"Some reflux stills do not have the knock down power for 100% water.
Do you have a coil condenser atop the column and a product condenser?
If water boils at 212, then your wash will boil at a temp gradient some where between the boiling point of water and the boiling point of alcohol. All this depends on the alcohol content of your wash.
This gradient will rise during your run as the alcohol gets liberated from the water.
This means that your distillate will likely come off cooler at the begining of the run and get progressively warmer as the run continues. Unless you have good knock capabilities with your product condenser.
Some say warm distillate is better as it helps some really volitile nasties evaporate/air off faster/better.
You reflux fellers often like a very high abv as most just want nuetural anyway. An 18 or 20% wash will run at a lower temp than a 10 or 12% wash. This means that the distillate can come off at a lower temp (depending on heat input) thus giving your condenser an easier job of knocking down vapor.
But I recon anything over 12 or 14% makes for stressed out off flavors that require,,,,,,,,,,,,,a reflux still,,,,,,,and clearing agents,,,,and carbon filtering and,,,,,,,,mo money mo money mo money."
