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I got an iRoast2 last October (from Les). Id already done some reading
about it, so wasnt surprised to find that, like many others, it ran hotter
than programmed. I figured I could live with that, and just make
corrections programming it.
Reading around, it quickly became obvious that performance is related to
voltage, and that one of the reasons they run too hot out of the box is
that theyre designed for Europe, 230V. There are many reports, from Aus
and the UK, of them running too hot on 240V supplies (e.g. at home,
typically over 242V). So I found some profiles used in such conditions,
and got quite good results.
I also found mention, on TMC (toomuchcoffee.com), of a modification that
some people were making to fix this problem. This involved changing a
resistor in the base of the unit. The resistor is attached to a circuit
board, inserted into a white nylon connector for reasonably easy removal.
It can be accessed by removing the inner three screws in the base, which
need a U-shaped screwdriver (such as in Dick Smith cat number T0098, mobile
phone toolkit). I got some information from Gouezeri (thanks!) at TMC
about how to do the replacement. For anyone with electronics experience,
its a trivial operation. For those less competent (like me), its not
hard, but there are a couple of gothchas worth looking out for. If you
want to try it, send me a PM and Ill pass on the information I have,
including what Ive figured out in the process of doing it.
I resisted the temptation to tinker for quite some time. The thing worked,
after all. But then came Harrar. I did a lousy roast, twice. Then I
discovered (on CS, of course) that it likes a nice long roast. So I tried to
make my profile longer, and couldnt. Which got me annoyed enough to try
out the mod, and do some measurements in the process. In particular, to
try to correlate changes with results in the cup, to be convinced that the
mod made an improvement, not just a difference
In short, Ive concluded that swapping the installed 1000 ohm resistor for
an 1800 ohm resistor, in my machine, effects an enormous improvement. If
thats all you want to know, skip to the end (next post) and look at the roast results.
What Ill do now is summarize some measurements with the original
resistor, a first try with a 2200 ohm resistor, and then various tests with
the 1k8 resistor.
I will show temps in this form:
TC DISPLAY PROGRAMMED.
So, 221 225 235 means a thermocouple measurement of 221C, the iR2
display showing 225C, and programmed at 235C.
WITH ORIGINAL 1KOHM RESISTOR
This can be made to work reasonably well with the profile I mentioned in
http://coffeesnobs.com.au/YaBB.pl?num=1175866065/13#13
This gives a quite good roast, with reasonable predictability of second
crack, and quite consistent results.
But sometimes you want to build up more slowly, such as with Harrar.
I tried to do this by stretching the 160 component of the above to 9 mins.
I tried
160 / 9 mins; 220 / 1 min ; / 230 1 min
trying to get a longer buildup before boosting to get SC.
It didnt work -- second crack came at about 7:30. Clearly too much heat
going in.
I verified this by running the extended profile without any beans (ie with
max airflow, which should tend to reduce heat buildup and keep the chamber
cooler). This showed, at the end of the 9 min 160C period,
250 209 160
At the end, at 11 mins:
268 228 230
CONCLUSION: The iR2, as it is supplied in Australia and the UK, runs too
hot out of the box. It can be used to give very good roasts, but in a
manner reminiscent of the earlier, fixed-profile models.
This makes the provison of ten profiles pointless. I know that a lot of
people do manage to use different profiles, and get roasts near its max of
15 mins, so I set out to find out how I can get this flexibility on mine. I
decided that the best way to get some sense out of this machine was to try
this resistor change.
In the UK, the most commonly used values were in the range 2 - 2.7K.
So I started with 2200 ohms (2k2).
Here is a summary of measurements taken at 2k2.
WITH 2k2 RESISTOR
As above (160C/9 mins): after 6 minutes, 195 209 160
With 210C/7mins: after 6 minutes 216 225 210
So this is looking promising, at low and medium temps. Clearly less
heat being generated.
Next test: can we make it run really hot, and get a dark roast?
Tried with 250C/15mins:
after 12 mins (no beans), 215 245 250
which suggests its running out of puff i.e. maybe we have cut back the heat flow
too much.
So tried with 150g beans: the temp ramps up quite nicely at 6 mins to
244 245 250
but then the temp actually starts to drop, and at 9 mins,
224 245 250
(the roast did actually struggle through to SC at 10 mins, and was quite
nice, but this isnt whats expected from a sustained max temp blast!)
Conclusion: 2k2 improves the situation, but goes too far.
Next step: try a lower value resistor. A bit of considered thought
suggests 1800 ohms (1k8).
