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Troubleshooting low brew water temperature in an E-61
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lttlscamp
Senior Member


Joined: 25 Dec 2009
Posts: 45
Location: Toronto
Expertise: I like coffee

Espresso: Rocket Giotto Evoluzione
Grinder: Baratza Vario
Posted Tue Jun 17, 2014, 5:59pm
Subject: Troubleshooting low brew water temperature in an E-61
 

My Evolutionze is sick.

I'm having a problem with low brew water temperature at the grouphead that is really confusing me and was hoping you folks could give me some direction in troubleshooting it.

When I first got my machine five or so years ago I put a thermometer in it.  At idle the thermometer consistently read around 207F.  When I'd do a cooling flush the temp would shoot up to around 213F, I'd get the "water dance" of super heated water at the shower screen and I'd pull my shot as it came down to around 208F.  Everything was great.

About a year or so ago I noticed a significant drop in idle temperature.  It never got over more than 202 or 203F, the "water dance" was gone and moreover the flush temperature never went above 208F.  Recovery time was really long...minutes..after just a single shot and it never recovered to above the low idle temperature.

Fast forward to around a month ago and the exhaust port developed a leak while pulling a shot.  So I got a hold of a rebuild kit for the grouphead and replaced all of the gaskets, o-rings, springs, pins and the gliceur.  While I had it open I took a good look for scale and it all looked pretty clean.  The unit is plumbed in and I only use softened RO water and descale a few times a year.

After the rebuild it was like a new machine!  Idle temps around 207F and flush temps back up around 215F.  And I really had to flush for a long time to get the temp to drop below 210F at the grouphead.  The "water dance" was back!  Recovery time was fast. I could easily pull several back to back shots.  

This lasted about a month.  Now I'm right back to where I was before the rebuild.  Low idle temp, low flush temp slow recovery and lousy tasting espresso.

I'm frustrated because I really thought I had put the problem to bed (well, at least my leaky exhaust port is fixed!).  When I measure the temperature of the water in the cup it's a full 20F or more cooler than what's at the grouphead...with three different thermometers!  Is it really possible to lose that much water temp so quickly?

Can anyone help me out with this?
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SStones
Senior Member
SStones
Joined: 24 Nov 2012
Posts: 474
Location: Canada
Expertise: Professional

Espresso: Giga 5, ECM Giotto, Rocket...
Grinder: Anfim Milano-Best
Vac Pot: No  :(
Drip: Some $30 thing from Walmart
Roaster: I buy pre-roasted.
Posted Tue Jun 17, 2014, 6:28pm
Subject: Re: Troubleshooting low brew water temperature in an E-61
 

Sounds like something is blocking the flow from the upper Heat-exchanger outlet to the upper grouphead inlet. With that blocked, you'll get poor siphoning, so the grouphead won't heat itself properly; and when brewing, you'll get almost entirely lower-pipe flow, less heated water from the low end of the heat-exchanger; cool, nasty coffee.

Visually inspect the Gicleur again, to make sure it's not scaling up. This is a fast way to get some idea of how much calcium to expect.
Then carefully remove the upper tubing from the top of the heat exchanger to the top of the grouphead. Almost certainly the blockage will be visible once that tubing is removed from such great big connections to great big holes.

When retightening the tubing in its compression fittings, get the tube positioned well and tighten both fittings loosely, ensuring good alignment. Then tighten just a little bit more.
Overtightening the compression fittings doesn't make them last longer, it just stresses them and makes it the last time you'll ever tighten them.
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boar_d_laze
Senior Member


Joined: 21 Nov 2006
Posts: 1,066
Location: Monrovia, CA
Expertise: I live coffee

Espresso: La Cimbali M21 DT/1 Junior...
Grinder: Ceado E92; "Bunnzilla"
Vac Pot: Royal Coffee Maker
Drip: Chemex + Kone; Espro Press
Roaster: USRC Sample Roaster
Posted Tue Jun 17, 2014, 6:33pm
Subject: Re: Troubleshooting low brew water temperature in an E-61
 

There are lots of possibilities.  If's Steve's suggestions don't work out for you, the first thing I'd look at first is the pressure gauge, and if pressure is low (compared to what it used to be) or inconsistent, or if your machine makes a clicking sound, consider the p-stat as the likely culprit.  

FWIW, the first rule of prosumer p-stat replacement is to swap the stock p-stat for a Sirai, if a Sirai fits.  

