Johnson controller

I just got a new chest freezer setup, but my Johnson controller seems to be 3-5 degrees off it's set point. I have another JC with my lager freezer and it's always within a degree or two. Any thoughts or am I being to anal?

If you check the temperature with an accurate thermometer and it doesn't quite agree with the JC control, I think you can adjust the offset parameter to correct for this.

That sounds right, adjust the displayed value if it is off from the actual by a few degrees. I don't think the probes are super high accuracy.

If on the other hand you mean it is swinging the temperature too much you may need to turn down the d1f dif to 1 degree even. I would keep the short cycle delay timer as high as she goes though, or at least three minutes.

If you mean the temperature keeps dropping after the Johnson turns the freezer off, there isn't anything the Johnson can do about that, it's just on/off control, it is not tunable like a PID.

Also you might have to check the cut in/out options/settings, like is it cutting in a setpoint and cutting out at setpoint minus differential? If so it might seem like the temp is too low.