My aging (6 years old?) Expobar Office Control has a sporadic problem that blew a hole in a plastic supply line the other morning. Every once in a while, maybe once every two months, it seems like the boiler pressure goes sky high. If I turn either steam or water nob, steam comes rocketing out and continues to do so even after the machine is turned off. Then a couple of days ago this blew a hole through a plastic water supply line between the OPV and the pump and dumped the contents of the water supply container into the kitchen cabinet below.

After this incident, I repaired the supply line, reset the switch on top of the boiler and powered the machine back up. The boiler got very hot again very fast and I can hear the heating element clicking off and on every 5 seconds or so while steam slowly seeps out of what I assume is the pressure relief device (bolted on top of the boiler and has a pin that steam pushes up).

The machine has been in daily use for a while and the day before the incident I pulled (for me) a lot of shots through it (maybe 10 or so throughout the day).

FWIW, I descaled the machine around 9 months ago.

Any idea what could be going wrong here?

turbodog wrote:The boiler got very hot again very fast and I can hear the heating element clicking off and on every 5 seconds or so while steam slowly seeps out of what I assume is the pressure relief device...

Sounds like the classical description of a sticky pressurestat. It's easily replaceable, see How to adjust an espresso machine pressurestat for hints on identifying the correct part and adjusting it once you've replaced the old one.

Thanks for the reply. I have a new pressurestat on the way from WLL now.

For future reference, the part number for this pressure stat is EX60000008:
http://www.eunasa.com/en/producto.php/coffee/23452/piris-pressure-ce-expobar
http://www.expobar-germany.de/product_info.php/language/en/info/p95_.html

Edit: the pressurestat is a Signal Lux M3

And a few photos as well:

Fully descale that feed tube to the pressure stat and make sure there is good flow from the boiler port. Either could be partially clogged and be causing part of the problem.

-Cecil

Fully descale that feed tube to the pressure stat and make sure there is good flow from the boiler port. Either could be partially clogged and be causing part of the problem.

Would the typical HX descaling procedure cover that or is there something special I'd need to do? Maybe get citric acid into the boiler and let it drain up and out of the pstat port?

For checking and descaling the tube I would totally remove it and test and clean it outside the machine. Take a peek at the boiler port with the tube out and make sure you don't see a bunch of scale.

A standard descale process would not be a bad idea once you know you have the temp problem licked.

-Cecil

For checking and descaling the tube I would totally remove it and test and clean it outside the machine. Take a peek at the boiler port with the tube out and make sure you don't see a bunch of scale.

I disconnected the copper line from the boiler port to the pstat and it didn't seem to have great flow, but I'm not sure what great is since it's a pretty narrow (1/4" OD?) line. I did try to descale it and seemed to flow a little better.

I can't really get a good look at the boiler port, but I was able to freely poke a safety pin into it so I don't think it's overly obstructed.

However, once I got the new pstat installed I had the same problem: boiler pressure is way high, steam continues to leak slowly from the relief valve pin and heating element cycles off and on every few seconds. I did notice that the line from the boiler to the pstat is cold though. Perhaps there really is an obstruction between the boiler and the pstat?

Over the weekend, I removed the pressurestat supply line again and gave descaling it another try. Over several hours, I did see some more blue drip out and mild improvement in flow. I reassembled it with the new pstat, but my problem persists.

Any ideas on what else I could try or check on?

Thanks. After some googling, it is the vacuum breaker where steam is leaking.

I'm aware of Stefano's from past HB reading, but they're actually over 120 miles from me and I'm afraid that's a little too far to drive when I could probably find qualified repair more locally.

Also I will probably try a full HX descaling and see if that helps, then get some professional service unless there are other ideas for me to explore.