Use two timer relays, first make a half-hour timer, 18000X0.1=1800 seconds, this timer will trigger an M point again, use this M point to trigger another half-hour timer again.
How to use the gx developer timer to time one hour
Use two timer relays, first make a half-hour timer, 18000X0.1=1800 seconds, this timer will trigger an M point again, use this M point to trigger another half-hour timer again.