Probat L12 Newbie Questions: Thermocouples, Roasting, Pilot, Stuck Beans


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Feb 14, 2017
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Hey All,

I am fairly new to roasting coffee and have started roasting on the side. I have been roasting on a Huky 500 and have recently jumped to a Probat L12. The learning curve is a little rough (just like my bean curves :)). Below are my issues and curiosities as of now:

1. The thermocouple appears to be bad as the max temp it has read is 154 degrees F. I want to connect the bean probe to artisan, but also like the safety feature of the L12 (bean probe connects to Watlow SD 90 and shuts the system off if beans exceed 500 degrees). In order to do this, I need a 4 lead wire which Probat did not appear to have. I have looked on omega and various other websites, but there are way too many choices. Also I want to connect an ET as well. I have phidget I/O I plan to use to interface with Artisan. What are the favorite probes out there? Any sites that are easy to order from? Or will I need to ask for custom job from a place like Omega?

2. Making the jump from the Huky to the L12 has been interesting. I knew buying a L12 would not allow me to roast and cool at the same time, but can I use the cooling slide gate as a damper to control air flow? I tried it once and things became a little smokey.

3. Airflow seems to be okay, but I am having trouble keeping the pilot flame going when I place the sides on the roaster. The flame becomes wavey and then shuts off the gas valve as the flame sensor isn't detecting a constant flame. Any suggestions? The machine works fine without the side panel (see pic), but I feel I am changing the airflow or losing heat by doing keeping it off.
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4. Also, I am noticing quite a few green, partially roasted, and pinched/burnt beans. I think this is because there appears to be a gap between the drum and the faceplate. How do you eliminate the gap? Thank you in advance for the advice.
Dunno about the L12 but I do about the P12

1. dunno
2. dunno
3.Probat likes constant air, that is not adjusted, though on the L12 you can adjust it (not on the P12 though). ARe you adjusting air ?
4.You need to set the drum gap, i can't remember what it should be on the P12, but I will check on the weekend.
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Thanks wmark!

3. I was using the lever to switch air flow between the drum and stirrer tray.
4. Is this adjustment made using the spanner bar on the front of the drum? I tried turning it left and right but my gap did not change.

P series drum gap is 0.5 mm
It is adjusted at the front. DO NOT ADJUST WHILE COLD. I have not adjusted a probat drum in over 15 suggestion would be call Probat. I know on my Ambex 60 kilo when I adjust the drum that it moves super slow...I have to turn the thing a few times before I notice any movement. But like I said if if you adjust cold you will hear a horrible noise once it gets to temp maybe even stop the drum. Let us know how you make out ;)
Call Probat ? Good luck with that!

I think one of the reasons Mill Street is here is due to the customer support. As I have read (and experienced), getting (relevant) information is harder than pulling teeth

You probably just got more information from Topher by not trying than you will from Probat from trying hard.
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Thank you. I will try it warm. The manual, if you can call it one, talks about removing 3 set screws behind the bearing cap. I removed the bearing cover and seal, but do not see any set screws. I know it has been a while, but any clues?

Let's go down the list:

1 - just go to Omega and order a new probe, no need for a custom order.

2 - you can roast and cool at the same time. I usually give the cooling a minute before dropped in the next roast. Have the airflow at 80/20 cooling tray to drum till the beans are cooled down. You can also use it for airflow. A little goes a long way on ours.

3 - the suction kind of messed with the pilot, I've seen people make a shield around the pilot with tin foil and that helps. Does it go out mid roast or just has trouble lighting the burners?

4 - is the gate on your hopper closed all the way when you load green coffee up top? We don't load until we're about to drop the roast in, but some green might be spilling in. If not can you send a picture or two of the gap on the drum? What's your drop temp and roast times? The scorching might be because you're dropping in too hot.
Also, in addition, where are your temp probes? We have our probes going to display (two Dwyer love controllers) on the side of the roastery that gives us the temps, and also into a yactopus thermocouple thing that allows us to connect to artisan. Super simple set up.