Raypak INLET SEN

What does Raypak INLET SEN mean?

The controller has detected an abnormal reading from the inlet water temperature sensor. The inlet sensor lets the control measure return-water temperature and calculate the temperature rise across the heat exchanger, so a bad reading triggers the INLET SEN error. The condition may be temporary or may lock the unit out until the sensor and wiring are corrected and the control is reset.

Symptoms

• INLET SEN shown as the active error on the display
• Heater may lock out or fail to hold setpoint
• Possible companion DELTA T error if rise cannot be calculated
• Red fault LED on the PIM

Common causes

• Failed or out-of-range inlet water sensor
• Damaged or loose inlet sensor wiring
• Disconnected sensor at the PIM
• Sensor resistance outside the published range

Diagnostic steps

1. 01

   Check the inlet sensor and its wiring

   Per the manual, inspect the inlet water sensor and the length of its wiring for damage or loose connections.

2. 02

   Verify sensor resistance

   Measure the sensor and compare it to the Sensor Resistance Values table for the measured water temperature; replace if out of range.

3. 03

   Inspect the PIM connection

   Confirm the inlet sensor leads are securely landed at the PIM.

4. 04

   Reset the control

   After the sensor and wiring are confirmed good, press and release the RESET button to clear the fault.

5. 05

   Observe operation

   Watch several cycles to confirm correct operation and no recurrence.

When to call a professional

Confirming a sensor fault requires a multimeter and the manufacturer's resistance table, and any sensor work happens around hot water, gas, and live electrical connections. The manual requires verifying the heater is depressurized, cooled, gas-off, and de-energized before servicing. If you are not equipped to make those checks safely, call a qualified Raypak service technician.