Common problems guide

The most common Navien NCM 1130HH problems

The faults most likely to send a Navien NCM 1130HH into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

This model is discontinued. Parts can be harder to source and expensive. If repair costs are mounting, a new A-rated boiler may be the smarter choice.
77 documented codes
6 most common
4 DIY-safe checks
2 engineer needed

The 6 most common faults

01
96 High DIY-safe

Your boiler has detected a minor internal software glitch and has temporarily stopped working to protect itself.

What to try first

Switch the boiler off at the fused spur or wall switch.Wait for 60 seconds to allow the internal system to completely reset.Switch the boiler back on and check if the error code clears.

Est. cost
£100-£250
Parts
Main PCB, Control Board
Full guide for 96
02
118 High DIY-safe

Your boiler has temporarily stopped working because the water pressure inside the system has dropped too low to operate safely.

What to try first

Locate the filling loop valves underneath your boiler.Open the valves slightly to let water into the system until the pressure gauge reaches between 1.0 and 1.5 bar.Close both valves firmly and check the pressure holds steady.

Parts
Pressure relief valve, Pressure sensor, Automatic air vent
Full guide for 118
03
158 High DIY-safe

Your boiler has temporarily stopped working because the pipe that drains away waste water is blocked or frozen, causing a safety switch to activate.

What to try first

Locate the external condensate pipe outside your home where it empties into a drain.Check if the pipe is frozen during cold weather by pouring warm (not boiling) water over it to thaw any ice.Inspect the pipe for any visible kinks, blockages, or sharp bends that might be stopping water from flowing freely.

Est. cost
£80-150
Parts
Condensate trap, Condensate pressure switch, Internal condensate hose
Full guide for 158
04
271 High DIY-safe

Your boiler has detected that the water pressure inside the system is currently too high, so it has safely stopped working until the pressure is reduced.

What to try first

Locate the filling loop connected to your boiler.Ensure both valves on the filling loop are firmly closed to stop more water from entering.Bleed one or two radiators in your home to release trapped air and drain a little water until the pressure gauge drops to the normal 1 to 1.5 bar range.

Parts
Pressure relief valve, Expansion vessel, Pressure sensor
Full guide for 271
05
97 High Engineer

Your boiler has detected an internal software or hardware error that prevents it from operating safely.

Est. cost
£150-350
Parts
PCB (Printed Circuit Board), Control board
Full guide for 97
06
98 High Engineer

Your boiler has lost communication with an extra system control module, which usually means the unit cannot coordinate its advanced heating zones properly.

Est. cost
£150-300
Parts
Extension module, Wiring harness, Main control board
Full guide for 98
Parts most often replaced

on the Navien NCM 1130HH

Main PCBControl BoardPressure relief valvePressure sensorAutomatic air ventCondensate trap

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Navien shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 77-code list for the Navien NCM 1130HH

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →