Worcester Bosch · Greenstar Highflow CDi ErP

A1 boiler fault code

Greenstar Highflow 440CDi ErP & 550CDi ErP

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What A1 means

Pump dry run detection or pump running in air.

Gas Safe engineer: If the pressure is not low, or the code returns after one reset, contact a Gas Safe registered engineer.

If you smell gas, a CO alarm sounds, anyone feels unwell, or there is an unsafe flame, leave and call 0800 111 999 from outside.

Safe check

Check the pressure gauge. If it is below 1 bar, use the filling loop to top up to about 1.5 bar as described in the installer or user guide. Do not remove any panel. Then press Reset once.

When to contact an engineer

If the pressure is not low, or the code returns after one reset, contact a Gas Safe registered engineer.

Source and provenance

Greenstar Highflow 440CDi ErP & 550CDi ErP Installation, commissioning and servicing instructions 6 720 818 077 (2016/04) · §7.5 Fault finding Table 17, printed p. 46
installation, commissioning and servicing instructions
2016/04

Renting? Report it to your landlord or housing provider first. They are responsible for gas safety and boiler repairs, and the repair should not cost you.

Did this fix it?

After: Repressurise the boiler