# PID problems - overheating, steam at the grouphead



## schmerg (Mar 17, 2015)

Hi all,

I have a 1st gen Silvia, and a couple of years ago I got the plain Auber PID and all has been going well since then (I work from home so the machine is on every day, maybe 2 or 3 espressos a day).

But recently I've been getting first a little and then later quite a lot of steam out of the group head, particularly noticeable when I pull an empty shot (warming up the machine, flushing the shower screen etc), to the extent that using a bottomless portafilter it can be quite uncomfortable to hold the cup (drawing empty shots the first burst tends to spray around so I hold the cup up around the grouphead).

Suspecting the (screw in) temperature sensor was at fault, I removed and reseated it, but in doing so seems I broke the wires ("EEEE" display on the PID) so ordered one of @MrShades excellent more-robust replacement sensors (which I'd recommend to anyone) and fitted that.

That fixed the EEEE error, but the whole machine still seemed to be running too hot.

Thinking maybe scale could be causing a false reading, I descaled the machine (twice in a week, just to be sure), and cleaned off the old thermal paste at the sensor and reseated it, more carefully this time, using a thin scraping of another thermal paste (silver based) that I use for CPUs, but still no difference.

If I wind the temperature on the PID down to 95 it seems to make little difference, down to 85 and there's less steam.. but interestingly if I point an infrared contactless thermometer at an empty shot, it's still showing the water temperature (of an empty shot) to be about 90C.

Pointing the same at the outside walls of the boiler similarly shows high temperatures (greater than the PID shows)

Slight aside here - I never understood why the PID would be set to 105 or whatever - surely the actual wall of the boiler cannot be hotter than the water inside which is surrounding the element - basic laws of thermodynamics. Surely if we want the water at, say, 95, so that it comes out of the grouphead at 92, and then into the cup at 85, then the sensor on the boiler would be set to slightly below 95... maybe 85 or 90, not 105 ! What am I missing here?

So, long and short of it... either my machine has suddenly become aware of the 1st law of thermodynamics (heat energy can only ever pass from a hotter to a colder system), or something has broken on my machine, quite possibly the PID.

I haven't fiddled with the PID other than using the up and down arrows to change the temperature... any suggestions as to how I can check/reset the PID (the temperature shown does seem to be jump 2 or 3C up and down almost at random sometimes).

Or some other thing to do to the machine?

I suppose I can order a new PID from Auber (wonder if they'd sell just the programmed PID without the relay and sensor etc) but if anyone has any bright ideas, I'm all ears...

Cheers

--

Tim


----------



## AussieEx (Jul 10, 2013)

schmerg said:


> Slight aside here - I never understood why the PID would be set to 105 or whatever - surely the actual wall of the boiler cannot be hotter than the water inside which is surrounding the element - basic laws of thermodynamics. Surely if we want the water at, say, 95, so that it comes out of the grouphead at 92, and then into the cup at 85, then the sensor on the boiler would be set to slightly below 95... maybe 85 or 90, not 105 ! What am I missing here?


PID shows temp of boiler, but the important temperature is water temperature when it hits the puck - there is heat loss between the boiler and the group (exact amount varies), hence the offset on the PID


----------



## schmerg (Mar 17, 2015)

AussieExpat said:


> PID shows temp of boiler, but the important temperature is water temperature when it hits the puck - there is heat loss between the boiler and the group (exact amount varies), hence the offset on the PID


Cheers - I get that bit, but was just questioning the size of the offset. If the outside of the boiler is 105, then the water in the boiler is at least 105, meaning that for it to be down to 92 when it hits the puck, we're anticipating a temperature drop of 13C or more.

On a cold machine maybe, but for a machine that's been on for an hour or so and has pulled a shot during that time, this seems a large drop for a short section of pipe and a grouphead that are all inside the machine and directly connected to the boiler (ie heat transferred to them by conduction, temperature of the surfaces thereby comparable to the boiler wall itself).

I'm not doubting that people use these settings and it all seems to work OK, hey, it seemed to work for me until recently, I'm more asking to try and understand why I'm getting so much steam and overly hot water - is there some thermal break between the boiler body and the grouphead that perhaps has failed in my machine meaning my grouphead etc is hotter than normal (so the temperature drop is not as much)?

Thanks for the reply... (educated but still a little baffled)


----------



## schmerg (Mar 17, 2015)

Closing this out for any future readers with similar issues...

*Summary:*

I contacted Auber (via email) and they were very helpful in diagnosing the issue, which came down to the controller unit losing calibration with regards to the sensor: a rare but not completely unknown failure.

A new controller has resolved the issue, and I'm back to normal.

*Longer version:*

Auber tech support (via email) were prompt and attentive, replying to each email within a day (which, allowing for timezone differences, seems fair enough).

I was concerned that they'd insist I swap back to their temperature sensor (which I'd broken in checking) but they were happy to diagnose with the other sensor in place and walked me through various settings (including a not so documented setting for what I guess was 50Hz/60Hz AC power), and pointed me at the resistance vs temperature table for their sensor which matched my replacement sensor's spec.

Measuring the resistance of the sensor and comparing it to the temperature as displayed on the controller (1st thing in the morning with a machine at room temperature is a handy way to do this) showed that the sensor was being given the right resistance, but had lost calibration and was reporting this as about 20C cooler (~200 Ohms) than it should.

They suggested a fix of adding a resistor to the load, to fix the calibration, or to replace just the controller at a discounted price which seemed a better idea (the fact that the temperature was jumping around by ~5C implies to me that some circuitry was perhaps shorting or making intermittent contact).

It was delivered a week later and all seems to be working well now - electronic components do have failures, small run engineering even more so through no real fault, so I'm more than happy that tech support was so helpful and resolved the issue (now if only Samsung were so helpful when it comes to the "PC ERR" display that flashes up every now and then on my top end fridge-freezer requiring a reboot).


----------

