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My Gaggia TS suddenly changed how it brews
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Discussions > Espresso > Machines > My Gaggia TS...  
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Rescue28
Senior Member


Joined: 12 Aug 2011
Posts: 12
Location: Colorado
Expertise: I like coffee

Posted Sun Nov 25, 2012, 10:11pm
Subject: My Gaggia TS suddenly changed how it brews
 

Several months ago, I purchased a Gaggia TS machine.  For the first several months, I would pull an espresso shot (wonderful), and as I did so I noticed that the pressure gage would drop to zero.  Then, after waiting a minute or two, it would be back up to 1.0 bar, the steam would be fine and I'd foam the milk.  Notice that I could NOT immediately steam the milk.

About a week ago two things occurred.  First, the espresso shot is different.  As the espresso is exiting the head, it gets very foamy and the crema is mostly large bubbles and not at all thick.  The foam in the cup dissipates quickly, leaving only the espresso with no crema whatsoever (see below; I know what causes it).  Second, I now notice that the pressure gage never drops at all, i.e., it remains at 1.0 bar.  But the other side of the coin is that I can now steam the milk immediately.

What has happened is that the water is almost super hot, causing a steam/water mixture that, in turn, is causing the large bubbles of boiling water to eliminate any crema.  So, what I have to do is to first 'bleed' the excess boiling water off the head for several seconds and then pull the shot.  It works okay, but why on earth would the machine just change overnight?  Is it now working properly whereas it wasn't before?  Is it now working improperly?  I am perplexed.  Clearly, the water is much, much hotter, because it appears to almost be steam when it exits the brew head, making for the foamy coffee, unless I bleed off the steam/water mixture first.  And the fact that the pressure gage doesn't budge, whereas it used to dip to zero and as I was pulling the shot.

Any suggestions would be appreciated.  The engineer in me tells me that things (especially mechcanical) don't just change for no reason!
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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
Posts: 7,947
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Mon Nov 26, 2012, 6:56am
Subject: Re: My Gaggia TS suddenly changed how it brews
 

Interesting.

First off, the machine is a HX machine and the one thing you did NOT say was if you bought the machine new or use, nor,  how long you let the machine warm up before use. I strongly suspect that either you now are waiting for the machine properly or that the vacuum breaker was stuck and now it is working properly. What you describe NOW is the proper operation for a HX machine.

Overtemp water in the HX brew system when the machine sits idle, is NORMAL and you should not have been able to walk up and pull a shot. The fact that the pressure dropped to zero also points to a stuck vacuum breaker valve. The valve allows the air in the boiler to escape until the boiler starts to boil water and producing pressure at a rate faster than the valve allows pressure to escape at, thus closing the valve. It is gravity operated so they commonly have problems on used machines.

If the valve has been stuck, the boiler will build up false pressure and turn the heater off too soon, once you let the pressure out (there isn't much pressure there to begin with as the water really isn't at boiling temp) the heater will turn back on and the system will operate normally.

The temp of a HX machine is controlled by a device that measures pressure in the boiler (the Pstat). If the valve is operating properly, the air trapped in the boiler will escape to the room until the water truly starts to boil at which time the valve closes and pressure builds up in the boiler. If the valve is stuck, the trapped air in the boiler will pressurize also but the Pstat will sense this and turn the heater off before the boiler is to temp. Once the false pressure is bled off, the system will operate normally.

At 1 bar of boiler pressure, you will have (from memory, see a chart for exact temp) about 250 deg F water in the boiler, the heat exchanger is designed to tap into that heat and provide water to the brew system at a given rate. If that rate is too slow or the system has sat idle for a while the temp in the HX tube will be too high and the water will need to be purged from the system until it is operating properly. This over temp water is "boiling hot" in your words, as it is flashing to steam as it leaves the group head, you need to flush the water until the water stops flashing to steam.

Please see how I learned to love the HX http://www.home-barista.com/hx-love.html for a better idea how to work your machine.

I work different than this document though, I prep my PF and flush the machine without anything in the group head, it is VERY easy to see the water "dance" and thus detect the temp of the water with the empty gropup head VS through the empty PF. YMMV!

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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Rescue28
Senior Member


Joined: 12 Aug 2011
Posts: 12
Location: Colorado
Expertise: I like coffee

Posted Mon Nov 26, 2012, 8:08am
Subject: Re: My Gaggia TS suddenly changed how it brews
 

Wow!  Thank you.  I think you have figured it out.  By the way, the machine was new.  Also, the machine is generally on for, oh, around 1 to 1.5 hours before I pull my wife's espresso.

