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Glow-Worm Boiler F20 Fault Code

The Glow-Worm fault code F20 relates to a software compatibility and here we have Q & A or require an engineer for an emergency boiler repair.


The Glow-Worm Boiler Fault Code F20 Error Common Q & A

Just below, we have a list of common questions relating to the F10 fault code on the Glow-Worm Boiler.

Glow-Worm boiler error code F20
  • What does the F20 fault code mean on my Glow-Worm boiler?
  • If I reset my boiler, will this clear the software fault?
  • What are the most likely causes of the software compatibility issue with my Glow-Worm boiler?
  • Why would the installation and setup of the PCB be incorrect?
  • If my boiler’s PCB is faulty, how will my boiler engineer know?
  • My boiler engineer thinks its water damage that has caused my PCB to fail, is this right?
  • How much is it going to cost to replace the PCB on my Glow-Worm boiler?
  • Should I replace my boiler, rather than my PCB?
  • What is a boiler chip card?

What does the F20 fault code mean on my Glow-Worm boiler

If you are seeing the F20 fault code on your Glow-Worm boiler, the manual will state that this is a “software compatibility” issue.

Your boiler is controlled by a printed circuit board (PCB). It’s the PCB that gives and receives signals to a range of electronic components. This includes sensors such as thermistors that help to monitor temperature, through to the pump and gas valve.

For your boiler to work correctly, the PCB needs to be 100% operational. In this case, there’s a problem with the software, setup, or the PCB itself.

If I reset my boiler, will this clear the software fault

Unfortunately, the reset function on Glow-Worm boilers isn’t designed to fix problems. It’s designed to let you know there’s an issue. And, the fault code being displayed helps your boiler engineer to narrow down the issue to a few potential culprits.

You shouldn’t reset your boiler. Instead, you should call an emergency boiler repair company. Once they’ve diagnosed and fixed the fault, only then, will they reset the boiler. This will clear the fault code from the display panel.

What are the most likely causes of the software compatibility issue with my Glow-Worm boiler

Electronic faults are never as simple as they seem. Your boiler engineer is going to start by checking:

  • The installation and setup of the PCB is correct
  • The PCB isn’t faulty
  • Your boiler’s chip card is present, installed correctly and isn’t faulty.

Why would the installation and setup of the PCB be incorrect

This is a potential problem if you’ve either:

  • Recently had a new boiler
  • Had a replacement PCB fitted to an existing boiler.

In each scenario, the PCB will need to be configured. This setup is usually basic, consisting of an engineer inputting a specific product code. That helps the PCB register with the boiler, so it works seamlessly.

If your PCB hasn’t been configured correctly, the boiler won’t work, and the F20 fault code is going to be displayed. In its current state, the software can’t communicate with the PCB or the boiler.

If my boiler’s PCB is faulty, how will my boiler engineer know

If your boiler is old, there is a chance that the PCB is to blame, and it’s nothing to do with configuration, or software.

On old boilers, anything from overheating causing connections to burn out, through to water damage, can cause a PCB to fail.

But, there are some obvious signs that give an indication that a PCB is to blame. For example, if there’s a problem with the PCB, it’s likely that the display panel is flickering. And during operation, there’s a chance that the boiler cycles on and off randomly. Essentially, the appliance will be incredibly unpredictable.

Your boiler engineer can use a multi-meter to test all wires and connections that work with the PCB. Alongside this, they can also test the PCB for power.

Hopefully, the issue is a simple case of loose or damaged connections, which can easily be repaired. Although the fault might be small, the implications will be huge. Even one loose connection could cause the communication between the boiler and the PCB to be intermittent, or non-existent.

But on some occasions, there is no way to salvage the PCB. In these cases, the PCB is going to need to be replaced.

My boiler engineer thinks its water damage that has caused my PCB to fail, is this right

If your boiler engineer suspects water damage, they’ll want to diagnose and fix this right away. Electrical components in these appliances are incredibly fragile. Exposure to even the smallest amount of water, will completely ruin them.

This is especially the case with older boilers. The electronics don’t tend to be sealed as well as they would be with a newer appliance. And, that means that damage occurs quickly, and spreads rapidly.

It’s most likely that water damage on your boiler has come from a faulty pump. When a pump’s seals fail, water starts to escape, and that can find its way onto a whole host of electronic components, including the PCB.

The cause could be anything from a heating sludge blockage, old age, or even the pump being set on the incorrect speed setting.

Whatever the problem is, you’ll need your boiler engineer to find and fix it. If they don’t, not only is your PCB going to get damaged again, other components are too.

How much is it going to cost to replace the PCB on my Glow-Worm boiler

Your boiler engineer isn’t going to replace the PCB unless they are 100% sure that this is the issue; this is the most expensive component on a boiler to replace.

Typically, we’d expect the cost of a PCB replacement to be in the region of £450. That includes parts and labour, with the job taking around one day.

However, these aren’t parts that most repair companies have lying around on their van. It’s going to need to be ordered into a local plumbing merchants, so it could take a few days for your boiler to be fixed.

Should I replace my boiler, rather than my PCB

With expensive boiler repairs like this, it makes sense to check out all the options. A new boiler can cost as little as £1,800. So, spending £450+ on an old and inefficient boiler, especially if it’s out of warranty, might not be the best option.

The best thing you can do here, is have your boiler engineer inspect the general health of your appliance. It might be that your boiler is relatively new, and the PCB is the only component that needs replacing.

However, if they assess parts like the gas valve, pump, fan and heat exchanger, finding other faults, costs for repairs are going to spiral quickly.

What is a boiler chip card

As we’ve mentioned, the PCB is the most important component in your boiler. But, there are 100s of different boilers on the market. And, when manufacturers release a new one, they tend to use a generic PCB unit, rather than making one specifically for that boiler.

However, the appliance wouldn’t function, simply with a generic PCB installed. For the PCB to communicate correctly with the boiler, a boiler chip card needs to be installed.

So, before replacing your PCB, your engineer will want to check:

  • The chip card hasn’t come loose
  • The chip card is in good condition

And, they’ll need to make sure the chip card is the right one to match your PCB, with your appliance. If the wrong chip card is installed, your boiler isn’t going to work.

Other Glow Worm boiler issues

For more boiler issues regarding the Glow Worm then please visit the Glow Worm Boiler Problems And Cures page.