Roaster Airflow: How much control do I need?

[samuelstafford]

I am almost at a decision point in buying a roaster and had a question about airflow. The two machines I'm comparing are the San Franciscan SF6 and the Diedrich IR-2.5.

The SF6 appears to have airflow through the drum that is either fully on or fully off.

The IR roaster has airflow in the drum that is either off (it's actually slightly on), 50/50 thru the drum and cooling bin or fully thru the drum.

I'm used to having 5 different airflow settings thru the drum on my Hottop.

Is having more control over the airflow better?

Thanks - Sam

 

[sae]

I have a fully adjustable airflow on my machine (0-100%). I will use 100% most of the time, 50% sometimes and 75% rarely. If I had 0, 50/50 or 100 I would be ok. I use my gas to control my roast.

 

[MSM]

Hello,

Are you considering a new SF6? I cannot speak for some of the earliest models, but I know all of the machines built within the past 15 years have multiple damper settings for airflow intensity, and some of the newer ones have the option of a variable speed fan motor in addition to the damper. I've used a few different Diedrichs, a couple Ambex, a couple Probats, and an older SF 25. I really love things about each of these roasters, but my opinion is that in stock state, there is no airflow design as efficient as a San Franciscan. You have an incredible amount of control between the flame and the airflow, to the point of even being able to utilize a convective heat by pulling hot air over the charge, as opposed to a Diedrich, which pulls air out the back of the drum. I feel like a Diedrich is easier to use and understand at first, but hands down, a San Franciscan offers more flexibility and efficiency, while having an easier potential for a clean roast.

Plus, on a practical note, you can roast smaller batches on a San Franciscan, but you can't roast up to 6 lbs efficiently on a 2.5 kilo. No matter what the manufacturer claims, I have always found 80% of the rated capacity on a Diedrich to be the maximum point for operating efficiency and good airflow. I still do love them, though. You really could not go wrong with either of those machines. Just consider growth potential. Even if a little more expensive, an extra couple pounds capacity per roast will go a long way.

I hope that helps. Let us know what you decide!

Michael

 

[Redswing]

i have an sf6 built in 2004 that has a lever that directs air either through the drum OR through the cooling tray. i have no way of monitoring the volume of airflow in either drum or tray, so i can't tell you what would happen if you tried to leave the damper only a little open to the cooling tray. i do know it is intended to either be all on or all off, there aren't built in stops for splitting the airflow. and the fan is either on or off. i am sure you could talk with bill kennedy about modifications he would suggest, and you probably wouldn't be the first. betting they are pretty low tech. or perhaps the newer models have more airflow controls? here are pics opf my roaster with the cooling bin removed: picture one shows the damper closed, directing all the air it can through the drum, picture two is with the damper open, all air through the tray. (i love my roaster, couldn't be happier)

 

[peterjschmidt]

i can't tell you what would happen if you tried to leave the damper only a little open to the cooling tray. i do know it is intended to either be all on or all off, there aren't built in stops for splitting the airflow. and the fan is either on or off.

What happens if you leave the handle somewhere in between? There isn't sufficient friction to hold the damper partly open?

 

[Redswing]

You could leave the handle in the middle, but without any sort of guage (besides cupping, eh?). I wonder if just because the damper is 1/2 open if 1/2 of the air would be through the drum. I figured the majority of the air would be pulled through the path of least resistance, whichever way that would be. Seem true?

 

[peterjschmidt]

I'm sure you're right about not really knowing if 1/2 the air is coming from both the cooling tray and the drum, simply because the damper is at 1/2. I never thought about until the last time I roasted on my Ambex. I use my roaster in the basement, with the exhausts going out a basement window, and every time I roast I take the storm window out and put in a plywood baffle that has ductwork mounted to it. Sounds like a hassle, but it only takes a minute to set up and remove when I'm done roasting. But last time I finished roasting and the roaster was cooling down, I had the damper set to pull air from the drum and checked the exhaust to see if it had increased since I tore down and cleaned the blower and all the roaster's air passages. Then I switched the damper to pull from the cooling tray, and the volume of exhaust about tripled. Same blower speed, but much less resistance on where the air was coming from. So now I know the damper may have to go to 3/4 from the drum to really be balanced.

Last year I was doing two batches of Guat, and did one w/ air fully closed (all air from the cooling tray), and the other w/ air fully open (all air from the drum). I used the gas to control the heat to match the profile time and temps on the second batch, so the profiles were close and the only difference was the airflow. There was very little difference between the two, the the full air batch had a little more brightness and nuance, and the closed air batch had more depth of flavor, but overall it was good either way.

 

[MSM]

My misunderstanding. I talked with Bill to confirm. The newer SF6 features the environmental damper I was talking about in addition to the cooling tray damper. They are working on a retrofit for any models prior to that addition. I assumed that the SF6 would have the same airflow control as the SF25. So, what year is the SF6 you are considering? Or, like Redswing suggested, you could talk with Bill about options. Peter, are you talking about a YM2? I basically learned how to roast on one of those. I love them! I used to mess around with closing the damper half or 3/4, though I agree, it's a guessing game. But I yielded similar results. With full air, I got a little cleaner coffee with a touch brighter acidity, while messing around with the airflow at different phases yielded a more complex cup.

 

[Redswing]

Samuel,
Hope this conversation is helpful for you. Not sure if we're getting at your question too well. One more thought from me about the SF6 and a modification. A quick search on amazon found a $21 air flow/ digital wind speed guage. I'm wondering what would happen if you just got two of something like those and inserted one probe in the exaust and one in the tray cooling plenum. For $42 you could see what the air flow is normally in either position, then try to balance it out.

I have heard that running a higher airflow results in brighter notes with more acidity without having to roast lighter, but it also causing the cup to be lacking sweetness and body, and visa versa. I'd love to hear from some more of the veteran roasters on this site in regards to the importance of airflow.

 

[sae]

the full air batch had a little more brightness and nuance, and the closed air batch had more depth of flavor, but overall it was good either way.

This has been my experience as well!