HVACopedia

Rinnai · Tankless water heater

52 Gas valve / modulating solenoid valve (POV) signal fault

High severity Non-SENSEIRH180 hybridSENSEI RX/CXSENSEI

What the control is telling you

Fault in the gas valve circuit. On SENSEI and SENSEI RX/CX units it involves the gas valve solenoid; on Non-SENSEI units it means the modulating solenoid valve (POV) signal is abnormal.

Applies to: SENSEI Series, SENSEI RX/CX Series, Non-SENSEI Series

Likely causes

  • Loose, broken or damaged flame rod or flame rod wiring
  • Loose or damaged terminals on the gas solenoid harness
  • Failed gas valve solenoid or gas valve/venturi assembly
  • Open POV coil on the gas valve (Non-SENSEI)
  • No voltage reaching the gas valve / POV during ignition
  • Faulty PC board

Test and repair steps

  1. Warning: Shut off both power and gas to the unit before starting work.
  2. SENSEI / SENSEI RX/CX Inspect the flame rod and its wiring for loose, broken or damaged parts or connections.
  3. SENSEI / SENSEI RX/CX Inspect the gas solenoid harness for loose or damaged terminals.
  4. SENSEI At PC board connector D, black pin #27 to yellow pin #29 should read 18 ~ 22 ohms or 11 ~ 13 VDC. SENSEI RX/CX: at connector CN9, black pin #3 to yellow pin #4 should read 11 ~ 13 VDC.
  5. SENSEI / SENSEI RX/CX Restore power and confirm voltage reaches the gas valve during an ignition attempt.
  6. SENSEI / SENSEI RX/CX Replace the gas valve and venturi assembly. If 52 still shows afterward, run the PC board button reset described in the next step.
  7. SENSEI / RX/CX reset controller off, tap PC board button B (1 s each) through the menu until "E" appears, then hold A and B for 10 s until "ECL" shows. Menu order per series: see source manual (p.46–47).
  8. SENSEI / SENSEI RX/CX If code 52 will not clear after the reset, contact Rinnai technical support.
  9. Non-SENSEI Inspect the harness running from the POV valve to the PC board for loose, broken or damaged connections.
  10. Non-SENSEI Unplug the POV and measure its coil resistance; compare with the Tech Data Sheet (back of the front panel) or the service manual. Replace the gas valve if the coil is open.
  11. Non-SENSEI For accurate readings use a meter with a good battery on the correct ohm range, and isolate the part from the circuit and power supply.
  12. Non-SENSEI Check for voltage at the POV while the unit attempts to fire; if voltage is correct but the code remains, go to the next step.
  13. Warning: Disconnect power to the water heater, then replace the PC board if code 52 persists.

Settings for these units

Save it for the next call

Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.

Open the app

Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.46–48. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.