Post By Dimal
PID with boiler insulated
Hi, I was wondering whether anyone else has experienced this.
I have a Silvia in which I installed a PID to a while ago and its been working very well. A few day ago I insulated the boiling using the original insulation used in the latest V5 Silvia.... a straight forward job.
The issue is now that when the PID is set for 105c, the brew water temperature is now too high creating a bitter taste to the shot. I'm guessing that with the insulation installed, the boiler is more efficient and preventing the temperature of the water to drop quickly.
Does that mean the SV of the PID should be set more towards the required brew water temperature then before? Previously I was following the supplied graph to work out the temperature eg. 105c = 95c water temp.
Has anyone else insulated their boiler and had this issue?
Thanks in advance.
Is it easy to lower the PID temp. if so try 103degrees. It may be your grind is to fine or your tamp too heavy. On my old Sylvia it was very simple to alter the temp. Without insulation I had mine set to 106.
Yes that is what I'm going to do but do I need to change any of the parameters? Like I said, the only thing I did was insulate the boiler. The shots tasted fine before that.
Logically a PID controller will need change to settings with a change to the physical machine. Insulating the boiler will mean the response from the heating element will heat the water faster as there is less heat escaping from the walls of the boiler.
I would doubt it would be hugely different, but I would also put money on you will need to change the second value slightly. If the graph you had was calibrated for a non-insulated boiler then the graph is no longer as valid as the actual conditions of the machine have changed. It will mean for every extra bit of energy transferred form the element to the water you will get a slight improvement in the increase in water temp - for example, if before 100 joules of energy raised the temp of the boiler by 1 deg it will now be 1.1 deg (don't take these numbers as gospel however!)
Can't help you with the actual set point unfortunately.
Thank you WhatEverBeansNecessary. I might try running the tuning feature and see whether that changes much. Do you know whether that is run from cold or after the machine has warmed up?
I would think after it is warm. I will admit I haven't had any experience tuning a PID for an espresso machine, but I did get a lot of experience with PID's from my Engineering degree days. Essentially what any PID is trying to do is stabilize the machine condition (temperature/pressure in this case) when given some change to the input (like steaming milk or pulling a shot means topping up with more cold water, thus temp decreases).
The PID tuning will definitely be the way to go, but make sure you note down your settings for each of the controller values first! The PID tuning is a pretty interesting subject (at least to me!). The controller attempts to work out the most efficient settings for each setting by getting the system to perfectly oscillate the feedback loop at steady state and apply a calculation to determine what should be the optimal settings.
The tuning will introduce small variations to the output (energy supplied to the element) and determine what the effect is on the input (boiler temp) until its satisfied the system is at stable at the desired set point (ie temp).
This means you should let the machine heat up to desired temp and then run the tuning tool. Each temperature set point will have slightly different optimal setting, but a few degrees in temperature set point change will be unlikely to change the PID controller settings much.
Don't know if the PID Controller you have has the "Auto-Tune" function, but if it does, then I would use this to re-establish the PID parameters with the insulated boiler. Afterwards, if you want to fine-tune the PID Parameters, there is a plethora of info available on the Net on how to go about this...