The control system checks the spa water for temperatures equal to or above 110ºF(43ºC). If the water temperature is equal to or above 110ºF(43ºC), The topside control will display the code “Ht” - current water Temp - “Ht”. All the Jets will shut down. The air blower (if equipped) is automatically energized to assist in lowering the water temperature when equal to or greater than 110ºF. The blower will be deactivated after the spa temperature drops below 107ºF. This issue can be caused by ambient temperatures in the summer time or excessive high speed jet operation, for example resetting the high speed Jets continuously after each 20 minute shut down cycle may eventually cause the “HT” condition. Allow time for the system to reset. This must be repaired by a service technician if the problem persists.