Potterton Promax HE Plus Repair London — 24A, 28A, 33A Specialist

Potterton Promax HE Plus — Repair and Servicing in London

The Potterton Promax HE Plus was one of the most widely installed boilers across London’s social and private rented sectors from approximately 2005 to 2015. You will find Promax boilers in housing association properties across Newham, Tower Hamlets, Hackney and Southwark, in council managed blocks throughout the outer boroughs, and in private rentals across every part of the city. These boilers are now between ten and twenty years old and repairs are increasingly common.

The Promax HE Plus is a robust and straightforward boiler to work on. Potterton shares its parent company with Baxi and the Promax uses many components also found in Baxi boilers, which means parts availability is excellent and we carry the most commonly needed components on the van. Your local Potterton specialist at 247 Plumber London attends Promax breakdowns across London every day.

Promax HE Plus Models and Outputs

Model	Output	Best For
Promax HE Plus 24A	24 kW	Flat or smaller house, 1 bathroom
Promax HE Plus 28A	28 kW	2 bed house, 1 bathroom
Promax HE Plus 33A	33 kW	3 bed house, 1 to 2 bathrooms

Most Common Promax HE Plus Faults in London

E01 — Ignition Lockout

The boiler attempted to ignite and failed. The most common cause on Promax boilers of this age is a worn ignition electrode. The electrode tip erodes over years of use and the spark quality degrades to the point where reliable ignition is no longer possible. Electrode replacement is the standard repair and we carry the correct electrode for all Promax outputs. On boilers that have not been serviced for several years, a full service including electrode replacement and burner cleaning usually resolves persistent E01 faults.

E119 — Low Water Pressure

The system pressure has dropped below the minimum operating level and the boiler has locked out. The pressure gauge on the Promax front panel shows below 0.5 bar. Find the filling loop under the boiler, open both valves slowly until the gauge reads 1.2 to 1.5 bar, close both valves and press the reset button. If the pressure drops again within a few days, there is a leak in the system. Call us to locate and repair it.

E110 — Overtemperature Safety Trip

The boiler has overheated and the high limit thermostat has operated to protect the heat exchanger. On Promax boilers this is most commonly caused by a pump that is slowing down with age and not moving water fast enough through the heat exchanger, or by significant limescale buildup on the heat exchanger surfaces reducing flow. In London’s hard water areas, E110 faults on Promax boilers aged eight or more years are frequently related to scale accumulation. We check and replace the pump if needed and assess the heat exchanger condition.

E168 — PCB or Power Fault

A PCB or power supply fault on the Promax. The display shows E168 and the boiler does not respond to controls. Sometimes this is caused by a power surge rather than actual PCB failure and a full power cycle, switching off at the wall for five minutes and back on, can clear it. If the fault persists, the PCB needs testing. We carry replacement PCBs for the main Promax outputs and can replace them on the first visit in most cases.

Diverter Valve Failure

On Promax boilers of eight or more years, the diverter valve wears internally and loses the ability to fully divert flow between the heating and hot water circuits. You get the familiar symptom of either heating or hot water working but not both correctly at the same time. Diverter valve replacement on the Promax is a straightforward repair and we carry the assembly on the van.

Promax HE Plus Servicing

Annual servicing on the Promax keeps it running efficiently and prevents the progressive buildup of problems that leads to breakdowns. Our Potterton Promax service includes cleaning the burner and heat exchanger, replacing the electrode if needed, carrying out combustion analysis, testing all safety devices, and checking the flue. We provide a written service record. For Promax boilers in London properties in hard water areas, we strongly recommend fitting a scale reducer and maintaining a corrosion inhibitor in the central heating circuit.