Lower ABV output on pot still with sight glass?

[andrew_987789]

Hi all,

I've had my alembic pot still for a while as stock. On my last few runs I was, from memory, getting about 70% ABV at the beginning of the run, which declined over time, of course.

I've recently added a sight glass and copper scrubbers to the setup, and run a few stripping runs. All fine, but didn't measure ABV.

I ran my first spirit run last night with the glass, and after measuring ABV found the initial output was closer to 50%.

Not sure why the drop.

A few changes between the 70 and 50 run.

70% runs
Was using a 2000w, 25L boiler.
The last few runs were TPW wash or blackstrap rum.

50% run
Sight glass + Scrubbers
Was using a 2400w, 35L boiler
Rye mash

A few thoughts on contributing factors.

Lower output from the Rye, compared to the basically pure sure TPW and molasses?

I was using a more powerful boiler, but it had only the 1900w element on and was powered down as well, the same as I did before - Maybe it's more efficient though and I'm underestimating the output compared to my last one? It's running hotter than I think, and blasting out more water?

Other people's thoughts?

If anything I'd have thought the sight glass might increase ABV a fraction, what with the scrubbers providing a tiny amount of reflux.

Not sure where the 20% drop has come from.

Cheers all.