Andreja Premium Limit Stat Failure

This describes the function of the Limit Stat, fault finding and replacement

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The Limit Stat (hi Limit Stat, or Safety Thermostat), prevents the coffee machine from damage during overheating. e.g. by failure of the pressurestat to switch the heating element off. The Limit stat is set so that it cuts power to the machine, or heating element once the internal boiler temperature reaches 165C, or just over 4 bar on your pressure gauge (if it goes that high).

The Limit stat is resettable, by pressing in the red button, if pressing the red button resets the machine, then you probably don’t have the problem below and should look to your Pressurestat (pressure stat), either CEME or MATER as the probably cause of the problem.

There have a number of incidents of the Limit Stats failing on the Andreja Premium, symptoms of this failure include:

  • A pop or bang from inside the machine (possibly accompanied by a brief flash of light)
  • Trips out electrics (fuse)
  • Machine fails to heat
  • Machine looks like it’s off

It may even be that when you leave the machine for a while and switch it back on it might work OK for a few minutes and then trip out the electrics or switch off again. fairly quickly it will short and stop working altogether.


Under these circumstances, it’s possibly the “Limit Stat” that has failed and for a few excellent reasons, it’s possibly the first component you should look at.

  1. It’s one of the cheapest fixes
  2. It’s one of the quickest and easiest fixes

All other problems that could cause something similar are a lot more expensive and harder to fix!

Probable reasons for Failure

The picture above shows the limit stat and it is quite near the vacuum breaker valve. This spits some water when the machine warms up (sometimes quite vigorously), when it scales, this spitting can be worse. The water can splash on to the Limit Stat an eventually couples with the scaling that forms, cause a short. This short circuit damages the limit stat and can often be clearly seen as a black burn mark on the limit stat body.

Note the picture shows a new machine, a machine that has been used for a year will usually show clear evidence of water splashing and scaling.

Fault Identification

This is easy if there is a visible burn mark above. If you are not sure and feel competent, you can actually take the limit stat out of circuit, by simply removing one wire and reconnecting one of the wires internally. The limit stat is quite simply connected in series with the heating element and the power supply to that element. I have not made a picture of this process, and will not provide instructions….because if you need instructions, then you definitely are not technically competent enough to do this.

Warning: if you do this, do NOT leave the machine unattended and I would NOT recommend operating the machine like this to make coffee whilst waiting for your new limit stat to arrive.

Replacement of Limit Stat

Remove the two electrical connectors to the limit stat, it’s not that important which one goes back onto which terminal, because it’s an “in series” connection. You can just see from this image that the limit stat is held onto the boiler by two “crosshead” screws, these hold it down via a small metal clamp. Simply undo these screws, remove the limit stat and replace by reversing the procedure. The whole thing should take about 2 minutes.


How to prevent the problem happening again

There have been a number of ingenious solutions, shown below:

The stainless steel mesh one. It does still allow a few spits through so the inventor may glue another layer of mesh on top


The bit of tee-shirt, or hoodie solution


These all rely on doing 2 things

  1. Not impeding/preventing the movement off the little pin on the Vacuum breaker
  2. Minimising, or eliminating “splash” from the vacuum breaker valve hitting the limit stat or other components within the machine.

Of course once the machine is hot (the vacuum breaker is closed) there is no spitting and any water within the “solutions” shown quickly dries out. When you switch the machine off, there is never any spitting as the heating element is not on and the water in the boiler is not “bubbling”