Noritz NR98 & NR111 Code 20
High limit switch triggered. The high limit switch has tripped. Noritz's checks on this range are short: whether the switch is triggered, and whether it is improperly connected. It is the safety device that stops the unit when the water gets too hot, so it sits downstream of everything that can overheat the appliance.
Also displayed as: F20
Call a proThe verdict
Call a licensed plumber
Cycling the power clears it. If it returns, the switch is doing its job and something upstream is genuinely overheating — scale, 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 NR98 & NR111 — not averaged across the brand.
Source: Noritz Service Manual — NR50 / NR66 / NR71 / NR98 / NCC199 / NRC111 / NR111 / NC380 (Rev. July 2011) (p. 56), 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 quickly it returns after a power cycle.
- Check the water filters are not restricting flow.
- If it returns, call a licensed professional. Never bypass or jumper a high limit switch.
Frequently asked questions
The NCC199 page says that model has two high limit switches. Does mine?
Noritz makes that note against the NCC199 and NRC111 table, not this one. The check here is a single switch. It is a good example of why the two tables are separate files rather than one Noritz page.
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:
Don't confuse this with
One other Noritz NR98 & NR111 code points at a switch 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: