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

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

RSC supply connection sizes · SENSEI

The PRV and its adapter come in the box; PRV must be rated 150 psi and at least the heater Btu/h.

Condensate drain line must stay at least 1/2 in. over its whole length.

RSC water quality limits · SENSEI

Damage from water above these limits is not covered by warranty.

Hard water should be treated; use the Service Soon (SS) reminder (parameter 03) for flushing intervals.

• RSC clearances to combustibles · SENSEI
• RSC temperature settings available · SENSEI
• RX supply connection sizes · SENSEI RX/CX
• RX water quality limits · SENSEI RX/CX
• RX water treatment and flushing by hardness · SENSEI RX/CX
• RX clearances to combustibles · SENSEI RX/CX

Models that show this code

89 models in Non-SENSEI, RH180 hybrid, SENSEI RX/CX, SENSEI

Other codes on the same units

• 35 Tank temperature sensor fault
• 38 Exhaust gas temperature sensor (CO sensor on RH180)
• 41 Freeze protection / outdoor air temperature sensor fault
• 51 Inlet water temperature thermistor fault
• 54 High exhaust gas temperature
• 57 Burner overheat bi-metal switch open
• 58 Secondary heat exchanger bi-metal switch open
• 61 Combustion fan motor fault