Combi boiler troubleshooting guides

4 guides. Heating and hot water problems on combi boilers. Each one lists the likely causes and what to check, in order.

Navien (4)

• Hot water is cold or turns cold - Navien NCB-H
  Water at the tap stays cold or goes cold during a draw.
• Hot water not hot enough or too hot - Navien NCB-H
  DHW temperature at the taps is lower or higher than wanted.
• No space heating - Navien NCB-H
  The heating side does not work while the unit has power.
• No water from hot water tap - Navien NCB-H
  Nothing comes out when a hot tap is opened.

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.