[well I exceeded max post length to be continued ... ]
about it, so wasnt surprised to find that, like many others, it ran hotter
than programmed. I figured I could live with that, and just make
corrections programming it.
Reading around, it quickly became obvious that performance is related to
voltage, and that one of the reasons they run too hot out of the box is
that theyre designed for Europe, 230V. There are many reports, from Aus
and the UK, of them running too hot on 240V supplies (e.g. at home,
typically over 242V). So I found some profiles used in such conditions,
and got quite good results.
I also found mention, on TMC (toomuchcoffee.com), of a modification that
some people were making to fix this problem. This involved changing a
resistor in the base of the unit. The resistor is attached to a circuit
board, inserted into a white nylon connector for reasonably easy removal.
It can be accessed by removing the inner three screws in the base, which
need a U-shaped screwdriver (such as in Dick Smith cat number T0098, mobile
phone toolkit). I got some information from Gouezeri (thanks!) at TMC
about how to do the replacement. For anyone with electronics experience,
its a trivial operation. For those less competent (like me), its not
hard, but there are a couple of gothchas worth looking out for. If you
want to try it, send me a PM and Ill pass on the information I have,
including what Ive figured out in the process of doing it.
I resisted the temptation to tinker for quite some time. The thing worked,
after all. But then came Harrar. I did a lousy roast, twice. Then I
discovered (on CS, of course) that it likes a nice long roast. So I tried to
make my profile longer, and couldnt. Which got me annoyed enough to try
out the mod, and do some measurements in the process. In particular, to
try to correlate changes with results in the cup, to be convinced that the
mod made an improvement, not just a difference
In short, Ive concluded that swapping the installed 1000 ohm resistor for
an 1800 ohm resistor, in my machine, effects an enormous improvement. If
thats all you want to know, skip to the end (next post) and look at the roast results.
What Ill do now is summarize some measurements with the original
resistor, a first try with a 2200 ohm resistor, and then various tests with
the 1k8 resistor.
I will show temps in this form:
TC DISPLAY PROGRAMMED.
So, 221 225 235 means a thermocouple measurement of 221C, the iR2
display showing 225C, and programmed at 235C.
WITH ORIGINAL 1KOHM RESISTOR
This can be made to work reasonably well with the profile I mentioned in
http://coffeesnobs.com.au/YaBB.pl?num=1175866065/13#13
This gives a quite good roast, with reasonable predictability of second
crack, and quite consistent results.
But sometimes you want to build up more slowly, such as with Harrar.
I tried to do this by stretching the 160 component of the above to 9 mins.
I tried
160 / 9 mins; 220 / 1 min ; / 230 1 min
trying to get a longer buildup before boosting to get SC.
It didnt work -- second crack came at about 7:30. Clearly too much heat
going in.
I verified this by running the extended profile without any beans (ie with
max airflow, which should tend to reduce heat buildup and keep the chamber
cooler). This showed, at the end of the 9 min 160C period,
250 209 160
At the end, at 11 mins:
268 228 230
CONCLUSION: The iR2, as it is supplied in Australia and the UK, runs too
hot out of the box. It can be used to give very good roasts, but in a
manner reminiscent of the earlier, fixed-profile models.
This makes the provison of ten profiles pointless. I know that a lot of
people do manage to use different profiles, and get roasts near its max of
15 mins, so I set out to find out how I can get this flexibility on mine. I
decided that the best way to get some sense out of this machine was to try
this resistor change.
In the UK, the most commonly used values were in the range 2 - 2.7K.
So I started with 2200 ohms (2k2).
Here is a summary of measurements taken at 2k2.
WITH 2k2 RESISTOR
As above (160C/9 mins): after 6 minutes, 195 209 160
With 210C/7mins: after 6 minutes 216 225 210
So this is looking promising, at low and medium temps. Clearly less
heat being generated.
Next test: can we make it run really hot, and get a dark roast?
Tried with 250C/15mins:
after 12 mins (no beans), 215 245 250
which suggests its running out of puff i.e. maybe we have cut back the heat flow
too much.
So tried with 150g beans: the temp ramps up quite nicely at 6 mins to
244 245 250
but then the temp actually starts to drop, and at 9 mins,
224 245 250
(the roast did actually struggle through to SC at 10 mins, and was quite
nice, but this isnt whats expected from a sustained max temp blast!)
Conclusion: 2k2 improves the situation, but goes too far.
Next step: try a lower value resistor. A bit of considered thought
suggests 1800 ohms (1k8).
[well I exceeded max post length
to be continued ... ]
)
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