# Water temp drop whilst brewing



## newdent (Feb 20, 2021)

Has anyone ever modded the silvia to not automatically fill the boiler whilst brewing so that the water temp doesn't drop during the shot? Is it even worth the effort?

I'll be PIDing my silvia with an arduino or similar, I assume there will be a fair amount of spare i/o on board to control other bits and pieces. Could maybe monitor level in the boiler and only fill when low instead of filling all the time. Also, maybe a separate thread require but has anyone done low pressure pre-infusion? I wonder how easy it would be to run the pump on variable speed instead of fixed speed control the pressure to a setpoint as well...


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## 29243 (Feb 8, 2021)

Hi Newdent. It's an interesting idea, but I don't think it's possible.

When brewing an espresso the pump pushing cold water into the boiler is what generates the required pressure for brewing (with any excess pressure vented via the OPV to the water reservoir). If you didn't run the pump you wouldn't have any pressure. For some diagrams see: https://www.ranciliosilvia.info/silvia/exploded-view/

A PID is well worth it though.

I know a lot of people like the pre-infusion option on the auber PID. I haven't tried it, but I believe it is equivalent to just pressing the pump switch for a short time and then turning it off and waiting, then pressing again to start the main extraction. This means the 3 way valve will activate releasing pressure. I can't help but think releasing all the pressure part way through the extraction isn't a good idea. Having said that though, one of the beauties of this hobby is everyone has different tastes, so if you try it and prefer it then it is worth it.

Enjoy moding your Silvia


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## 28267 (Dec 8, 2020)

@newdent as mentioned the pump is pushing water from the tank to create the pressure so you can't not fill the boiler when brewing, the only water being added will be the volume of the shot you are pulling so not much. There is no water level sensor in the Silvia boiler.

The Silvia Pro has the same boiler/element on the brew side, with the Rancilio PID the temperature stability is very good. I've only seen the temperature drop once and that was when I'd got the grind way off so it was a mega fast shot. After running the cleaning program (10 back flushes and 5 normal runs) the temperature had only dropped by 3c.

@BenH - Issue with turning off the brew switch for a few seconds as you mention is that it releases the three way value so removes the pressure from the puck. You want it to hold the pressure for that pause, pre-infusion will stop the pump but not release the pressure on the Auber PID.


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## El carajillo (Mar 16, 2013)

If you do not keep the boiler filled you risk exposing the heating element = overheating + burnout of the element.


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## newdent (Feb 20, 2021)

Thanks guys, that obviously makes sense regarding the pressure having to come from cold water entering the tank, so that's that idea out the window!

I read that pre-infusion is better under lower pressure but I don't even know if variable speed is possible on the installed pump. I read something about pump output become pulsed at low speeds and causing issues with the puck. Think some people have done things with a lower pressure path through to the baller for pre-infusion but doesn't seem particularly successful either.

I write software to control pumps to pressure for work, so assumed it'd be fairly straight forward but the variables speed electronics are quite pricey and large. I guess it's probably not work the effort. May as well get the PID done and see how I get on from there. Thanks again


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## ajohn (Sep 23, 2017)

The vibratory pumps that are used can be controlled with a simple triac mains speed controller. That is loosely how pre infusion is added to them. There will be limits on how much reliable control can be achieved and in the extreme control can do some odd things to taste. I saw a video of a machine using a 30sec plus infusion time before any coffee came out recently. I really wonder what that will do to taste.

Some don't realise the limitations of PID. Say it's heating some water to some exact temperature. When it gets their the element will be at the same temperature as the water if not it would continue heating it. Say pulling a shot normally causes the temperature to drop by 5C. The same problem crops up - only so much heat can be put in at some rate that doesn't cause temperature to overshoot. The rate of change will depend on how fast the coffee is flowing. Net effect with simple small boiler machines is a compromise will be the best option.

 I did wonder about having a go on a machine I owned. Maybe an answer is to set some power level in the heating while a shot is being pulled. Or maybe different PID constants. Good luck. What ever it's still likely to be a compromise.


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## comgnd (Feb 22, 2021)

Hi Newdent,

I recently fell down a similar rabbit hole, adding pre-infusion to my older Lelit Anna machine (similar to Silvia but with built in temperature PID). The Pre-infusion part is relatively easy to add with off-the-shelf parts and without much additional effort you can get a more advanced pressure PID system going. It sounds like you are familiar with embedded programming / Arduino development so you might interested to see the approach I took - the project is open source and available on github at https://github.com/COM-GND/com-gnd-espresso.

If you're willing to install a pressure sensor, i've found that a pressure PID offers much better control then directly modulating the power to the pump. The pump pressure is a dynamic system, so setting the pump power directly doesn't define a constant pressure.

Using a pressure sensor and pressure PID also opens the door to more advanced software-controlled pressure profiling...


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## shadow745 (Apr 29, 2012)

Thing is although incoming water from the tank (into the boiler) during an extraction will drop the temp a bit, it really doesn't affect the end result much at all. By the time the water being used for an extraction makes it to the group it's fairly well stabilized/consistent. By the time the puck is knocked out and a dose is ground, weighed, distributed and tamped the machine will have jumped back up to temp and should be good to go for the next extraction. I have done 5-6 doubles in a 15-20 minute time frame and that was when I was time/temp surfing every extraction and it still remained very consistent for every one of them.


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