I have had a problem with my Alex Duetto II for the past 6 months... I should have asked for advice here before. It is 2 years old, and was working fine.

Suddenly, the steam boiler started overheating - i.e. not shutting off at the PID-set temperature. I discovered this when the machine discharged itself spontaneously of steam when the boiler reached 150C. I checked the PID, values seemed ok (and hadn't been changed in 2 years), then reset and reprogrammed the PID, but to no avail. The steam boiler heats until it discharges itself, or the pressure stat pops.

Turning off the power to the steam boiler, using the auxiliary power switch on the side of the machine has no effect - the steam boiler is still able to draw current. Even turning off the machine's main power switch has no effect - the machine must be disconnected at the power source to stop the steam boiler heating.

I contacted the vendor (Bella Barista), who suggested that the most likely fault was the PID itself. It has taken me 6 months to source a new one (eventually from Chris Coffee - I should have looked there first). I swapped the new PID in today - same problem. Steam boiler overheats, power switches have no effect.

Anyone have any idea what the problem might be? Is it the power block in the machine?

Anyone who suggests the PID was remotely probable fault when heater element draws power even with machine turned off is totally incompetent and ignorant of electrical and electronic basics. The PID simply "tells" a relay or SSR to switch and feed power to the heater element. Don't know the component particulars of the Duetto but sounds likely a relay (can a SSR do that too, don't recall?) fried/stuck closed. Need to start tracing what's happening with voltmeter...

Thanks for the advice.

An espresso technician looked at the machine briefly, and said that the SSRs were ok...

Could it be a problem with the power unit? The light for the steam boiler on the front of the machine flickers when it is supposed to be "off".

Certainly the steam boiler is drawing continuous power from somewhere.

I live in Ireland, and the machine was specially imported, so I'm at a bit of a loss - the vendor has no real interest in taking the machine back for a look, due to the hassle of shipping.

I believe there are separate ssr's for steam and brew boilers. If they are and rated the same - I would swap them. If the trouble moves- then the SSR is at fault. Pids have been known to fail on these machines due to temp exposure. Time to trouble shoot. Good luck

Did you talk to Chris Coffee on the phone, or did you just place an order online? Call them and talk to a technician. Tell them you bought the PID from them, so what would be the next step....

Strange behaviour. Sounds like you have a short circuit somewhere. (cross over).

You didn't say, but what does the PID shows as the temp on the steam? What do you have it set to, and what temp does it go up to?

Secondly, what is the temp on the PID for the steam when the steam boiler switch is turned off? I am not understanding from you if the PID shows the temp going up.

And you are aware of this?: http://coffeeforums.co.uk/forumdisplay. ... etto-Forum

While it seems your Alex has some of the features of the US model, there is the obvious voltage difference and it just may be that the US models and yours are different in other ways.

I would simply disconnect the wiring to the steam boiler's heating element and wire it such that it powers a simple table lamp. The connections to the heating element should be simple female spades. Maybe add a simple switch to power the lamp on/off.

With no power going to the table lamp, is the machine fully operational? i.e., does the machine operate normally as regards temperature and pressure?

I have tried multiple steam settings on the PID. It was originally set at 120C, but I reduced it to 100C for testing purposes.

The PID shows the temp rising appropriately, as the steam boiler heats. It just simply keeps on heating though, past the temp set on the PID. When the boiler spontaneously discharged, it was reading 150C on the PID.

If I turn the separate steam boiler power switch off, the heating light reduces to a flicker, but stays on, and the steam boiler keeps heating.

Interestingly, if the steam boiler power switch if OFF when the machine is first powered on, the steam boiler does not start heating / drawing power immediately. It starts to heat only when the hot water boiler has reached temp (~93C). Once it starts heating though, it cannot be stopped without cutting power to the entire machine.

kize wrote:I believe there are separate ssr's for steam and brew boilers. If they are and rated the same - I would swap them. If the trouble moves- then the SSR is at fault. Pids have been known to fail on these machines due to temp exposure. Time to trouble shoot. Good luck

I like the suggestion of swapping the SSRs. First, I need to work out where they are, and whether something like that lies within my capabilities...

s0uthpaw wrote:Once it starts heating though, it cannot be stopped without cutting power to the entire machine.

Oh my. If the power switch for the steam boiler isn't working, something is very wrong.

s0uthpaw wrote:First, I need to work out where they are, and whether something like that lies within my capabilities...

If you are wondering if further diagnosis is within your capabilities, then it's a safe bet it's not. Turn it over to a qualified repair technician; the hope of saving money the DIY route isn't worth the risk of a painful electrical shock (or worse).

You can disconnect the control/low voltage side of the SSR. If that doesn't stop the heating, then the SSR is bad.