Noritz NRC Series Code 72
Flame rod circuit fault. The unit is detecting a flame when there should not be one. Noritz's procedure is to measure the current from the flame rod with no flame present and to check for a ground fault. This is the reverse of code 12: instead of failing to see a flame that is burning, the appliance believes it can see one that is not.
Call a proThe verdict
Call a licensed plumber
A false flame signal is a safety fault, because the logic that decides whether it is safe to open the gas valves depends on it being right. Noritz's remark is that power must be cycled to clear the code — but if it returns, leave it off.
Typical cost: $150–$700
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 NRC Series — not averaged across the brand.
Source: Noritz Service Manual — NR501-OD, NR662-OD, NRC661, NRC711 (Rev. Dec 2013) (p. 28), read Sep 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.
- Cut the power for a minute and restore it, which is Noritz's documented reset for this code.
- If 72 returns, switch the unit off and leave it off.
- Call a licensed professional — a ground fault is one of Noritz's two named causes and it needs measuring, not guessing.
Code 72 on other Noritz series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit:
Don't confuse this with
One other Noritz NRC Series code points at flame detection too. They are different components in different places, and ordering a part against the wrong one is the most common way this fault gets expensive: