Rinnai IP150S Error Codes

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

Rinnai IP150S error codes and diagnostic codes (also listed as REB-B4400FF-US). The IP150S is a Rinnai boiler in the I-Series Plus 150K and smaller series.

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Rinnai IP150S error codes list

Code	Meaning	Severity
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
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
310	Freeze protection thermistor fault	Medium
353	CH supply thermistor fault	Medium
363	CH return thermistor fault	Medium
371	Indirect tank 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
700	PC Board fault	High
710	Gas solenoid circuit – valve position mismatch	High
720	Flame rod fault	High
831	Indirect tank call running too long	Medium
890	Freeze condition detected	High
999	PC Board / software mismatch	High
FFF	Maintenance performed marker	Low
SS	Service Soon reminder	Low

Troubleshooting the IP150S

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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 IP150S error codes list

Troubleshooting the IP150S

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