Thanks for sharing!
Originally Posted by geoffey
But so far my system has proven capable of holding temperatures steady very precisely. I've over-shot my temp a couple of times, but I think I've got the system calibrated accurately now. I will say this: my system at this point seems to be fairly slow to adjust/respond when I want it to. For example, Mashout will take probably 15 minutes or so unless I go to manual mode and set it for 90%. But then I need to sit and watch my temps so that I don't overshoot! This may get better over time, but it's the biggest drag for me so far.
Your PID will learn your system over time and become more accurate. Many PIDs have a learning mode where you can force it to spend about ~15 minutes to learn to speed up this process.
Once trained it should be nearly impossible to overshoot since the PID will be in control. It should also be nearly impossible to do it faster yourself by going to manual mode. Once the PID understands your system behaviour it will crank the heat at 100% and then back off by cycling the heat as it nears the target temperature so that you don't overshoot.
I say "nearly" simply because environmental differences between batch to batch can have have a slight effect. Things like the rate at which you recirculate (if you don't always do the same), ambient temp, or (the biggest one): The amount of grain. The more grain you have, the more heat it takes.
Got any pictures of the relays you used?
These relays are made for switching up to 30amps of 277v circuits multiple times a day with lighting loads which carry a huge current inrush. They are warranteed for 5 years and have a 20 year expected lifecycle.
What's the expected duty cycle for such a warranty? They may be meant to be switched off many times/day but what about many times/minute or even a few times per second? If you can, I would set your PID to "relay output" so that it doesn't switch on/off too fast.
Best of luck!