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Alex Duetto Owners-Please speak up!
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Discussions > Espresso > Machines > Alex Duetto...  
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,461
Location: UK
Expertise: I love coffee

Posted Wed May 4, 2011, 12:56am
Subject: Re: Alex Duetto Owners-Please speak up!
 

Bob_McBob Said:

I see where you are going from the description of the issue on the wiki.  I will check the next time it happens, but I got the distinct impression the humming was electrical and the motor was not actually starting, given the complete lack of noise and vibration.

Posted May 3, 2011 link

It's possible the pump has failed and jammed, or perhaps the motor, motors are not prone to failure on these machines used in a domestic environment.. However, if the pump chamber is empty and it spins against nothing, it is pretty much as you describe.... a vibration-less hum.
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Bob_McBob
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Bob_McBob
Joined: 30 Jan 2006
Posts: 456
Location: Waterloo, ON
Expertise: I live coffee

Posted Wed May 4, 2011, 1:03am
Subject: Re: Alex Duetto Owners-Please speak up!
 

DavecUK Said:

Test by running the pump on a cold machine and ensure water comes from the group, then lift the inlet tube out of the tank and hold upright whilst the machine fills, watch the water level in the tube, if it rises, then you need to clean the anti backflow valve.

Posted May 3, 2011 link

Could you please clarify this test description?  What do you mean by "whilst the machine fills"?  Cold machine, make sure water comes from group (turn off pump or not afterwards?), remove inlet tube and hold upright, then...

 
Chris
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MrShades
Senior Member


Joined: 16 Mar 2010
Posts: 16
Location: Swindon, Wiltshire, UK
Expertise: I love coffee

Espresso: Izzo Alex Duetto II
Grinder: Mazzer Super Jolly
Posted Wed May 4, 2011, 1:56am
Subject: Re: Alex Duetto Owners-Please speak up!
 

Whilst I appreciate that the original intention of this thread wasn't for it to become the "Ask DaveC a technical question" thread, it does seem to have evolved that way - and as you've been a great help in the past can I ask another quick (related) question Dave?

I've noticed that sometimes, when I fill the tank in my Duetto (pretty much to the top) and then leave it for a while (ie it doesnt do this immediately or on every occasion) my wife will call me and say "There's water coming out of your coffee machine" - and I find that there is puddle of water underneath the machine, where it appears that the water tank has overflowed.

Reading your previous comment concerning the anti-backflow valve - is it possible that a clean of the anti-backflow valve will solve this problem also, or am I barking up the wrong tree? I'm guessing that it's doing it during a tank refill.

To put the issue into perspective - the machine is 14 months old, used for a couple of shots every day and it's probably done this two or three times in total. Right now my insurance policy is to fill the tank, but not to brim it.

Any pointers or assistance would be much appreciated.

Thanks,

Shades
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,461
Location: UK
Expertise: I love coffee

Posted Wed May 4, 2011, 3:36am
Subject: Re: Alex Duetto Owners-Please speak up!
 

MrShades Said:

I've noticed that sometimes, when I fill the tank in my Duetto (pretty much to the top) and then leave it for a while (ie it doesnt do this immediately or on every occasion) my wife will call me and say "There's water coming out of your coffee machine" - and I find that there is puddle of water underneath the machine, where it appears that the water tank has overflowed.

Reading your previous comment concerning the anti-backflow valve - is it possible that a clean of the anti-backflow valve will solve this problem also, or am I barking up the wrong tree? I'm guessing that it's doing it during a tank refill.

Posted May 4, 2011 link

So many model revisions can't remember if yours vents from the expansion valve back to the holding tank, if not then 2 thru 4 don't apply).

  1. could be your overfilled or spilled some and it's trickling out later
  2. Could be the expansion valve venting back to the tank and causing it to overflow (would happen usually when filling tank and warming machine  up from cold).
  3. Could be the expansion valve venting back to the tank because it's set incorrectly (e.g. less than pump pressure) and/or pump pressure too high. Expansion valve should be set at 12 bar.
  4. Could be expansion valve leaking
  5. Anti-backflow valve could be letting by, but unless  steam boiler on this is unlikely to push much water into the tank, I would not expect more than 10 ml.
  6. The water is coming from somewhere else, or does it NEVER happen unless the tank is filled to the brim.

The expansion valve will allow approx 35ml water to escape when heating from cold, if you did fill the tank, you would have to fill it so that another 35ml would cause it to overflow, for the problem to be cause by a properly functioning expansion valve that vents back to the tank and then only on a cold machine.
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MrShades
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Joined: 16 Mar 2010
Posts: 16
Location: Swindon, Wiltshire, UK
Expertise: I love coffee

Espresso: Izzo Alex Duetto II
Grinder: Mazzer Super Jolly
Posted Wed May 4, 2011, 5:44am
Subject: Re: Alex Duetto Owners-Please speak up!
 

Many thanks for those pointers Dave... Yes, mine vents back into the tank (ie there's two pipes going into the tank).

It'd be great to catch it doing it - then it'd be pretty obvious whats happening, but your pointers will at least give me something to look for. (It's quite possible that it's the 35ml overflowing from the brimmed tank when cold and warming up).

I've certainly seen the drips left over from this 'leak' and they are coming from the back of the unit, directly under the tank.

