I guess I still don't understand what the r2 setting does.
Operation mode ON/OFF ON1 with r0 set to ind
, c2= inv.
Relay #2 turns on when temp probe 1 is less than SP2-r2
If we set SP2 to 60° F and r2 to .5°F
the relay 2 turns on at 60 - .5= 59.5°Fturns off at SP2 or 60°F
If we set SP2 to 60° F and r2 to 2°F
the relay 2turns on at 60 - 2°F= 58°Fturns off at SP2 or 60°F
Operation mode ON/OFF ON1 with r0 set to dep
, c2= inv.
Relay #2 turns on when temp probe 1 is less than SP1+SP2-r2, off at SP2
If we set SP1 to 60°F, SP2 to 50°F and r2 to 1°F the relay 2 turns on because temp is less than (60+50°F-1°F=) 109°Fturns off at 50°F
I set SP1 to 65 and I set SP2 to 40. When the temp hits 65 - SP1 output becomes hot, but it seems SP2 output is always hot.
See example #2 if r0 was set to dep
Heating and cooling automatically without changing SP2 every time you change SP1 to have the same temp differential between cooling & heating.
You can set SP2 = 0, r0 set to dep
, r2= 25°F
and SP1 65°F as per your above settings without worrying about SP2 and have the same result.
Relay #2 turns on when temp probe 1 is less than SP1+SP2-r2, off SP1+SP2
65°F+0°F-25°F= 40°F relay turns on
65°F+0°F= 65°F relay turns off
Every time you change SP1 the heater comes on when the temp is 25°F below SP1 (r2 setting) without changing SP2.
What do you mean by:
"If you need to coast toward the set point like I require SP2 can be less than 0." ?
Since my setup has a very narrow band between cooling and heating (1.5° F)
I turn the heater off before the temp reaches the set point SP1 to prevent an overshoot, and unnecessary cooling cycle.
My SP2 is set to -1.4°F for my requirement, heater has large terminal mass compared to the heating volume of my cube fridge.
If you need more info about negative temp for SP2 send PM, boring subject.