heatgunroast Senior Member Joined: 10 Feb 2003 Posts: 360 Location: NYC Expertise: I love coffee
Espresso: Dalla Corte Grinder: Mazzer Mini; Zass, Baratza... Vac Pot: Royal Balance Brewer (wanna... Drip: Various press and pour-overs Roaster: Heatgun, Dogbowl
Posted Mon May 26, 2003, 8:13pm Subject: Iso Tea wants to stay on 10 bar
Can't get new Tea to pour between 8 and 9. Grind adjustments seem to affect only the speed of the pour. First few seconds dark and syrupy, quickly change to lighter brown crema. Ideas? Lighter roasts tend toward sour.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Tue May 27, 2003, 4:39am Subject: Re: Iso Tea wants to stay on 10 bar
10 bar is about right. The pressure relief valve (which bypasses water back into the tank via the second hose) is set to around there. I get 10 bar for a single or double ristretto and about 9 3/4 for a double. When I first got the machine it was maybe a 1/2 bar higher, but the valve spring settles.
The Ulka pump develops about 18 bar max. People who have put on adjustable relief valves report that it is very difficult to get below 10 bar. This is the drawback of vibe pumps, the pressure can be controlled to be "about right," but it can't be set precisely.
To do better, you have to go with a rotary pump machine. These start at around $1600. They definitely do better than uncontrolled vibe pumps which put out 12 to 15 bar depending on shot time, but it's unclear how much difference they make compared to vibe pumps at 10 bar.
doubleristretto Senior Member Joined: 8 Feb 2002 Posts: 273 Location: Seattle Expertise: Just starting
Espresso: Expobar Brewtus Grinder: Versalab M3 Drip: French Press
Posted Wed Sep 10, 2003, 10:29pm Subject: Re: Iso Tea wants to stay on 10 bar
another_jim Said:
10 bar is about right. The pressure relief valve (which bypasses water back into the tank via the second hose) is set to around there. I get 10 bar for a single or double ristretto and about 9 3/4 for a double. When I first got the machine it was maybe a 1/2 bar higher, but the valve spring settles.
The Ulka pump develops about 18 bar max. People who have put on adjustable relief valves report that it is very difficult to get below 10 bar. This is the drawback of vibe pumps, the pressure can be controlled to be "about right," but it can't be set precisely.
To do better, you have to go with a rotary pump machine. These start at around $1600. They definitely do better than uncontrolled vibe pumps which put out 12 to 15 bar depending on shot time, but it's unclear how much difference they make compared to vibe pumps at 10 bar.
I was bored...too late to have coffee, so I started surfing various threads and ran across the above quote. This has probably been discussed again in the intervening months. In case it hasn't, I must say that I *have* successfully adjusted my Isomac Tea down to 9 bars (not 10) and I like it. Based on the discussion here perhaps the pressure in the PF is actually around 8.5. Nevertheless, I've decided I definitely like it better than 10. And I *definitely* like it better than 8.5 (tried that too). I doubt I'd notice a difference between 9 and 9.5, but I've settled for 9 and I'm happy.
Anyway, my real point is the Tea can be adjusted down to 9 bar, in case anyone's still under the impression it can't. You just need a phillips to take the housing off and a pair of pliers to adjust the spring.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Thu Sep 11, 2003, 10:51am Subject: Re: Iso Tea wants to stay on 10 bar
doubleristretto Said:
Anyway, my real point is the Tea can be adjusted down to 9 bar, in case anyone's still under the impression it can't. You just need a phillips to take the housing off and a pair of pliers to adjust the spring.
jeru Senior Member Joined: 18 Sep 2002 Posts: 44 Location: Corvallis, OR Expertise: Intermediate
Espresso: Isomac Tea Grinder: Mazzer Mini
Posted Thu Sep 11, 2003, 1:29pm Subject: Re: Iso Tea wants to stay on 10 bar
ok, since we're talking pressure on the Tea, I have a question for other Tea users:
During a typical shot for me, the heating element comes on (or sometimes goes off) and this results in an immediate pressure jump of close to 1 bar? I guess first off, just to verify, do other people get the heating element cycling during a shot? If so, do they get a jump in their pressure?
