Announcement

Collapse
No announcement yet.

Silvia temperature control & PID

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Silvia temperature control & PID

    Like many, i have a Silvia with PID control on the brew temperature which works wonders at stabilizing the temp......
    .....untill you pull a shot !
    Then, as i guess we all know , the boiler gets cooled by the incoming water and the temp dives down into the 80s until the heater catches up and the PID settles her back at the preset temp. ..usually about 2 mins later.
    I was just wondering if anybody had tried installing a water "pre-heater" system ( possibly a small thermoblock or "snail" heater unit from a pod machine) into the boiler water feed line to prevent this "thermal jolt" and help the boiler stay at the preset temp. ?
    This could be simply powered from the pump "brew" switch to only power on when water is being transferred to the boiler.
    Has it been tried / considered ?
    Is it worth it ? ( IE: can you tell the difference in a few degrees temp change during the shot flow ?)
    Any reasons NOT to consider this mod ?

    IDEA ! .. Maybe i will just fill the tank with boiling water instead to see if there is any difference detectable to coffee taste ? ;D

  • #2
    Re: Silvia temperature control & PID

    Remember, youre measuring the temperature at the boiler, not at the brew head. Ive never tested it myself, but Ive read about tests which showed very little temperature drop at the head during a normal pour. I dont believe the small temp drop at the head will effect the extraction at all.

    Im very surprised your boiler temp varies so much. When I pull a double (about 50ml in 25-30 seconds) the boiler temp will only drop from 105 to about 98-100 dependng on the flow rate. The only time it drops into the 80s is when I flush water through to heat my cups - and even then it recovers to 105 by the time Ive prepared the portafilter for the next shot.

    I wonder if you have a build-up of scale on the element slowing your heating. When did you last de-scale?

    Comment


    • #3
      Re: Silvia temperature control & PID

        Yes the temp drop will depend on your shot volume ( mine are always doubles )
      Descaled less than 6 months ago. not a heavy user , and this (filtered) Sydney water doesnt generate much if any, scale.
        Heating is generally fast ( cold to 109 C ) in less than 5 mins, but i do feel the PID is slow to react some times .( with PID control, the heater is usually "pulsed"  rather than on 100% of the time  until set temp is reached )

      EDIT: ..I am not too unusual...
        Just found PID Silvia graphs on another site showing temp running down from 222 F ( 106 C) set point to 170 F ( 78 C) , drawing a  after shot 

      Comment


      • #4
        Re: Silvia temperature control & PID

        Originally posted by 010F060D075651630 link=1333337613/2#2 date=1333349787
        but i do feel the PID is slow to react some times .( with PID control, the heater is usually "pulsed" rather than on 100% of the time until set temp is reached
        depends on how far you are from the setpoint. As you can see in the business zone, the element is on 100% (Can you verify yours is?)

        Interesting to see the setpoint jump up though - must be some attempt at countering the heavy expected losses by fooling the controller into thinking you want 300 degrees, so the output winds up very fast. It seems to do this when you hit the brew switch.

        It looks like the recover is about 1 minute after a 30s shot - how long is your shot blend42?

        Comment


        • #5
          Re: Silvia temperature control & PID

          I tried a pre-heating pipe in my Salda, and I am pretty pleased with the way its turned out. I dont use a PID, but if I pre-empt the temperature drop and hit the steam switch just before brewing I can have the element ramp up just before the cold water comes in and keep things pretty stable during a longer extraction.

          The hardest thing to account for is the lag in the response of the thermocouple from the thermal mass of the brass - there is a delay of maybe 5 seconds until I see switching the heater on reflect in a temperature rise.

          See the thread here: http://coffeesnobs.com.au/YaBB.pl?num=1319264679

          Comment


          • #6
            Re: Silvia temperature control & PID

            ...It looks like the recover is about 1 minute after a 30s shot
            Well its actually more like 5 mins before the temp has stabilized back to his set point.
            but i dont have as much "overshoot" as his and mine is stabilized again within 1.5-2.0 mins.
            I try to aim for the usual 25-30 sec shots.
            does anyone have detailed "scace" puck temperature readings for a PID silvia ?.
            I have to think that for the thermocouple to see such a rapid temp fall on the surface of the boiler, the water temp muct be somewhat colder than actually recorded by the TC ?

            Rick, thanks...I didnt think i was the only CS to have considered this possibility ( I even imagined the same copper coil as you !)..  yes and there is several seconds delay between starting to pull a shot ( cold water into the boiler) and the PID seeing any temp change and turning the heater on. ( and of course there is lag between the heater being energized and the water temp actually rising too )

            Comment

            Working...
            X