BoilerFaultCodesWhat the manual says
Manufacturer manualWater Pressure Switch Not Operated / primary water pressure is less than 0.5 bar
What causes this fault?
This fault occurs when the pressure of the water circulating inside your heating system drops below a safe working level, usually because of a small leak or after you have recently bled your radiators. Without enough water pressure, the boiler cannot safely move heat around your home, so it shuts down to prevent the internal components from overheating. While often fixed by topping up the system, persistent pressure loss may indicate a failing part like the expansion vessel.
This code is frequently seen in autumn when homeowners turn their heating back on for the first time after summer, as natural pressure loss often occurs during periods of inactivity.
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.
Avoid the next call-out bill
A cover plan would handle faults like E119: no call-out fees, no surprise bills.
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Related fault codes
All 21 fault codes on the Promax HE Store
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