What Do I Do With The Boiler That Has A Fault Code 118?

Error code 118 could mean that the system pressure is too low. The system pressure gauge may indicate that the system pressure is below 1 bar.

The pressure within the system can be seen in two ways. There is an analogue gauge under the bottom left-hand side of the boiler, or you can find a digital reading from the control panel's digital display. The digital display can be seen by pressing the Eco button for 6 seconds and then scrolling through (tap + plus button) to ‘A6,’ which will display the water pressure.

The system pressure should be set around 1.0 – 1.2 bar when the water is cold.

When the system is working and the water is heated up within the system, the water expands due to heat, and you may see the pressure rise to around 1.8 – 2.4 bar when hot. This is normal as water system pressure increases due to heat.

So, when the water is cold, we want the system pressure to be set around 1.0 – 1.2 bar.

Turn off any clocks and room thermostats for heating or hot water controls.

On the iC and iC Economiser Plus models, to re-pressurise the system, you will need to find the filling loop (a copper ‘U’ shaped tube with two nuts at each end). On the underside of the boiler, there is a filling loop position where this copper ‘U’ shaped tube will connect between the small blue and black isolation valve connection. If it is not in position, remove the caps and install as shown, then tighten up the nuts hand tight.

The taps should be opened a quarter of a turn, and the water will start to refill the system (water should be heard filling the system). You should see the pressure gauge rise back up between 1 bar and 1.2 bar pressure and then stop filling. The error code 118 will stop, and the boiler will now operate. If the error code 118 is still active, fill up the system a little more but not over 1.5 bar.

The display should now show ‘OK’, which means the pressure level is correct and the boiler is ready to operate.

(If you fill the system too much and the pressure gauge is too high, just bleed water from a radiator until the pressure on the gauge drops to below 1.2 bar.)