BoilerFaultCodesWhat the manual says
Manufacturer manualCH system pressure less than 0.5 bar / water pressure switch fault
What causes this fault?
This fault occurs when the internal sensor detects that the water pressure has dropped below the minimum level required for the boiler to operate safely. The most common reason is a slow leak somewhere in your radiators or pipework, or simply that the expansion vessel needs recharging. Without enough water pressure, the boiler cannot circulate heat effectively and will shut down to prevent internal damage.
This fault is frequently seen in autumn when the heating is turned on for the first time after summer, as air can trapped in radiators and settled leaks become apparent.
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 119: no call-out fees, no surprise bills.
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Related fault codes
All 20 fault codes on the Promax Combi HE Plus
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Related guides you might find useful
Boiler keeps losing pressure
Six most common causes of dropping pressure.
Read →Hot water works but heating does not
On a combi it is usually the diverter valve. On a system boiler, the motorised valve.
Read →What pressure should my boiler be?
1 to 1.5 bar when cold on most UK boilers, from the manuals.
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