Hottop K2+

Discuss roast levels and profiles for espresso, equipment for roasting coffee.

#1: Post by K-Mac »

Has anyone tried the 160° bypass with the K2+ ?
what other functions does this thermocoupler control?
I'm also curious if anyone has put a SCR instead of the momentary switch?


#2: Post by BarryR »

I did it on my 2K. You need a momentary switch or else it will always think the temp is low. This might be OK with PC control (which I have) but at a minimum would override safety alarms.

Momentary works fine.


#3: Post by rmongiovi »

My entire interest in the 2k+ was USB control with Artisan. I've never encountered an alarm. Doesn't USB override that?

K-Mac (original poster)

#4: Post by K-Mac (original poster) »

Even with artisan, the k2+ goes through a cooling period. I cannot do back-to-back roasts without cooling and reheating the machine.


#5: Post by rmongiovi »

I've never tried because without cooling the second roast wouldn't work with my artisan alarms, but what are you saying? I'm not clear on what "cannot do back-to-back roasts" means. That it literally won't turn the heater on when artisan sends it the command? If it's just that the second roast behaves differently from the first then I think that's to be expected. The Hottop doesn't have any insulation and precious little thermal mass so I'd expect it to be very sensitive to its starting condition.

The Hottop documentation says:
The use of a computer (or similar device) and third party software applications is out of the control of Hottop Americas. The connecting and/or disconnecting of our coffee roasters to a computer or similar external device running a software application that connects to, interfaces and/or communicates with, and/or monitors and/or controls a Hottop Coffee Roaster can cause unexpected behavior. This may include bypassing safety features such as the high-temperature safety point and disabling of the chaff tray reminder.
Which I always assumed meant that it just did what the USB commands told it to do. It's not something I've experimented with, though. Just getting it to follow the profile I want for one roast has been more than a big enough battle for me.

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#6: Post by baldheadracing »

rmongiovi wrote: I'm not clear on what "cannot do back-to-back roasts" means.
In models previous to the 2K+:
The HotTop is programmed to prevent another roast from starting until the chamber has cooled to 165F; it is an annoying barrier standing in the way of your next roast. The delay caused by the 165F Barrier can be especially annoying for those wishing to drop green beans at much higher chamber temperatures. Cracking the 165F Barrier has enhanced my enjoyment by speeding up my back to back roasting considerably. Breaking the 165F Barrier is one of my favorite mods for two reasons: 1) it allows me to launch the next roast as soon as the recently ejected beans have finished cooling, and 2) I find that dropping green beans in a roasting chamber that is already pre-heated to 350F can yield much more flavorful results in my cup.

This modification involves disconnecting the Thermal Sensor (found inside the roasting chamber) from the Control Panel ...
- ... post_40018

I don't know whether this is true on the 2K+. The mod works well on the prior models, although if a lot of back-to-back roasting is done, then the reverse airflow mod is desirable to keep hot air away from the motor, transmission, electronics, etc.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada


#7: Post by rmongiovi »

Yes, it's specifically the USB control that's new to the 2k+ which (I thought) took over complete control. It's not something I can test, though. I found the thermocouples/temperature measurement that comes with the 2k+ to be inadequate. The values it returns are integers with no digits after the decimal point. So when the RoR is relatively low the temperature stays at one value for a while (0 RoR) and then jumps suddenly to the next value. It makes the RoR with smoothing pretty wonky. So I replaced the Hottop ET and BT thermocouples with my own. The original ones are just folded up in the motor compartment so they don't really measure any useful temperature (and only get up to a hundred degrees or so). I had some fear I'd get a "roaster isn't heating up" alarm but nothing happens. I definitely don't get a "roaster is too hot" alarm for obvious reasons. it just does whatever Artisan tells it to do as far as I can tell.


#8: Post by BarryR »

So, even though I have the override switch installed on my 2K, I usually cool it down the 165 on the assumption that it wouldn't be good for the machine not to do so and that's why they built it that way.


#9: Post by rmongiovi »

The problem seems to be that the exhaust fan pulls air from the roast chamber and over the motor and the PCB. That's what the "reverse airflow" mod is all about. It reroutes the fan so that it sucks air up through the vent on the top of the roaster rather than out through the back so the internal machinery stays cooler. I don't have any idea how much the normal air flow actually hurts the lifetime of the roaster, though. It leaks from everywhere so I'd suspect some outside unheated air also gets pulled out the back. I know when I have the fan on and feel the air coming out it doesn't seem excessively warm to me. You'd have to put a thermocouple in the PCB/motor compartment and measure it in back-to-back versus single roasts.


#10: Post by DSNORD »

I've had my 2K+ for 4-5 years now and have never had an issue running back to back roasts at high starting drum temperatures while using Artisan.

Just today I roasted two SWP Decafs. My drop temperature is always ET 400 degrees.

Both batches followed my routine Decaf schedule: At Charge, HEAT 100/AIR 10; at DE, HEAT 90/AIR 40; at FC, HEAT 75/AIR 80; and Drop at 392-396 depending on development percentage. The roast drops into the tray either just shy of SC or 1-2 pops into it.

After chasing hundreds of various roast profiles over the years, this simplified profile allows me to get my SWP Decaf espresso roasts one micron shy of the point of giving off oil post roasting which I've found is the best endpoint for my taste and gives maximum freshness longevity.

Today as usual, after the first batch was dropped, HEAT was turned off while AIR remained at 80 to allow the ET to drop to about 360 or so. At that point then with HEAT 100/AIR 10, I began temperature monitoring, and once the ET got back to 400, the second batch was dropped uneventfully.

Because of the inherent lag in ET temperature change of my electric element compared to the more rapid response of a gas burner, I've found that charging with a red hot burner and a rising ET at 400 degrees works best for me with this unit, so that's why I cool down to the 360 or so point before starting the next batch.

If instead I let the ET drop back to 400 with a black, "cold" element then being energized to start the roast, my results have usually sucked.

I've NEVER had a consecutive roast be disallowed using this method when profiling with Artisan. I've also had ZERO electronic problems from overheating the boards doing consecutive roasts of up to 4 a session, so I think that cooking the electronics is a theoretical rather than practical concern. I DID have to take the motor apart to clean it a few weeks ago because the bearings had become stuck from coagulated roasting oil being sucked past it over the years, but the repair was not a big deal at all and was a fun winter project. I posted some pictures about the tear down a few pages back if anyone runs into the same issue.