After using an 8 gal brewhaus cm still with a 2" column for several years, I decided to go larger and recently got the 15 gallon version with a 3" column. Everything I have read has said that a 3" column should be able to run roughly twice as fast as a 2" column, so I figure with double the charge, double the heat (2 x 2000 watt elements), and the increased speed, a run shouldn't take much longer than it did on the 2", but yield around twice as much.

Well I've only run the 3" a couple times now, and I don't know what I'm doing wrong, but it doesn't seem to output any faster. I get it close to boiling then turn off one element and control the other as usual. If I crank the heat to try to get it to go faster, the proof drops way too much. I am just running it as a pot still, not using the CM, as I mainly do stripping runs and then rerun them with botanicals to make gin.

Is there something I am missing or should be doing differently with the increased column size?

The only other explanation I can think of is that my wash was just lower than usual in abv. I switched to larger fermenters as well and just increased the volume of the usual Deathwish Wheat Germ recipe I always use, but maybe I did some math wrong and watered it down too much? I didn't take the starting gravity because I've made that wash a hundred times or so and after a while I stopped bothering to measure. I will measure the next one though!