Ideal Logic Boiler FD Fault – Error Code Guide

If the display on your Ideal Logic boiler is showing F and D, you will need to take action before it will start working again.

The good news is that this code is unlikely to mean your boiler is dangerous, and it will have stopped functioning to prevent any internal damage to the unit that could require costly repairs.

The code isn’t always listed in the user manual that you will have been given when your boiler was installed, so this guide will help you to understand the fault and what may have caused it.

It will also cover the steps you can try at home to fix the issue, and when you will need to call your installer or an engineer. 

What Does the FD Fault Code Mean?

The Fd fault code means there is no water flow.

This refers to the water that comes into your home from the mains supply, making its way through the pipes and through the boiler unit.

This water needs to be flowing at an appropriate pressure for the boiler to register that there is water to heat, so if it cannot confirm this for any reason it will stop functioning until the problem has been rectified. 

What Causes the FD Fault Code?

Water Pressure is Too Low

While the Fd fault code indicates that the boiler isn’t registering any water available within your house’s heating system, it doesn’t usually mean that water is failing to enter your property entirely.

In order for your boiler to recognise the water and subsequently heat it up, enough of it needs to be in the system at any one time, which requires a high enough pressure. 

The term “pressure” refers to the amount of force required to carry water through the pipes to your home, and is measured in “bars”.

Your boiler has a pressure gauge which displays the bars currently present in your heating system. The recommended reading is 1.3 bar, though slight fluctuations between 1 and 2 won’t usually cause a significant issue.

If the water pressure drops far below 1.3 bar, the boiler may fail to register that water is present, leading it to lock out and display the FD fault code.

It’s not uncommon for boilers to lose pressure over time, which means that it doesn’t necessarily indicate a faulty part.

However the unit should not require frequent repressurising, so if the problem continues then an engineer will need to find the source of the issue.

Boiler Pump is Blocked or Damaged

The role of the pump in your boiler is to control the circulation of water through the unit. If this part becomes blocked or stops functioning, water flow can be impeded or totally stopped, leading to fault codes such as FD. 

If you have had your boiler for some time, the bearings and shaft of the pump may have become worn out. This is particularly likely if the unit has been very noisy recently.

The pump can also become blocked by something called heating sludge. This is a mixture of rust and minerals that collects around the house’s pipes, eventually forming a thick mixture that can clog various parts of your boiler, stopping water from flowing through them.

Pump Has Been Installed Incorrectly

If the FD fault code is appearing on a your boiler that has been newly fitted or relocated, the pump may not have been installed correctly.

In order to have full range of motion, it needs to be sitting horizontally. Even on slightly older boilers this can’t be ruled out, as an incorrectly installed pump can still function, it will just wear out more quickly.

A Leak Within the Heating System

A leak within the boiler unit itself, or anywhere in your home’s heating system, will interrupt the flow of water to the boiler.

Common reasons behind a leak include wear and tear to pipes, and damage to the seals of the boiler’s pump.

In some instances it will be obvious that you have a leak, as you will be able to see or hear water escaping from your boiler or other pipes.

However you won’t always be able to identify the source of the leak yourself, as even small breaches can be enough to affect the boiler’s capacity to register an adequate flow of water.

Can I Fix My Own Boiler with the FD Fault Code?

This fault code is one of the few that can commonly be fixed by the homeowner. The following steps may be enough to get your boiler working again, but if the problem persists you will need to call a registered Gas Safe engineer.

This is the case for any work that would involve taking the boiler’s cover off, as homeowners are not legally permitted to inspect or repair any parts of the unit which may interfere with the gas supply.

How to Fix an FD Fault

If repressurising the boiler yourself didn’t work, a Gas Safe engineer will need to determine the cause of the issue. As there are a number of potential causes, the time and costs associated with fixing this fault code vary widely.

If the Water Pressure is Too Low

This is a fix you can do yourself.

Check the pressure gauge on the front of your boiler, if it reads below 1 bar then low pressure is likely to have caused the fault code. If it is below 1.3 bar then you should still adjust the pressure while you are here.

To repressurise your Ideal Logic boiler, look directly underneath the unit. On the right hand side you will see two blue handles coming out of a connected loop of pipe, known as an integral filling loop.

The right-hand blue tap controls this loop, and the left-hand blue tap is called the cold isolation valve. To repressurise your boiler, do the following:

  • Turn the left-hand tap (cold isolation valve) off – until it is perpendicular to the pipe
  • Turn the right-hand tap (integral filling loop) on – until it is parallel with the pipe
  • Watch the pressure gauge rise until it hits the required bar reading
  • Turn the right-hand tap off – until it is perpendicular to the pipe
  • Turn the left-hand tap on – until it is parallel with the pipe

If low pressure was causing a lack of water that led to the Fd fault code, it should disappear once the pressure has reached an adequate bar reading. 

If simply repressurising the boiler didn’t fix the issue, or if it continues to lose pressure intermittently, a Gas Safe engineer will be needed.

They will to diagnose where the pressure is being lost. If they suspect a leak, they may need to inspect all parts of the heating system including the boiler, the pipe network, and the radiators.

Once they have repaired the site of the leak, they will be able to repressurise and reset your boiler to clear the fault code.

If a Boiler Pump is Blocked or Damaged

If the pump is damaged beyond repair, an engineer will need to replace the part.

Pumps tend to cost between £100-200, but this will depend on the model and age of your boiler. Once installed they typically last around ten years.

If heating sludge has caused a blockage, the engineer will likely perform a hot flush to clear it out. This involves sending specific chemicals through the whole heating system, which should remove any remaining debris.

If the pump itself is not damaged, they won’t need to replace it, only clean it out. To prevent future sludge build up, they may install a filter which can catch the tiny bits of metal with a magnet, preventing them from collecting into sludge.

If the Pump Has Been Installed Incorrectly

A boiler engineer will be able to tell immediately if this is the cause of the problem, as the pump will have been installed vertically rather than horizontally.

If your boiler was recently fitted, they may be able to correct the installation without replacing the part. If the pump has already become worn out by its bad placement, they may need to replace it entirely.

As this was an installation issue, it’s likely that you will still be in the warranty period for this service.

If There is a Leak Within the Heating System

The first step will be to find the source of the leak, which may require an inspection of the whole heating system if the location is not immediately obvious. The cost and time required to fix the leak will vary greatly.

For example, a damaged copper joint will be quick to diagnose and cheap to repair. More complex issues like damaged pump seals may take longer to discover, and could lead to costly replacement parts. 

A secondary issue with leaks is the damage they can cause to other parts. If the leak is within your boiler unit, your engineer will check that no water damage has occurred.

In the worst case scenario, the Printed Circuit Board (PCB) could have been affected by the leak. This is usually the most expensive part of a boiler to replace.

Which Ideal Models Use the FD Fault Code?

All of the Ideal Logic range use a standardised code system, so the information in this guide will be relevant no matter what model you have installed. This includes the different types of boilers such as Combi, System, or Heat Only.

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