Bumpless Transfer is a method used to prevent sudden changes to the correcting variable, when switching between automatic PI or PID control and Manual control modes.
During a transition from PI or PID to Manual control, the initial Manual Power value is set to the previous automatic mode value. The operator then adjusts the power output value as required.
During a transition from Manual control to PI or PID, the initial automatic value is set to the previous Manual mode value. The correcting variable level will gradually adjusted by the control algorithm at a rate dependant on the integral action resulting from the Integral Time Constant value.
Since integral action is essential to Bumpless Transfer, this feature is not available if Integral is turned off.