to generator 230 generator 230 has an output cfmrn the reference neutral flow when in the neutral mode or otherwise 0 the output cfmrn is supplied to single zone neutral mode control 232 which is identical to the single zone cooling mode control 208 of fig1 except that 1 cooling damper actuator 72 is replaced by neutral heating damper actuator 74 2 there is no addition or removal of heat as represented by coils 32 and 3 there is no need for tz to be fed back as to coils 32 if in the fig3 a and b examples tz is less than thsp 2 where 2 is an adjustable heating range then tz will be fed through detector 200h and the control will operate in the heating region otherwise the output of detector 200h is 0 which takes away any active change in the loop if the control is in the heating region the output tz from detector 200h is fed as a negative first input to summing junction 240 thsp is supplied as a second input to summing junction 240 the difference between u03b4t2 and thsp tz is the temperature set point error and is supplied to integrator 242 which has a reset function integrator 242 acts like integrator 204 and adds the u03b4t2s and saves them until an 34 event 34 takes place whereupon it resets an 34 event 34 can be the moving out of the heating range or a change in thsp the output of integrator 242 u03b4t 39 2 shifts the heating region along the curve in fig3 and is supplied as a first input to heating junction generator 244 u03b4t 39 2 adds stability so that the system does not overshoot when making a correction by taking.