I wonder if the service amps to my outlet are not adequate to satisfy the pump and heater simultaneously?
Hi Jim. It's *very* easy to do. It's behind the boiler and near the bottom of the boiler. Easiest thing would be to post pictures. Trouble is I'll be off until next week. If I can, I'll post something tomorrow. But more likely will post pictures next week. I'm sure Chris Coffee could walk you through it as well. I can't emphasize enough that it's very easy. Adjusting the spring towards you lowers the pressure. Adjust in small increments. Small increments can lower the pressure 1/2 bar.
I think you'll like 9 bar which, based of posts I've read, may actually be approx 8 1/2 with pressure dropping at the head. Is that your understanding? Of course different blends probably do better at different pressure. I'm using Vivace's Vita for macchiati and I *love* what 9 bar does to the blend.
doubleristretto Senior Member Joined: 8 Feb 2002 Posts: 273 Location: Seattle Expertise: Just starting
Espresso: Expobar Brewtus Grinder: Versalab M3 Drip: French Press
Posted Thu Sep 11, 2003, 4:13pm Subject: Re: Iso Tea wants to stay on 10 bar
jeru Said:
ok, since we're talking pressure on the Tea, I have a question for other Tea users:
During a typical shot for me, the heating element comes on (or sometimes goes off) and this results in an immediate pressure jump of close to 1 bar? I guess first off, just to verify, do other people get the heating element cycling during a shot? If so, do they get a jump in their pressure?
I wonder if the service amps to my outlet are not adequate to satisfy the pump and heater simultaneously?
There is no doubt a technical solution to this that I'll leave to others more electrically. However, 1 whole bar is *not* normal. Approximately .2 bar is what I notice. Once I started adjusting pressure I started worrying about this as well. So I started opening the steam wand when brewing a shot to avoid any change. I never was able to observe any difference in shot quality. I've ignored it for now, but some day hope to get my EE dad to fix this (while he's adding a thermocouple to the e61 plug ;-)
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Thu Sep 11, 2003, 4:29pm Subject: Re: Iso Tea wants to stay on 10 bar
doubleristretto Said:
Hi Jim. It's *very* easy to do. It's behind the boiler and near the bottom of the boiler.
Thanks, I'll wait for a pic.
I like longish pull ristrettos, and the lower pressure of the Tea compared to unregulated vibe pumps is certainly an improvement for these (they ar undrinkable if the pressure is unregulated). I'd be curious to see if a further lowering helps.
jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Thu Sep 11, 2003, 8:47pm Subject: Re: Iso Tea wants to stay on 10 bar
Chris asked me to post a short explanation of what limiting a Vibe pump will and won't do for you.
The illustration is the "pump curve" (black graph) of most Ulka espresso pump models, showing the pressure (vertical axis) for a 25 second shot with the volume shown on the horizontal axis.
As you see can see, if you're pulling a ristretto or single on an unregulated Ulka, you're going to get a pretty awful shot, since it's pumping out at around 15 bar. If you're pulling a regular sized double of 50 to 60 cc, you'll be fine, getting 8 to 9 bar pressure.
If you put in a pressure limiting relief valve, you improve SHORT SHOTS ONLY.
Chris sets the Isomacs up at 10.5 to 11 bar, so all shots below about 50cc will be at that level. According to him, this is the industry standard setting for commercial vibe pumps. Reset it at 9 bar, and all shots below about 55cc will be at 9 bar.
If you insist on 80 - 90cc lungo shots, you'll be getting strong coffee brewed at 3 to 4 bar, not espresso. The pressure limiter won't help, the Ulka pump simply cannot maintain 9 bar pressure at that flow rate.
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