Rinnai SENSEI Code 19
Electrical grounding fault. The heater has detected a grounding problem in its own 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 inside a live unit. Have the circuit and the heater checked; a licensed electrician may be needed too if it turns out to be 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 — 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.
- Do not open the unit or test its wiring yourself.
Frequently asked questions
Is this the house wiring or the heater?
Either, and both get checked. A poorly grounded or reverse-polarity outlet produces the same symptom as a short inside the unit, and it is much cheaper to fix.
Code 19 on other Rinnai series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: