Glow-Worm Boiler F5 Fault Code
The Glow-Worm fault code F5 relates to an overheat fault and here we have Q & A or require an engineer for an emergency boiler repair.
The Glow-Worm Boiler Fault Code F5 Error Common Q & A
Just below, we have a list of common questions relating to the F5 fault code on the Glow-Worm Boiler.
- What does the F5 fault code mean on my Glow-Worm boiler?
- Can I reset my boiler to fix the F5 fault code?
- What causes a boiler to overheat?
- How can limescale cause my boiler to overheat?
- How can limescale be removed from my heating system?
- What does the PRV do?
- How could the thermistors contribute to the boiler overheating and the F5 fault code being displayed?
- If the pump fails in anyway, what’s going to happen?
- What can cause a boiler pump to fail?
- What are airway blockages, and how can they affect my boiler?
What does the F5 fault code mean on my Glow-Worm boiler
If your Glow-Worm boiler is showing the F5 fault code on the display panel, it means there has been an overheat fault.
The fault code system helps your boiler engineer to determine either the component that’s causing the issue, or in this case, the type of problem that has occurred. This makes the fix a much quicker process, saving you money on repair bills.
And, it’s likely that your boiler has locked out, so it will no longer ignite. In the case of an overheat fault, this ensures that no further damage is caused to internal components.
Can I reset my boiler to fix the F5 fault code
The reset function on modern boilers isn’t designed to fix a boiler. Instead, you need to call a boiler repair company, and get them to fault-find the problem. Once fixed, they’ll be able to reset the boiler on your behalf, which will clear the fault code on the display panel.
What causes a boiler to overheat
There are a range of things that can cause a boiler to overheat. Here are some of the most common faults that can lead to a boiler overheating:
- Limescale build-up
- Faulty pressure release valve (PRV)
- Failed thermistor
- Pump failure
- Airway blockages
How can limescale cause my boiler to overheat
For your boiler to heat water, it transfers heat from the burner, via the heat exchanger. Without a heat exchanger, the burner would be aimlessly burning gas.
Heat exchangers are prone to limescale build-up. And, where this limescale build-up occurs, the heat exchanger burns much hotter than it should.
Typically, the problem here is that the heat exchanger will crack, leak and that all leads to an expensive replacement.
But, it can also overheat water. As this water passes through the thermistor that monitors its temperature, it feeds back the information to the printed circuit board (PCB). And, when the PCB notices that there’s a high differential between the flow and return thermistors, or that the flow thermistor is too hot, it will lock out the boiler.
How can limescale be removed from my heating system
Limescale can be removed from your central heating system. The best thing to get your boiler engineer to do, is to run a hot flush. Usually, they’ll use central heating cleaner, but in this case, specifically designed limescale remover can be used.
Once they’re confident the majority of limescale has been removed, they can then dose the system with central heating inhibitor. This sits in the central heating system, breaking down limescale, ready to be caught. And, for this limescale to be removed from your heating system, they’ll need to fit a limescale reducer.
There are plenty of brands supplying these filters. Some of the best, include Scalemaster, Mangaclean and Fernox.
What does the PRV do
A PRV does exactly what it says on the tin, it relieves pressure when it’s too high. If you’ve noticed your boiler’s pressure gauge increasing dramatically when you turn on hot water or heating, it’s likely that the PRV could be to blame.
Your boiler engineer needs to check that your PRV is fully functional. If it’s not, it’s going to help contribute to excess pressure, and that’s going to make your boiler overheat.
How could the thermistors contribute to the boiler overheating and the F5 fault code being displayed
The role of thermistors on your boiler is to monitor resistance. The thermistors send the resistance readings to the printed circuit board (PCB), which then converts them to a temperature reading. This helps the PCB determine what it needs to do next.
For instance, if the differential between the flow and return thermistors is within tolerance, but the flow water temperature isn’t high enough, it might demand more gas from the gas valve to the burner.
The problem is, if the thermistor is faulty, the temperature passing through that thermistor might already be inline with what’s being demanded by taps, showers, or the heating thermostat. Increasing this temperature is going to mean that other parts in the boiler get hot, and other sensors notice an anomaly in temperature.
So, your boiler engineer needs to test the thermistors on your boiler using a multi-meter. Typically, they’ll want to see a reading of 12,000 ohms at 20C. If this isn’t the case, or there isn’t any power when tested using a multi-meter, it’s likely the thermistor needs to be replaced and the boiler reset, to fix the problem and clear the F5 fault code.
If the pump fails in anyway, what’s going to happen
Most circulation faults are going to relate to the pump. And, circulation faults can also cause a boiler to overheat. After water is heated in the heat exchange, it needs to be pushed around the central heating system where it loses temperature, and returns to the boiler to be re-heated.
But, if there’s any kind of blockage, or fault with the pump, the circulation might be restricted. This can cause water to overheat, and the thermistor will recognise this. It feeds back a signal to the PCB and recognising the fault, the PCB will lock out the boiler.
What can cause a boiler pump to fail
There are lots of different things that can cause a pump to fail. A typical problem with find with old boilers, is that pumps are blocked with heating sludge. That means that the majority of the capacity they used to have, has been eliminated.
If heating sludge is present, your boiler engineer is going to need to hot flush the system with chemicals. They can also manually remove any heating sludge from the pump.
Once this has been done, they can dose the system with inhibitor. Inhibitor will break down heating sludge into small particles. They’ll then fit a boiler filter. With the central heating inhibitor breaking down the particles into small chunks, this filter will be able to catch them, removing them from the heating system.
But, not all faults relate to heating sludge. There’s a chance that the pump has been put on the incorrect speed setting. Adjusting this setting can boost the flow rate, and sometimes cause the F5 fault code to be cleared from the control panel.
Unfortunately, not all faults can be fixed. Or, sometimes it just makes more sense to replace the pump. If this is the case, you should expect to pay in the region of £250 for a new pump.
What are airway blockages, and how can they affect my boiler
Airway blockages will relate to the flue and condensate pipe being blocked. If these are blocked, internal components are put under excess pressure, and eventually overheat.
Your boiler should lock out as soon as it notices an airway blockage, as it’s the flue and condensate pipe that vent harmful gases from your boiler.
Typically, we find that it’s the condensate pipe that tends to cause most boiler problems, especially in winter. In winter, it’s not uncommon for the condensed gases in the condensate pipe to freeze.
Luckily, this is a quick fix. Your boiler engineer will be able to thaw out the pipe using warm water and reset the boiler. To prevent this from happening again, they can lag the pipes using insulation.
Other Glow Worm boiler issues
For more boiler issues regarding the Glow Worm then please visit the Glow Worm Boiler Problems And Cures page.