Worcester Bosch [Blue light flashing]what it means

Several Greenstars were built without a screen — the 24i and 28i Junior, the 25Si and 30Si Mk4, the Ri and the Ri Compact — and on those the blue mains indicator does the job a display would otherwise do. The user guide for these boilers only goes so far: it says the reset button flashes once a second and the blue light flashes to indicate a fault, and tells you to ring Worcester. The installation and servicing instructions for the same boilers go further, and publish the decode. Read the blue light together with the reset button. A slow flash that is mostly off, flicking on, with the reset button flashing, is an ignition lockout — the boiler tried to light and could not. A slow flash that is mostly on, flicking off, with the reset button flashing, is an overheat: the flue thermostat or the heat exchanger thermostat has tripped, and on the Ri the flue pressure switch is added to that list. A fast flash with the reset button dark is what Worcester call a volatile lockout — a temperature sensor, the fan or the code plug — and the Si manual adds a useful tell: if the light starts flashing immediately after a reset the fault is likely the code plug or a sensor, and if it starts after about thirty seconds it is more likely the fan. A fast flash with the reset button also flashing is an internal control fault.

Two pulses or five pulses are not faults at all: an engineer has left the boiler in its minimum or maximum service mode. No light is no power, and a steady light with no heat is a boiler waiting for a demand that is not arriving. That is the whole published account for the Junior, the Si and the 9-24 Ri, and it is enough to tell the difference between a frozen condensate pipe and a failed fan before anyone arrives. The 27Ri and 30Ri Compact from 2015 are different: their installation instructions publish a counted system instead.

After a five-second dark gap the light gives one to five flashes, on its own for group one, preceded by four fast flashes for group two, or followed by four fast flashes for group three — fifteen codes in all. Group one is ignition and gas: one flash is no flame after four attempts, two a flame lost while running, three the gas valve coil disconnected, four the flame not established inside four seconds, five a flame sensed when there should be none or a gas valve leak test failed. Group two is temperature: one is the sensor check at power-up failing, two the heat exchanger past 105 °C, three the flue thermostat or air pressure switch tripped, four the return too hot, five the flow past 110 °C. Group three is electronics: one is the heat control module, two the fan, three power interrupted during a lockout, four an internal board fault, five everything else. Those are the same faults the Compact combis show as EA 227, EA 228, EA 234, EA 261, Fb 365, E9 219, E9 224, D1 286, b1 and C6 215 — the Ri Compact simply has no screen to write them on.

1. 1

   Watch the light for a full minute and decide which pattern it is: mostly off with brief flashes on, mostly on with brief flashes off, or a fast even flash. Then look at the reset button and note whether it is flashing too. On a 27Ri or 30Ri Compact count instead: the number of slow flashes after the five-second gap, and whether a burst of four fast flashes comes before them, after them, or not at all.

2. 2

   If it is the slow, mostly-off pattern in freezing weather, check the white plastic condensate pipe outside. If it is frozen, thaw it with warm — not boiling — water along its length. Worcester's own guide gives this as the householder's check.

3. 3

   Check the pressure gauge reads between 1 and 1.5 bar cold. Low pressure sits behind the overheat pattern, and topping up is yours to do.

4. 4

   Reset once. On a Junior or Si, press the reset button for about five seconds until it goes out. On an Ri or Ri Compact there is no button: turn the heating temperature knob fully anticlockwise to RESET, hold it for five seconds, and turn it back.

   Once. If the slow mostly-off pattern returns, the boiler is failing to light, and repeated resets on an ignition fault are not safe. Call a Gas Safe registered engineer.
5. 5

   Tell whoever comes which pattern you saw and whether the reset button was flashing. That is the decode Worcester give their engineers, and it turns a vague call into a specific one.