20
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Noritz · Tankless Water Heaters
High-limit safety switch was triggered.
Quick Answer
Error code 20 on your Noritz Tankless Water Heaters means: High-limit safety switch was triggered.. This is usually fixable — see the step-by-step guide below.
Affected Models
Likely Causes
How to Fix It
1
Stop operation and let system cool.
2
Check vent and airflow conditions.
3
Flush heat exchanger if scaling is present.
4
Technician should test high-limit switch and controls.
5
Replace failed safety components before normal use.
Pro Tip
This issue typically requires professional diagnosis. Attempting this fix without proper training could cause further problems.
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