Water cooled COBs

Discussion in 'LED and other Lighting' started by loftygoals, May 19, 2016.


    loftygoals Well-Known Member

    Thought I'd share my water cooled COB build here.

    I've built 8 light bars with cheapo chinese COBs. The idea being to initially build them cheaply and then swap chips to something more efficient after a couple of grows. As this is a bit of an experiment I didn't want to spend thousands and thousands on expensive COBs from the outset (I knew there was a chance this would fail miserably as nobody else has jumped on water cooling yet).

    Anyway I made a steel frame from 4cm flat steel sections. The frame is 100cm long and 25cm wide. I epoxied the water blocks onto a steel frame and then made "clamps" out of flat steel sections and 4mm bolts (epoxy alone was slightly dubious). The water blocks aren't going anywhere when clamped! I then used thermal glue to mount the COBs onto the water blocks. The glue can be separated with a razor blade easily which would make upgrading straightforward.


    I've used Meanwell HLG-600H-36A drivers because I have no interest in dimming the lights. They're just over 96% efficient at full power. Each COB is running at 0.835A (16.7A total for 20 COBs).

    I've used 8mm ID (14mm OD) hose on the 10mm barbs with 12mm hose clips.

    Here's the hoses mounted and wiring done:



    I've alternated cheap warm and cool COBs. If I were doing this again I'd pick one and stick to it because the power draw of different chips is unpredictable when running off a HLG-600H in parallel. Certainly when I upgrade the COBs later this year I'll be going for 1 uniform type.

    Anyway here's the money shot of the lights in action (excuse the lonely auto):


    I made an earlier version of these with voltage controlled drivers and current limiting resistors. That's the 8 COB bar you can see at the top. I learnt a lot from building those which I used to make better lights with version 2 (these 20 COB lights).

    The water gets pumped around the system with an Eheim 1250 water pump. All the water flows through the water blocks and then into a car radiator mounted on a timber frame where it's cooled:


    I have a 16 inch 1800cfm car radiator fan running off a 12V PSU.

    The main advantage of this setup is temps inside the tent are dramatically lower than when running air cooled lights as I'm not relying on the air in the tent to remove the heat any more. When running an 8x4 tent at full blast at 2100W (2x600W and 2x450W lights) the tent stays at 25C under lights and 20C in the shade (room where the tents are located is at 19C). If I run only the 2x600W lights so 1200W total, the temp stays at 22C in the tent under lights. COB surface temp is around 45-55C (measured with FLIR camera).

    I could make some improvements but this will do for now :) Promised myself there'd be no more tinkering with lights for 2 grows and have put my tools away!

    Edit: I should probably mention cost. £167 for the Meanwell HLG-600H, £60 for water blocks, £10 for hoses, £5 for hose clips, £20 for wiring and terminal blocks, £44 for COBs, £10 for steel, sections, £10 for bolts (inc eye bolts for hanging). £326 approx for each light bar.

    £15 for car radiator, £15 for radiator fan, £12 for PSU, £65 for water pump. £107 total for radiator and pump.
    Last edited: May 19, 2016

    mc130p Well-Known Member


    SPLFreak808 Well-Known Member

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    loftygoals Well-Known Member

    Yeah, the system is filled with RO water and I've added an antimicrobial additive.

    Also made sure the radiator is aluminium to match the water blocks. Mixing copper with aluminium would have been a disaster.
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    loftygoals Well-Known Member

    Yeah it's fine. I used a very similar Eheim pump (1048 I think) when I first got into computer water cooling around 2000-2001 and ran it for around 2 years 24/7 with 1/4 antifreeze in the loop. There were no specialist computer water pumps or coolants back then.
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    SPLFreak808 Well-Known Member

    Lmao, it is a total disaster. 500-1000$ mistake on a computer. Actually, i find the newer style kits give more problems then before.

    ttystikk Well-Known Member

    Bill Lidgate

    Bill Lidgate Active Member

    Nice design! I'd be quite interested to measure the water temp on a single circuit of the system, you can actually calculate calories of heating with a given volume of water. In most systems like this (including big audio amps) you do not want to go totally serial on the water supply as the last chip in line sees a ton more heat than the first. If you have decent fluid flow the difference may not be meaningful but I'd check the substrate temp of the first and last to be sure.

