The Sirai pressurestat on my 8+ year old La Valentina failed a couple days ago. One of the contacts was heavily pitted and worn, and the other was moderately worn. I cleaned up the connections and put some dielectric grease on the contact points, but that didn't work. To get it working again, I moved the wiring from the really bad contact to the unused one, which has fixed my machine for now, however the other contact looks pretty worn. I have a new pressurestat on the way but will wait to install it until the original one dies again....or should I just install it now? I know parts wear out eventually, so is 8+ years acceptable for this part? For all I know, I'll get another few years out of it when the worn contact finally bites the dust.
My Sirai PS on my Oscar failed all 3 connections in 2 years, the first connection failed at around 1 year, this is not normal. When mine failed the first time it stayed closed which allowed the machine to super heat until the pressure valve opened and a connection lead burned through, when the other two connections failed they would stick open so I was always walking up to a cold machine. The replacement has been trouble free for over 1 year and I suspect my original Sirai was defective from the get go. I would just replace it for the peace of mind.
puma996 Senior Member Joined: 28 Mar 2007 Posts: 136 Location: Oregon City, OR Expertise: I love coffee
Espresso: La Valentina Grinder: Mazzer Mini
Posted Sun Oct 7, 2012, 12:31pm Subject: Re: typical Sirai pressurestat lifespan?
Well, I put it off until my weekend because it seemed to be working. I was thinking about doing it yesterday and again put it off. Out of the blue, I hear a super loud noise from the kitchen and see steam shooting out of the top of my machine. It appears the pressurestat kept heating until the boiler reached max pressure, and it vented from one of the relief valves atop the boiler. Dang, it was loud!
I swapped the pressurestat once the machine was off and cooled enough, and after making sure the relief valve was fully closed, it now works perfectly. When "those in the know" advise to get the work done, LISTEN! ;)
To protect the contact points on mine I isolated the heating element circuit with a 20 amp relay, pretty simple to do. Prior to the mod a very hot spark arced across the contact point's gap every time the p-stat cycled, burning the points a little each time. After the mod only the very small amount of power used to throw the relay switch runs through the 20 amp rated contacts of the p-stat. Any pitting due to burns occur on the inexpensive and easily replaced relay switch rather than the p-stat.
The short version of the mod: Run leads from the machines main power inputs to the switch terminals of the relay and then to the heating element terminals and attach the leads from the p-stat to the trigger terminals. Now the power surge created when the heating element cycles is isolated from all the other circuits of the machine. This may also increase the life of your electronic control module depending on how your machine is wired.
This is not the relay I used (I didn't find it when I did the original mod and purchased one that was more expensive) so I can't vouch for it but it actually looks sturdier than the one in my machine.
More about contactors vs relays and arc suppression can be found here for those intrested. click here
If the diaphragm becomes stiff it can be replaced with a kit: click here.
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