HVACopediaNavien · Combi boiler troubleshooting
No space heating - Navien NCB-H
What is going on
The heating side does not work while the unit has power.
Likely causes
- No power or unit in standby
- Unit is busy making DHW (DHW has priority)
- Restricted heating-side filter
- Set temperature too low
Check in this order
- Check power to the unit and that it is plugged into a grounded 120 V outlet; press the Power button to turn it on.
- Raise the space heating set temperature.
- Remember heating stops while the unit is making domestic hot water.
- Clean the space-heating return water filter.
- If heating performance has dropped, also check for air in the system and check the boiler pump in Test Mode.
Applies to: Navien NCB-H combi boilers: NCB-250/150H, NCB-240/130H, NCB-240/110H, NCB-190/080H, NCB-190/060H
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Source: Navien NCB-H User's Information Manual Version 1.0 (April 2024), 5.1 Solving Basic Problems, p.24 and 4.4 Cleaning the Heating Return Water Filter, p.16. 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.