LoneGunman,
Depending on the system, that could be a little more involved than just installing a simple timer in the circulator control circuit.
On many larger systems, the chiller PLC also controls the circulator pump operation based on inlet/outlet water temperature, among other things.
An interval timer’s input voltage would be disrupted every time the chiller’s PLC shuts down the motor, resetting the timer. You may need to tap a continuously energized circuit from ahead of the PLC output relay the to maintain input voltage on the timer. Maybe for your installation, you could then use a SSAC KSPU [up to 1000 hr.delay] interval timer to act as an input source for an SSAC ARP alternating relay to redirect the circulator motor control circuit.
Another issue that may arise is that many times the butterfly valves on the output side of the pump not being used are manually closed by maintenance personnel to prevent any pressure loss in the active loop and to keep backflow surge pressure from hammering the pressure gauges on the idle pump. These valves sets would need to be opened/closed when the pump change-over takes place.
Regards
