If a machine has an extraction manometer on it to read the extraction pressure, would a PID still be required? Couldn't the manometer tell you what your pressure is and from that you could know the corresponding temperature. I am hoping that someone who understands the function of these 2 added accessories could educate me. Im considering the Lelit PL41EM against the Lelit PL41TEM. One has a manometer the other has both a manometer and a PID. The difference in price is $150 in which I could spend towards a nice grinder.
The PID is a way to control the temp of the boiler in an accurate way, it is not a digital readout of what the temp is.
There are two manometers on most machines. One reads out temp in bar, the working pressure on this gauge is from 1 to 1.4 or so bar.
The other gauge reads the pressure of the shot that is being generated by the pump, this gauge reads about 9 bar in the pulling of the shot. It has NO connection with the static pressure in the boiler for the purpose of displaying the temp of the boiler.
They are two entirely different things. The PID makes a SBDU MUCH easier to use and be consistent with.
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
If we were dealing with gases rather than liquids, you could use the ideal gas law (pv=nrt) to extrapolate the temperature based on the pressure if you know the rest of the variables. Espresso machines pump liquids, however, and therefore this does not work. A PID is not necessary to know the temperature, but you can use thermocouple thermometers to read the temperature at the group head. Alternately, you can use your taste buds to figure out if your flush routine is getting you there like I do. I do use a portafilter pressure gauge to adjust my OPV so that I get optimal pressure. Boiler pressure can adjust the temperature of your shots, but frankly is overpowered by flushing the HX.
Now I can see the logic behind the two. I didnt understand what the 2 items were actually doing and or reading. Thanks guys for shining the light so I could see. I am a engineer and deal with thermodynamics all day at work. I actually work with large heating Boilers. Which in some ways help me understand the science behind the process. Thanks again for schooling me.
Mike, I am not calling into question anything on your post but the machine in question is a single boiler dual use machine so while with a static boiler you can convert pressure to temp, like on a HX machine, the only manometer on this machine is one to measure the pressure of the system during the brew process and it is an indication of the output of the pump and the restriction of the coffee, there is no way to infer temp into this gauge.
Tommy, your welcome!
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
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