Diy water cooles T5 fixture

[Neilharris]

Hi all
I have a 4x2" t5 fixture, it is 8 bulb. It runs well with half the bulbs off and I can get it close to the plants and they like that but with 8 bulbs all on it heats up really quick and even in winter it can only stay on in coldest part of day. Increasing ventilation or airflow really doesnt do much, and since it is just a simple early veg room for rooted cuttings and mothers, it isnt feasible to setup a/c.

I am wondering if any of you have input on water cooling. I dont know much about physics if this makes sense, but most of the heat is coming from the bulbs going down into the plants, and some heat is going up into the flat reflector and radiating up. If I find some copper coils and arrange them as a heatsink and run cold water thru it, would it "suck up" heat from the bulbs through the reflector and lessen the heat going down into the plants? That way I could run all 8 bulbs on for better veg growth. My other idea is a small heat exchanger shroud with PC case fans, attached to the sides of the reflector blowing cool air between the bulbs and plants, which would probably be a better idea, or maybe a combo of the two ideas, still the same water cooled idea.

 

[az2000]

I have a 4x2" t5 fixture, it is 8 bulb. It runs well with half the bulbs off and I can get it close to the plants and they like that but with 8 bulbs all on it heats up really quick and even in winter it can only stay on in coldest part of day. Increasing ventilation or airflow really doesnt do much, and since it is just a simple early veg room for rooted cuttings and mothers, it isnt feasible to setup a/c.

In a 4x2 you should only need 6 bulbs. I.e., 40w/sq ft is the optimum for T5HO. Total 320w. That's six 54w tubes (324w).

An additional 100w would make a difference in heat. I add some LED lightbulbs around the corners during mid to late flower, as sidelight. Abut 80w. but, that's more effective than 100w from the top (adding to 320w already at the top. It's more efficient coverage putting the watts around the sides, closer.).

You can buy replacement ballasts which can be remote-mounted outside the tent. That will make a significant difference. It's like half the heat right there. Fulham makes two "Racehorse" ballasts that are remote mountable: RHA-UNV-245-LT5 or RHA-UNV-454-LT5. (The 245 is for 2 tubes. The 454 is for 2, 3 or 4.). They also make a "Longhorse" LH5-120-L for 2 tubes.

I have attached the spec sheets. You can call and talk to Fulham about what's available, what you're replacing. You need to look at your existing ballasts. Probably two 4-tube ballasts. You'd replace those with the 454 Racehorse. The specs say it can be mounted up to 18' away. But, you probably just need 8' of wire to get it outside the tent. You probably need wire rated for 600v because I think the ballast steps things up that way. (Not some cheap speaker wire. It might be best to use an extension cord made for HID ballast-to-hood. Cut it in the middle, wire the two cut ends, and use the male/female ends for a breakable connection. You might have to replace the male/female ends with some heavy-duty 3-prong twist connector from Home Depot. The two connectors that com with a HID remote-mount extension cord might not plug into each other. I don't know what all's available.).