HVACopediaNoritz · Tankless water heater troubleshooting
Heater does not fire when hot water is opened - Noritz tankless
What is going on
Unit stays off when a faucet is opened, or shuts off after the temperature is changed, with no error code.
Likely causes
- Flow below activation rate
- Reversed or crossed plumbing
- Clogged inlet filter
- Power off or gas off
- Frozen unit
Check in this order
- Read MM14 to see if the unit sees flow; it needs about 0.5 GPM (EZ/NRCR: 0.4 GPM to start).
- Check for reversed hot/cold connections or crossed pipes (owner's guide).
- Close the valves and clean the water drain valve / inlet filter (NRCR: also the return filter).
- Check the power button/switch and the 120 VAC supply.
- Check gas valves are open and gas is available (other appliances work, LP tank not empty).
- If it tries to light but fails, reset and retry (air in gas line), then check inlet gas pressure.
- A recirculation pump alone may not move enough flow to fire the unit; check with MM14.
Applies to: All Noritz residential tankless (EZ, NRCR, NCC199CDV, NRC/NRCP)
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Source: Noritz EZ/NRCR/CDV Level 2 Maintenance & Troubleshooting (Premix R2 V2), MM14 flow rate, p.19; Noritz Residential Level 2 Maintenance & Troubleshooting (NRC/NRCP and older, R2 V1), Flow rate, p.13; Noritz EZ/NRCR Owner's Guide (Rev. 10-25), Troubleshooting, p.28-29. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.