Honeywell SDC Service Manual page 179

SDC / DHC Hydraulic Components
of room setpoint, thermostat function, room controller setpoint
etc.).
Switch-over from heating mode to cooling mode:
If the outside temperature is greater than summer switch-off (see
"System Parameters", summer parameter) and the switch-on
temperature for cooling, the cooling function is active.
If the outside temperature is lower than the summer switch-off and
the cooling switch-on temperature of cooling –1 K, the cooling
function is not active. A switching differential is required.
With the cooling function active, the "cooling switch-over" output
in the "Hydraulics" menu, parameter 06/07, setting 25 = ON. This
is switched on inversely via an input on the heat pump. If cooling
mode is interrupted due to the switching conditions of the timer
(ECO lowering phase), the output switches OFF, even if the
switching conditions are present otherwise.
Heating circuit correction:
For cooling operation, the mixed heating circuit corrects to the
setpoint temperature at the flow sensor (see the "Heating Circuit"
menu, heating circuit cooling setpoint temperature parameter) and
functions as a heating controller.
EN2H-0221GE51 R0812 179