La Cimbali M29-Select pressurestat adjustment

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berkinet
Posts: 68
Joined: 14 years ago

#1: Post by berkinet »

I have had my M29 for several years (purchased new around 2007 in Italy) and I know I knew how to adjust the pressure at the time. But, now, years later, I cannot, for the life of me, remember where the switch is located. This is made somewhat harder by the significant amount of insulation I packed around the tank.

In any case, over time the pressure indicated by the built-in gauge is just below 0.8 and slightly in the blue zone. When I check at the group heads with a manometer attached to a portafilter I get pretty much the same reading. So, I would like to raise the pressure a bit to see if it makes any difference to the coffee produced.

So, the question: Can someone point me to a diagram showing where the pressurestat is located in the machine? (BTW, I have looked online and all the diagrams show the pressurestat exploded and not in its actual location).

Thanks in advance....

Richard

Axxam
Posts: 23
Joined: 3 years ago

#2: Post by Axxam »

Did you ever find an answer? If not what pressure are you trying to adjust? Boiler pressure is adjusted with the Pressure Switch (normal boiler operating pressure is typically 1.2 bar). I have a Cimbali M29 Start 2 Group collecting dust in my basement I can check and post a picture if you need it still.

JRising
Team HB
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#3: Post by JRising »

Or better yet, can you tell us what you want to find or adjust?

The pressostat is a pressure activated switch that will shut off the heating element when the boiler is at pressure. Yes, it will have an effect on the pressure that the boiler pressure gauge displays.

Checking pressure with a portafilter mounted gauge will show you the pressure at which the machine is brewing, totally unrelated to the boiler's temp and pressure.

I hope this makes sense, or that I'm not misunderstanding what the initial purpose of the post was.

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berkinet (original poster)
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#4: Post by berkinet (original poster) »

Thanks for the recent replies. What I want to adjust is the tank pressure. I am quite familiar with the machine and machines in general. Right now, the pressure gauge on the machine is reading right at the low end of the green area - roughly 0.9. I have verified this with a manometer attached to a portafilter. So yes, I would love to have a diagram that points me to the location of the pressure switch.

JRising
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#5: Post by JRising replying to berkinet »

If tank pressure means boiler pressure, then you'd adjust it at the pressostat, and obviously that wouldn't affect anything that the portafilter gauge would display.
If tank pressure means something else, please explain.

The M29's pressostat should be a three-pole Sirai, with the black metal top on the galvanized housing. Clockwise from above on the adjusting screw increases pressure. You might want to get a technician to look at it if you're not sure what is affected by which adjustments.

I don't have the hydraulic diagram, but the pressostat looks like this (upside down and sidways in the assorted pictures). It should, of course, always be mounted with the diaphragm side down, if possible. If liquid water is allowed to get to it and eventually evaporate, it will leave deposits. If you're facing the machine, it's on your right hand side of the boiler, upper rear-ward port.
https://www.espresso-parts.com/Pressure ... 320531.htm

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berkinet (original poster)
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#6: Post by berkinet (original poster) »

Thank you. Yes, tank = boiler. I have no problem adjusting the switch. My problem was locating it inside the machine. Knowing what to look for will make it a lot easier.