Error code 118 could mean that the system pressure is too low and you may see that
the system pressure gauge indicates that the pressure is below 0.8 - 1
bar.
The pressure within the system can be seen in two ways. There is an analogue gauge,
which can be found under the bottom left hand side of the boiler or you can find a
digital reading from the digital display of the control panel. The digital display
can be seen by pressing the Eco button for 6 seconds and then scroll 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, since water
expands due to heat and you may see the pressure rise up to around 1.8 - 2.4bar.
This is normal as water system pressure increases due to heat.
So we are looking for the system pressure to be set around 1.0 - 1.2 bar when the
water is cold.
Turn off any clocks and room thermostat 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 (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 not in position, remove the caps and install as shown and 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 1.4bar.
The display should now show 'OK', which means the pressure level is correct and the
boiler is ready to operate.
(If you do fill the system too much and the pressure gauge is too high, just bleed
water from a radiator until the pressure on the gauge goes down to below 1.2 bar).