Some have discussed this potential improvement to temperature stability. (Like an impeller approach, or similar.) I connected a potable water, high temperature circulator pump from one grouphead to the adjacent one and insulated the connecting pipes. Basically it constantly circulates (at pretty high speed) the water in the entire boiler-group system to keep a uniform temperature. The closeup photo shows one of the pipes exiting one head at its group cap. I drilled and tapped the caps for pipe fittings. In addition, I disconnected the two remaining groups and connected the outlet of one of them to the inlet of the boiler with the circulator, so it's preheated. This machine has two boilers, so now the first boiler is dedicated to preheating the second. Finally, the banjo tube of one head is lengthened and the element controlled by PID controller with a thermocouple in the boiler thermowell. The result is an amazingly predictable and stable temperature in the puck. Basically what this gets me is the ability to dial in a temperature and simply know that's the temperature hitting the cake. I can postflush for cleaning until the cows come home because the preheating boiler prevents cooling during this flush. Sorry for the stinky pictures but thought some would be interested anyway. I've had this working flawlessly for more than six months now. The pump is only rated to 125 psi (~8.6 bars) but seems to be ok so far. This has not made every shot perfect. I still need to learn to roast better and tamp and/or distribute consistently, but any question on my temperature has been completely eliminated.

Keith

Interesting. The idea of preheating the two left groups with the right boiler is a good one, particularly if one has an ex starbies machine in yo house. How did you handle the flowmeter and group solenoid heating? Unless I'm mistaken those two components still cool the first couple of shots unless the machine is well flushed.

Ain't them Chronos keypads great?


-Greg

gscace wrote:Interesting. The idea of preheating the two left groups with the right boiler is a good one, particularly if one has an ex starbies machine in yo house. How did you handle the flowmeter and group solenoid heating? Unless I'm mistaken those two components still cool the first couple of shots unless the machine is well flushed.

Ain't them Chronos keypads great?


-Greg

Keypads? What keypads? O yeah, those keypads...

I removed the flowmeter and connected the solenoid right to the group neck like an EE. Note in the picture that the leftmost keypad is invisible. The first stage of my espresso cloaking device is working, to conceal the sheer volume of equipment from my wife!

I also wrap-insulated the pipes going to and from the solenoid the same way as with the convection pump as shown in the closeup picture above. I wanted to pull a "Pratt" by inserting the solenoid in the group but I don't have the machines, skill, time, patience, etc. The insulation, really long banjo tube, and getting rid of the flowmeter is enough.

Keith

Hi Keith,

I just saw this impressive convection mod to your 3AV. Since you removed the flowmeters, I wondered why the LED's of your Linea do not start flashing when you pull a shot. I thought the machine's brain would do so, when it does not receive any signal from the flowmeter to tell the barista that there is something that blocks (or that he tamped a little bit to hard this time)... I am considering to buy a set of chronos pads for my machine and to set the flowmeters aside, too -- that's why I am asking.

BTW: Are these two buttons on the left of the chronos pad classical volumetrically dosing keys? Or can you program an extraction time for these buttons?

Thanks,
Martin

chelonae wrote:BTW: Are these two buttons on the left of the chronos pad classical volumetrically dosing keys? Or can you program an extraction time for these buttons?

Paul Pratt has a good explanation of the controls on LM AV machines here, http://www.espresso-restorations....Mcontrolunits.html

Yes, the two left buttons are programmable volumetric dosing keys.


Gicar LM Chronos keypad (foreground) from http://www.espresso-restorations.com

I have a non-LM machine that I *think* I can use a Chronos pad with, I'll be curious to know if you have any trouble sourcing one.