Hi,

I recently fitted Eric's infamous thermometer into my Rocket Giotto Premium Plus. Seems to work as billed.

Initially, I had my boiler pstat set to cut off at 1.3 Bar. Using my usual short flush and wait, then flush and go routine after warmup - 3-4 seconds before fitting the portafilter - I was getting readings of around 203.5-204.0 F. I've since wound the pstat a couple of turns anticlockwise and dropped the cutoff to a smidgen over 1.2 Bar. I'm now (generally) seeing temps more in the order of 201-202 F. (But, it's little more complicated than that.)

So I'm wondering: how would this reading likely translate to what the puck would be seeing?

And: now that I have the thermometer as a guide, should I be switching to a more disciplined flush and wait ritual?

Madrooter wrote:So I'm wondering: how would this reading likely translate to what the puck would be seeing?

Eric's the authority on this topic, but you may want to peruse Monitoring Brew Temperature - E61 & Silvia, notably this diagram:



Note the thermometer adapter and thermofilter temperatures converge around the 15 second mark.

HB wrote:Note the thermometer adapter and thermofilter temperatures converge around the 15 second mark.

Thanks, that's very reassuring. One thing though: the graph you provided, does that equally apply to both the Flush & Go and Flush & Wait approaches?

One thing though: the graph you provided, does that equally apply to both the Flush & Go and Flush & Wait approaches?

The very best way to approach the Rocket line of machines is "flush-n-go" as explained in the latest manual available from my crude FTP site - http://users.rcn.com/erics/ .

These machines are fitted with a restrictor (~ 3.0 mm) in the thermosyphon system which makes flush-n-wait a substantial wait and contrary to the typical operation of most hx machines.

I would adjust the pstat such that the maximum reading on the gage is 1.10 bar and do a small flush for the initial shot. More later as it is past my bedtime.

I must be blind: I can't see anything about flush-n-go in your manuals.

I'm guessing this is what you describe as a substantial wait. Following your guidelines to flush to 185F and wait until it hits 198F: takes 72 seconds of flushing to reach 185F and 18 minutes to get back to 198F, with a long plateau from 196 onwards. Running water through the group starts at 206F and drops slowly to 202F.

So would your approach be to flush until the grouphead reads 198F, pack the portafilter, flush again quickly and then extract aiming to get a flow temperature in the vicinity of 201F?

Page 6 of this: http://users.rcn.com/erics/DigThermAdptr6.pdf

edit - the subject starts on page 6 but you need to at least get to page 9 .

Ah yes, thanks, there it is. What a numpty I am.

So here's what I found this morning.

Pstat cutoff: 1.2
Idle temp after 70 minutes warmup: 197F

First cup

Flush 4 seconds to 204F (plateau).
Brew temp after 15 seconds 200.5, dropping to 200.0

Second cup

Flush 4 seconds to 202F (plateau).
Brew temp after 15 seconds 200, dropping to 199.5

Am I doing it right?

Am I doing it right?

As far as I'm concerned, no, but you are the boss. With a group idle temp of 197, all you should need is a cursory screen flush (1 second) and then brew away.

At the conclusion of your 1st shot, the thermometer should dip to 195ish AFTER you stop the flow. When it hits 196-197 rising you can initiate another shot.

Rocket machines for the US market are fitted with a 3.00 mm thermosyphon restrictor . . . your machine is APPARENTLY fitted with something smaller. Can you inquire about that? Australian distributor?

Skol,

Eric

Thanks Eric, the thermosyphon restrictor on the Rocket Giotto Premium Plus V1 that I have is 2.5mm.

I'm just giving the group a descale now. When it's back up to temp, I'll follow your advice.

Should I consider ratcheting the boiler pressure up slightly if the brew temperature falls below 200F?

Should I consider ratcheting the boiler pressure up slightly if the brew temperature falls below 200F?

No. From an outsider looking in (and thus with a grain o' salt), the Australian distributors of espresso machines appear to have things well under control with the various manufacturers.