Izzo Alex Duetto II Need Help - Page 2

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
Team HB

#11: Post by JRising »

g12196 wrote: I thought the brew boiler water fill line only passes through the steam boiler for pre-heating, and that it did not source water to the steam boiler, and that seems to be confirmed in the (incomplete) diagram. In my actual machine I see that the two boilers are only connected via the expansion valve, (which I'm not 100% sure what function it performs), could the brew boiler be back-feeding water into the steam boiler via a faulty expansion valve device?

Last 2 questions for now,
1) is there a way to test the ruptured heat exchanger hypothesis as I'm sure they are not cheap?
2) does your hypothesis still hold true when you consider that if I only run the steam circuit, eg. power up both boilers, wait till they both come up to temp, and operate the steam valve to steam milk that works fine? It is only when I try to activate the group head and draw water from the brew boiler that all the problems I previously described occurred.
Thank you
The brew boiler could be leaking into the steam boiler at that "heat exchange pipe" that passes through the steam boiler if the heat exchange pipe were ruptured, but that's very unlikely if the machine's never been frozen.

Testing it would be a lot of work, ie. removing the expansion valve and the little trapeze it lives on, removing the inlet fitting to the heat exchange pipe and the valve, capping the outlet where the expansion valve used to be (Or capping at the bottom), pressurizing the pipe and watching the vacuum breaker to see if the pipe is leaking out into the boiler or not... But removing the boiler-fill-solenoid and seeing if you can suck air through it in either direction would be easier.

Side note: The expansion valve relieves pressure from the brew circuit before it gets dangerously high. When water gets hot, it expands, with the brew valve closed and the check valve closed, that's like heating water in a closed can. It will explode if not released safely.


#12: Post by DaveC »

I have a test for you to try and identify the problem.

Turn the service boiler off.....

Then power on the machine, place a blind filter in the group and pull a shot against the blind filter for a minute or two, repeat this 4 or 5 times. Stop when you see water pooling under the machine, or (if the vac breaker is stuck closed, or it's so full the pressure from the pump closes it)...if you see the steam pressure gauge going up. If you see this stop, ASAP as overpressure can damage the gauge, or open the hot water valve.

It's extremely unlikely the HX unit has fractured or has a hole in it...and more likely the autofill solenoi (as advised earlier in the thread)d. If the HX in the service boiler had a hole in it...you would also experience brew boiler over heating and other issues from the group when the service boiler is on.

If you do suspect an HX problem a simple test would be to turn the brew boiler off (I think the MKII still allowed that with a long press of the right hand PID button), and then lift the group lever all the way...the steam pressure in the service boiler will push water out of the group (much more than the passive amount that usually comes out) and steam pressure will drop.

P.S. If the Brew Boiler off function is removed...then get the machine (both boilers) up to temp and switch off..then proceed with the test.

g12196 (original poster)

#13: Post by g12196 (original poster) »

Thank you for your test suggestion, I've been away the last several days so I just got to your post. Anyhow I plan to double-check the autofill solenoid tonight because of your suggestion, because of Ockham's razor, and to be sure I'm not going down a rabbit hole with the HX idea.
I'll check it for debris possibly holding the valve open and I will also open the port 2 side and activate and deactivate the pump to be sure the valve is opening and closing properly. I've done this test already but I plan to repeat it again just to be sure.

Then after that, I will try your test recommendation for the HX.

While I was away I also thought of a test of the HX and wanted to get your opinion. Here are the steps.
1. Completely drain the Steam boiler of water with the machine off by removing the hot water feed line at the bottom of the boiler, once drained tighten this backdown.
2. remove the electrical leads to the autofill solenoid to be 100% sure it will not open during this test.
3. Power up the machine and only activate the brew boiler leaving the steam boiler off.
4. Pinch the clear hose line from the expansion valve or remove the connection to the steam boiler altogether so that there is no sneak path for water to get from the brew boiler to the steam boiler. (keep a close eye on the pressure as I understand this is here for safety)
5. Remove the fill level probe and nut on the steam boiler, and confirm with a flashlight and or Qtip that there is no water in the steam boiler before doing the next step.
6. Activate the group lever, to draw water from the pump through the HX through the group head.
7. Closely monitor the opened fill probe hole for water rising inside the steam boiler.

If the HX pipe is in fact ruptured, water would leak into the steam boiler, thereby filling the boiler with water and eventually beginning to leak out the opened fill probe hole or the steam wind as I've witnessed in the previous testing.

If the steam boiler does not fill with water then I can conclusively say the HX is not ruptured. I could then run a second test doing to see if the expansion valve has failed by doing all the steps above except removing the pinched hose isolation of the expansion valve. Again if the steam boiler fills with water because the autofill valve is turned off the only way would be through a failed expansion valve back-feeding water from the brew boiler.

