High Lockout
P27 on Ideal HP290

Your boiler's internal wiring has been connected incorrectly, causing it to confuse high and low pressure readings.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

High Pressure Sensor and Low Pressure Sensor Wiring Reversed

What causes this fault?

This fault occurs when the electrical wires for the high and low pressure sensors have been swapped or plugged into the wrong terminals on the main control board. The boiler detects that the readings are the opposite of what is expected, causing it to shut down for safety. This is usually the result of a manufacturing error or a mistake made during a recent repair or part replacement.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Related fault codes

F1View →

Related guides you might find useful

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Low pressure — repressurise guide

Step-by-step using the filling loop.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →