PID on a HX...this is my thinking, is it flawed? - Page 4

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jimoncaffeine

#31: Post by jimoncaffeine »

A couple of people asked me to post a link to the 'pid your h/x machine' article when I wrote it. I checked with HB and he said it would be ok so here it is...

http://homeroasters.org/php/forum/viewt ... ead_id=366

Sorry it's a bit late. The holidays and a 9 day stretch without electricity ate up a lot of time in December. It still needs a bit of polish so please let me know if you see any inaccuracies or confusing descriptions.

Thank you,

Jim

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cafeIKE

#32: Post by cafeIKE »

coffee_monkey wrote:Oh, make sure you put in voltage regulation or replace the vibe pump w/ a rotary pump if you choose to PID the TEA. The voltage drop as result of the PID will cause the pump pressure to pulse at PID interval (1 sec usually) and the clarity of the shot will really suffer...
OR add a relay to cut out the PID drive to the SSR when the brew switch is closed.

I added a PID to my Vibiemme Domobar Super HX to reduce the amount of water needed to flush the group and end the pStat clack.

I currently have the PID set to 234°F in the winter. This produces a temperature at the thermosyphon inlet to the group of ~210°F and ~190°F at the outlet. As the brew flow is a mix of the two, the brew temp is about 200°F.

I'm able to walk up to my machine, pull a first shot, again a few or many minutes later, or after several hours and pull a shot without flushing @ 201°F ±1.5°F measured in the puck with a K TC probe. The temperature remains very constant for much longer than needed to pull a shot.

Taste consistency is better than achieved on the water dance.

For a latte for the missus and a machiatto for YHC, steam power is adequate.

For a dinner party, crank the temp up to 248°F which allows many shots in a row and plenty of high power steam for multiple lattes.

NOTE : This performance may not transfer to another machine. When deciding on a prosumer HX machine I chose the Vibiemme Domobar Super because it has a large boiler, heating capacity and original e61. YMMV