Rinnai SENSEI RX Code 19
Electrical grounding fault. The heater has detected a grounding problem in its own electrical circuit. Rinnai groups code 19 with an immediate code 12: if it appears as soon as water starts flowing and no flame is visible in the burner box, the fault is an electrical short in one of the unit's components — a wiring harness, the water flow control, the bypass valve, or anything else on the DC circuit.
Call a proThe verdict
Call a licensed plumber
A grounding fault on a gas appliance is not a reset-and-hope situation. Rinnai's diagnosis is to isolate the shorted component by unplugging one at a time inside a live unit — technician work. Have the circuit and the unit checked; a licensed electrician may be needed as well if the fault turns out to be in the house wiring.
Typical cost: $150–$800
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the SENSEI RX — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 31), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Turn the heater off and leave it off.
- Note whether the code appears the instant you open a hot tap — that detail narrows the diagnosis and is worth telling the technician.
- Do not open the unit or test its wiring yourself.
Frequently asked questions
Is this my house wiring or the heater?
Either. Rinnai's note covers a short inside the unit; a poorly grounded or reverse-polarity outlet produces the same symptom. Both get checked, and the outlet is the cheaper of the two to fix.
Can moisture cause code 19?
Yes. Rinnai's related checks include damp or wet electrical connections inside the cabinet — which is also a warning that water is getting somewhere it should not.