Was thinking about trying this, but don't want to damage the heating elements or the machine in general. Was thinking about running it for a little while, then just stopping w/o fan, etc. Is it even necessary? Any one done this?

I'd almost think it could be a disadvantage, since you then have the chamber at a vastly different temperature than the bean mass when you start. As the thermistor in the Behmor is reading environmental temp in the chamber, rather than the temp of the bean mass, you could end up with the heating elements cycling off earlier, thereby slowing the ramp up of bean temp to roasting levels. Looking at the diagrams in the Behmor manual, all profiles seem designed with a ramp up figured in, so you would potentially throwing off power level changes, which are triggered by time only, not by temp. Of course, if you're just running P1 pedal to the metal all the time and not using any of the other profiles, that seems a relatively minimal concern.

I pretty good data to support that roasting one batch right after another (mine is modified to do this) will not measurably shorten the subsequent roast time. One of the design features/limitations of the Behmor is that it doesn't have a lot of thermal mass. While another 5lbs of steel in the drum and roasting chamber might make it more stable during the roast, it would take longer to heat up, be 5lbs heavier, be more expensive and likely necessitate ejection for cooling.

Something that I have tried, since I roast in a basement that can be 50 degrees, is to load the beans into it and let it run for a period of time to bring the greens temp up. I then cancel the cycle, reset everything and begin again. Essentially I'm trying to bring the 320g of greens up to 100-150 degrees to give the little guy a boost in the beginning of the drying phase. (Disclaimer: My ET is under PID control but I do not have a Bean Temp probe.) This will shorten the "cycle" but you are essentially roasting twice and have to worry about forgetting to turn it off quickly enough and tripping a thermal switch. (It won't start or restart a roast if a portion of the chamber is above 170.) Again, my experience is with a heavily modified unit and I don't do it often since I can get good 15-17 minute roasts with my setup.

GVDub makes a good point that I can't speak to in detail because I have PID control over my elements. I would counter with the knowledge that the rotating drum and moving greens do circulate air and will lower the ET in a hot machine so there might be an offset to that pre-heat from circulating the cold greens.

What is your intent with the pre-heating?

I've been putting the coffee in, pressing 1Lb then Start. At 16 minutes I press Off and choose the profile I want and then press start again. It tends to smoke a bit around 7 or 8 minutes till the afterburner turns on, but it's kept me from ever hitting Cool before the roast was done. Clearly it's not "recommended" practice and if you have a hot Behmor 2 minutes might be long enough to put it into "Don't start a roast" mode, but it's worked perfect for me every time.

Wesley: I don't know if you still or ever used BehmorThing, but with the latest version you can log, save and review temperature profiles.

Ira

http://www.extrasensory.com/BehmorThing.htm

I've been running Behmor thing under the Windows 7 beta in a virtual machine on my MacBook Pro (If I want to get really geeky, I'll VNC into my Mac from my Linux machine and then boot Windows in VMWare, just for perversity's sake), and have been finding it quite useful. Nice program, Ira. If I had an iPhone I could offer to you so you could develop a version as an iPhone app, I would. As it is, I may just have to download the iPhone SDK and see if I can remember anything about coding.

kaffidrinker - still there?

Ira - I haven't dowloaded the latest Behmor thing yet. When you say "save temperature profiles" does that mean it can be fed with some sort of flat file from a datalogger? Since I installed the PID for the elements, I haven't used the software as the PID does it's own "profiling". (With a 320g load, it's an expensive on/off switch.) Only the draw fan that comes on near the 10:00 mark is controlled by the motherboard.

Your preheating mode is similar to what I do when it's really cold. I don't base it on time though, I wait for the ET to come up to 100+ degrees then start the Behmor cycle.

All of these gymnastics lead me to my conclusion is that you can't really roast more than 200-300g of coffee on a 110v residential branch circuit not matter what you do or have. We killed a toaster oven a couple weeks ago and I kept the carcass thinking that I could install those heating elements in the Behmor. However, I would need to run a 50A 220v lline to the roasting area and split that into three 110v branches to support two 20A heater element loops and a 15A fan/vacuum/computer/PID loop. Or I can keep looking for a used Diedrich/Probat/others 1kg roaster.

Wes

Posting this not from my own experience, but from what someone I know has done--

Check out what Jim has done over here.

Jim states that from his reading of the charts from Michael Sivitz's book, Coffee Technology, it does not require nearly the amount of energy that can be produced by a 15A 120VAC circuit (~1800W without tripping a breaker) to roasted 20oz. green. I don't have the figures in front of me.

I suspect, and Jim shows, that the problem with most of our 120V roasters is thermal losses. It's too expensive (and perhaps difficult to get UL approval for) home roasters with sufficient thermal insulation to more effectively roast 20 oz. green. 1800W is about 6100 BTU--the Ambex .5 K roaster has a gas burner with 7500 BTU. The USRC 0.5K is 5000 BTU max. I don't think the problem is lack of energy, it's how well it's used.

Even easier if you run dedicated 20A circuits like I put in for my hottop.

djmonkeyhater wrote:Ira - I haven't dowloaded the latest Behmor thing yet. When you say "save temperature profiles" does that mean it can be fed with some sort of flat file from a datalogger?

At the moment you click "Log" every N degrees, one of these days I'll finish the USB to thermocouple interface so it logs by itself.

Ira Said:

I've been putting the coffee in, pressing 1Lb then Start. At 16 minutes I press Off and choose the profile I want and then press start again. It tends to smoke a bit around 7 or 8 minutes till the afterburner turns on, but it's kept me from ever hitting Cool before the roast was done. Clearly it's not "recommended" practice and if you have a hot Behmor 2 minutes might be long enough to put it into "Don't start a roast" mode, but it's worked perfect for me every time.

I've tried this trick once and did observe that this delays the kick-in of the afterburner (and subsequent ET temp drop) from starting at 7:30 in to 9:30 in. I was thinking that you could shorten the pre-roast to less then 2:00 (16:00 on the countdown timer) to better coincide with first crack, depending on your load size.

I'm attaching two BehmorThing roast charts, one a P2 Costa Rica without pre-roast (showing the temp drop at 7:30) and one a P1 Tanzanian Peaberry roast showing the temp drop at about 9:30. These roasts were 10 ounces. I'm measuring ET with a thermocouple taped to the top of the Behmor just to the right side of the light as shown in the last picture.

As to the profile for the Tanzanian Peaberry, I'm still working on this one. The roast tasted a little sour so I'm thinking of either roasting longer (even though the chart indicates C2, I believe that I was still in C1, C1 on these beans is very quiet and hard to her) or maybe a longer drying phase with a different profile (P3 or P4 maybe).







-Chris

djmonkeyhater wrote:kaffidrinker - still there?

Haven't been, sorry. Working some crazy hours in the past week. Good gracious this discussion went way above my head very quickly. That's why i like HB so much, tons of knowledge to glean for us novices. Thanks guys. I was mostly wondering because i felt like the roasts were taking a little long. I roast in a very cold laundry room in a house that probably hasn't been rewired since the 50s. What i'm gleaning from the above posts is that at my level of ability and experience it doesn't make much of a difference.

BUT does anyone know if stopping everything w/o a cooling period damages the heating elements?