Hi there --

I'm working to clean up and rehab a Rancilio S24. I've made some progress, but I have a qusetion about why it might be hitting such high pressures. I took the boiler off and descaled it and the internals. I saw some parts on this machine with 1995 dates, and I doubt that this machine has been cleaned since it was new -- maybe not even a backflush... Anyway, it's a mess.

I put everything back together and it seems to start working, but the pressure gauge will get to the max in the red (I think it's 2.5 or 3.0 bar) with no sign of stopping. I turn it off and release the pressure. The owners said that they never saw it hit such high temps when it was working.

So what can cause this? Failed pressurestat is a possibility, but before I drop $100 on that part, what else can I consider? I'm thinking that there could be scale or gunk in there such that the pressurestat isn't getting the pressure correctly, therefore never asserting. I have no problem tearing it all apart, but I'm new to this and want to hear others' ideas and experiences first.

Also, shouldn't there be a safety valve that will blow off once it gets so hot? That doesn't seem to be working, either, but I'm not sure if it might not activate until even higher pressures.

Thoughts? Thanks.

It really sounds like a faulty pressurestat to me. Does it start at zero when the machine's cold? It should be zero. The safety valve should pop before it gets too dangerous. Also the 3 phase temperature reset should pop as well at some point.

Those pressure stats can also rebuilt. However, you'll need something to calibrate it.

The pressure gauge reads somewhere just around 1.0 bar at cold. The pressurestat and the pressure gauge appear to be fed from the same point on the boiler, but it doesn't appear that the pressurestat is controlling the gauge (and that seems correct in my limited knowledge).

Any ideas on when the fail safes will engage? I'd have thought before we maxed out in the red, but maybe there's no real danger yet...

Thanks.

Replace your gauge to start with. It needs to be somewhat reliable to make proper adjustments. Most OPV's will pop at around 2.5 bar if I remember correctly. So assuming the gauge still reads correctly, but the needle is off by 1 bar it should top off at 2.1-2.2 bar which is really 1.1-1.2 bar. Either your pressurestat is stuck closed or it just needs adjusted down.

How to adjust an espresso machine pressurestat (boiler temperature)

OttoMatic wrote:The pressure gauge reads somewhere just around 1.0 bar at cold. The pressurestat and the pressure gauge appear to be fed from the same point on the boiler, but it doesn't appear that the pressurestat is controlling the gauge (and that seems correct in my limited knowledge).

Any ideas on when the fail safes will engage? I'd have thought before we maxed out in the red, but maybe there's no real danger yet...

Thanks.

Yep, the pressurestat is off. It should be at 0 when cold. First thing you need to do is swap it out or get it rebuilt.

Thanks for the replies, guys. I'll work on the gauge first.

cebseb wrote:Yep, the pressurestat is off. It should be at 0 when cold. First thing you need to do is swap it out or get it rebuilt.

No the pressurestat is not off. The gauge is off and should read 0 when cold.

Right, that's how I read it. The gauge is driven directly from a copper line from the boiler, not through the pstat. The gauge is definitely sitting around 1.2 at cold. Thanks a lot for all comments. I will get this thing working properly, one way or another!

cannonfodder wrote:No the pressurestat is not off. The gauge is off and should read 0 when cold.

My apologies. That's what I meant. That's what I get for posting late. Thank you for the correction!