I'm with Hazy, Rick. The right voltage for each log will depend on the resistance of the heating element, and perhaps in some extend also on the size of the vape and the type of wood that is used. I have a resistance of 23,45 ohm in my UD (I've never used any one of your products so I have no idea how they compare exactly, accept from what I gather through reviews and comparisons of other members) and I usually use mine on 14,3V. But when it's cold and just turned on it's a little on the low side (if I'm in a rush I go as high as 14,8V to speed up the warm up time, that's the highest my PSU will go), and when it has been on for hours and the entire mass has warmed up thoroughly I can go down a bit to 13,8V. The voltage I choose also depends a bit on which strain I use and if I'm vaping hash or kief too.
Perhaps it's an idea to inform each owner of the resistance of their particular Vape so they know where to start approximately? I know that the first thing I'd do as soon as a new log vape arrives is measure the resistance to know at which voltage to start, but not everyone has a multi meter so perhaps you can do it for your customers already and print it on the bottom or something?
edit: I use
this particular PSU which also allows me to monitor what Amperage is drawn up to one decimal behind the comma, and I noticed the biggest temperature changes occur when the Amperage changes. On mine it goes from 0,3A to 0,4A at 12,3V and from 0,4 to 0,5A at 13,9V. Not sure if this is helpful or not but I thought I may as well share it too.
Oh, I hope this isn't considered as spamming, but I'd like everyone to have a look at
this thread in case anyone may feel like helping out a fellow vaporist in trouble.