What is a PID?
Pressurestat
In an espresso machine without a PID, a pressurestat controls the temperature of the boiler by detecting pressure. When it’s too high or too low, the pressuestat sends a signal to the heating element to either heat up or cool down the temperature.
PID
A PID is a digital temperature controller in place of a pressurestat, directly measuring the temperature of the water in the boiler tank and switching on and off.
PID: More accurate control of temperature
You have more accurate control over the temperature as the PID device reacts directly to the temperature of the water versus the pressurestat measuring the pressure created by the heated water which has a larger margin of error.
For example, at a set temperature, the boiler water in a PID espresso machine may vary by 0.2°C, while the water from pressurestat may vary by about 2°C or more.
This might be useful when exploring different flavours from the same coffee at different temperatures and finding your balance between bitter and acidity.
The PID device plays its role together with a solid static relay, an LCD display, water probe and regulator. The solid state relay component lasts longer than the regulator and display which are susceptible to moisture damage or power surges, and the water probe is affected by limescale buildup
Pressurestat: More durable
Pressurestats should last for many years depending on the water condition, power stability and ambient temperature. Some versions are heavy duty pressurestats with higher resistance and are expected to last longer. Breakdowns are due to limescale blockage and component malfunction, so it’s important to soften water and descale your tank at least once a year.
Pressurestat is just one component in the power relay which powers the heating element. This relay which switches on and off to regulate the temperature of the machine is subjected to wear and tear as the relay’s contact points can be corroded. Many factors such as ambient temperature, length of usage and stability of power. While they are relatively inexpensive and require replacement from time to time, we do not recommend that they are switched on all the time.
Soooo which is better?
While having direct control over your water temperature is beneficial, having more electronics as in the PID may increase the possibilities of failure. Setting the PID above the boiling point may trigger the safety control to trip and shut off the power completely, needing you to remove the hood of the machine.
So, it's your decision on which positives outweigh the other.
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