Hey folks: I need a temp controller for my fermentation chamber. I know most folks buy the Johnson A419 which controls heating or cooling. I have that on my keezer. I only need the controller to heat so do I need one where the SPST opens high with a range of 30-100F? These are much cheaper $20.00 vs. $50.00 for the models that heat and cool. The model I am currently looking at is A19AAB. Thanks for any info. Charlie