Something obviously isn't right. Post a RoastPATH profile so we can see what you are doing?

Yes, Sorry i thought i had included a link with the origional Post.

Here was our first 15kg test batch:

https://portal.roastpath.com/publicroasts/index/7470794210119050123

also a 17kg we tried yesterday:

https://portal.roastpath.com/publicroasts/index/7460355532319110123

Anyone have thoughts on this one?

What is your drum speed and air ?

@GostCoffeeRoasters said:

What is your drum speed and air ?

Profiles are posted in the above post but fan and drum were as follows

50Hz for drum speed held throughout entire roast.

Fan 17hz 0-11:30 22Hz 11:30-15:00 27Hz 15-17:00 30Hz 17-end

Any progress? I'm new to RP software but it looks like you're starting out with no gas pressure? I could be reading things incorrectly since I'm a bit unfamiliar. When I've run into this issue, I charge with full heat on, ramping up to my charge temp, and increase airflow earlier to get more convection. Another minor thing, are your green temps significantly different (colder?). Just throwing out some ideas.

Thanks for the reply.. No Progress. Just screwing up a lot of coffee trying new things....

To answer your questions. In the first batch above we had gas to full pressure (3.0kpa) at 0:45 seconds in. The second profile posted above I had adjusted the valve so i could get some more gas and had it at full pressure 0:08 seconds into the roast (basically from the start). Air flow is a factor but at this point i'm not convinced airflow adjustments would have that great of an effect on the overall profile. Not to the point of solving the problem that is, Anyone have some data to show me otherwise? Is the "convection" of increased airflow going to add that much heat where I can cut roast time down by 5-10minutes?...

Yesterday I adjusted our valve again so i can now get 3.5kPa of pressure into the machine. I tried a full batch. Charged at 462, Air at 18hz (0.5 pascals on our magnetelic. ) had gas at 100% from charge to FC (which i normally would not do) and we hit FC at 16:30 at which point i started backing off the gas slightly and as expected had a big uncontrollable spike at the end of the roast. Droped out of the roaster at 20:30. Im at a loss. I did the Highest possible charge temp (before the machine kills my gas for overheating), highest possible gas pressure for a long time, and low air setting and im not even able to hit FC before 15:00...

I work with an MCR-20 with batch sizes of 8.0 kg, 10.8 kg, and 13.6 kg depending on shop demand. It looks like your turning point temp is quite low. The beans are absorbing too much thermal energy from the roaster and the roaster is having to do a lot of catch up to get through the rest of the process. For an 8kg batch, I'm charging between 390*F to 400*F and I have the gas to immediately kick up to 3.5 KPa. For my 13.6 kg roasts, I'm kicking off with at least 4.1 kPa. This typically gets me to a turning point temp of around 190*F-200*F, G->Y between 6:00-7:00, and 1C between 385*F-392*F. I find air and drums settings primarily help with maintaining an even distribution of heat.

Looking at your graph, are you doing a soak at the beginning? Maybe decreasing the soak time or even eliminating it all together for 15 kg will give your roast enough energy and momentum to get through the process in a reasonable amount of time.

Quick questions about your gas supply.

You've raised the pressure to 3.5Kpa, correct?

But how is your gas supply?

• How many bottles do you have hoked up to the roaster?
• How cold is the place where the bottles are stored?

I ask that because if there aren't enough bottles the liquid gas in the bottles doesnt have enough surface area to turn into gas as quickly as your big 15Kg roaster needs. So basically your burners could be starving for gas.

Repeat the exact same roast with the drum speed set to maximum (60 hz), burners on full heat at charge and bump the airflow to a strong medium. That's probably closer to 4-5 pa on the drum gauge.

Use a lighter at the tryer port to calibrate airflow relative to our "lighter trick" video on YouTube.

Minimum airflow will be the hz that just starts pulling the flame toward the tryer port with the lighter 1/4" or less from the tryer port. Medium will be a strong 90* pull. Max is the point the lighter will barely stay lit.

Figure all of that out and post the new profile.

If you haven't had the support guys inspect your installation, you can buy some support time and have them video conference a walk around to make certain this isn't an installation problem. -and that you aren't going to burn up your roaster or burn you building down.

Lastly, if you haven't attended the roasting class, register here: Roasting 101: Minneapolis Class – Mill City Roasters