[Homeroast] Puzzled by Quest

Josh Schwartz veganjosh at gmail.com
Sun Mar 13 14:16:46 CDT 2011


I think it must be that your temperature measurement is off somehow --- as
far as I understand, it's physically impossible that your coffee is cracking
at anything near 290.

On Sun, Mar 13, 2011 at 2:54 PM, Robert Bedwell <rlb at triad.rr.com> wrote:

> I have had my Quest for about three months and have done about 30 roasts on
> it.  It has worked like a charm until the last three sessions and I have no
> clue what is going on.
>
> I have Eric's thermocouple installed in two places and attached to an Omega
> 806.  Plans are to connect it to my Mac for data logging after I become
> consistent with using it.
>
> The first indication of a problem was when it took so long to preheat with
> the amps set at 10 and the fan at 4.5.  The ambient temperature was around
> 55F in the garage so I assumed
> it was due the cooler temp.  Incidentally my Quest has an insulation
> blanket installed over the drum.   The last three sessions have required
> around 45 minutes to reach 400F which is the temp
> that I use to load the beans.  Prior to these roasts it has taken no more
> than 15-20 minutes.
>
> Today I roasted Quatemala Zumay Santa Elena del Jumay......thinking it was
> the Ethiopian Sidama Bonka that was the source of the problem in the
> previous 5 roasts.   However the Quatemala mirrored
> the Bonko roasts.....only faster.
>
>
> After loading the beans at 400F the temperature drops to around 210 and a
> minute later is back up to 220 with a environmental (ET) temp of around 580.
>   With the AMP set at 8.5 and the Fan at 4.5 it is taking 9.5 minutes to
> reach 300F.  Unfortunately, and this is where I am stumped, the first sign
> of first crack is at around 290 (not 390) and first crack is over by 11.5
> minutes at 320F.  The low point of ET is 534 and the high is 583.
>
> The above has occurred for the last five batches I have roasted.   I have
> checked the temperature recordings of the Omega to my Fluke using the
> thermocouples use on the Quest and compared them to temp readings
> I am getting on the Fluke.  They all read within a degree of each other.
>  Both the Fluke and the Omega are set for K type thermocouples and there is
> not an offset on either one.  Both are set for fahrenheit recording.
>
> So, to say that I am puzzled is an understatement.
>
> I removed the drum about 15-20 roasts ago and cleaned it but it there was
> hardly anything that came off.  I have cleaned the thermocouples to make
> sure they weren't affecting the temps.
>
> To sum up;
>
> Last five roasts have required at least 45 minutes to heat up to the 400F
> bean load temperature with amps set at 10 and fan at 4.5
> Taking 9-1/2  minutes to hit 300F and 1C  has already started at around
> 290F
> !C is over at around 11-3/4 minutes at 325F
> Both probes used in the Quest have been checked with the FLuke I have and
> are very close to the same readings
> Probes have been cleaned
>
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