Seems that I need to replace the pressurestat on my domobar junior. This got me to wondering if it was possible to aftermarket a PID on junior? I know folks have put them on Silvia... just thinking out load. Any thoughts are appreciated. Even, "just replace the pressurestat you numbskull" advice.

Theoretically sure but why? Benefits of a PID on HX machine dubious at best IMO. Pressurestat is easy to replace.

Thanks. That what I was wanting to know. I assume then, that all these new version hx machines that are coming out with PIDs (eg. Rocket, etc...) are more about marketing than a "functional" improvement in temp stability?

With a HX machine the heating is indirect so the benefit is lessened. With a double boiler there is no steam in the brew boiler so keeping the larger volume of water at a set temperature has greater benefit. And once you design the PID for brewing, it is easier to also have is as a dual-channel model to also control the steam/hot water boiler as well. The real benefit of a PID in a HX machine (or steam boiler) is that you eliminate the mechanical pressurestat and its contact points which are, as you have found, prone to wear and failure.

kray wrote:Thanks. That what I was wanting to know. I assume then, that all these new version hx machines that are coming out with PIDs (eg. Rocket, etc...) are more about marketing than a "functional" improvement in temp stability?

As to me the stability is not better. But it is easier to change something (the boiler pressure).

Technically, if you put a thermometer in the boiler's water the temperature stability is better. But this does not always mean that temperature stability at the coffee is better. While the PID could not hurt temperature stability at the group, it seldom will make it better. There are too many other factors involved such as:
- the volume of the heat exchanger
- the length of the pipes from the boiler to the group
- the mass of the group
- design of the brew water injector into the HX
etc.

The real benefits are longer life, more easily adjustable, can be remotely located anywhere in or out of case, and quieter.

Randy G. wrote:Technically, if you put a thermometer in the boiler's water the temperature stability is better. But this does not always mean that temperature stability at the coffee is better.

correct.