Setting up my dual ranco temperature controller?

[Allekornbrauer]

Hello I just have a question about my ranco dual temperature controller setting’s? I have the controller set to 70f with a 2 degree differential an the controller is telling me it’s at 68f. I am testing this with water in my 6.5gal carboy the reason why I am testing it is because I just got a new used refrigerator an want to make sure everything is line up for brewing an also I forgot to to mention the probe to my dual ranco temperature controller is in a Thermowell. Basically what I am asking is why is my controller telling me it’s at 68f an not 70f where I have My dual temperature controller set too?

 

[day_trippr]

Do you have a heater connected to your Ranco controller as well?

The Ranco dual stage is an interesting beast, it appears to contain twin independent controllers that apparently have no inter-communication skills.

The question this image immediately brings to mind is how small can that Deadband be?

Anyway...Note that the Differential settings for the two Stages are inverted - the Cooling (Stage 1) Differential allows the temperature to rise above Set Point before activating the Cool relay, while the Heating (Stage 2) Differential allows the temperature to drop below Set Point before turning on the Heat Relay.

With Stage 1 set for Cooling with a Set Point of 70°F, if the chamber temperature is below Set Point the Cool relay will never turn on.
It would be the job of Stage 2 set for Heating with a Set Point of 70°F to bring the temperature up (assuming some kind of heating device was connected to the Stage 2 relay, of course).

That assumes using a shared Set Point between the two Stages wouldn't be an issue, but the Differential settings should keep the peace.

Bottom line, a fridge can't be warmer inside than the ambient conditions in which it resides. If you have a fridge in a basement and it's not maintaining a warm enough fermentation temperature, you need to add a heater and program the controller to use it...

Cheers!