Overview
E270 on a Baxi 600 Combi normally means a circulation fault often described as a “dry fire” condition. In plain terms the boiler has detected poor or no water flow through the primary circuit (the pump/heat exchanger side). That can be caused by low system pressure, air in the system, closed or seized valves, a stuck or failed pump, a blocked filter or heat exchanger, or a condensate/freeze issue creating a circulation restriction. Severity ranges from low to high depending on the root cause. If it is caused by low pressure or trapped air it is usually a simple homeowner fix and the boiler may recover after topping up and bleeding. If it is caused by a seized pump, blocked heat exchanger, internal leak or repeated dry firing, it is more serious and can damage the boiler if repeatedly reset and left unaddressed. Work on gas and internal components should only be performed by a Gas Safe engineer, so many causes will require a professional visit.
Possible Cause: Circulation fault (dry fire).
Troubleshooting Steps
Safety precautions:
- If you smell gas, do not attempt any checks — evacuate, ventilate windows, shut off gas supply if safe, and call the emergency gas number/Gas Emergency Service immediately.
- Turn off electrical power to the boiler at the isolator before doing any physical checks that require opening panels or touching wiring. Do not attempt gas-side repairs unless you are Gas Safe qualified.
- Be careful with hot surfaces and hot water when checking pipes or radiators.
Initial homeowner checks you can do now:
1) Check the boiler display and note if E270 is steady or intermittent. If the code has just appeared, try a single reset first (hold the boiler reset button for 5–10 seconds or follow your model’s reset method) and watch what happens. Do not keep repeatedly resetting.
2) Check the system water pressure on the boiler pressure gauge. Normal is approximately 1.0–1.5 bar for most domestic systems (safe range 1–3 bar). If pressure is below about 0.8–1.0 bar, topping up is needed.
3) Confirm there is mains gas and mains electricity to the boiler (check other gas appliances and that the boiler display is powered).
If pressure is low: topping up procedure (homeowner):
- Locate the filling loop (usually a braided hose with two isolating valves or a built-in valve). Ensure both ends are connected and valves are closed before you start.
- Open the filling loop valves slowly while watching the pressure gauge. Stop as soon as pressure reaches about 1.0–1.5 bar. Do not over-pressurise above 2.5–3.0 bar.
- Close the filling loop valves and, if it is a removable loop, disconnect it or ensure it is left closed and secured. Restart the boiler and see if the error clears. If the pressure falls again quickly, there is a leak or a fault and you must call a Gas Safe engineer.
Bleeding radiators and removing air:
- Turn heating off and allow the system to cool somewhat to avoid scalding. Use a radiator key to release air from radiators (start at the highest radiator and work downwards). Stop when water begins to flow steadily, then re-check boiler pressure and top up again if needed. If you are not comfortable bleeding radiators, call a qualified plumber/engineer.
Check simple circulation items:
- Ensure thermostatic radiator valves (TRVs) and room thermostats are open and calling for heat. Confirm all isolation valves on the boiler flow and return are fully open.
- With the heating on and boiler powered, listen for the pump (a low hum/vibration). Carefully feel the pipes near the pump (avoid hot parts): you should feel a temperature difference between flow and return. If the pump is silent or pipes are cold, circulation is not happening.
- Check for strange noises (gurgling, banging) which suggest trapped air or poor flow.
Condensate/ freeze and external pipe checks:
- If temperature is very cold, a frozen condensate pipe can cause faults. Locate the condensate pipe (often runs outside) and thaw with warm water or a hot water bottle (do not use boiling water). Insulate the pipe afterward. If a blocked condensate pipe was the cause, the error may clear after thawing and a reset.
When to stop and call a professional now:
- If pressure will not stay up after topping up or after bleeding radiators (indicates leak or component failure).
- If the pump does not run or you suspect the pump is seized, or you hear abnormal noises from the pump.
- If you suspect internal blockage, scale build-up, a blocked heat exchanger, or magnetic filter full of debris.
- If E270 returns after the simple fixes above or the boiler locks out repeatedly after resets.
- If you are not confident performing any of the checks above.
Professional intervention:
- Contact a Gas Safe registered engineer to inspect and diagnose pump operation, check/replace the pump if seized, inspect and clean magnetic filter, check for airlocks and trapped air, test sensors and pressure switch, inspect heat exchanger and pipework for blockages or leaks, and check the PCB if required. The engineer will also ensure the boiler has not suffered damage from dry firing.
Final notes:
- Do not repeatedly reset the boiler if the fault returns; repeated resets can cause more damage. Use reset only after doing the initial checks (pressure, condensate thawing) once.
- Keep a record of the fault occurrences and any actions you took to share with the engineer (pressure readings, when it happens, noises, recent work on system). This helps speed diagnosis and repair.
Helpful Resources
Boiler Manual
Download the official PDF manual for the Baxi 600 Combi Gas Boiler.