I just use a DIY alcohol lamp burning methyl hydrate for my CO2 generator so it's fully manual and I don't want to have to be going down there twice a day just to light it and put it out. I bought a CO2 controller and solenoid as I already had a regulator but after running some tests with how high the levels got with even just a candle or hanging out in the grow room for a while said fuggit to all the money to get tanks of gas.
I tried this first but it was a bit of overkill and the fuel is expensive.
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The little unit at the bottom uses around 100ml of methanol in 12 hours and keeps the CO2 over 1500 unless the exhaust fan turns on then only takes 10 min to get it back up to 1500 so. In cold weather like -30C for 3 weeks the exhaust fan never turns on with a 600W light and the room is fairly airtight. It's just a short piece of 3/16" copper tubing soldered onto a mason jar lid and uses a cotton shoelace for a wick. Ve. 1.0 and 2.0 used 3/8" tubing and tiki torch wicks but made way more gas and burned way more fuel. 2 wicks in the first one and one in the 2nd.
Ver. 1.0 Crappy looking soldering job but it didn't leak.
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Ver. 2.0 With the wicks really short there's a very faint blue flame and not the torch seen there.
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Ver. 3.0 If you look real close you can see the faint blue flame and that's all it takes to make enough CO2 for my room. I just put that wire nut you see at the bottom of the pic on to snuff out the flame and slow evaporation when not in use.
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A 4L jug of 99.9 methyl costs about $12 and lasts a whole grow. Nothing to catch fire around it or over it so even if the jar broke it would just sit there and burn itself out. When I poured a cup in the metal can and lit it the flame went out after I closed the door then 15 min later checked. Used up all the oxygen in there and self-extinguished. Got all but 75ml back.
Works for this broke-ass old grower.