The Dirty Portafilter

My corner of the Internet, mostly espresso related but occasionally life will interfere.

Thursday, December 15, 2005

Caveat to Lever Machine Temperature Controller

Here is the problem, these types of machines require at least .5 bar pressure to operate, that is around 228F water temp, much higher than the accepted norm of 205 for brew water. Even after I added the digital controller my water temp at the grouphead is still to hot. It is better and I do notice a difference, but was it worth all of the work, still undecided.

I let my machine preheat for about a half hour at 190F, then I ramped the temp up to 230F (brew temp), took a type K thermocouple and held it suspended in the opening of my single spout PF. I raised the lever and watched the temp. After about 8oz of water it stabilized at 213F. I have to assume that if I was pulling a normal shot the temp at the shower screen would be lower than that due to group head temperature, but after slowly streaming out 8oz of water it was hot.

Now for the sake of fun, I let it cool, repeated the process but ran the temp up to steam pressure, 242F (about 1 bar) and took the water temp using the same method. That is about where the machine ran at using the OEM pressurestat. Guess what the water temp was, 213F again.

So in the end, the water I got from the machine at the lower setting, and the water that would have been dispensed at the normal pressure level appear to be the same. I have to emphasize, appear. While I do have access to a couple thermocouples, I have no desire to spend hundreds of dollars on testing equipment. I have become somewhat less enchanted with all of the tech tricks and gizmos over the past month and gone back to concentrating on what is most important. My barista skills and what ends up in the cup.

So take it with a grain of salt. Can you improve on the stability of these styles of machines, yes, but is it worth all of the work, undecided. You also loose some of the old world classic design by putting a digital controller or big old variac on the counter beside the machine.

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