Has your Glow Worm boiler locked out and presented you with the F28 error code? Find out what it means with costs to fix in this handy guide.
As with boiler brands across the board, Glow Worm boilers come with a whole host of in-built fault codes.
These codes are designed to let homeowners know when there is an issue.
Furthermore, with the help of the Glow Worm manual, you can find out what any given code means and explore a list of potential causes and solutions.
However, fault codes can, more often than not, also help heating engineers diagnose a problem.
But, what about the F28 fault code in particular?
Let’s dive in!
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What Is the Glow Worm F28 Fault Code?
Put simply, the F28 fault code means that there has been a failed attempt at boiler ignition.
Unfortunately, the F28 error code won’t tell you the exact reason for the fault.
There are, in fact, several potential causes, and therefore, several possible fixes for an F28 error code.
Causes of the Glow Worm F28 Error Code
The most likely explanations for a Glow Worm F28 fault are as follows:
Gas pressure
If you have a new boiler, there’s a very good chance that the problem lies with your gas pressure. If this is the case, it’s possible that your gas mains can’t cope with an increased gas demand from a new boiler, if it’s more powerful than your last one.
You would need to have your gas main upgraded in this scenario. Alternatively, a boiler (of any age), may be suffering from an air pocket in the gas main.
It’s also possible that your gas meter regulator has frozen, although we would only expect this to happen when it’s noticeably cold out (i.e., this isn’t usually a summer issue).
Flue airway blockage
While an air pocket in the gas main can lead to an F28, an airway blockage in the flue can also result in an F28 error. An issue may lie with the flue or even the condensate pipe.
Moreover, flues can even block themselves from breaking apart due to wear and tear. As you can see, identifying the exact cause of an F28 fault is no walk in the park.
Incorrectly adjusted gas valve
Another potential explanation is that your gas valve was not adjusted correctly. This would prevent the right amount of gas from having access to the burner.
Faulty gas valve
Your gas valve should supply your burner with gas consistently. If there is a fault, the supply may be hit-and-miss or nonexistent.
A faulty electrode or/and ignition leads
The ignition problem may simply come down to your boiler’s electrics.
Wear and tear, an accumulation of moisture, and boiler vibrations can all lead to faulty electrode leads or/and faulty ignition leads.
Faulty spark generator
This is another electrical issue that can result in an F28 error. This component is designed to spark so that the burner (when supplied with gas) can cause boiler ignition.
A faulty spark generator will mean that a boiler can’t ignite. In most cases, a faulty spark generator will simply be replaced.
Burner debris
Debris in the boiler burner can also prevent ignition. In most cases, a carbon blockage will be the culprit.
Since the burner jet (which supplies gas) is very small, it doesn’t take much debris to cause a blockage and ultimately an F28 error.
Broken PCB
A PCB or printed circuit board controls a boiler’s various electrical components. It’s basically the control centre that rules the roost.
If it is suffering from a fault or it’s just outright broken, your boiler’s components may be receiving incorrect signals. Should this be the case, an F28 error (along with many other errors) can arise.
If your PCB is broken it should result in a boiler lockout either way since, without a working PCB, your boiler cannot function.
Frozen condensate pipe
While unlikely, it’s also possible that your condensate pipe has frozen. This can happen if the weather is especially cold.
Essentially, when this occurs, the water inside the pipe freezes over, forming ice, and, ultimately, blocking the pipe. With a blocked/frozen condensate pipe, your boiler cannot function.
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Can I Fix an F28 Fault DIY?
Unfortunately, fixing an F28 fault cannot generally be undertaken DIY.
The only exception is if a frozen condensate pipe is to blame.
In this scenario, you could take either of the following actions:
Pour hot, albeit non-boiling water over the condensate pipe using a watering can. It should be hot but not boiling since it could otherwise melt the plastic pipe.
Position a hot water bottle around the part of the condensate that is frozen. Alternatively, you could use a warm cloth or a microwavable heating pack.
Regardless of which approach you choose to go with, you should proceed with caution.
Also, watch your feet as water drips off the condensate pipe from ice melting on the exterior of it.
Once the job is done, unless your boiler automatically resets, you should reset your boiler manually per the manufacturer’s instructions.
If a frozen condensate pipe was the sole cause of the F28 error, this should solve the problem. If it doesn’t, however, you’ll need to hire a heating engineer.
Thawing out a frozen condensate pipe is the only potential fix for an F28 that a DIYer can undertake.
In fact, most gas boiler fixes, in general, must be dealt with by a Gas Safe Register engineer.
This is in accordance with the law and in the interest of your safety and the safety of those living on your property.
While some boiler fault errors can be fixed DIY, a Glow Worm F28 error is usually not one of them.
Cost of Hiring a Heating Engineer to Fix an F28
The average labour cost of hiring a Gas Safe Register engineer in the UK is £30 to £60 per hour.
The exact price will vary based on a range of factors including your location.
Here are the costs of specific F28 fixes:
Upgrading your gas mains
£250 to £580Fixing or replacing a frozen gas meter regulator
£130 to £320Unblocking a flue or condensate pipe
£30 to £120Replacing a boiler flue
£80 to £320Adjusting a gas valve
£30 to £120Replacing a gas valve
£160 to £400New electrode leads
£50 to £160New ignition leads
£130 to £380New electrode leads + New ignition leads
£180 to £540Replacing a spark generator
£50 to £250Removing burner debris
£30 to £120Replacing a PCB
£530 to £680New boiler installation
£800 to £2,800
Contact us if you’ve any further queries about an F28 error or a related concern with your Glow Worm boiler.
Will my Guarantee Cover Repairs or Replacement Work for an F28 Fault?
As with most boiler guarantees/warranties, Glow Worm will only cover the cost of repairs or replacement work if they have been necessitated by a defect resulting from the manufacture of the boiler.
In other words, the problem must initially lie with Glow Worm themselves.
Moreover, your guarantee must be currently active.
If it is and you meet all the terms and conditions of the Glow Worm boiler guarantee (some of which are listed below), a Vaillant Service Engineer must undertake the repair.
And then, in that scenario, you would have the labour and supply costs of the repair work covered by your guarantee.
The Glow Worm guarantee comes with a range of Ts and Cs, including:
Your boiler was installed and commissioned by a Gas Safe Register engineer (or an equivalent body of Gas Safe) and this must have taken place within six months of the boiler being despatched.
You must have your boiler serviced annually by a Gas Safe Register engineer. This service must be done in accordance with the Glow Worm instructions.
It is necessary to register your guarantee within 30 days of the boiler being installed. Otherwise, your guarantee will revert to a timeframe of twelve months after the installation date. So, let’s say you were originally offered a five-year guarantee, if you fail to register it, you’d end up with a one-year guarantee.
All in all, it’s generally unlikely that a Glow Worm warranty will cover a repair or replacement job to fix an F28 error.
However, if you suspect a manufacturing error may be at play, it’s best to hire a Glow Worm heating engineer to perform the repair/replacement job.
After all, if they discover that a manufacturing defect is an initial culprit, your labour/supply costs would then be covered, whereas they wouldn’t if you hired a non-Glow Worm engineer.
Glow Worm boiler displaying the F75 fault code? Find out how to fix it here.
PS You may be interested in Gas Engineer Allen Hart explaining the most common boiler problems and how you can resolve them in the video below:
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