Rinnai Combi Boiler Error Codes

Updated October 13, 2026 · by Aurora Star Tech Inc.

42 Rinnai Combi Boiler error codes and diagnostic codes, with causes and troubleshooting steps for each. Select a code, or find your model below.

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Rinnai Combi Boiler error codes list

Code	Meaning	Severity
021	DHW continuous operation time exceeded	Low
100	Air intake/exhaust blockage or full condensate trap	Critical
110	Ignition failure	High
120	Flame failure (flame lost during operation)	High
140	Overheat switch tripped (heat exchanger overheating)	Critical
150	Venturi control fault	High
161	High DHW outgoing water temperature	Critical
170	Venturi blockage / position mismatch	High
180	Gas valve air/fuel adjustment limit reached	High
190	Electrical grounding / short in DC circuit	High
210	Data transfer error	Medium
220	Gas valve position not detected (reed switch)	Medium
250	Condensate pump switch tripped (accessory)	High
303	Secondary system thermistor fault	Medium
310	Freeze protection thermistor fault	Medium
321	Outgoing (DHW) water temperature thermistor fault	Medium
331	Plate heat exchanger thermistor fault (DHW)	Medium
341	DHW inlet thermistor fault	Medium
353	CH supply thermistor fault	Medium
363	CH return thermistor fault	Medium
380	Exhaust thermistor fault	Medium
393	Outdoor temperature sensor fault	Medium
400	Water pressure sensor communication fault	Medium
430	High or low system water pressure	High
443	Low water cut-off (LWCO) activated	High
520	Gas solenoid valve circuit – flame after valve close	Critical
540	High exhaust (flue gas) temperature	Critical
610	Combustion fan motor speed fault	High
631	DHW recirculation pump – insufficient flow	Medium
651	Water flow control valve fault	Medium
661	Bypass valve fault	Medium
670	Three-way valve fault	Medium
681	DHW supply temperature abnormality	Medium
700	PC Board fault	High
710	Gas solenoid circuit – valve position mismatch	High
720	Flame rod fault	High
763	0-10V external control input over-voltage	Medium
890	Freeze condition detected	High
999	PC Board / software mismatch	High
FFF	Maintenance performed marker	Low
LC	Lime condition – flush plate heat exchanger	Low
SS	Service Soon reminder	Low

Find codes by Rinnai model

I-Series Plus 150K and smaller

IP060160C IP090099C IP090160C IP090199C IP120199C IP150199C

I-Series Plus 175K and higher

IP175199C IP199199C

Homeowner help: Tankless Water Heater No Hot Water: What to Check · Boiler Not Heating: What to Check

General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.

Rinnai Combi Boiler error codes list

Find codes by Rinnai model

I-Series Plus 150K and smaller

I-Series Plus 175K and higher

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