The most common Navien boiler problems

Locate the filling loop (usually two silver flexible hoses) underneath the boiler.Open the valves slowly to allow mains cold water into the system.Watch the pressure gauge on the front of the boiler until the needle reaches the green zone (typically 1.0 to 1.5 bar).Close both valves tightly to stop the flow of water.

Locate the external filling loop, which is a flexible silver hose connected to two valves under your boiler.Open both taps on the filling loop slowly to let water into the system while watching the pressure gauge.Close both taps firmly once the needle sits in the green zone, typically between 1.0 and 1.5 bar.

Locate a radiator in your home that is easy to access.Open the bleed valve on the radiator using a radiator key to release a small amount of water.Monitor the pressure gauge on the front of your boiler until it drops back into the green zone (typically 1.0 to 1.5 bar) and then close the valve.

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.

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.