Error 111

Safety precautions:

1) If you smell gas or suspect a gas leak, leave the property immediately and call the gas emergency number — do not attempt any checks. 2) If there is visible water leaking from the boiler or PRV discharge, place a bucket under the drip and turn the boiler off at the electrical isolation switch; isolate the mains water to the filling loop if it is accessible. 3) Only perform checks when the boiler is cold or has cooled down to avoid scalding; isolate electrical supply before accessing internal items. 4) Do not attempt to dismantle gas valves, burners, the heat exchanger, or electrical controls yourself — those require a Gas Safe engineer.

Initial homeowner checks you can safely do:

1) Look at the pressure reading on the boiler display or the analogue gauge. Note the value. Typical healthy pressure when cold is about 1–1.5 bar; some systems run slightly higher but anything clearly above the boiler's Pmax (often around 2.5–3 bar) is a problem. 2) Check for signs of water on the floor, around the boiler casing, or under the PRV discharge pipe (usually a small plastic pipe running to outside or to a drain). 3) Check whether the filling loop (the flexible braided hose or taps used to repressurise the system) is closed; it should be shut after filling. An open filling loop can cause continuous over-pressurisation.

Steps to safely reduce pressure (homeowner):

1) Turn the boiler off and allow the system to cool. 2) Bleed radiators to reduce system pressure: start with the highest radiators and bleed slowly using a radiator key until the gauge drops into the acceptable range (around 1–1.5 bar when cold). Catch water in a bowl or towel. 3) If bleeding radiators does not reduce pressure, and you are confident, you can drain a small amount from a system drain-off point or the lowest radiator drain to lower pressure; close valves afterwards. If you do not have an accessible drain point or are unsure, skip this and call a professional.

After lowering pressure:

1) Close bleeder valves, wipe up any water, restore power to the boiler and attempt a reset following the boiler manual or control panel instructions. 2) Monitor the pressure for several hours while the system cycles. If pressure stays stable within the normal range, the boiler may return to normal operation. 3) If the boiler immediately shows error 111 again or pressure climbs back up quickly, do not continue to operate the boiler.

What this may indicate and when to call a professional:

1) Recurrent or rapidly rising pressure commonly indicates a failed expansion vessel (lost air charge), a faulty pressure sensor, a stuck/failed automatic fill valve, or a malfunctioning PRV. These parts require specialist tools and safe procedures (e.g., isolating water and gas, depressurising the system, testing/changing the expansion vessel pre-charge, replacing the PRV or pressure sensor) and must be carried out by a Gas Safe registered engineer. 2) If you see water coming from the PRV discharge pipe or from the boiler casing, call an engineer immediately to prevent water damage and to replace the faulty PRV if needed.

Final notes and important advice:

1) Do not tamper with or replace sealed components, gas valves, the burner, or internal PCB components yourself. 2) If you cannot safely reduce pressure, if the filling loop is open and you cannot close it, if pressure repeatedly exceeds safe limits, or if the reset does not clear the fault, contact a qualified Gas Safe engineer to diagnose and repair the fault. 3) Keep a record of the error and the pressure readings you observed to give the engineer useful information when they attend.