I have recently installed a Diedrich ir-3tt in my new roastery. I have installed approx. 6-7 meters of ducting, maybe I would need a fan to back up the airflow. My first roast went along very well, I had good control on the roast and the airflow seemed to function in a similar way as my electric Diedrich. But when I cool the beans it takes over 10 minutes before the coffee hit room temperature. I therefore conclude that the long ducting is the reason for my long cooling times due to bad airflow. To test this I do a similar batch with only 1 meter ducting to see how this influence the cooling time. After dropping the coffee the cooling of the beans still takes 10 minutes:-0 I feel that it goes smooth roasting on it, but the problems is when cooling. I dont get tipping, and the airflow removes a lot of the chaff, although it is some chaff under the cooling bin. When removing the cooling bin, I see five holes with approx. 5 cm diameter. This holes are in the bottom of the roaster, right underneath the cooling bin. When checking I notice that these holes are sucking air, a piece of paper is dragged right in when put underneath the roaster. I simply dont understand why these holes are there, but it seems to me that the air will find the easiest way in to the roaster - but at the same time it kills my cooling-times. If anyone on this forum has a Diedrich tabletop roaster, could you please check if these holes are there - for me it seem logical to cover this holes so the air can be forced through my beans instead. I added a photo of the holes. I would appreciate comments on this matter:-)  

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Hello Jorgen,
I am not familiar with your model but I may have an idea. You should a three lever on the Diedrich with setting for 50/50 airflow, 80/20, and 20/80. Is your picture taken in the front of the roaster? The first thing I would check is the airflow at the back of the roaster. Diedrich manual or the office should be able to supply the spec for the amount of air movement needed. You will need to get a HVAC guy out to measure or drill the hole in the duct where it attaches to the roaster, insert probe and take measurement. Ten minutes to cool is on the very long side. You need to cut this down to 3-4 minutes. Once you have this number you can determine if you have to much resistance on your exhaust run. If the number is too low, break into your exhaust line part way out and measure again. Do this a number of times as you work your way back to the roaster. If you can not get an adequate number within 6-8 of the roaster, you probably have a problem with your blower motor or fan. Check these for their output. If you get a good reading within 6-8 of the roaster then you may have too much resistance or a blockage in your exhaust. If it turns out to be too long a run(Diedrich will comment on this) a simple way to correct the problem is to install a y fitting in your exhaust line and install a fan at the end of the exhaust to help it along. The fan at the end is nothing more than a box with a squirrel type blower fan. If you go this route just make sure you install a motor with a variable output or at least the ability to change the output on the blower. It is possible to pull too hard on your roaster. Goods luck.
Tim

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