    A good pump brand is KNF Flodos, they can run nearly forever and can be had cheap on Ebay.
    these do 3L/min at 24VDC / 2A, Swiss made! $25

    Water has the highest heat capacity, you only need to add ethylene/propylene glycol if you approach 100C.
    Last edited: May 19, 2016
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    ScaryGaryLed Active Member

    I'm gald loftygoals is listening. water cooling is the way to go in tight spots. all you need to add to the water to watch out for bugs is some sort of disinfectant. even chlorine will work and you don't even have to mix it in strong. in computer liquid cooling it's recommend to use dish soap or alcohol a little bit.

    You might want to get a little more support on the light bar material looks curved. you even might want to curve it the other way so you get better penetration. you can probably accomplish that by hanging it from the center not the ends. I can only imagine that power supply is at least 6-7 pounds.

    Also mixing the cobs is a good idea but yeah next time a constant current or at least adjustable current so you can control the power draw of that beast!
    You could also try to match the cobs and run one bank of warm whites and then the other bank whites (across the power supplies). that way you can sorta match them a little better, just an idea :blsmoke:

    I'm sure you will have a great crop and looks amazing so far buddy!

    Good luck with the grow, keep in mind these cobs are powerful, regardless what the haters say. :weed:

    At the temp you have them running you will be getting more than than 100 lpw that they are rated at and your lights will last next to forever.

    Will Thayer

    Will Thayer Well-Known Member

    Alright loftygoals ,
    I have been following your original thread with interest. You are not one for doing things in half measures. Really impressive loft conversion. You should link to your original thread to show all the effort you put into your grow lab. If my memory serves me correctly this is your first grow?

    I have experienced the trials and tribulations of a loft grow in the U.K. There is nothing between your grow and the sky except for some roofing slate. June,July and August have proved the most difficult months for me. I ended up installing a positive pressure ventilation system to move fresh air from the cool side of the house and run the lights at night. The initial investment of kingspan was a ball ache but will pay dividends for sure.

    I am very much looking forward to following your grow and updates will be most appreciated. You have done a grand job thus far.


    Millsie Well-Known Member

    Could you please take closer photos of the water cooling rig, I'd like to see how you fixed the COBs to the water blocks and possibly even a link to the type of water block you're using

    Cant wait to see what you do under it :)
    salmonetin likes this.
    Bill Lidgate

    Bill Lidgate Active Member

    FYI keeping things dead in water usually uses a biocide like the DOW Kathon family, or ProClin, similar to the preservatives in eye saline but better than old thimerosal. They are really biostatics; things do not grow. Some are sold on Ebay and a very little goes a long way.

    ttystikk Well-Known Member

    This is only necessary if the water in the cooling system ever sees any light, such as a Fresca Sol water cooled HID fixture.
    bicit likes this.
    Bill Lidgate

    Bill Lidgate Active Member

    The OPs pump (Eheim 1250) has many great reviews and is described as running continuously for over 5 years! Another good choice could be a Grundfos UPS15-58FC 3-Speed Pump, about $82, very quiet, popular for hot water circulators and very durable.

    Also here is a suitable $50 all aluminum radiator
    http://www.amazon.com/1992-2000-Aluminum-Radiator-Manual-Transmission/dp/B00EUJZ7UA?ie=UTF8&keywords=All aluminum radiator&qid=1463773928&ref_=sr_1_12&refinements=p_36:1253494011&s=automotive&sr=1-12

    (as always hot in the top and pump out cold at the bottom)
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    BOBBY_G Well-Known Member

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    optzulu Well-Known Member

    Wow very nice! the big advantage with water is that you can move the heat produced how you want it.
    Joe34 likes this.

    VegasWinner Well-Known Member

    nice setup, great engineering and design. peace

    ttystikk Well-Known Member

    Did someone say moving heat with water?
    Bill Lidgate

    Bill Lidgate Active Member

    How are COBS held on the water blocks? I see no screws and its tricky to screw into water blocks and avoid the water.

    loftygoals Well-Known Member

    Thermal glue. Doesn't quite have the same heat transfer properties as thermal paste but it's good enough. Big advantage is no drilling, no screws, no kapton tape, cheaper than anything else (a 0.99 tube on ebay will be enough for around 40 COBs). Leave it to dry for 24 hours and it's pretty solid but can be removed in a few seconds with a razor blade. Video cards have had their heatsinks stuck on with the stuff for years (although you might find thermal paste in high end cards these days).

    My eventual idea is underfloor heating. Not feasible in my current house it'll be in the back of my mind in the future for sure.

    Imagine a wet underfloor heating system where some of your rooms are heated with waste heat from your grow lights. Energy efficiency goes from 50% to 100%.

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