Inline Fan (Cloudline) Roast Profile Effect

I have found an extremally frustrating and at the same delightful change in my roasting profiles after installing a 6in cloudline to help in exhausting the smoke in house.

Delightful in the manner that the fan performed well in keeping the miss happy and it changed my profiles immensely.

Wait, Changing my profiles was not the objective. That’s the frustrating part and profoundly changed the way I roast.

Previous Setup:
Bullet => Direct Exhaust by a duct out the window.

Previous Procedure:
Play with Power and fan to keep the profile.

Current Setup:
Bullet => Elevated 8to6in reducer => 6in splitter (Sucking the air from cooling tray => Cloudline 6in => Window.

Current Procedure:
Play with Power and fan to keep the profile
Cloudline starts at 50%, at the start of yellowing (usually at 150’c) up it to 75%, 5’C prior to FC up it to 100%.

Sample Roast of previous setup:

Sample Roast of current setup:

Things I have found out:

  1. Requiring less preheat. It dropped from 20’c to 30’c on most of the coffees I roast.
  2. Less overall heating from the bullet. Usually I start at P7 and keep it running. I find myself dropping to P6 at yellowing and P5 prior to first crack.
  3. ROR after FC usually drops bad and crashes even at P7. At P5 now and just keeps rising.

Only thing I can concur is that somehow the inline is basically working to remove excessive humidity from building inside the drum.

Anybody faced the same?

I suspect the in-line fan is connected directly to your Bullet exhaust which will alter how much air the Bullet exhaust fan moves thru the roaster- you need an air gap between the 2. Additionally you must provide a source for ‘make-up air’ to compensate for the air moved out doors by the in-line fan… open a window, leave a door ajar, whatever.


A picture is worth a thousand words I guess:

Window is always partially open.

You’ve checked all the boxes- air-gap at the Bullet exhaust and make-up air. That should eliminate any variations caused by the exhaust fan.

Beyond the exhaust fan the variables that are left are line voltage and ambient temperature. From the photo I can’t imagine your ambient changes much and line voltage variations shouldn’t be a problem without getting reported as a fault (faults get reported in the Logs entry in the Info window).


Thanks Bab for the support.

Ambient is checked. It stays stable with only 1-2’C variation.

Voltage is all clear.

There is something seriously happening here that is both sweet and mind boggling.