Anyway - will keep an eye on it. Thanks again.
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chriscoffee
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Joined: 5 Mar 2002
Posts: 246
Location: Albany
Expertise: Professional

Posted Mon May 9, 2011, 4:56am
Subject: Re: Alex Duetto Owners-Please speak up!
 

The expansion valve on the Duetto II does NOT vent back to the water tank and has not on all production machine for the past year. I vents back to the drip tray in the right side. The second tube you see in the tank is from the top of the vacuum breaker valve not the expansion valve.

Chris Nachtrieb, Pres.
Chris' Coffee Service, Inc.
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MarkCan
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Joined: 19 Jul 2009
Posts: 8
Location: Canada
Expertise: I love coffee

Posted Mon May 9, 2011, 2:24pm
Subject: Re: Alex Duetto Owners-Please speak up!
 

Mine does the same thing.  Water does come out of the long hose that fits in the water reservoir.  How do you clean the anti-back flow valve?

I have taken my machine in for service twice now.  The pump runs but there is no pressure to the group head (the guage measures zero).  The vendor can't duplicate the problem when the machine is in his shop so has been unable to fix the problem.  On occasion there does not appear to be pressure to the steam wand and the hot water valve.  Very frustrating.  

I googled the problem and there was at least one other owner that appeared to be experiencing similar issues.  

Any thoughts?  My warranty runs out in August and I want this fixed before then.
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,461
Location: UK
Expertise: I love coffee

Posted Mon May 9, 2011, 4:19pm
Subject: Re: Alex Duetto Owners-Please speak up!
 

chriscoffee Said:

The expansion valve on the Duetto II does NOT vent back to the water tank and has not on all production machine for the past year. I vents back to the drip tray in the right side. The second tube you see in the tank is from the top of the vacuum breaker valve not the expansion valve.

Chris Nachtrieb, Pres.
Chris' Coffee Service, Inc.

Posted May 9, 2011 link

Chris, the posters machine is 14 months old and a UK model, this makes it quite possible for it to be the expansion valve tube venting back to the tank. I am aware that the US models had the expansion valve venting to the drip tray for at least a year.

Dave
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DavecUK
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Joined: 21 Sep 2005
Posts: 1,461
Location: UK
Expertise: I love coffee

Posted Mon May 9, 2011, 4:32pm
Subject: Re: Alex Duetto Owners-Please speak up!
 

MarkCan Said:

Mine does the same thing.  Water does come out of the long hose that fits in the water reservoir.  How do you clean the anti-back flow valve?

I have taken my machine in for service twice now.  The pump runs but there is no pressure to the group head (the guage measures zero).  The vendor can't duplicate the problem when the machine is in his shop so has been unable to fix the problem.  On occasion there does not appear to be pressure to the steam wand and the hot water valve.  Very frustrating.  

Posted May 9, 2011 link

To take the second issue first: does the pump pressurise the system and push water out of the group when the machine is cold....if not you may have another problem?

Cleaning the anti-backflow valve is simple, but does involve removing about 3 or 4 fittings starting with the one connected to the pump and working your way towards the valve fitting. My prototype was not PTFE taped and it was difficult to break the thread-lock, I did recommend to Izzo they use PTFE tape in future to make this procedure easier. If it's thread-locked, use care when undoing not to damage anything, when refitting clean all the thread-lock off (careful to not let any get in the pipes or pump), then use PTFE tape to refit (usually 7 turns on a thread is sufficient and it should go the same way as the thread is tightened). remember, ff you do the PTFE right, tightening things very hard is unnecessary, just nipped up to be sure they don't vibrate loose on the pump and on the pipes enough to line them up. Be mindful of how much of the thread you tape, because as you tighten if the threaded end gets exposed in the fitting you risk bits of tape coming off.

Use this link to see how to clean the valve, which is quite obvious really...the machine was an Izzo Alex II, but the part is the same.

Click Here (coffeetime.wikidot.com)

P.S If you use the machine in a very hard water area and don't treat the water correctly then this problem will recur, regular de scaling of the brew path can help, but is quite aggressive and a PITA, plus will not always cure the problem. You could try a simple de-scale of the brew path first and see if that fixes it before disassembly This problem will occur on all rotary pumped tanked machines used in hard water areas, when plumbed it's not noticeable because of the positive pressure of the mains water supply. It is not a problem unique to the Duetto.
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MarkCan
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Joined: 19 Jul 2009
Posts: 8
Location: Canada
Expertise: I love coffee

Posted Mon May 9, 2011, 7:37pm
Subject: Re: Alex Duetto Owners-Please speak up!
 

To answer your question - yes - when I turn the machine on cold the pump will push water through the group head.  Pressure measures around 9 bars.  Assuming I live in a hard water area - how often should I be de-scaling?  I was told 4 times per year.  I am using a product called "Ascor DC".  Is this a good product?  According to the instructions I need to mix the product with 1.5 litres of water then flush it through the system, 500 ml at a time in 2 mintue intervals.  

Should I set up a filtration system to improve the water quality?  Suggestions? Cost?

Sorry to be so naive but what is PTFE taped?  Is that the white teflon tape used by plumbers to help seal threaded pipes?

The long hose in my system does back-flow when the machine heats up.  Is that normal or should I be doing something about it?  

Sorry for the flood of questions but I am getting very frustrated with my machine's pperformance.
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