Do I really need a PID temperature controller?

What is a PID?

Imagine your boiler heats up, how can the machine detects that the machine is too hot and stop heating or heats up further if it’s getting too cold?

Traditionally, a pressurestat controls the temperature of the boiler by detecting the amount of pressure it has. If the pressure gets too high, it will switch off the heating element, and switch on when the pressure falls below.
A PID is an electronic temperature controller that replaces the pressurestat. It measures the temperature of the water in the boiler directly and switch on and off as needed.

A PID has two additional features over the pressurestat.

  1. Full control of the temperature
  2. Narrows the deadband of temperature fluctuation

The user can have full control on the temperature and tune to his preference. This might be useful for exploring different flavours coming from the same coffee at different temperature, as well as controlling the intensity of its bitterness and sourness. It might  be more noticeable if the user tunes by at least 2°C.

The pressurestat will create a fluctuation of temperature in the boiler, as it switches on and off according to the measured pressure. The PID is more reactive and will keep the deadband smaller, so temperature is more stable.

Here is an example of PID versus Pressurestat.

PID Versus Pressurestat

If 90°C is the set temperature, a PID may sway around 0.2°C up and down, a pressurestat may sway approximately 2°C or more.

Another commonly raised question, “Which is more durable?”. Pressurestats by itself, are pretty hardy and seldom fail prematurely. In some models, they have the option for heavy duty pressurestats with higher resistance, and longer longevity. For the PID, they seem to last pretty long too. However, some may deem that the PID’s sensitivity to detect and correct the temperature so rapidly may add more stress to the heating element, which is a component that is also pretty hardy, but not as easy to replace.

For PID espresso machines, it is important to not set the temperature above boiling point. As it may trigger the overheat safety control to trip and shut off the power completely, and you will have a problem. As you will need to remove the hood to fix it.

Back to the question, do you really need the PID? You decide.

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