Good luck,
Rich
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DavecUK
Senior Member


Joined: 21 Sep 2005
Posts: 1,378
Location: UK
Expertise: I love coffee

Posted Wed Jun 18, 2014, 5:45am
Subject: Re: Troubleshooting low brew water temperature in an E-61
 

You don't give enough factual information about the problem, but if the sealed brew circuit is leaking in some way, sufficient air in the system will stop the thermosyphon and the group will cool. The best way to spot this is, when you next get a cool group,  with no portafilter on, lift the lever and engage the pump. if there is a significant delay until water comes out of the shower screen, then air is in the system.
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lttlscamp
Senior Member


Joined: 25 Dec 2009
Posts: 45
Location: Toronto
Expertise: I like coffee

Espresso: Rocket Giotto Evoluzione
Grinder: Baratza Vario
Posted Wed Jun 18, 2014, 10:45am
Subject: Re: Troubleshooting low brew water temperature in an E-61
 

SSTones:

Thanks for the pointers. I'll open things up and take a look for any obstructions.

d_laze:

The pressure gauge reads 1.1 bars which is what the pressurestat is factory set for.  It also has a Sirai pressurestat but there's nothing saying it or the gauge could be malfunctioning.   I do hear a clicking when the p-stat kicks in but no other clicking.

DaveUK:

What more factual information can I provide other than the behavior I'm witnessing?  I'll test for the delay.

Thanks
Jay
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DavecUK
Senior Member


Joined: 21 Sep 2005
Posts: 1,378
Location: UK
Expertise: I love coffee

Posted Wed Jun 18, 2014, 4:46pm
Subject: Re: Troubleshooting low brew water temperature in an E-61
 

lttlscamp Said:

What more factual information can I provide other than the behavior I'm witnessing?  I'll test for the delay. Thanks
Jay

Posted June 18, 2014 link

you give a lot of information, but it generates more questions,  things like

  1. You mention it's plumbed in which should make emptying of the brew circuit very difficult indeed, even from slow leaks as the normally 2+bar water pressure prevents this. However you say it's softened RO water, so is your feed directly from the RO system, what's the pressure?

  2. Why are you descaling

  3. Running on pure RO water will give you copper corrosion problems, unless you  run a calcite re-hardener or treat the water in the correct way. I know because I use RO water which i then treat

  4. As I don't know how much positive pressure you have or indeed if air is entering the system from other sources, did you disassemble and clean the anti back flow valve? Is any water coming from the expansion valve when it shouldn't be, have you checked it? Have you checked for any leaking fittings around the brew circuit internally. As I say plumbed into positive pressure should eliminate these as a cause of minor cooling problems, the positive pressure is usually enough to keep the circuit full. However if your feed pressure is lower than 1.2 bar, then it's possible the brew circuit could still be loosing water somehow.


The feed tubes to in the thermosyphon circuit on that machine have a larger diameter than standard, so it's unlikely they have blocked...it's always possible I suppose, but fairly difficult to block on that specific machine. The one I reviewed/tested for about a month was in July 2010, so with yours, 1 year earlier, there may have been changes, but unlikely.
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F1
Senior Member


Joined: 28 Dec 2010
Posts: 6
Location: Unitred States
Expertise: I like coffee

Posted Fri Jul 18, 2014, 12:54am
Subject: Re: Troubleshooting low brew water temperature in an E-61
 

Did you find a solution lttlscamp? I have a Rocket giotto PP V2 that for the past 4 months has been behaving just like yours. Normal operation for almost a year was idle temp at the brew head of 206F after one hour using Eric's thermometer. I could pull consecutive shots 2-3 minutes apart at 200F measured with a Scace device. Now the machine idles at 199F, sometimes at 201.5 and sometimes at 203F. It's all over the place. If I pull a shot it takes about 6-7 minutes to recover to a group temp of 197F which is what I need to be able pull a shot at 200F at the puck. The pressurestat seemed to be working fine but I went ahead and got a new one. It made no change. I replaced all the valves, springs, and gaskets in the group. Again, it made no change. I changed the OPV, Vaccum breaker, safety valve, and Ulka Pump. No change. I've descaled the machine even though the mushroom was completely clean. No change. I am at a loss. In the Home Barista forum I have found several people with a very similar problem all with Rocket HX machines and none has found a solution.
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