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10/17/2020 7:46 PM
Roasted Ethiopian Burka Guidina Estate Natural Organic from Limmu

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6kW Electric Air Roaster
Made a new video this morning:

very nice. How does your system work it appears to be rectangular? I like the bean dump feature too.

Yes, it's a roast chamber between these vertical plates, with a curved wall in between the plates to guide the bean flow. Tije recently narrowed the top bit inside to there is an easy airflow but no beans flying out with the chaff.

Some details of the setup are on my blog and on Jan van der Weel's blog
Edited by allenb on 03/11/2018 1:26 PM
A little update.

I receive an alternative funnel for the base of the roast chamber and it works slightly better than the previous one. I can get 1.25kg circulating at 60% blower power compared to 70% with the previous base. This was with the 61 x 4mm holes. I hope to try a larger perforated area soon to get a thicker plume.
Edited by greencardigan on 03/27/2018 1:20 AM
Another circulation test with the steeper funnel and a different perf plate (50 holes with 310mm2 open area).

I think the circulation is improved but minimum blower power required to maintain circulation was back up to 80%. But with the more restricted perf plate, the airflow is probably similar to the more open plate at 60% blower?

greencardigan attached the following image:
I finally got my new 3600W power circuit installed and was able to do an initial test roast with some old beans. Everything went reasonable well (ie I didn't burn the house down).

Although I'm hoping to roast 1.25kg green, I tested 800g for this initial test.

The 5400W of heat, combined with a completely different thermocouple placement caught me out, and I hit first crack at 5min 45s at BT of 190 degrees C. Second crack came soon after at about 7 minutes and about 208 degrees C.

Bean circulation was ok. A bit too energetic I think, but I could turn the fan down further.

Conclusion: I think I have enough power and airflow to try at least a 1kg green load. What do you think?

This looks first rate to me! Excellent circulation. I don't think you'll have any problem roasting a kg.

Nice work!

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
I roasted 1kg of decaf on the weekend reasonably successfully. Still need to do a few more roasts to learn the new temps.

However I've had a very annoying controller issue. I'm getting some blower cut outs and slow downs. I suspect I'm getting some interference that is mucking up the phase angle control. If I recall correctly I had a similar issue on a previous controller. EDIT: found it from back in 2012

On the upside, the standard glass tube (not borosilicate) I'm using has not cracked with the heat yet.
Edited by greencardigan on 07/08/2018 10:36 PM
I've had that issue, but it involved slow writing times to a LCD or tft display. Found that the zc detection, and the triac firing times both have to be handled by hardware interrupts. The zc can be handled by Arduino / sketch, but the firing has to be done a level lower.
I think it might be a grounding problem. I noticed that the blower hicuped a bit when connecting my thermocouples. Connecting the TC4 ground to mains ground may have solved my problem, however I need to test a bit more before I'm certain. Seems like my roaster body was grounded but the TC4 wasn't.
I've just finished a successful evening of roasting without any controller/blower issues. It seems that grounding the TC4 was the solution.

I tried a few batch sizes ranging from 550 grams (1.2lb) up to 1.2kg (2.6lb) using decaf Colombian and all went well. The 1.2 kg batch was right on 1kg roasted so I've achieved my goal with this roaster. ThumbsUp

For the record, this was 5400W heating for 1.2kg or 4500W per kg with a bit of spare heat.

Next task is to build a chaff collector so I can roast non decaf without making too much mess.
Edited by greencardigan on 07/10/2018 7:35 AM
Another goal for this roaster was to be low cost. Excluding the controller it came to $235 AUD which is around $175 USD. Some parts were free from my junk bin.

- 3 x Heatgun - Ozito XU1 2000W - 3 x $23.50 = $70.50
- Vacuum Motor - ONIX 2 - in - 1 STICK & HANDHELD VACUUM 600W - $40
- 2 x Brass waste 40mm - 2 x $13.55 = $27
- Brass nuts to fit waste - Free
- 90mm PVC - Free
- 90mm PVC cap - $2.55
- 3D Printed manifold - Free
- RTV silicon - $31.55
- Liquid funnel stainless for heat gun joiner - $3.59
- Large funnel for base of roast chamber - $8
- Bin for roaster housing - Free
- Timber and aluminium supports for roaster - Free
- 1mm Aluminium sheet for various brackets - Free
- PCV mesh vent - $4.78
- Glass tube for Roast chamber - Free
- Threaded rod supports - Free
- Aluminium sheet 0.5mm for Roast Chamber extension tube - $35.75
- Aluminium tape - $11.95
- Power cables - Free
This roaster is proving to be a real workhorse. I'm really happy with it's performance.

I increased my bean load to 1.5kg (3.3 pounds) and the roaster handled it easily. A 12 minute roast required about 85% heater. Now I'm wondering if I could possibly reach 1.8kg (4 pounds) which would be 1.5kg roasted.

Cooling in the roast chamber is taking 3 mins to reach 100C.
Just a quick question about the power requirements. I was hoping to increase my roaster from 1 x 2000W heating element to 2 so that I have a total of 4000W available. Not sure what the best wiring would be and whether I would need a 15amp source in my house?
15 Amp 230V I guess...
Because 15 Amps @ 115 V make 1725W.
yeh thats fair enough, perhaps I can just run the two elements from different points and have a single SSR fire them both


greencardigan wrote:

Any thoughts on perforated areas? Funnel shape?

I drilled out a colander for a bean cooler and to get maximum air flow I drilled out all the holes to maximum and placed a piece of stainless steel screen over it. Only a thin framework is needed to support the screen which seemed to pass a lot of air.

"Espresso is a miracle of chemistry in a cup."
Andrea Illy
Hi greencardigan, i was wondering where you got the glass tube for the RC from? also did you seal the funnel which connects all 3 heating elements or is that open air?
Edited by jooi123 on 10/21/2018 11:37 AM
The glass roast chamber was an unused vase that I 'borrowed' from work and cut the base off. It's standard glass but I have not had any issues with it yet.

It's all sealed with RTV silicon. The three heatgun nozzels go through an aluminium plate which is sealed in the upside down funnel.

My elements are all in parallel. Two are on one 15A circuit and the other on a separate 10A circuit. An SSR for each circuit.
JSA Coffee
Is there a link available for the funnel used as the base of the roast chamber?
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