Raypak INLET SEN Error Code
Inlet water sensor fault on the XTherm/MVB controller display.
Source: hvac/raypak/47951c62__h-1005a__ryp-xtherm-1005a-2005a-iom.pdf
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
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Diagnostic steps
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.
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.
Inspect the PIM connection
Confirm the inlet sensor leads are securely landed at the PIM.
Reset the control
After the sensor and wiring are confirmed good, press and release the RESET button to clear the fault.
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.
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Other Raypak Error Codes
Outlet water sensor fault on the XTherm/MVB controller display.
High limit sensor fault on the XTherm/MVB controller display.
Gas pressure / PIM wiring related error on the XTherm/MVB controller display.
Ignition fault on the XTherm/MVB controller; clear with RESET.
Heater temperature tripped the high limit on the XTherm/MVB controller.
False flame detected on the XTherm/MVB controller display.
Identity card fault on the XTherm/MVB controller; check ID card and wiring.
Internal control fault on the XTherm/MVB controller; reset power, replace control.
Temperature difference between inlet and outlet exceeded the setpoint.
Low 24 VAC power; check power supply wiring and transformer.
Blower speed out of range; check blower wiring and blower.
Unit not detecting enough flow to allow the ignition sequence.