As a possible point of interest, I live at almost 10,000 ft altitude in the Colorado Rockies and I sometimes wonder if the high altitude affects any of this stuff.  Probably not since the water is under pressure, but I do wonder.  I stumbled upon the bleed off method, and thanks to your comments I will now pay more attention to ensuring I am letting the steam purge out of the machine.  I let it purge for a longer period of time today and the espresso was a LOT better.  And it is really nice that I can immediately foam the milk.  I'll have to admit that one of the reasons I got the Gaggia was because I was under the impression that I could steam milk right away, and not have to wait as I did with my old (and much cheaper) machine.  So when I got the Gaggia going, it was a bit of a let down when that wasn't possible.  Now I am a happier espresso maker!

Not sure what some of the acronyms mean:  PF, VS, YMMV!!  But I get the gist!

Thanks again.  Cheers mate.
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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
Posts: 7,947
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Mon Nov 26, 2012, 8:20am
Subject: Re: My Gaggia TS suddenly changed how it brews
 

Glad to help.
PF           Porta Filter
GH          Group Head
YMMV      Your Millage May Vary (as in gas millage claims from car manufacturers in advertising or in other words, you might have a different view/result)
VS           Versus

Inside the machine the pressure vs outside is more constant but when you let the pressure out, as you know, the water will boil at a lower temp so you will need to adjust your purge to account for this, you should be brewing at 195 to 205 F

An hour should be fine but longer does not hurt anything, I sometimes leave my machine on (like this last weekend) for 4 days straight. If the machine has auto fill (yours does) as long as there is water either in the machines water tank or the machine is plumbed in, the machines can do this with no problem.

New, well it sounds like there was some gum or something causing the valve to stick shut. Now that it is working properly, you should be fine. You might get some dirt in it and it may stick OPEN until the dirt is cleaned out

I bought a used 2 gp (group) commercial machine because it would not hold pressure for the cost of salvage, $75. All that was wrong was some dirt in the Vacuum breaker valve so it did not seal. A quick twist of the stem of the valve while it was trying to heat up and the dirt got cleaned out and the machine is in service for me now, no extra money for parts etc. spent.

You should be able to pull your shot AND steam at the same time. At first it is a lot going on at the same time but with some practice you get the hang of it. YMMV! LOL! CYA, IMHO..

Enjoy!

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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Rescue28
Senior Member


Joined: 12 Aug 2011
Posts: 12
Location: Colorado
Expertise: I like coffee

Posted Mon Nov 26, 2012, 11:10am
Subject: Re: My Gaggia TS suddenly changed how it brews
 

Now I'm feeling positively 21st century!  Maybe I should try that Twitter thing?!!

As luck would have it, I was bleeding off the high temp water without the PF attached and as you indicated I was noticing the water/steam dancing around where it exited and you could indeed see when the water was reduced to a good brew temperature.

So, life is good and my wife is no longer threatening to move to Italy or France to get a good espresso again.  My next challenge is to find good decaf espresso beans, since I have a serious reaction to caffeine.  I know, I know, that's sacreligious in the world of espresso, but I have no choice (my wife, on the other hand, gets the good stuff).  I am sure that when I order a decaf cappuccino in Italy they cringe ... but they all have them!

Ciao e grazie.
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calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 7,947
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Mon Nov 26, 2012, 1:03pm
Subject: Re: My Gaggia TS suddenly changed how it brews
 

Remember at your altitude, the water will boil at a lower temp. An internet search turned up the following info.....  
At higher altitudes, water will come to a boil at lower temperatures than at sea level. The pressure at 10,000 ft is 20.58 inches Hg, and so the boiling point is 194.7 F.

That is just at the LOWEST you want to brew at, espresso and coffee should be brewed at 195 to 205 F so if you flush until the water stops flashing to steam, you will need to wait a little until the temp climbs back up to the brew zone. So in your case, you will be brewing slightly ABOVE boiling. You should get back pressure from the coffee and the pressure in the PF should be at the 9 bar of brew pressure so it will not be flashing into steam while brewing but you need to learn what that temp looks like and how long to wait after your flush to be at the correct temp.

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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Rescue28
Senior Member


Joined: 12 Aug 2011
Posts: 12
Location: Colorado
Expertise: I like coffee

Posted Mon Nov 26, 2012, 1:26pm
Subject: Re: My Gaggia TS suddenly changed how it brews
 

Great information.  Thanks.  I'll work on finding the proper temperature.
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