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
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: