Hi All,
My Cimbali M30 Dosatron has recently started behaving strangely on start-up.
It has a built in timer that is set to give it 2 hours of heating time before I use it in the morning.
Recently however, while it shows the correct boiler pressure, the machine is way below proper working temperature. Opening the steam wand causes the pressure to drop to nothing (steam pressure is not normally affected by opening the valves) and it then heats to its correct temperature.

It seems to me that the P'stat is suppressing the temperature by reducing the heating cycles. However, I think it is behaving correctly because the boiler pressure is correct as verified by the (completely independant) pressure gauge.

The problem is kind-of intermittent, but more bad than good. I have checked the heater coils an all show the same resistance (I'm using 2 out of three). I have switched the feeds from the contactor to rule out a bad path through that too. No result..

Has anyone experienced anything similar?
Is it possible for boiler pressures to read "falsely"?

Any pointers on how to tackle it??

Many thanks,
Thom.

False pressure on start up explains what's happening. Briefly, the vacuum breaker is stuck, so the steam boiler is a mixture of air and water vapor, not pure water vapor. Clean the vacuum breaker with vinegar and all will be well. The steam boiler may be overdue for a descaling, but that's another topic.

Longer answer: Since air exerts a greater force than water vapor at the same temperature, the pressurestat is "fooled" into thinking that the heating element should be turned off. When you bled off the air via the steam wand, water vapor replaced it; since water vapor exerts less pressure than the air/water vapor mixture it replaced, the steam pressure gauge reading dropped and the pressurestat turned on the heating element.

Thanks Dan!
For some reason, I used the term "false pressure" only after I had given up searching the site and found nothing.

Many thanks,
Thom.

Dan's right, but I suggest replacing the breaker with a new and better one. Once the stock Cimbali breaker starts sticking it will continue to do so on an irregular and highly inconvenient basis.

Chris Coffee sells a breaker which is both far more durable and quite inexpensive. I suspect the other folks who do machine parts do as well.

BDL

Mine started sticking on my Junior when I first bought it (used). I just replaced the O-ring for about $.25 and re-installed. Worked perfectly the entire time I had it.