Glow-Worm Boiler F25 Fault Code
The Glow-Worm fault code F25 relates to a circulation fault and here we have Q & A or require an engineer for an emergency boiler repair.
The Glow-Worm Boiler Fault Code F25 Error Common Q & A
Just below, we have a list of common questions relating to the F25 fault code on the Glow-Worm Boiler.
- What does the F25 fault code mean on my Glow-Worm boiler?
- If I reset my Glow-Worm boiler, is this going to fix the problem?
- What can cause the F25 error to occur?
- What things will my boiler engineer be searching for when checking the pump?
- What happens if my pump isn’t set to the correct speed?
- What do air locks do, and can they be removed?
- How do blockages occur, and can they be removed?
- What preventative measures can be put into place to stop blockages occurring?
- My boiler engineer thinks I need a new pump, how much is this going to cost?
- How can the heat exchanger contribute to the F25 fault code being displayed?
- Limescale has caused a crack in my heat exchanger, how much is this going to cost to fix?
- Should I just buy a new boiler?
What does the F25 fault code mean on my Glow-Worm boiler
If you’ve noticed the F25 fault code being displayed on your boiler, it means there’s a circulation fault. A circulation fault means that your boiler’s ability to circulate heated water is being compromised.
Whilst most fault codes on boilers are specific to highlighting the problem, the fault-finding process isn’t so specific. There are lots of potential faulty components, and potential problems in the heating system that are going to need to be checked.
What the fault code does do, is allow your boiler engineer to narrow down the problem (in this case, to parts that relate to water circulation and temperature), to make the fault-finding process faster than starting with no prior knowledge of the fault.
If I reset my Glow-Worm boiler, is this going to fix the problem
Unfortunately, when a problem occurs with your boiler, the reset function isn’t designed to fix it. It’s designed to be used to clear the fault code, after the appliance has been fixed.
You’ll need to call a Gas Safe registered boiler repair company. Once they’ve fixed the problem, they will reset your boiler to clear the F25 fault code from the display panel.
What can cause the F25 error to occur
Your boiler repair company will want to inspect parts that are directly related to the heating and distribution of water throughout the central heating system. That means checking components such as the pump and heat exchanger.
Here, they’ll be looking at settings, searching for air locks, and checking the overall condition of the parts.
But, before doing that, they’ll check the most obvious reason there’d be a lack of circulation in your heating system. Beneath your boiler are isolation valves. If for whatever reason these are closed, that’s going to mean that water isn’t allowed into the system, and your boiler won’t operate.
Even if water has been allowed into the system, they’ll need to ensure that the boiler is set to the right operating pressure. If it’s not, this is going to hinder circulation.
Finally, they’ll want to check that the NTC thermistors aren’t faulty.
What things will my boiler engineer be searching for when checking the pump
Without a pump working at its optimum, your boiler isn’t going to heat towel rails, radiators, or hot water correctly.
Your boiler engineer will want to assess the pump for:
- The correct speed setting
- Air locks
- Blockages
What happens if my pump isn’t set to the correct speed
Central heating systems vary in size. Smaller systems might have 3-6 radiators. Large properties might have huge runs of copper pipe, and 15+ radiators. For water to circulate correctly, the pump needs to be set to the correct speed. Otherwise, in small properties, the water would reach the return and be too hot.
More importantly, in larger properties, the water would have lost too much temperature by the time it reaches the last few radiators on the heating run, failing to increase their temperature.
Most modern pumps have three speed settings, and your boiler engineer will be able to select the setting that’s most suitable for your property.
What do air locks do, and can they be removed
Air locks act like blockages, and that’s going to reduce the pump’s ability to circulate water throughout your property. Luckily, they can be removed.
You’ll need to call a Gas Safe heating repair company, as working on the pump means taking the boiler apart. Once the casing is off the boiler, your engineer will be able to bleed the pump using the bleed screw. They’ll hear a hissing noise and when this stops that signifies that the air lock has been removed.
They’ll then need to check that the installation of the pump is correct. If the pump is even slightly off centre, this can induce air locks. Without adjusting the pump, the air lock is likely to happen again.
