Re: Pics of my 'Gronk' thermocouple attachment to Silvia

On Jan 28, 2:06 am, "Bertie Doe" <montebrasi...@xxxxxxx> wrote:
"anthony" < wrote in message

On Jan 26, 6:13 pm, "Bertie Doe" wrote:



"anthony" < wrote in message
Thanks to everyone for advice, especially to the creator of the first
GRONK mod!

http://coffeesnobs.com.au/YaBB.pl?num=1232768860/0#0

Nice pics Anthony. I have an Omega HH12A with K type t/c that sits at the
bottom of the dry thermowell inside the Zaffiro boiler.

It would be interesting to know the 3 readings you are getting from your
boiler cycle at 30 mins and 60 mins - that's lowest temp, heater off temp
and max temp (after overshoot).

By now, you've probably worked out, that a short blast on the pump (via
the
steamwand) or a quick blip on the steam switch, will 'walk' you towards
your
target temperature.

Bertie
Lowest temp (for machine fully warmed up) seems to be around 78
degrees Celsius (174 F) . It cycles up to around 111 (232) and I find
that if I catch the right temp on the upswing, the best result for my
current blend is 106 C (223F). When I've finished pulling my shot,
it's risen to 107.
A PID is the most desirable option, but the thermocouple is certainly
a really cost-effective alternative while I save, and wait for the
Australian exchange rate to improve. I bought the unit from the States
a year back for around $US 18 from memory, and of course the result
when pulling a shot is identical to a PIDded unit....
Anthony in the Blue Mountains, NSW, Australia

Well it's not identical to shots on a PID unit. You can see the problem, the
huge temperature range you have 78/174 to 111/232, caused by a fairly small
boiler and a large heating element. Picture a time/temperature graph.

The heavy metalwork of p/f and group, to some extent, helps to stabilise the
spikes of heat coming from the boiler. However, Silvia boiler is off for
about 15mins, which is subjecting the group to heavy cooling. With a PID,
the boiler and the group are stable.

You are hitting the shot on the upswing, which is high risk. The Silvia
heater 'on' cycle is about 20 seconds, so your boiler is rising by 1.56C/3F
per second. If you are 3 seconds early or late with the pour, due to grind,
distribution, bean variety or age, you've missed the optimum
taste/temperature window of about 3C/6F.

If you aim at hitting the shot on the downswing (reverse surfing), the
temperature range of the boiler is still the same 33C/58F, but this change
happens over 15 minutes rather than 20 seconds. The temp change per second
is miniscule. So it doesn't matter if you are early or late with the shot,
you won't miss the window.

Bertie

Makes sense. So I'll go with the down-swing every time. It works in
golf, so why not in coffee too!
.

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