Noritz NRC Series Code 94
Exhaust temperature too high. The flue is running hotter than it should. Noritz's check is a single line — check for abnormal combustion — pointing at the exhaust thermistor as the input. The 2017 service manual for the NRC663-FSV labels the two display-window codes explicitly, 941 as a warning indication and 942 as the unit shutting off; the 2013 manual prints the same two numbers without those labels. Below both sits a locked state that Noritz says requires a Noritz agent to clear.
Also displayed as: 941, 942
Call a proThe verdict
Call a licensed plumber
An overheating flue is usually a heat exchanger that is no longer transferring heat into the water — which means scale — or combustion that has drifted. Both get worse, and the second one puts heat into vent materials that were sized for a cooler exhaust.
Typical cost: $200–$1,000
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.
- Note whether the display shows 941 or 942: one is a warning, the other is a shutdown.
- Note when the unit was last flushed — scale is the common route to a hot flue.
- Call a licensed professional. Do not keep resetting it to get through the week.
Code 94 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: