Temperature Surfing the New Rancilio Silvia 100C Thermostat - Page 2

by **Psyd** on Fri Dec 07, 2007 4:52 pm

ChrisC wrote:My understanding is that the water gets hottest about 1 minute after the thermostat cuts the power to the heater. This is because there is residual heat in the element that continues to pass into the water during that time. (Maybe you could try brewing at this time for a little extra heat, Psyd?)

I'm pushing a bit further back every morning til I find a sweet spot. I've heard the same thing, but I'll have to see what happens

ChrisC wrote:Seeing as 200F (a good average start temp for espresso) is 93C, and the heater is turned off when the water is 100C and then the water gets hotter than that for a minute, you'd want to wait at least a minute to stand a chance of getting closer to 93C/200F as your starting temp.

200F is a good starting point, and 100C is 212F*. If the boiler element cuts off at 212F, why would we wait to get to 200F, if the temp increases with waiting? It seems to me that the 212F cutoff would get you nearer to 200F at teh PF basket than letting it heat up further, neh?

ChrisC wrote:Hopefully cold water is not a big one right away, as it sinks to the bottom and the water to the GH is drawn off the top. And hopefully heating the metal isn't either if your Silvia is properly warmed up

'Cool' is relative. I'm able to hold onto metal that's at 160F to near 180F (although, at the latter, I tend to juggle a bit) and I've developed 'hot hands' to the point where waiters freak when I take plates from them ; >. That being said, running 200F water over a 185F portafilter will soak a lot of energy from that water.

*100 x 1.8 + 32 = 212

http://users.rcn.com/erics/ · by **erics** on Fri Dec 07, 2007 5:24 pm

I'd love to see charts of the intra-shot temp on Silvia with the steam switch on and off. Perhaps someone like Eric has already done this?

Early on in the development of the thermocouple adaptor, I was running graphs on Silvia because that is all I had. I installed a simple switch to cut power to the heating element and mounted it on the side frame of the machine. The reason for doing this was that the Chinese PID I was using (no longer available) was unusually responsive and was unusually well tuned. The responsiveness was inherent and the tuning was a lot of luck and a lot of playing around.

The graphs are buried in here:

http://www.home-barista.com/forum...-silvia-t1352.html

I was sensing boiler WATER temperature and the machine could easily be back to Sv and stable within 5 seconds of pulling a shot. The temperature graphs would show a rising temp towards the end of the shot. When I cut the power to the heating element at the very beginning of the shot, the temperature graphs became essentially straight lines.

These graphs show Silvia's water temp variations with the 100 C thermostat:

http://www.home-barista.com/forum...out-pid-t4691.html

The most interesting thing to note, IMO, is that Silvia's grouphead temp rises about 10-15 F with a typical PID application. These "tests" were also done with a newer version of the same Chinese PID which was not as responsive and thus, I don't remember having to cut power to the element but I can't be sure of that. In any event, I think you would be pressed to taste the difference.

by **ChrisC** on Fri Dec 07, 2007 5:29 pm

Well, it does get hotter when you wait, but then gets colder after the first minute. As you've pointed out, if the t-stat cuts the heater at 100C, which is 212F, it's already too hot at that point. So even though waiting one minute is going to shoot you even further up, eventually you'll hit 93C/200F on the way down. But then as you point out, there are a bunch of other factors that may be already cooling it as much as or more than it needs before it hits the coffee.

And of course, even if we figure out my perfect wait time, that won't work for you, with your individual thermostat, altitude, barista techniques, grinder, grind setting, blend/roast, etc.

Back to, what tastes good to you?

by **ChrisC** on Fri Dec 07, 2007 5:42 pm

Thanks Eric -- I figured these existed. I've even seen the second batch before, but I must admit that often your posts are right at the threshold where I stop really understanding. :-)

If I'm not mistaken though, your research seems to indicate that with a decent PID and a standard shot time of 25 seconds or so, the temperature at the coffee is basically flat. So there's really no need for me to be engaging the steam switch at the same time as the brew switch -- if anything, I may be increasing the temp over the course of the shot by doing so.

http://users.rcn.com/erics/ · by **erics** on Fri Dec 07, 2007 7:15 pm

If I'm not mistaken though, your research seems to indicate that with a decent PID and a standard shot time of 25 seconds or so, the temperature at the coffee is basically flat.

That's correct.

Where Silvia gets "messed up" is when you implant some steaming into the routine. As was originally posted by Mike McKoffee some years back, successive shots with Silvia tend to rise in temp - two shots back to back would probably be OK but when you are having a barista jam, trying to do 3, 4, 5 shots etc., the rise in GH temp will affect subsequent shots.

This rising temperature action would be most apparent if you had an unusually responsive PID and least apparent if you had a PID that took its time in returning Pv to the Sv value.

If you wanted to pull a shot after steaming, you need to flush about 4 ounces and then all will be OK - this being with a PID'ed Silvia.

by **japa_fi** on Sat Dec 08, 2007 4:26 am

ChrisC wrote:Well, it does get hotter when you wait, but then gets colder after the first minute. As you've pointed out, if the t-stat cuts the heater at 100C, which is 212F, it's already too hot at that point.

Don't forget that 212F/100C in the boiler is not too hot. Water temperature drops on its way to group head. PIDs are usually set somewhere around 229F/109C, yet they result to about 205F/96C at group head (one example available at http://www.pidkits.com/thermofilter.html). Based on that, one would like to have temperature continue rise over 212F/100C

by **ChrisC** on Sat Dec 08, 2007 1:14 pm

Yes, but I'm assuming that that 212F/100C is water temp INSIDE the boiler, or at least an approximation thereof. Otherwise it would be way too low. As you note, PIDs usually indicate much higher temps, but that's measuring the metal on the outside of the boiler, where the thermocouple is attached. Difference from the PID temp displayed to what you get at the GH has been approximated to be about 25 degrees F (your example lists 24). I don't think the water temp drops that much from inside the boiler to when it hits the coffee.

by **Psyd** on Sat Dec 08, 2007 8:06 pm

ChrisC wrote:Yes, but I'm assuming that that 212F/100C is water temp INSIDE the boiler... ... PIDs usually indicate much higher temps, but that's measuring the metal on the outside of the boiler, where the thermocouple is attached.

Ehm, isn't Silvia's t-stat also attached to the outside of the boiler? I'd suggest that either the t-stat is set to turn off when the metal that it is attached to reaches 100C, or that it is sufficiently offset to turn off when the water behind the metal reaches 100C. I'm betting that it's a stock manufactured part, and that the former is the case.
So, again I'd like to see the specs on the different iterations of the Silvia. you'd think with all the connected folk on this here forum, someone would be able to get a Rancilio rep to explain just which Silvia is which, and which changes were just cosmetic, which were bits, and which were functionality changes. Once we have a designator for each Silvia, we have a better method to compare. Stuff that worked really well on my 2000 Silvia (stick-on badge, and cursive 'Silvia' sticker underneath it) with her 110C t-stat probably wouldn't translate well to someone's 'yesterday' purchase.

by **ChrisC** on Sat Dec 08, 2007 10:06 pm

This does exist, I've seen a post either here or on CG listing them, but I can't find it now.... Can anyone help?

(And I was assuming that the Silvia T-stat had an offset -- that calling it a 100C thermostat was because it was adjusted so that it turned off when the water inside the boiler hit 100C.)

by **japa_fi** on Mon Dec 10, 2007 3:55 pm

ChrisC wrote:Yes, but I'm assuming that that 212F/100C is water temp INSIDE the boiler, or at least an approximation thereof. Otherwise it would be way too low. As you note, PIDs usually indicate much higher temps, but that's measuring the metal on the outside of the boiler, where the thermocouple is attached.

With PID and silvia stabilized to 109c, I'm 99% sure the water inside is also 109c or pretty close. After all, the water is surrounded with metallic surface (=boiler) that is 109c.


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