How do blockages occur, and can they be removed
After adjusting the speed setting on the pump, checking for correct installation and removing air locks, the next step is to ensure there isn’t any form of blockage in the pump.
The most common form of blockage is heating sludge. This is a combination of minerals in water, as well as rust that breaks off radiators, towel rails and pipework. Over time, pieces of heating sludge can get lodged in the pump. Naturally, this is going to reduce the pump’s ability to operate and cause a circulation fault.
The sludge from the pump can be removed manually. However, there’s a bigger problem at hand. If sludge is in the pump, it’s in the rest of the heating system too, so it needs to be removed.
The best way to remove heating sludge is using cleaning chemicals and doing a hot flush. This will flush out most of the heating sludge, not just from the pump, but from towel rails, radiators and pipework.
Another option is a power flush. However, a power flush puts a heating system under an immense amount of strain. Old systems are the only ones that would benefit from this procedure, and it’s likely they are too weak, so we’d not recommend it.
What preventative measures can be put into place to stop blockages occurring
The hot flush using chemicals is going to clean the system, but it won’t keep it clean.
As your heating engineer tops up the system with water, they’ll want to dose it with inhibitor. This is a chemical that’s strong enough to break down heating sludge.
Your heating engineer will also fit a magnetic boiler filter. This is designed to catch all the particles that the central heating inhibitor has managed to break down, keeping your system free from the most harmful heating sludge.
And, as an added bonus, heating systems free from heating sludge operate much more efficiently; so, you’ll be saving money on energy bills too.
My boiler engineer thinks I need a new pump, how much is this going to cost
Almost anything can be fixed, but at what cost? Depending on the level of damage, and therefore, repairs needed, it might be worth considering a replacement.
A new pump in a Glow-Worm boiler is likely to cost around £250. And, that’s a high-quality pump from a brand like Grundfos, inclusive of labour.
How can the heat exchanger contribute to the F25 fault code being displayed
The heat exchanger is incredibly important. This is the component that transfers heat from the burner, to your water. If this is even slightly compromised, the best-case scenario is that your boiler works extremely inefficiently. In a worst-case scenario, it will fail to heat water correctly, and you’ll end up with a circulation fault.
Although the heat exchanger isn’t responsible for circulation, water being pushed out of the boiler’s flow pipe needs to be at a certain temperature. If it’s not, the printed circuit board (PCB) will recognise that there’s a problem and display a fault code.
Like the pump, it’s likely there’s some form of blockage that’s causing the issue. Typically, the problem here is limescale build-up rather than heating sludge. So, rather than using generic chemicals, your boiler engineer will use limescale specific chemicals to flush limescale from the system.
And, if limescale is present, it’s likely you’re in a hard water area. Limescale is a big killer of boilers in these areas. One preventative measure worth mentioning, is the installation of a limescale filter. This can be fitted alongside a magnetic boiler filter, ensuring that all sludge and limescale is caught, before it reaches important parts like the heat exchanger.
Limescale has caused a crack in my heat exchanger, how much is this going to cost to fix
Where limescale builds-up, it creates a hot spot. In most parts of the heating system, that’s not a major problem. But, on old heat exchangers, it causes huge issues. Older heat exchangers are not particularly durable. This hot spot weakens the heat exchanger, to the point where it cracks.
Unfortunately, a replacement heat exchanger isn’t cheap. You should expect to pay somewhere in the region of £475.
Should I just buy a new boiler
When looking at repair costs of £400 upwards, it’s worth considering all the options. For a boiler that’s in good condition, with some degree of warranty, a repair is most likely the most cost-effective option.
However, if your boiler is old, inefficient and out of warranty, it might be worth considering a replacement (replacements tend to start at around £1,800). Before deciding, speak to your boiler repair company.
They’ll be able to asses the wear and tear on important and expensive boiler parts such as the PCB, heat exchanger, gas valve and pump. If multiple components show signs they’ll fail soon, the replacement might be the best route to take.
Other Glow Worm boiler issues
For more boiler issues regarding the Glow Worm then please visit the Glow Worm Boiler Problems And Cures page.