Error H.02 – .06

Safety precautions:

1) If you smell gas, leave the property immediately, do not operate electrical switches, and call the gas emergency service. 2) If there is a significant water leak under or from the boiler that is wetting electrics, switch the boiler off at the mains electrical isolator and turn off the mains water stopcock to the house if safe to do so. 3) Wear gloves and eye protection when working around boiler components; keep the area clear.

Initial checks a homeowner can do:

1) Read and record the exact fault code shown on the display (H.02 – .06) and any other codes. 2) Check the boiler pressure gauge/indicator with the boiler cold. Target cold pressure is about 1.0–1.5 bar for most combi boilers. Note the value. 3) Visually inspect around and under the boiler and pipework for obvious signs of water: wet floor, drips, green/brown staining on PRV discharge pipe, wet radiator valves, or pooling. 4) Check radiators you recently bled – bleeding lowers system pressure.

Diagnostic and simple fix steps you can try (step by step):

1) If pressure is low (below ~1.0 bar): repressurise using the filling loop. Locate the filling loop (flexible hose with two valves) under the boiler. Open the valves slowly until the pressure rises to about 1.0–1.5 bar, watching the gauge. Close both valves fully and ensure the filling loop is secured. 2) After repressurising, reset the boiler using the reset procedure on your model (press and hold the reset button for the time recommended in your manual, typically 3–10 seconds) and observe whether H.02 clears. Do not repeatedly reset more than once or twice if the fault returns. 3) If the pressure was correct or topping up did not fix it, inspect the PRV discharge pipework (usually a small plastic pipe coming from the boiler to waste or outside). Brown staining or moisture on this pipe indicates the PRV is discharging — a sign of a faulty PRV, expansion vessel issue, or overpressure events. 4) Check all visible pipe joints, radiator valves and the condensate pipe for leaks. Tighten loose compression fittings cautiously—do not overtighten—only if you are confident and the leak source is external to the boiler. 5) If you tightened anything, repressurise if needed, reset the boiler and monitor pressure. 6) Monitor the pressure over 24–48 hours: note the pressure when cold, then re-check after the system has been used. A steady drop after repressurising indicates a leak or a faulty PRV/expansion vessel.

When to call a professional (Gas Safe engineer):

1) If you find a leak inside the boiler casing, water pooling beneath the boiler, or persistent pressure loss after repressurising. 2) If the PRV is discharging regularly or you see staining on the discharge pipe. 3) If the fault code won’t clear after sensible checks and a proper repressurise/reset, or the code returns repeatedly. 4) If you are not comfortable performing the filling loop operation or isolating electricity/water safely. 5) If you smell gas or suspect a gas-related issue.

Notes and precautions:

- DIY steps are limited to safe visual checks, bleeding radiators, and repressurising via the filling loop. Do not open the boiler casing or attempt internal repairs. Gas and internal hydraulic repairs must be done by a Gas Safe registered engineer. - Do not keep repeatedly resetting the boiler; this can mask recurring faults and can be unsafe. - If the problem turns out to be an internal leak, faulty heat exchanger, failed PRV, or expansion vessel failure, professional diagnosis and repair are required.

If you are unsure at any stage, switch the boiler off at the electrical isolator, turn off the mains water stopcock if there is a leak, and call a Gas Safe engineer to inspect and repair the appliance.