PID help for furnace.


 

Brian Mc

TVWBB Member
I know its not BBQ related but its still a forum for the heatermeter.
I'd like to use the heatermeter to run an SSR opening and closing the circuit for my garage NG furnace.
No idea what to do with PID values, search didn't find anyone trying it...
Anyone got a good jump off for settings to start with?
 
Absolutely can be, I have a thermostat that works fine.

I'd like to figure out how to get as much as possible out my heatermeter is all. I'd also like to figure out how to run time based scripts for it if possible. But one step at a time.
 
Dealing with time based scripts on the HM is just a matter of writing cron jobs

Typically with a furnace, there's a lag time from the time that the signal is sent, to the time the furnace starts doing something. Also, you don't normally have control over the heating mechanism, so unlike a heating element on a sous vide controller. where the heatermeter can modulate it, this would be rather hard to do, and could potentially damage the furnace.
 
It would be direct control of the gas valve. and it would still be modulating but only 2 states on & off. Basically I want to be able to overshoot and undershoot a setpoint by around 3-5 deg before the output switchs state.
The issue I see is that at the switching points the SSR switchs on and off multiple times, which would probably be bad for the gas valve.
 
So a bit of a walk around that doesn't need PID tuning really. I used the Alarm settings, so when it hits the High threshold a new (much lower than desired) setpoint is triggered, and then when it hits the Low threshold a new (much higher than desired) setpoint it triggered. Seems to be working just fine so far.






The SSR and how it's connected:



 

 

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