I can't remember where I learned this, but if watts x amps = more than 50, the ProVari isn't happy. I may have found it somewhere on the ProVape site.
ETA: I have actually read of members getting them to fire below 1.0Ω, but why one would want to do that is beyond me.
DISCLAIMER: Sarcastic bit to follow
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Because sub-ohm is like super radical! You cannot shred a righteous vape over 0.9 ohms...duh.
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I did it just to see where the limit is. It is 0.8 ohms on my devices. I agree that the vapor between 1 and 1.5 ohms is terrific, and there is no need to go sub-ohm, but for those who wish to, that is the limit with a ProVari (in my experience). Hell, one of my favorite coils right now is a 2.0 ohm coil that I accidentally put an extra wrap on.

And I'm still in the hole as far as spending more on vaping than cigarettes. There are always new stuff to try out and I've learned not to buy in quantity until trying it first. I'm kind of excited trying this new tank though.