CRUZMISL Senior Member Joined: 21 Dec 2003 Posts: 111 Location: Ontario Expertise: I love coffee
Posted Tue Sep 21, 2004, 9:00am Subject: OK to bring boiler pressure past 1.3 bar?
Hi Everyone, I currently have my S27 set up at 1.3 bar ( at least that's what my guage says). Steam pressure is fantastic but brew water temp seems a bit on the low side (depending on the coffee). Is it ok to push up the pressure to get higher brew water temps? Is there a relationship with an increase in pressure to an increase in brew water temp? For example a .1 bar increase adds 4 degrees to the brew temp? Thanks, JOE
espressoDOM Senior Member Joined: 1 May 2003 Posts: 2,189 Location: Bay Area Expertise: I love coffee
Espresso: WEGA Lyra (vibe) Grinder: Mazzer Mini Vac Pot: (no more coffee equipment) Drip: French Press Roaster: Hot Top Roaster; Fresh Roast...
Posted Tue Sep 21, 2004, 9:25am Subject: Re: OK to bring boiler pressure past 1.3 bar?
my Wega was originally set @ 1.5 bars... the only downside for me was that I needed to flush more often so I tweaked it back to 0.9 bars to 1.1 bars and it works fine....
I don't think you will have a problem @ 1.5 bars except the machine may run too hot to pull shots w/o flushing a lot... 8oz. range...
DOM...evil genius ...Up to no good in espresso at all times... VIVA la parts de Espresso
terryz Senior Member Joined: 19 Dec 2001 Posts: 578 Location: Olympia, WA. Expertise: Professional
Posted Tue Sep 21, 2004, 10:15am Subject: Re: OK to bring boiler pressure past 1.3 bar?
CRUZMISL Said:
Hi Everyone, I currently have my S27 set up at 1.3 bar ( at least that's what my guage says). Steam pressure is fantastic but brew water temp seems a bit on the low side (depending on the coffee). Is it ok to push up the pressure to get higher brew water temps? Is there a relationship with an increase in pressure to an increase in brew water temp? For example a .1 bar increase adds 4 degrees to the brew temp? Thanks, JOE
1.5 bar is a reading on a gauge only. All gauges read somewhat different and accuracy is poor.
Raising the brew temp of your machine by changing the pressurstat is a touchy thing, but with patience you can accomplish it. !.5 is not a problem. Boiler saftey valves are typically set for 1.8 bar. so anywhere below that works.
I suggest that if you are trying to achieve higher brew temp that you make very small changes and wait 15 minutes between the changes. This will allow the machine to become stable with regards to tempurature.
Measure your temp with a digital thermometer of the strofoam cup and thermometer trick.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Tue Sep 21, 2004, 10:23am Subject: Re: OK to bring boiler pressure past 1.3 bar?
0.1 bar should raise your brew temperature by about 1F to 2F.
I've heard that on Sirai Pstats, the deadband starts increasing when they are set higher than 1.3 bar, although I don't know this for sure. Also, on some machines the safety valve will start to hiss as you approach 1.5 bar (like mine, for instance).
An alternative is to slightly raise the water level in the boiler, by raising the autifill wand a few millimeters at a time, and testing the result. Heat exchangers are set at a slant, so partially in the water, partially in the steam; raising the water level in the boiler, increases the length of HX in the water and makes it run hotter.
gamgra Senior Member Joined: 5 Aug 2003 Posts: 8 Location: Holland Expertise: I love coffee
Espresso: Futurmat Rimini, Vibiemme... Grinder: Fiorenzato t80 Roaster: Electr. hot air oven
Posted Tue Sep 21, 2004, 1:06pm Subject: Re: OK to bring boiler pressure past 1.3 bar?
At a boiler pressure of 1.3 Bar your boiler temp is about 125 C or 256 F , seems to me plenty hot enough. For your information I have added a pressure / temp list based on the "steam tables"
Perhaps you need to have your pressure gauge checked, I keep my machine, a two piston Futurmat Rimini, at 0.8 bar. this pressure gives me a perfect brewing temperature. Remember, no matter how high the pressure, your machine should still preheat for at least 30 minutes before use.
CRUZMISL Senior Member Joined: 21 Dec 2003 Posts: 111 Location: Ontario Expertise: I love coffee
Posted Tue Sep 21, 2004, 7:21pm Subject: Re: OK to bring boiler pressure past 1.3 bar?
My machine is on 24/7 so that's not the problem. My guage could be off though which wouldn't surprise me. Jim, I'd like to try your advice of a higher water level in the boiler. Do I want to push the wire in for a higher water level or pull it out? I forget. Also, how much should I be moving it while testing? 1mm at a time? Thanks, Joe
Posted Tue Sep 21, 2004, 8:33pm Subject: Re: OK to bring boiler pressure past 1.3 bar?
Just out of curiosity, how much are you flushing before pulling a shot?
I ask because when I tried out a Cimbali Junior for the first time, I flushed the usual amount for an E61 (around six ounces). Well, that was way-y-y too much. As Jim pointed out, how much of the heat exchanger is immersed makes a difference, in addition to its total volume and how aggressively the group design heats up. In Junior's case, the right amount is closer to 120ml max, and if you've pulled a shot in the last five minutes, about half that. It's a guess, but given that yours is also a commericial machine, the S27 may be similar.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Tue Sep 21, 2004, 9:32pm Subject: Re: OK to bring boiler pressure past 1.3 bar?
CRUZMISL Said:
My machine is on 24/7 so that's not the problem. My guage could be off though which wouldn't surprise me. Jim, I'd like to try your advice of a higher water level in the boiler. Do I want to push the wire in for a higher water level or pull it out? I forget. Also, how much should I be moving it while testing? 1mm at a time? Thanks, Joe
If the probe is straight down from the top of the boiler, you move it out (the boiler stops filling when the water touches the probe).
How much? Who knows? I'm told this is one of the things Italian Baristas do to tune their their machines (i.e get the watr temperature they want at the boiler pressure they want), but the amount will depend on the details o your heatexchanger, which I don't know.
Before doing anything, measure where it is now, so you can reset it.
Judging by the nuova ricambi page, the boiler is vertical, and the heatexchanger itself a vertical bladder, so you'll need to change the water level a lot more than 1mm, more like 1 cm to get any change. You'll need to measure the temperature before and after the change to interpolate or project the right amount.
Finally, what Dan says will apply even more to the S27, since it looks like a "cold-nose" machine, with a light group bolted to the boiler for heat. You probably want to flush no more than 2 ounces to heat the group, and stabilize the heat exchanger.
This stuff absolutly requires a thermocouple in the PF. Theres a cheap one here
Posted Thu Sep 23, 2004, 12:07pm Subject: Re: OK to bring boiler pressure past 1.3 bar?
jim_schulman Said:
0.1 bar should raise your brew temperature by about 1F to 2F.
I've heard that on Sirai Pstats, the deadband starts increasing when they are set higher than 1.3 bar, although I don't know this for sure. Also, on some machines the safety valve will start to hiss as you approach 1.5 bar (like mine, for instance).
An alternative is to slightly raise the water level in the boiler, by raising the autifill wand a few millimeters at a time, and testing the result. Heat exchangers are set at a slant, so partially in the water, partially in the steam; raising the water level in the boiler, increases the length of HX in the water and makes it run hotter.
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