While I am well versed in the technical and applications specific aspects of PID control (and others), I believe JGG, a fellow CS member in the States may be able to help you out with this specific information, as he has tested quite a few of these controllers..... You can contact him here.... http://coffeesnobs.com.au/YaBB.pl?ac...rname=jggall01 or wait until he picks up on this thread.
All the best,
Re: the reason for the scarcity of the presence of PID in Commercial machines..... In a nutshell, they dont really need them. Because most Commercial equipment use the Heat eXchanger method of controlling the brew water temperature, and in turn use the pressure contained above the water in the boiler to control this temperature (more temperature means more pressure) via the method of a PressureStat.... It is possible to control the Boiler Water Temperature within a couple of degrees of the desired target so therefore, a PID controller doesnt offer any real significant gains over what is already being achieved. Also, even a small low specification PID controller will be more expensive than a reasonable quality PressureStat.
Of course, in the situation of a Dual Boiler machine, there might be some advantage to be gained by having extreme control over the Brew Water Boiler temperature via the use of PID, especially since the temperature target may be below boiling point and hence no steam production. Hope that helps,