Noritz NRC Series Code 20
High limit switch triggered. The high limit switch has tripped. This is the safety device that stops the unit when the water gets too hot, and Noritz's checks are whether it has actually triggered and whether it is properly connected. It sits downstream of everything that can overheat the appliance, so it is the symptom rather than the cause.
Call a proThe verdict
Call a licensed plumber
A tripped high limit is the appliance protecting itself. Resetting power clears the code, but if it comes back the switch is doing its job and something upstream is genuinely overheating — scale, a restricted flow, or overfiring.
Typical cost: $150–$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.
- Note how many times this has happened and how quickly it returns after a power cycle.
- Check the water filters are not restricting flow — low flow through a firing heat exchanger is a common route here.
- Call a licensed professional if it returns. Do not bypass or jumper the switch under any circumstances.
Frequently asked questions
How is 20 different from 14?
Code 20 is the high limit switch, which is resettable — cut the power and restore it and the unit runs again. Code 14 is the thermal fuse, which is not: it is a one-shot part that has to be replaced. Repeated 20s are the warning that a 14 is coming.
Code 20 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: