The F28 fault code references a boiler lockout. It happens when the boiler cannot detect a flame inside the boiler. The boiler will attempt to light 3 times. If it detects no gas, the boiler will display this code until it is manually reset. This blog explains what is wrong and how to fix the situation.
Understand what is happening to cause F28 fault code
When you place a demand on the boiler, either heating or hot water, the boiler starts a lighting sequence. Several sensors check to ensure it is safe to heat the system. Next, the gas valve will open into the fan and the fan will mix gas with air to provide the correct mixture for combustion. This mix is injected into the burner as an igniter starts sparking. The gas catches and lights, and a sensor detectors the flame. This stops the ignition sparking, and the boiler increases the fan speed (and gas input) to the required level for the demand.
A breakdown in this sequence can cause the boiler to lockout, displaying the F28 fault code. This fault code can appear for a number of reasons, even when there isn’t a fault with the boiler at all. The F.28 fault code activates when the boiler fails to light once the ignition sequence has started. In short, the boiler cannot detect a flame. However, there are many reasons for the boiler to activate the F.28 code
As part of the ignition process, the fan mixes gas and air together and injects it into the burner. This blows the products of combustion out through the flue. As the flue gases move through the boiler they cool down, causing condensation. A sump collects the condensation and discharges the water. Why is this information relevant? Well, a frozen condensate pipe causes a blockage The condensation water then backs up in the sump. As a result, the boiler cannot blow the products of combustion out of the flue, which prevents the boiler from lighting, or staying alight.
Are you currently experiencing very cold weather? If so, the condensate pipe can freeze which will cause the boiler to lockout. We have a guide on how to safely defrost a frozen condensate pipe here. If you are unsure, please call a Gas Safe Qualified Engineer
No gas supply to the boiler.
Sounds obvious? However, many engineers have visited properties to discover that this is the case. It is always good practice to check the gas meter and any gas isolation valves leading to the boiler. It could save an embarrassing call out fee! For those of you that have a prepaid meter, check that there is plenty of credit on the meter. Also, there could be a fault with the electronic in the meter and you would need to call your gas supplier to get it fixed. Some boilers use LPG (Liquid Petroleum Gas), stored in tanks. Check to make sure you have enough gas available.
What F28 fault code issues do I need a Gas Safe Qualified Engineer for?
There are a number of other issues that can cause a F28 which include:
- Gas pressure too low
- Faulty Gas Valve
- Defective electronics
These issues need a qualified Gas Safe Engineer to rectify. Do not attempt these yourself.