Dear Home Baristi

I own an E61 type machine with a rather small boiler/HX unit. My daily routine is to get up, switch on the machine and have a single espresso 45 min later before I'm off to work.

Over time, I've become increasingly frustrated with the lack of intra-shot temperature stability, and as a consequence, the inconsistent quality of my espresso (depending on the beans, too hot or too cold water seems to have a greater impact). I'm aware of and practice flushing, but pulling a really good shot happens rarely, as I can't keep the temperature within the desired range over the whole shot. This suggests modifying my existing machine, which brings me to the following idea:

1. PID the boiler, and run the HX/boiler/group as close as possible to brew temperature.

2. Draw from a heated reservoir, e.g. a laboratory heated bath, set to brew temperature plus whatever is necessary to compensate for thermal loss later on.

3. Draw water from the reservoir until the system has stabilized, then pull the shot.

This would delegate the function of the boiler/HX to minimize thermal loss while transporting the water from the heated bath to the puck. Essentially, I'm looking for a thermal system that is in equilibrium, instead of the endless surfing and hoping that the group head dampens the dynamics.

My three questions are:

1. Has anyone tried heating the water tank, or something similar?

2. Can I run the boiler at brew temperature (i.e. below boiling point), and will the E61 thermo-syphon still work?

3. Will the vibratory pump be happy with drawing heated water? I imagine that the design relies on cold water to avoid over-heating.

Note that I'm entirely willing to give up on steaming ability.

Thanks for your input,
Christian

Edited to improve title (thanks to Dan for the suggestion) and clarity.

First of all, it would be helpful to know what espresso machine and grinder you are using. Would you fill in your equipment profile? It would also be helpful to know what coffee you're using, and how fresh it is.

christiandavid wrote:I'm aware of and practice flushing, but pulling a really good shot still happens rarely, and I don't have the time for multiple attempts.

Based on your post, I am assuming that the extractions are consistent shot-to-shot. Correct? If temperature consistency is the issue with your E61 HX espresso machine, Eric's E61 thermcouple/thermometer adapter is the answer. There's no need to reinvent.

christiandavid wrote:PID the boiler, and run the HX/boiler/group as close as possible to brew temperature.

If you want to eliminate flushing an HX and don't mind the lack of on-demand steam, that will work. See Ian's HX Heaven or 1½ Boiler for details.

And to answer your third question, vibe pumps want to use room temp water, it may not last long if you try to use hot water in the tank.

Randy

HB wrote:First of all, it would be helpful to know what espresso machine and grinder you are using. Would you fill in your equipment profile? It would also be helpful to know what coffee you're using, and how fresh it is.

Done. The machine has the brand of a local dealer, and will therefore not be known outside of Switzerland. Judging from looks and features, it is fairly similar to a Quickmill "La Certa". I buy a variety of freshly roasted beans or roast my own (using a GeneCafe roaster).

HB wrote:If you want to eliminate flushing an HX and don't mind the lack of on-demand steam, that will work. See Ian's HX Heaven or 1½ Boiler for details.

Thanks for the link, that (and other threads) made me consider PIDding the boiler. However, as my machine doesn't have the 1.8 l boiler capacity of the Vibiemme Domobar Super, I wonder if this is enough. The numbers reported by Geoffrey for his Anita (again with larger boiler than mine) show a significant delta between PID and group head temperature, and dynamics while pulling the shot.

I am hoping for a true steady state solution, and therefore thought about delegating the water heating job to an external reservoir. I agree that sending hot water through the vibratory pump could be the show-stopper. Maybe another pump design might work?

Regards
Christian