Note that older 3.5kW heaters are replaced by the 3.0kW heater now.
This assembly comes with new high-temperature sensors and water sensor. Standalone elements are not available. Does not suit other Spa Power Controllers.
Once fitted, heaters cannot be returned if this does not fix your problem, as they show immediate signs of use. These Spa Power control systems are now at least 15 years old, so other issues may be the cause of failures.