The S1 Cafe - Helping Your Espresso Dreams Become Reality

It was my understanding that the line pressure to the S1 influences the output pressure at the group. I assumed that the group pump pressure was adjusted for what a typical municipal water pressure would be. Since I have my S1 plumbed with bottled water supplied by a lower pressure (I assume) Flojet pump, I ordered a group pressure guage from Chris Coffee to make any needed corrections. When I first took a measurement it came to precisely 9bar, so maybe my assumption was wrong. I stopped the water flow and then restarted it, but this time the pressure climbed right up to 12.5bar! I didn't think a procon pump was supposed to do that. Has anyone experienced any of this kind of pressure increase? After I stopped and restarted the flow I got a normal reading of 9bar again, and for all 5 or so measurements I took immediately afterwards.

I think most of us that have a PF pressure guage have noted this. Theories abound. We'd like to think it is a side effect of air getting caught in the PF and affecting the reading. At least we want to believe that it's not a problem with the machine.

Try filling the PF with hot water before locking and loading the PF pressure gauge. That may stabilize your readings. I've been doing this and have not seen this behavior in my last several uses.

OK, I'll try that. I think I do recall reading about that here awhile ago.

Thank you.

Yes, I believe I posted that some time ago.
As Chas said, that's most likely airbubbles. When air gets heated, it expands much faster than water (ever got your tire pressure before and after you were driving on the highway?). And since the tube is thin, this could have a strong effect. One other point where that air could get cought is the chamber above the group (for the "natural pre-infusion" of the S1).
Solution: fill the PF gauge with hot water (I take it directly from the steamboiler spout) to bring the temperature up, then lock it in, and engage the pump several times for a few seconds (like backflushing), that get's most residual air out of the system. After a few times the pressure reading stabilizes.

W.

Sounds good to me. Appreciate it.

NewEnglandCliff wrote:When I first took a measurement it came to precisely 9bar, so maybe my assumption was wrong. I stopped the water flow and then restarted it, but this time the pressure climbed right up to 12.5bar! I didn't think a procon pump was supposed to do that. Has anyone experienced any of this kind of pressure increase?

I'm working on an article for the Cimbali Junior and puzzled over this same observation.

To make a long story short, I found that the cause was the incoming municipality water pressure, which changes a lot more than I realized. Initially the static line pressure was 110 PSI (!?!), which I traced to the house's failing pressure regulator. It turns out that several of my neighbors had had the same problem and replaced theirs over the years. With even the slightest water release, the inlet line pressure dropped to the (failing) pressure regulator's setpoint of 60 PSI, but if I let the pump run against a PF pressure gauge, the static pressure quickly climbed back to the street pressure of 110 PSI. This showed up as an almost 2 bar increase at the grouphead.

This lesson learned, I replaced the house pressure regulator and set it to a more reasonable 40 PSI (good enough for showers and appliances, probably too low for watering the lawn, but I digress). I then installed a second smaller pressure regulator at Junior's inlet and set it to 20 PSI. Now the readings at the group don't budge. I have a Flojet and should see if the same effect reoccurs...

Anyway, while I was having such fun, I also installed a temporary pump pressure gauge (below). Hours of twiddling with pressure ensued shortly thereafter. I settled on 9.5 bar as my preferred setting for good crema production and channel-free shots, which is slightly higher than Schomer's recommended 8.2 bar.

Dan,
the municipal water pressure sometimes can be a problem, I agree.

However, I believe the issue with the LaSpaziale S1 PF gauge is more likely air in the system (Chas also noticed that). Once you got the air out of the system (like noted in previous messages) and the temperature of the gauge close to the temperature of the brewing water, the reading stays really constant. I always have this issue when starting up the pressure measurements, but in my case it's practically not affected by the pressure of the water supply. Once I get a stable reading I tried to run a lot of water in the sink, I drew water from the S1 hot water spout in between measurements and did anything to vary the incoming pressure, but the PF pressure readings were barely affected.

Wolfgang

Wolfgang,

Indeed, trapped air is a more likely explanation. I only mentioned my experience to alert members to another possible cause whose consequences potentially pose a more serious impact on the dryness of one's household than increased channeling.

dan_kehn wrote:
Anyway, while I was having such fun, I also installed a temporary pump pressure gauge (below). Hours of twiddling with pressure ensued shortly thereafter. I settled on 9.5 bar as my preferred setting for good crema production and channel-free shots, which is slightly higher than Schomer's recommended 8.2 bar.

Dan: Do I understand you correctly that you think channeling is reduced at 9.5bar versus 8.2bar?

Chas,

No, I meant to say 9.5 bar was a reasonable tradeoff between the risk of channeling and good crema production, although I don't claim that pressure setting is carved in stone by any means. The risk of channeling is perhaps marginally reduced from 9.5 to 8.2 bar, but it wasn't until 11 bar that the difference was flagrantly obvious. I produced some spectacularly bad channeling above 11 bar as part of an extraction diagnosis how-to I'm working on (inspired by Chris Tacy's http://malachi.coffeed.com/naked-diagnosis.html).

This topic actually brings up a related one I've been pondering lately.

The conventional wisdom of the perfect coffee shot depends on grind, tamp, 8.2-9.5bar group pressure and the 25 secondish shot. This has all been developed for the most part by users of the 58mm portafilter. However, we are using a 53mm PF.

If I compare this to a garden house in a house with 60psi water service, the water will flow slower out of the hose than it will if you screw a smaller diameter nozzle on the end of the hose. By the same token, it seems like at a given group pressure water will flow faster through the 53mm group than through a 58mm group even though the volume per unit time should be approximately equal.

So if you compare a 58mm machine with an S1 and both are adjusted to 9 bar, for example, then a 25 second shot from each machine will be the result of a faster flow rate in the S1. If keeping the flow rate the same in both machines is important for consistent extraction, then it seems like a lower group pressure on the S1 is necessary.

Am I on to something here or is there something else I am missing?

Concerning the Flojet, it cycles on and off quickly, presumably between zero pressure and full pressure. However, I don't notice any fluctuation in the water output at the grouphead. Hmmm.

Looking forward to Dan's Cimbali report.

Chas, I think you have a valid point and it bears out to my experiments leading me to the lower group pressure rather than the higher setting.