Error D.82

Safety precautions:

1) If you smell gas immediately evacuate the property, do not operate electrical switches or appliances, open windows/doors if safe, and call your gas emergency number. Do not attempt to light boilers or appliances.

2) Turn off the boiler using its on/off control or the isolator if you need to do checks. Allow any obvious faults to cool before touching the unit. Never remove covers or access the burner or gas components unless you are a Gas Safe qualified engineer.

3) If you are unsure or uncomfortable at any stage, stop and call a qualified Gas Safe engineer.

Initial checks a homeowner can safely do:

1) Note the full display: write down D.82 and any other codes (especially F‑codes) shown. These details are important for the engineer.

2) Reset the boiler once: many Vaillant boilers have a reset button or soft reset procedure. Hold as instructed in the manual (typically a short press or a few seconds). If the boiler restarts and runs normally, monitor it. If it locks out again, do not repeatedly reset; record the error.

3) Check boiler power supply: confirm the fused spur or switch feeding the boiler is on and there are no tripped RCDs/MCBs.

4) Check system water pressure: the boiler pressure gauge should normally be about 1–1.5 bar when cold. If pressure is low, top up using the filling loop following your manual. Low pressure can prevent proper operation.

5) Check thermostat and controls: confirm the room thermostat or programmer is set to call for heat and that any smart controls are active. Also check TRVs are not turned fully off throughout the house.

6) Check condensate pipe (combi boilers): in cold weather the external condensate pipe can freeze — inspect the external discharge and thaw it with warm (not boiling) water if frozen.

7) Check external vents and flue: ensure air intake and flue terminals are not blocked by debris, bird nests, snow or leaves.

8) Confirm gas supply: check other gas appliances (hob, oven) to see if gas supply appears normal. If all gas appliances are out, contact your gas supplier or engineer.

Specific diagnostic and safe next steps (do not attempt internal repairs):

1) If D.82 appears with no F codes and the boiler runs normally, log the event and monitor for repeat occurrences. Occasional logged start attempts are normal.

2) If D.82 is followed by ignition or flame fault codes (F28, F29, F68 etc.) or the boiler locks out:

a) Do not try to access the burner or gas valve. These faults commonly indicate ignition electrode issues, gas valve or supply problems, flame sensing problems, PCB faults, or a blocked flue/air intake.

b) Perform the safe checks above (power, pressure, condensate, flue, thermostat, gas supply) and then record every displayed code and any behavior (clicking, sparking noises, fan running, repeated attempts to ignite).

c) If the condensate is blocked or frozen and you can safely thaw it, do so and then try a single reset. If the boiler remains locked out or faults recur, stop and call a professional.

3) If you see temperature spread or sensor related diagnostic messages alongside D codes (indicating large flow/return spread): check radiators for cold spots, listen/feel for the pump running, and check system pressure. Air in the system or a failed pump, stuck 3‑port diverter valve or failed flow/return sensor can cause large temperature differences; these are service tasks for an engineer.

4) If there are any signs of electrical faults (display intermittence, unexplained reboots, multiple unrelated codes), do not attempt PCB or wiring repairs — call an engineer.

When to call a professional and what to tell them:

1) Call a Gas Safe qualified heating engineer if the boiler locks out with F‑codes, if you smell gas, if ignition repeatedly fails, if the condensate or flue appears blocked and you cannot safely clear it, or if you suspect pump/valve/sensor/PCB issues.

2) When you call, give the engineer: the exact model, all codes displayed (D.82 and any F‑codes), what you did to troubleshoot (resets, pressure checks, condensate thawing, etc.), whether gas appliances are working, and whether you smelled gas. This speeds diagnosis.

Final note: D.82 itself is normally a log of a burner start in heating mode; the need for repair depends on whether that start completed successfully. Any faults related to ignition, gas components, burner, flue or PCB are potentially dangerous and must be inspected and repaired only by a qualified Gas Safe engineer.