square aluminum tubing like that shown as a grow light water cooling tube and mount 28mm square quality COBs with a holder or screws on Chinese floodlight COBs and also use the cooling tube to significantly (15 C) cool the drivers as well.
Each 4' long 1" square tube cost about $4 for the aluminum tube and 2 x $2 CDN for the brass PEX end fittings,
or $8 per tube x 3 tubes= $24 CDN for a 4'x2' water cooled light rig. Some silicone caulking to seal the ends of the tubes, a couple pieces of aluminum angle, some plastic fittings and hoses and something to dump heat out with on the other end of the cooling system.
This is about as cheap as water cooling gets and it's cheaper than air heat sinks for a large light rig, my new lamp described above will have a total of 15 COBs, that's a lot of pin heatsinks!