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Common Warmflow Boiler Problems


Warmflow was started in 1970. It is an award-winning boiler manufacturer in Northern Ireland. Over the years, it has expanded its market and has become a preferred choice in Ireland and the UK.

When your Warmflow boiler breaks down, it’s frustrating and confusing. You don’t know where to start even with the fault codes displayed. The E01, E02 all point to specific boiler problems. Understanding them helps you solve the problem faster.

Below we have explained the common boiler problem faults along with their codes. Read through to see what your Warmflow boiler code means.

Boiler does not ignite Solution

When the boiler flame fails to ignite, a red button will light. This indicates a boiler fault (E01) or lack of enough fuel getting to the burner.


Reset the boiler twice. If this doesn’t work, call a Gas Safe engineer to inspect, diagnose and fix the problem.

No heating and hot water

There are many causes for lack of heating and hot water. These causes include:

  • Airlocks in the system
  • Broken diaphragm
  • Faulty thermostat
  • Faulty motorized valve
  • Low water levels


Start by reviewing the reasons for not working. It could be the thermostat or boiler. Whichever boiler component is faulty, a Gas Safe engineer will repair or replace it for a fraction of the cost of a new boiler.

Low boiler pressure

Normal boiler pressure is marked with a green zone on the Warmflow pressure gauge. It is between 1 and 1.5 bar. When not in operation, the pressure may fall slightly out of the recommended range. But if there’s a sudden and large pressure drop, there is an underlying problem.


You can re-pressurise the system by adding water. However, if there’s a leak, this will not last long and the H20 fault will reappear. If the pressure still drops, hire a Gas Safe engineer to find the leak and seal it.

Fan Fault

A boiler fan creates draught that pushes harmful boiler gases into the flue. If the fan doesn’t start when the boiler is turned on, the boiler won’t start heating. Fan fault is represented with an E22 fault code.

Aside from fan fault, the fault code can be because of:

  • Loose or damaged wiring
  • Slow fan speed


The boiler engineer will adjust the fan speed. If this doesn’t work, they will inspect the wiring and tighten loose connections. Lastly, they will replace the faulty fan.

No flame during start-up

The cause of no boiler flame and the E01 fault code includes:

  • Insufficient or no gas
  • Ignition or electrode problems

Without a boiler flame, the boiler cannot heat or provide hot water. Before you call a boiler engineer, confirm you have gas supply.


Call a Gas Safe engineer to inspect and diagnose the cause of the no flame problem. They will unblock the burner and replace the gas valve depending on what’s faulty.

Heating sensor fault

Warmflow boilers have multiple sensors that keep track of the temperature in the system. The sensors help regulate room temperature and hot water temperature. When the sensors are faulty, incorrect signals are sent to the PCB.

Your Warmflow boiler will display an E05 error fault.


Call a boiler engineer to replace the temperature sensors. New sensors are cheap and last for long.

Faulty PCB

The PCB is the heart of the Warmflow boiler. It controls and communicates with boiler components. If it’s faulty, the boiler will be off-balance and components may be damaged.

PCB faults are caused by:

  • Normal wear and tear
  • Boiler vibrations
  • Water damage


Before replacing the PCB, the Gas Safe engineer will inspect the heat exchanger, pump, fan, and gas valve as well.

A new PCB boiler costs £450. If the replacement costs more than £500, and your boiler is out of warranty, install a new boiler instead.

Boiler switching off

Boilers provide heating and water 24/7 non-stop. Because of these, the components undergo wear and tear with time and some pathways get blocked.

The number one cause of boiler switching off is a blocked condensate pipe. The condensate pipe transports waste boiler water into the drainage. When it’s blocked, the acidic water backs into the boiler and it locks out. When this happens, do not attempt to restart it.

Another cause of boiler switching off is:

  • Fan fault
  • Low boiler pressure


When a boiler switches off, do not restart it. Boilers lockout to prevent further damage. Resetting your boiler without fixing the problem predisposes you to safety risks and boiler damage.

Call a Gas Safe engineer to replace the fan. You can thaw the condensate pipe with warm water and re-pressurise the boiler by adding water.


Warmflow boilers run quietly. If you are hearing a kettling or a gurgling sound, there is a problem in the boiler system. The most common kettling sound is sludge and limescale build-up in the heat exchanger. The limescale constricts the passage and causes the heat exchanger to overheat. The water boils and the steam therefore passes through with a whistling sound.


Hire a Gas Safe engineer to Power flush the boiler and remove the limescale and sludge. If the limescale is removed and the problem persists, the heat exchanger may be broken.

In this case, instead of repairing, boiler engineers opt to replace the heat exchanger or install a new boiler if the old boiler is out of warranty. It saves money in the long run. Also, install a magnetic filter to trap limescale and sludge.

Heating doesn’t get to required temperatures

Boiler heating is controlled by thermostats. The thermostats record heat and send signals to the PCB of when to shut down and turn on the boiler. The main cause of the boiler cutting out below-set temperatures is limescale build-up close to the thermostat. The limescale creates hot zone and fools the thermostat into thinking the set temperatures have been achieved when they’ve not.

This also happens when the thermostat is faulty, or the wiring is damaged or loose.


Before calling a boiler engineer, check you have the right temperatures set. If the settings are correct, call an engineer to inspect the thermostat and the circuit connections. They will replace faulty thermostats and reset the boiler to remove the fault code error.

Other fault codes and troubleshooting

Fault code E35 – Ionisation electrode fault

How to fix: Inspect combustion burner, clean the part or replace the part

Fault code E02 – Tripped safety thermostat

How to fix: Inspect thermostat wiring, or replace part

Fault code E03 – Tripped flue thermofuse

How to fix: inspect thermostat wiring or replace thermofuse

How to improve your boilers life?

Warmflow boiler warranty

Warmflow boilers have warranties for 1 year from the manufacture date. The guarantee protects against faulty workmanship and defective parts. For Combi boilers, the thermal store and water jacket are guaranteed for 5 years. However, this doesn’t include labour, shipping, handling or the burner.

Warmflow boiler cover

When the Warmflow boiler warranty expires, you can opt to pay a premium for a boiler. Most boiler covers include annual safety inspection and servicing. However, read the fine print to confirm this.

Warmflow boiler service

During the annual service, the Gas Safe engineer will:

  • Clean the heat exchanger
  • Oil the nozzle controls
  • Replace worn out electrodes

The annual service is important for maintaining the warranty. You’ll be provided with a certificate after the service.

With that, now you know what some of the common fault codes mean and how to fix them. If you need a Gas Safe engineer, get in touch with us and we shall provide 4 quotes from Gas Safe engineers close to you.

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