Hello all,
this is my first post, so be gentle!

I have had an Izzo Alex II dual for about 7 years, and it has always made good coffee. Then I recently realised that my shots were tasting sour, and it also occurred to me that the water no longer 'boiled' at the beginning of a cooling flush. I overhauled the grouphead, and increased the boiler pressure from 1.1 bar (where it had been happily sitting from new) to about 1.3 bar, which worked for a while, later I had to increase it to 1.5 bar (on the red line!), but even at that setting the brew water is still now too cold again. On the advice of the original seller, I replaced the pressurestat, in case the boiler temp was floating around, or the heating element was taking some time to cut in etc, but to no avail.

The only other thing that I can think is that there is a problem with the heat exchanger, maybe has a blockage? (it is regularly descaled and I always use filtered water). does anybody know if it is removable, or an integral part of the boiler?

Any other thoughts would be appreciated as I'm down to the Moka pot at the moment!

Cheers,
Trev

When was the last time you descaled the boiler and heat exchanger? Heavy scale will insulate the heat exchanger and make it run cold but that is just one possibility. Do you turn the machine off or let it run 24/7? If you open the steam wand control, does the boiler pressure drop like a rock and the steam fade to almost nothing (stuck vacuum breaker giving you false pressure)?

Thanks for your reply:
It's descaled on a regular basis, and I never seem to get much scale out of it anyway. The machine is only on when I want to make coffee, not all the time, allowing 45 mins to heat through. The vacuum breaker is working fine, and the boiler is giving plenty of steam. I found this site

http://coffeetime.wikidot.com/izzo-alex ... turn-valve

My return pipe passes a small amount of water after the brew water stops, but the non return valve seems to be ok internally.

I'm still at a bit of a loss

Thanks,
Trev

Just a thought - do you / have you run descaler (commercial strength Dezcal or equiv, concentration not critical) through the HX circuit only? If not, you might give this a try. Do you know the volume of your HX loop? If not, estimate it at 300ml or something in that order (over is better than under). You will need to run this equivalent volume of descaler into the HX several times to get anywhere near working strength in the HX circuit. Each time, at operating temp, let it sit for a half hour or so. Each time you run in the new volume of descaler, see if your temp seems to be going up a bit. The water coming out of the shower head should be very citrus flavored, really bitter. Run through a couple of liters (or more) of descaling solution. You might notice a significant rise in temp of the water coming out through your shower screen after a half dozen cycles of this. After, flush the HX thoroughly. Hope it works for you. It did for me once (same symptoms, except I never touched my pressurestat) when I was away from my Rocket for a couple of months.

If this doesn't do it, I'd revisit Dave's scale comments again, because for whatever the reason, your heat exchanger circuit is not exchanging heat. There have to be a very limited set of reasons for this, and if you followed the directions/advice carefully in the link you posted, you have eliminated one of them. The boiler water is hot as blazes (1.5 bar, plenty of steam - eventually you're gonna want to turn that pressurestat back down to 1.1 or so) - that's another one eliminated.

I have had an Izzo Alex II dual . . .

There's no such "animal". Is this an Izzo Alex II Duetto? i.e. a dual boiler machine? If so, you need to remove and inspect your temperature sensor in the brew boiler.

While this pressurestat increase to 1.50 bar will certainly affect brew water temp (the brew water passes though a hx in the stm boiler), the result will be minimal . . . assuming you do, in fact, have a dual boiler machine.

I assumed it was actually a Alex II which is the heat exchanger version.

http://www.chriscoffee.com/products/home/espresso/alex

As did I . . . especially from his description . . . until I saw the word "dual" and the statement about having it for seven years.

erics wrote:There's no such "animal".

Well I'm looking at it on my worktop! seriously the dual in those days (on the Izzo Alex) referred to dual water supply (tank or mains) that's what it was called on my paperwork, and I added it for completeness.

It doesn't look as if the problem is scale, I'm looking at the possibility that the problem is due to a breakdown in the thermosyphon system due to a leak. the OPV looks as it it is passing when the machine is idling, so when brew water is pumped there is a delay between the pump starting and the water being expelled from the grouphead. I've got a new OPV on order and will see if that makes a difference.
I'll post my findings when I've tried it
Cheers,
Trev

I'm looking at the possibility that the problem is due to a breakdown in the thermosyphon system due to a leak.

Sounds like a very good source of the problem (the leak) but not from the OPV in your particular case. If there is any flow from the OPV relief port as the machine is warming up or just sitting there idling, the check valve in the hydraulics to the hx has failed. This is the part referred to in the Coffeetime article you linked.

Another source for leaks is the brew valve in the E-61 group. I realize you said you rebuilt the group but . . . ..

A brew valve leak is NOT uncommon and is difficult to detect because the leak is typically small and that water goes to steam immediately. The delay in water flow is a key clue.

erics wrote:If there is any flow from the OPV relief port as the machine is warming up or just sitting there idling, the check valve in the hydraulics to the hx has failed

I'm afraid that this is not true, in the case of the Alex, a leak on the check valve (flow opposite to normal direction) would result in water coming back though the pump and out of the supply pipe (see my drawing below), not through the OPV.



I am still trying to track down the leak, but I have found that if I operate the brew water lever for a few seconds whilst the machine is heating up, filling the HX, there is enough pressure to allow the machine to heat up for an hour or so, and still retain enough HX pressure to operate the thermosyphon properly, allowing me to make coffee again, and showing that the leak isn't that bad (at present). Maybe the leak will get worse, to the point where I can actually pin point it, but until then, this work around seems to be working pretty well.

Thanks for your help,
Trev