Nibe SMO 40 User Manual page 51

Set the hot water circulation for up to three periods per day here. During the set
periods the hot water circulation pump will run according to the settings above.
"operating time" decide how long the hot water circulation pump must run per
operating instance.
"downtime" decide how long the hot water circulation pump must be stationary
between operating instances.
Hot water circulation is activated in menu 5.4 "soft inputs and outputs".
NIBE SMO 40 Chapter 3 | SMO 40 – at your service 51