Even in manual mode with a fixed fan and 1100W once the temperature reading hits 242.3C limit set in the studio, the power cuts off and drops around 20C then comes back on again only to repeat this oscillation.
So I can only assume this is a "safety feature" built into the actual roaster firmware not just a temp limit in the studio? If this is the case this should be lifted to 270C. I have let this oscillation play out and the coffee can not get past the stage just after full yellow - orange unless one holds a much lower temperature for longer.
I played around with the assumption that 120g green + 1050W + 14700 rpm of fan will give 240 inlet temp.
I upped my fan calibration to 0.97 as at 0.90 - 0.91 there was pretty much no movement. At 0.97 it seems acceptable and once heat is applied the bean mass loosens up quite quickly. This hangs around 200 - 205C which is actually perfect for starting a lot of air roast profiles and then how one ramps the temperature from there is up to you / green coffee / taste.
So with this in mind I lowered the fan rpm down over about the first 1:30 to 13700 to give a fixed airflow for the rest of the roast which gives pretty good agitation even at 120g and increased the power to 1100W which takes the inlet temp up to the 242 ceiling reasonably quick and then the roast is ruined by power on / off cycle.
At the very least in manual mode I should be able to fix and hold what ever temp reading I desire up to 270 without the power cutting in and out.
I have tried with bare thermocouple and have now added some sheathing which is the tip of an old cheap hand held instant read probe, very soft think squishy steel so it is kind of close to the thin soft aluminium?
the roast chamber is made of sitting next to it inside the heater chamber.
Obviously I am aware from my previous measurements that with the KL thermocouple in its stock position as a sort of BT / Exhaust Temp reading the inlet temps are allowed to hit well over 260 which means that this safety feature is complete unnecessary as the roaster is doing it anyway. So its basically just a limit by numbers?
What is the actual thermal safety fuse cut out temp for the heating element?
Anyways this finding feels like it explains a lot for me? happy to be told there is some other explanation though.
If you look at some of the Ikawa inlet air temp profiles for 50g, basically starting at 200C need to be able to gentle ramp up to 241 - 242 over 5 to 6 min for even the lightest of filter style roast and if you hit that final temp and the heater craps out, then that roast will be baked period.
You want an absolute rock solid environment temp going into and through first crack, ideally it might rise by 2 or 3C to account for the release of gases through first crack and the roast operator allows for this in the roast plan, this is using a drum roaster which has some thermal mass to back up the bean mass if there are slight drops in temp by a few degrees after. There is zero mass for KL and we are purely relying on the hot air stream to give the right conditions for proper development which in present configuration seems impossible as even with the thermocouple in the stock position there is no way of controlling the actual heat (inlet temp) the beans are receiving which is why there is so much roast defects.
If this roaster had a second probe or even just the original one located in a proper threaded pot seal through the heater chamber housing so that the tip was just a few mm away from from one of the central hottest vents this would be perfect!
Basic rules for 100g to 120g would be you want roast times around 5:30 to (7:00 max for a dark roast.)
People would be able to talk about temps between Ikawa home and ProV3 pretty closely.
I understand the increased costs of change of manufacture may push it into the same price or closer price bracket. From what I have seen inside the KL is incredible well built / super robust. I have 187 motor hours / 148 heater and apart from a light coating of dust inside the casing and on the fan blades it was spotless, no signs of failure yet, the element still looks good and the fan motor sounds pretty smooth.
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