Heater starts and stops frequently (short cycling), with only brief run times before shutting off.

Safety: Turn off power before adjusting internal components; plumbing adjustments should be done with pump off.

Steps:

• Observe cycle: Note how long the heater runs before shutting off and whether it immediately restarts. Check if the thermostat is quickly satisfied.
• Check bypass settings: If a manual bypass is installed, ensure it is adjusted so that recommended flow passes through the heater (refer to Lochinvar manual). Excessive flow can reduce temperature rise and cause rapid cycling.
• Verify sensor placement: External pool sensors should be installed downstream of the heater and at least several feet away to avoid sensing hot water too quickly.
• Confirm setpoint: Make sure the set temperature is significantly above current water temperature during testing.

If short cycling persists, a technician should verify sensor calibration and system design.