Noritz NRC Series Code 16
Abnormally high output temperature. The water leaving the unit is hotter than it should be. Noritz checks three things in order: the resistance of the hot water thermistor, the gas proportioning valve, and the manifold pressure. The first would mean the unit is measuring wrongly; the second and third mean it really is overfiring, which is a combustion problem rather than a measurement one.
Also displayed as: 161, 162, 163
Call a proThe verdict
Call a licensed plumber
Two of Noritz's three causes are gas-side, and overfiring is how a heat exchanger gets destroyed. Turn the temperature setting down while you wait if the unit still runs, and treat scalding as a real risk until someone has checked it.
Typical cost: $200–$900
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.
- Turn the set temperature down at the controller and warn anyone in the house before they use a tap.
- Note whether the unit has ever been converted between natural gas and propane.
- Call a licensed professional — measuring manifold pressure takes instruments and is not a homeowner check.
Code 16 on other Noritz series
Other Noritz series report code 16 under the same fault name, but each manual is transcribed separately and they do not read alike: