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Homeroasters - Home Roasting Coffee Community » BUILDING A ROASTER » Turbo Oven Roasters

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1300w halogen vs 1500w element
Gullygossner	#1 Posted on 07/21/2020 9:49 PM
1/4 Pounder Posts: 95 Joined: January 06, 2019	I'm currently roasting on a KKTO style roaster with a 1300W Big Boss turbo oven. The current TO is halogen based and I have removed the metal shroud to improve air movement. The halogen heater is wired to connect to a SSR relay for heat control. I find that the time between dry end and fc tends to be drawn out and may be a reason sub par roast flavours. The drying phase tends to finish around 4-5min mark with ~210C preheat. FC tends to start around 11-12min. I have a modified Poppery 1 that produced really great coffee but use the KKTO roaster for it's increased batch size. I feel that that the improved flavour from the Poppery 1 was due to the increased heat for faster roast times. I came across a 1500W Nuwave oven pro at a goodwill store the other day and am wondering if it is a worthy upgrade? I believe the KKTO design is based on 1500W TO lids.


Koffee Kosmo	#2 Posted on 07/22/2020 12:23 AM
Administrator Posts: 1620 Joined: December 31, 2008	The stronger wattage TO should be better But the design is based on roast chamber volume and good agitation It?s important that those 2 design features are spot on If you use a smaller wattage TO then either the times will increase based on a set green bean weight Or You need to roast smaller batches to compensate for lower / slower heat volume KK I home roast and I like it. Designer of the KKTO Roaster Build information https://homeroast...ad_id=1142 https://docs.goog...lide=id.i0 Blog - http://koffeekosm...gspot.com/ Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex, (KKTO) Turbo Oven Home Roaster.
	Web

renatoa	#3 Posted on 07/22/2020 2:13 AM
Administrator Posts: 3005 Joined: September 30, 2016	In Europe 1300W is standard. To improve airflow you should cut an opening the same size as the turbine fan, and let the rest as is, check the attached picture. There in the middle is where chaff accumulate and start clogging. The outer ring is not subject of turbine suction airflow, conversely it helps to direct the air around the bulb for better heat absorption There is another more important reason to keep a partial plate as a ring around the bulb, for shadowing/attenuation of direct IR from bulb to beans. That radiation is too strong when removing the plate completely, especially for distances under 10 cm from bulb to beans. Regarding workflow and performance, I am starting with 185 C preheat, load the beans, wait for TP, that happens about 45 seconds after load, then start ramp heat to reach the maximum ET, about 245C, between minute 3 and 4. % of power for that ET depends on load and ambient. 80% for half pound, up to full 100% power for one pound. Keep there to the end of dry, then slightly lower to 238 C, about 1% per minute, for a proper FC approach. FC around min 9-10. Check graph attached for a roast example. Volume of oven 8 litres, agitation 60 RPM. ... renatoa attached the following images: Edited by renatoa on 07/22/2020 6:18 AM


Gullygossner	#4 Posted on 07/22/2020 10:53 AM
1/4 Pounder Posts: 95 Joined: January 06, 2019	That?s a nice profile renatoa! My agitator motor is 60rpm and the stirring arms are based off the kkto arms. Typical batch sizes are 650g. I'll confirm the volume for certain but I believe it's In the 6-7L range plus whatever the TO dome ads.


renatoa	#5 Posted on 07/22/2020 11:04 AM
Administrator Posts: 3005 Joined: September 30, 2016	Then, I think the weight is the limiting factor... One of the recipes to find a machine capacity, is to charge at 200 C, ramp quickly to 250 C and keep there until FC. If under minute 12, then you are within limits. This is purely a thermal capacity test, not pretending the result of such roast is optimal for any coffee origin.


Gullygossner	#6 Posted on 07/22/2020 8:53 PM
1/4 Pounder Posts: 95 Joined: January 06, 2019	Quote renatoa wrote: Then, I think the weight is the limiting factor... One of the recipes to find a machine capacity, is to charge at 200 C, ramp quickly to 250 C and keep there until FC. If under minute 12, then you are within limits. This is purely a thermal capacity test, not pretending the result of such roast is optimal for any coffee origin. I tried a 500g charge weight tonight although my thermocouple was giving me grief so I was flying blind. Based on observations dry end was ~3:48min and FC start was 7:48min so charge size was definitely an issue before. I took some rough measurements: Outer pot 9 3/8? (23.8cm) wide 4.75? (12.0cm) deep 5.3L Inner Pot 9? (22.9cm) wide 5 3/8? (13.65cm) deep 5.6L Inner pot sits 1.5? above top lip (3.8cm) ~2.15cm space ~0.956L between bottom of inner pot and bottom of outer pot. So I think I am in the recommended ballpark for KKTO volume space. I will see how this batch tastes in a few days and maybe the reduced charge weight will be the ticket, which is something I can live with.


yamhill	#7 Posted on 07/24/2020 11:31 PM
1/4 Pounder Posts: 111 Joined: December 18, 2009	How / where are the thermocouples on your TO / KKTO roasters? Quest M3 w/ Artisan via ESP32 emulating TC4. Previous roasters include: IMEX digirosto 1500, various popcorn popper roasters, and Behmor. Espresso: Quick Mill Vetrano; previous espresso PIDed Rancilio Silvia. Also Chemex, Hario, and Melitta drip; Cory and Yama vacuum/siphon; bodum French press; aeropress; Mazzer Major, Hario mini, and PeDe Dienes grinders.


Gullygossner	#8 Posted on 07/25/2020 2:13 PM
1/4 Pounder Posts: 95 Joined: January 06, 2019	Quote yamhill wrote: How / where are the thermocouples on your TO / KKTO roasters? I currently only have BT probe and it is placed near the bottom of the inner pot at the outer edge of the pot to avoid getting hit by the agitator arms. I just used wire to hold the probe tight to the pot.


renatoa	#9 Posted on 07/26/2020 2:31 AM
Administrator Posts: 3005 Joined: September 30, 2016	Attached is a picture with mine, same location as described above ... renatoa attached the following image:

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