Let me know what you think of this test or if I may have missed something.

Team HB

#14: Post by JRising »

You could do your 7 step test in only 4 steps.

Remove the short straight copper tube between the Boiler Fill Solenoid and the elbow on top of the steam boiler where its water enters.

Put down a lot of towels to protect everything. Disconnect the electrical leads from the boiler fill solenoid so it can't open.

Run the pump for a short burst.

If the water flows through the closed boiler fill solenoid, clean it/descale it/inspect it. It's leaking.

If the water flows up and out of the elbow that's only supposed to take water IN TO the steam boiler, then the Heat Exchanger is ruptured and filling the boiler through its own leakage.

g12196 (original poster)

#15: Post by g12196 (original poster) »

I appreciate everyone's help with this, I've not been able to get back to it till last night but I've had a big discovery and I'm 95% of the way to my machine working normally again like it has for many years. First I feel some background is necessary to explain how I got to where I was with my first post on Home-Barista.
10 months ago, my Alex Duetto 2 exhibited an issue where the reservoir water was full, yet intermittently when we turn on in the morning it would sound a low-level water alarm, and basically stop working. After awhile it became every time we turned it on. I troubleshot it and believed it was a faulty fill valve and I ordered the solenoid and valve assembly from Chris's coffee. Powered up the machine it worked great for about 2 days then it began to have the water alarm issue and it wouldn't draw water from the reservoir. I took apart the fill solenoid and put the old one in and it worked, meaning the old one was never the root cause. It turns out it was scale blocking the fill valve orifice. At this point I was so annoyed with all these scale issues, I decided to take apart my entire machine, and removed every part, both boilers and anything that ran water through it. I soaked all these parts in descaler solutions for several days. After that, I put everything back together, the fill alarm problem was solved, but I now had multiple other problems that could not be explained; extreme temperature swings on the brew boiler temperature, at times rising to 239 degrees and as low as 160 F, the OPV valve would pop intermittently when trying to brew water. The pressure on the brew boiler was too low. I sent several videos to Chris' coffee and he gave me a lot of suggestions but in the end, I just gave up, I wasn't able to solve it so I walked away from it in March 2022. Work got busy and finally got back to looking at it this month with a fresh perspective.
Jan 1, 2023 - this is the point where I posted on this site what my symptoms were, low brew boiler pressure, high steam boiler pressure, and water spewing straight out of the OPV, realizing the steam boiler is flooding, excessive water flowing into the drip tray and brew temperatures sagging to around 170 F.
Jan 14, 2023 - I reinspected the fill solenoid as many of you had suggested, and I did find 3 salt size crystals on the perimeter of the small rubber plunger. This would prevent the plunger from closing and thereby allow water to flow past the valve when I was drawing water from it while operating the group lever. I cleaned it up, drained most of the water out of the steam boiler, turned it on, up to temp and pressure, and started drawing water through the group, I did this several times and the overfilling of the steam boiler and the steam boiler pressure was normal, temp was normal. No more flooding boiler. Thank you.
However this did not solve all my problems, I still had excessive water in the drip tray, and I still had very low pressure on the brew boiler. So now I focused on the Expansion valve as this is the only other way the steam and brew boilers are connected.
Upon examing the expansion valve to check if there were any deposits preventing it from working, I discovered something major; looking down into the body of the valve with my pen light I could see the spring and plunger were separated from each other and when I tried to pull the spring out it wouldn't come out something was blocking it from moving. Then I noticed the threads from the t-connection (that branches to the copper pipe to the drip tray and to the hose back to the steam boiler) were threaded in so far to the copper body of the expansion valve that the threads were impinging upon the spring and plunger assembly preventing it from moving or working at all.
I must have over-tightened that connection when I reassembled my machine after the major descaling project last year.
After I corrected this and put the expansion valve back in the machine it seems to be working, there are no pressure or temperature issues, and I made espresso and foamed milk twice since then.

The only issue remaining is there is a constant drip from the expansion valve into my drip tray, which becomes a small steady trickle while pulling shots. In addition, even though my steam pressure is where it should be about 1.3 bar, it barely has enough power to steam a small cup of milk as the pressure is dropping quicker than it used to.
Also when I put the blind basket in the portafilter I get a steady stream of water into the drip tray.
Do you think that although the spring and plunger looked physically okay perhaps they could have been damaged and need to be replaced to stop the dripping and hopefully restore longer continuous pressure out of my steam boiler?
I apologize for the long post but I think adding all the details may help someone else someday.
Thank you.