FB58 heating and cooling

For cooling /heating strategy I think you need a block that generates pulses for both positive and negative LMN values(3-step control).That is also possible with FB43.I think it can be used with ONE FB58 while using LMN as input.

I don't think the scenario you haave mentioned is practically possible. In case of starting from standstill when (SP>PV) and using PID controller for FB58_1 with positive gain,We automatically start from a positive LMN for heating valve.As error is positive in this case, the cooling valve is always close in this case(negative LMN).In case of overshoots,we encounter a negative gain and consequentlly a positive LMN for cooling valve.Because of using I-Part in case of FB58_1 , we never expect rapid jump to 0.A slight decrease is expected in output of heating while output of cooling section will react based on overshoot and the parametrs.You may select parametrs for the cooling part as aggressive values for fast response or small values for moderate action.