Hottop successive roasts take longer...?

[alsterlingcafe]

I have the Hottop Digital, purchased about a year ago. I recently replaced my heat sensor and heating coil through Michael at Hottop, when over a period of time I couldn't roast more than 150-180 grams to 2nd crack. Michael said the heat sensor is sometimes the culprit. After replaceing both items, all was back to normal.

My protocol for roasting on this machine is to set the timer for the maximum 21 minutes, let the machine warm up and then go into countdown. At 17 to 14 minutes, depending on the roast size, I dump in my beans. With my Malabar Gold and Emerald Mist, I usually hit 1st crack at 3.5 minutes on the timer, and 2nd crack at 2 to 1.5 minutes.

Tonight I ran three roasts in succession of Emerald Mist blend. I ran 250 grams of beans per roast. At the end of the roast, when I eject the beans, I usually put a large box fan next to the roaster, pull out the rear filter, bean fill cover and empty and keep removed through cool down, the chaff tray. I want to cool down the unit as fast and as cold as possible. Tonight I didn't use the box fan, but let the unit sit after full shutdown for maybe 5-10 minutes.

What I've noticed is that by the 3rd roast, all things being equal, I got very close to maximum available roast time on the countdown timer. I'm guessing that even with cool down, the heating coil and other metal remain warm to hot. Heat causes resistance and reduces current flow. I'm guessing that maybe the first roast or two benefit from a cold startup? When a heating coil is cold, it has less resistance and will draw more current, thus generating more heat.

Has anyone else noticed needing longer times for each successive roast? Do you think it's caused by residual heat from the earlier roasts? I still don't understand why the machine has a roasting time limit??!!!

[miKe mcKoffee]

Has anyone else noticed needing longer times for each successive roast? Do you think it's caused by residual heat from the earlier roasts? I still don't understand why the machine has a roasting time limit??!!!

I'm using a CCR HotTop and find back to back batches very repeatable. First batch pre-heat to 420f drum temp and hold temp for 7 minutes to stablize entire roaster before bean charge, sucessive batches pre-heat to 420f 1 minute stabilize. FWIW after a batch cooled usually drum air temp will be around 350f at the beginning of next batch pre-heat/stablize. While the CCR HotTop controls, drum environment and bean mass temp measuring are not stock the guts of the HotTop are straight original model analog HotTop. (Stock HT temp sensor and control panel not used at all.) Seems to tell me the mechanics of the HT may be consistent, the stock temp sensor and controls may not.

Having a maximum possible roast time is for safety mandated to get UL certification IIRC. All home appliance certified roasters have a built in maximum roast time.

[alsterlingcafe]

..........While the CCR HotTop controls, drum environment and bean mass temp measuring are not stock the guts of the HotTop are straight original model analog HotTop. (Stock HT temp sensor and control panel not used at all.) Seems to tell me the mechanics of the HT may be consistent, the stock temp sensor and controls may not.
Having a maximum possible roast time is for safety mandated to get UL certification IIRC. All home appliance certified roasters have a built in maximum roast time.

Mike, thanks for your input. I knew in the back of my mind that time limits on a heating device (toasters are a good example) were needed to meet safety spec's, but I guess frustration got the better of me. When I got the unit I investigated modifying the controls, and through discussions on the forum, realized that all I ever needed was the analog model. I just haven't had the time or inclination to spend bench time reworking the controls.

I read through related posts and believe that Dave "Cannonfodder" made a comment that he experienced best roasts using around 225 gram loads of beans. Most of my roasts go to full city plus, and I must admit I get a bit nervous when I'm not into second crack yet and the unit is beeping away on its final few seconds. Our line voltage is reasonably high, but I probably should monitor the line voltage throughout the entire roasting cycle to see if there is a voltage drop? I suppose using a variac on the heating element would be the least invasive way to add control to the roasting?

Best, Al in SoCal

[cannonfodder]

My batch size varies depending on what I am roasting. I will run anything from a few ounces to slightly over maximum. I cannot recall the last time I ran out of time before a roast completed. I usually set my HotTop for 19min and usually dump the roast with lots of time left. I also preheat my roaster to 200-250F before I drop in my greens.

I also rarely go further than the first snap of second crack.

[alsterlingcafe]

My batch size varies depending on what I am roasting. I will run anything from a few ounces to slightly over maximum. I cannot recall the last time I ran out of time before a roast completed. I usually set my HotTop for 19min and usually dump the roast with lots of time left. I also preheat my roaster to 200-250F before I drop in my greens. I also rarely go further than the first snap of second crack.

Dave..... I hadn't thought of changing the batch size based on bean type or blend, but then, I've been focused on our retail plan and haven't been very bean or blend adventurous only to the extend of testing some SO's that I brought in from Sul de Minas. I suppose that I've not modified the Hottop because, essentially, it works.

When I started roasting Malabar Gold in the Hottop, Dr. John was concerned that the beans would "bake" rather than "roast" if dumped in at the 21 minute marker. That's what got me into letting the unit run down in time to, originally, 12 minutes. As the temperature issue developed, I dropped the batch size and dumped the beans a bit earlier to compensate. Now that the Hottop is back to factory spec's, I suppose I should experiment and again dump the 250 grams around 14 minutes. I tried dumping them as early as 18 minutes, but the result was nearly the same as when I dumped them at 16 minutes. I think the Hottop temperature isn't as effected by the bean mass as I thought.

As I said earlier, it seems that the first roast when the unit is cold, yields the quickest roast. I was just wondering if others found that to happen. Since I've not invested as much interest in roasting as in beverage prep and retailing issues, I just haven't gotten very deep into the science of roasting. I separate roasting from specialty coffee retailing as two distinctly different activities and/or businesses. My belief is to remove as many variables as possible from the specialty beverage mix, and using the best brewing equipment (most temp stable) and running beans from a pro roaster seems to make the most sense at the outset.

Best, Al