After struggling to extract some flavours out of some pretty good coffees, i decided it was time to move on from my temperature surfing technique to something more reliable and repeatable. After convincing my fiancée about the idea, i went ahead and ordered a PID controller for the Silvia from Auber. I’ve received the package (from US to Europe) in three working days, which was surprisingly fast. The installation itself took about 1-2 hours as i absolutely didn’t want to rush with it. Auber has also provided a PDF with instructions.
The kit definitely looks better than i expected and feels great – very solid with a high quality built. The display is white and bright, the system itself is easy to navigate. The improvement is significantly noticeable.
Disclaimer : What you're about to read isn't science, but rather my observations and informations based on my personal research only.
If the machine is properly warmed up, the temperature stays within +/- 1°C for the whole duration of a standard double-shot. This has been measured many times by Auber with a Scace Thermofilter, the PID definitely does a great job. I’ll include Auber’s statement in regards to this bellow.
The temperature change during the 25 second period is less than 2°C normally. It should be noted that because the peak value is used, the data we obtained will be higher than some other studies that used the average value.The Correlation between PID Temperature Setting and Water Introduction – Brewing Temperature – By Auber Instruments April 2011
What i see on the controller during the extraction (indicating a temperature drop) does not matter all that much. The drop in the temperature on the controller doesn’t necessarily represent a temperature drop at the grouphead. The RTD temperature sensor is located at the top of the boiler, where also colder water is being pumped from – which means the drop in temperature displayed on the screen is completely normal and expected. The grouphead does a great job at keeping the water hot and at a stable temperature. The PID also starts heating the water in the boiler during the extraction in order to avoid a significant temperature drop.
It was also really helpful to determine and adjust the offset (
Atdu setting on the controller, menu
0089) between the set temperature and the water temperature (at the group). The controller comes set to 105°C as default, with a default offset setting of 10°C. Which would mean, that by default i should be having brew temperature 95°C at the grouphead if i keep the controller set to 105°C.
In my case for example, i found my offset to be 5°C.
This means if i have 105°C set on the controller, the water at the grouphead is coming out at 100°C. I’ve changed the default offset (
Atdu) from 10°C to 5°C.
There’s also another setting on the controller –
PSb. Adjusting this parameter (located in menu
0089) allows me to adjust the display to show 5°C less (by setting it to
-005) , which will result in seeing 100°C on the controller instead of 105°C.
Now that my controller is showing the actual brew temperature, i can go ahead from here and adjust my temperature for the coffee i’m currently using (95°C, works great for light-medium roasted coffee).
I’ve concluded that once the machine has been properly warmed up (i suggest letting it warm up for at least 45 minutes), the brew temperature won’t drastically drop bellow the set temperature by more than 1°C unless i run 80-100ml of water through. This seems to be consistent with the above statement from Auber.
Knowing what temperature i’m brewing at is definitely worth it. I think it’s really helpful to know that i’m brewing at +/- 1 °C of desired temperature – as opposed to not knowing and guessing.
The mass of the grouphead attached directly to the bottom of the boiler keeps the water at a stable brewing temperature. After i’m done with my shot, the recovery to desired temperature takes just a little while and stops right at 95°C and stays there. The PID also learns over time how to manage the temperature, so the more you use it the more data it gathers and more effective it becomes.
But how does having a PID compare to a Silvia without one? Other than not having to temperature surf, the stock bimetal thermostat is nowhere near as accurate as the RTD sensor. Without the RTD sensor and PID, i don’t really know if the orange light turned off at 90°C or 93°C, or even beyond that point on some older machines (even though it’s designed to turn off at 90°C). If the orange light correctly turns off at – let’s say precisely 90°C, i definitely have to start brewing right after the orange light turned off. And i still don’t know for sure if it really turned off at 90°C or 95°C. If i don’t start brewing right away, the temperature in the boiler continues to rise as the heating element remains hot. Some 5 seconds after the light turned off, the brewing temperature is at ~100°C+ and i’d have to temperature surf. Also, without the PID and with a stock bimetal thermostat, the heating does not begin in time and the drop in temperature of the boiler is far more extreme. The factory setting for the bimetal thermostat is limited to one parameter, which means it starts heating only once the bimetal strip detects a certain drop to a certain temperature. The PID is more intelligent than that and learns when to initiate heating in order to be as effective as possible and still not overshoot a set temperature. It sends pulses to the heating element, so that the temperature doesn’t overshoot beyond let’s say 95°C (my set temperature). I can set an exact temperature and the boiler temperature will stabilise and remain stable for as long as i’d like to keep the machine on. And as i start brewing, the heating element turns on when the PID decides based on an algorithm, not based on a bimetal strip that opens or closes.
The Rancilio Silvia with PID currently sells for around $1,099 (~910€). A stock Rancilio Silvia goes for around $735.00 (~605€) and the PID kit from Auber costs $159.50 (~130€). Installing the PID yourself will save you money, gives you a satisfying feeling of accomplishment and gives your Silvia some additional value. If you’re buying a Rancilio Silvia with PID preinstalled, you’re getting closer to a price range of machines with superior brew temp. control, such as the Silvia Pro. The Silvia Pro costs ~1450€ in Europe and is a dual boiler with dual PIDs. The machine’s temperature stability is superior to most machines used in WBC competitions and also proved to be capable of scoring remarkably in WBC benchmark tests. You can find more on that here:
I’m also very happy with the temperature-only kit. I think the kit with pre-infusion/steam is unnecessary, as the pre-infusion does nothing more than turning on/off the brew switch. For steam, if i start steaming soon enough, i’ll have enough steam power for the whole steaming cycle. The only additional feature the pre-infusion/steam kit has is an addition of a shot timer, which would be nice – but is also not super necessary. Plus, with the temperature-only kit, i get to use the brew switch just as you normally would.
To conclude this – it was totally worth it. If you’re seeking to perfect your espresso, PID is a way to go.
Let me know if you have any questions, i’d be more than happy to answer them!
I am not affiliated, associated, authorised, endorsed by, or in any way officially connected with Rancilio, Auber or any of their subsidiaries.