Vaillant Boiler F28 Fault Code
The Vaillant fault code F28 Q & A or require an engineer for an emergency boiler repair.
The Vaillant Boiler Fault Code F28 Fault Code Common Q&A
Just below, we have a list of common questions relating to the F28 fault code on the Vaillant boiler
- My boiler starts up, but now it displays the F28 fault code, why?
- What does the Vaillant Boiler F28 fault code mean?
- Can I fix a F28 fault on a DIY basis?
- Do I need a new boiler if the F28 error code is displayed?
- What can cause an in-adequate gas supply to a boiler?
- I’m using a pre-paid meter, I topped up, and the F28 fault code is still displayed?
- Can gas pressure be measured to fix the F28 fault code?
- What can cause a gas supply issue in pipework?
- Should I replace all pipework, or just the elbows and couplers to fix the F28 fault code?
- What if the F28 error on my Vaillant is due to a gas meter with low pressure?
- The F28 fault code only displays in freezing weather, what could be the issue?
- Could a faulty gas valve be causing the F28 fault code to be displayed?
- Would a gas leak lead to a Vaillant F28 boiler fault?
- My engineer wants to do a let-by test for gas leaks, is that right?
- The tightness test showed no leaks, and gas pressure is fine, now what?
- What can go wrong with the ignition to cause a F28 boiler fault?
- What else can cause a F28 boiler fault?
My boiler starts up, but now it displays the F28 fault code, why
Modern boilers have various fail-safes incorporated into their design. Sensors will monitor things such as water pressure, gas pressure and gas flow.
When one of these pressures isn’t operating within tolerance, the boiler will cease to function and display the relevant fault code.
In the case of the F28 fault code on a Vaillant boiler, there’s a good chance you’ll have heard it ignite 3 times and failed, and then the F28 fault code was displayed.
What does the Vaillant Boiler F28 fault code mean
The most common reason for an ignition attempt failing is an issue with the supply of gas to the boiler.
If that isn’t the problem, issues with the actual ignition system in the boiler are usually to blame.
For example, the ignition probe may be faulty (or clogged up with carbon) and need replacing, or other electronic units need repairing.
Can I fix a F28 fault on a DIY basis
Most faults connected to a F28 error code being displayed as gas related. By law, a Gas Safe qualified engineer needs to be used to fix a fault.
In rental properties, any work completed on gas appliances or gas pipework by someone unqualified couldn’t just put tenants in danger, landlords could be convicted in a court of law if anything was to go wrong.
Do I need a new boiler if the F28 error code is displayed
The issue usually lies with the gas supply. On rare occasions, this can relate to the boiler’s ignition.Depending on the part needed and the age of the boiler, it’s usually cost-effective to fix the boiler, rather than replace it.
However, boilers that are 10 or more years older, with a £400+ repair bill, are usually worth replacing rather than repairing.
What can cause an in-adequate gas supply to a boiler
Anything on the gas run can affect the flow of gas. That’s going to include the meter, all pipework and gas valves.
If you’re using a pre-paid meter, remember the meter will need to be topped up to offer a supply of gas.
I’m using a pre-paid meter, I topped up, and the F28 fault code is still displayed
Most modern boilers need to be reset after they lockout, or display a fault code. If you attempted to fire your boiler with no gas, it will need to reset.
Some Vaillant boilers have an ignition button on the display panel. Pressing this will cause the boiler to attempt an ignition.
Otherwise, consult your manual for details on how to reset your specific boiler.
Can gas pressure be measured to fix the F28 fault code
Simply measuring the gas pressure at various points on the gas run isn’t going to fix the problem, but it’s going to highlight what the issue is.
A frequent problem is a faulty meter. Or, the gas run between the meter and the boiler.
A gas engineer will be able to determine the pressure at the meter and the pressure at the boiler. If they differ dramatically, there’s a good chance there’s an issue with the pipework between the two units.
What can cause a gas supply issue in pipework
Small pockets of air or water, and general old-age can lead to small levels of interior pipe corrosion, or debris build up.
Gas pipework is generally 22mm-28mm (depending on the length and route of the gas run) which is not particularly wide.
The smallest amount of debris in pipes can affect the gas pressure considerably.
Copper joints can also be a culprit. The point at which joints have been soldered is a common place for debris to form; especially on elbows.
Should I replace all pipework, or just the elbows and couplers to fix the F28 fault code
If your engineer has determined the gas run from the meter to the boiler is the issue, replacing all the pipework is the best option.
Without chopping bits out and retesting the pressure, it’s hard to know whether the culprit is pipe or fitting related.
It will be much cheaper in terms of labour, to replace all the pipework in one go.
What if the F28 error on my Vaillant is due to a gas meter with low pressure
Your engineer will be able to test the gas meter to check pressure.
If they determine there’s a lack of pressure at the actual meter, then this is usually an issue for your utility company to deal with.
The F28 fault code only displays in freezing weather, what could be the issue
Gas meters have regulators to control the flow of gas. In the winter months, they can freeze.
So, is your gas meter situated outdoors? If it is, this could be the source of the issue.
Consider insulating wherever the gas meter is located to stop the F28 fault code becoming an issue in the future.
Could a faulty gas valve be causing the F28 fault code to be displayed
Gas valves supply the boiler with gas. So, any issue with the gas valve that is restricting the flow of gas could lead to the F28 error being displayed on your Vaillant.
Testing a gas valve is not something that should be done on a DIY basis for safety reasons, so always contact a Gas Safe engineer.
Would a gas leak lead to a Vaillant F28 boiler fault
Any lack of supply or ignition will cause a F28 fault code to appear; leaks included.
If you smell gas, turn off the gas, and call an emergency engineer.
With you clear of the property they’ll be able to run a gas tightness test to determine if there’s a leak, and exactly how bad the leak is.
My engineer wants to do a let-by test for gas leaks, is that right
A let-by test is the same (or, part of) a gas tightness test. Let-by refers to testing to see if gas is leaking, whereas tightness relates to making sure the system is sealed.
Different wording - the same principle.
The tightness test showed no leaks, and gas pressure is fine, now what
Gas valves work in conjunction with your boiler’s PCB (printed circuit board). A qualified engineer will be able to run an electrical test to determine that the gas valve is getting power from the PCB.
If it’s not, they’ll need to determine if it’s the PCB or gas valve that has failed. Gas valve replacement is cost-effective, but replacing a PCB on older boilers is not advised.
A new PCB (parts and labour) can run well into £400-500 and beyond. It rarely makes sense to invest this much money into an old boiler.
What can go wrong with the ignition to cause a F28 boiler fault
Like cars, parts in a boiler will wear out over time. Components that are liable to breakdown include the ignition leads, electrode and probe.
Ignition lead and electrode failures are solved with replacement parts, whereas a probe can be cleaned and retested.
What else can cause a F28 boiler fault
Although Vaillant state the F28 fault code is ignition and gas related, that’s not always the case. A boiler will display what it thinks is the most relevant fault code, but it’s not always correct.
The most widespread problem for a boiler breaking down in winter, is a frozen condensate pipe.
This is the pipe that vents from the boiler, and will usually be dripping outside (when the boiler is on).
The pipe needs to be thawed and the boiler reset. Consider insulating the pipe to stop the F28 code occurring in future.
Other Vaillant Fault Codes And Error
If your looking for the list of error codes relating to the Vaillant boiler then please read the article Vaillant Boiler Fault Codes And Cures