Rinnai code 63 (recirculation low flow): what to check

Rinnai display

63

“Recirculation Low Flow”

RU/RUR/RSC, RX, RE/REP · SENSEI RU Installation and Operation Manual, p. 74; SENSEI RUR Installation and Operation Manual, p. 73; SENSEI RSC Installation and Operation Manual, p. 73; SENSEI RX/CX Tech Sheet, p. 1; RE Series Installation and Operation Manual, p. 51; REP Series Installation and Operation Manual, p. 50; Troubleshooting Tankless Water Heater Diagnostic Codes, p. 53–54
Owner checks, then technician

What it means

Code 63 is about the hot water recirculation loop: too little water is moving through it RU manual, p. 74. The RX/CX tech sheet states that recirculation flow must be greater than 0.4 GPM (1.5 L/min) p. 1.

The tables name the usual causes: a dirty inlet water filter, recirculation parameters set wrong, the pump’s supply voltage, and air in the recirculation line RU manual, p. 74; RE manual, p. 51. The troubleshooting guide adds two more. On SENSEI and RX models, the heater shows 63 if parameter 04 is set for recirculation but no pump is connected. And a leak in the house plumbing can let the running pump draw air into the system p. 54.

Check these first

1. Clean the inlet water filter RU manual, p. 74; RE manual, p. 51. Rinnai’s maintenance steps: close the cold and hot water isolation valves, put a bucket under the filter at the bottom of the heater, unscrew the filter, rinse off the debris, refit it and open the valves again RU manual, p. 77; RE manual, p. 54. Before any maintenance, Rinnai says to turn off the electrical power, the gas at the manual gas control valve, and the incoming water supply RU manual, p. 7. The troubleshooting guide adds that the heater should be drained before the inlet water filter is removed p. 53. Rinnai also says repairs and maintenance shall be performed by a trained and qualified professional RU manual, p. 76; RE manual, p. 53, so if you are not sure of any of these steps, leave the filter to one.
2. To see how often 63 has appeared, view the code history. Turn the heater off with On/Off, hold On/Off for 2 seconds, then press Up; the last nine codes flash in turn RU manual, p. 73.
3. If 63 returns after the filter is clean, call for service. The tables give no separate reset step for this code.

When to call a licensed technician

• The recirculation parameter settings RU manual, p. 74. Only trained and qualified professionals may adjust parameters RU manual, p. 8. On RX models, if the recirculation water is not hot enough, the pump speed parameter (16A) should be set to Max SENSEI RX/CX Tech Sheet, p. 1. The REP table adds a check of the pump speed settings REP manual, p. 50.
• The pump’s supply voltage RU manual, p. 74, which the guide gives as 120 VAC at the pump wiring harness troubleshooting guide, p. 53, and the wiring between the pump and the PC board RE manual, p. 51.
• Removing air from the recirculation line RU manual, p. 74.
• On RU and RUR models in crossover (COV) mode, the bypass plug removed and a clean bypass filter installed RU manual, p. 74.
• Loop length. The guide caps the recirculation loop’s equivalent length at 400 ft (122 m) with 3/4 in. pipe or 100 ft (30 m) with 1/2 in. pipe troubleshooting guide, p. 54.
• Leaks in the house plumbing p. 54.

Notes for different models

The RSC table drops the bypass plug and bypass filter items that the RU and RUR tables carry RSC manual, p. 73. The Value, V53De and VC tables have no code 63, although the troubleshooting guide applies it to Non-SENSEI models too p. 53.

All Rinnai codes

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