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Boiler Advice

Ideal L1 Fault Code Meaning And How To Fix It

Ideal L1 Fault Code Meaning And How To Fix It

L1 Ideal Boiler fault code – Causes & How to fix!

As per the boiler manufacturers, Ideal, the L1 boiler fault code relates to a lack of water flow or an overheating of the hot water flow temperature.

As well as potentially damaging your boiler the L1 fault code on your Ideal boiler will mean that it will be using far more energy than usual making the boiler less efficient and this excess heat costs you more on your energy bills and repairs with the damage it is doing.

What is the hot water flow pipe of my Ideal boiler causing the L1 error?

The flow pipe on your boiler is where hot water leaves the boiler for your central heating system after it’s been heated and this will be hotter than other pipes and will show the Ideal boiler fault code L1

There are thermistors on the return and flow pipes on Ideal Logic boilers. These sensors measure resistance based on water temperature, and this resistance reading is sent via the printed circuit board (PCB).

The boiler will continue to function if the temperature is within its operating range, however, the L1 Ideal boiler fault code will display if the temperature rises above or drops below the operating range.

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How dangerous is the Ideal boiler L1 fault code

Your Ideal boiler should show a boiler fault code, and then to protect itself, it will lock out. The lock-out means the boiler will cease to work, and this usually makes the boiler safe preventing any boiler explosions.

You can generally stop these issues by getting an annual Ideal boiler service.

Ideal boiler fault codes are there for your and your boiler’s protection, so if your boiler shows any fault code but doesn’t lock out, it is best to turn it off and call a Gas Safe registered engineer.

The lockout protects the boiler’s components in case of damage and it also serves as a safety device and will stop the boiler’s power.

How can I reset my boiler to clear the L1 fault code

As mentioned, the safety lock-out mode function is a safety measure, therefore, you shouldn’t be resetting your boiler until a Gas Safe registered engineer has the problem fixed.

Only a Gas Safe engineer should work on boilers, so do not try and fix the boiler fault codes yourself as it may cause more issues, and if you have a faulty gas valve, you could cause a leak.

What causes the Ideal L1 fault code to appear?

As with any ideal fault code, the issue can usually be caused by several different things, but however, it does narrow your problems down to the following reasons:

This could be the root cause of your problem.

  • Faulty flow thermometer
  • Limescale buildup on the flow pipe
  • Broken heating pump
  • Malfunctioning PCB

What happens if there is a flow thermistor fault?

If the flow thermistor on your Ideal boiler is faulty, the readings it’s passing on to your PCB could be incorrect. In this case, the temperature reading might be much higher.

This is recognised by the boiler’s PCB and locks it out.

The PCB will give out the Ideal boiler fault codes relating to the problem; in this case, L1

What is the problem with my boiler’s thermistor?

Generally, a thermistor issue is caused by wear and tear due to a boiler’s age. The vibrations from the boiler could have worked loose or damaged the connections to the thermistor, causing it to pass on intermittent readings to the PCB.

What is the cost of repairing a flow thermistor problem on an Ideal boiler?

Always check if your ideal boiler is still under warranty, as it should be fixed for free.

Repairing this issue isn’t that difficult, and this is one of the cheaper repairs on boilers. The thermistor will cost £40-50 on its own.

You should expect to pay a Gas Safe engineer, then £80-£100 to come out to check your boiler, figure out what is going on, and then fix it.

The cost of the repair will run between £120-£150. It is expected that the work will take about an hour for a boiler engineer.

Limescale in a central heating system

Central heating systems hold their pressure thanks to the water that they contain. This water isn’t purified, as it comes straight from the main supply.

Mains water can contain a lot of minerals, some more than others. These minerals can settle on central heating systems.

Limescale tends to settle most on the heat exchanger and the flow tube.

What happens if limescale builds up in my boiler’s flow pipe?

Where limescale settles, the water tends to burn hotter than it does in the rest of the heating system.

Although it is not dangerous, this can pose a problem.

The flow thermistor monitors the flow of water’s temperature. If limescale settles near the temperature sensor, it will be reading a temperature that is higher than it should.

The temperature reading at your thermistor may be too high because of limescale, but the rest might be the right temperature.

The problem is the PCB can only recognise the temperature reading from the thermometer. It will not recognise the water temperature.

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What can I do to solve my limescale issue?

Manufacturers such as Fernox and Sentinel produce limescale removers.

They’re sometimes called heating silencers.

This is fluid that you add to your central heating system. When they come into contact with limescale, they start to break it up, keeping your water flowing more freely.

You can catch it in a limescale remover (a small filter) or flush the system to get rid of all limescale. A magnetic boiler filter will also be installed.

If that doesn’t solve the problem, then the pipework or thermistor responsible may have to be replaced.

Could my central heating pump cause the L1 fault code to be displayed?

Your heating pump is what circulates the water around the central heating system to your radiators. So, if there’s a water circulation fault, this central heating pump must be checked.

You can also link it to overheating. The boiler will heat up too much if the water isn’t circulated quickly enough.

A Gas Safe engineer will first check that the pump is set to the correct setting.

The Grundfos UPS2 pumps, which are newer than the UPS1, have three-speed settings. You will need the fastest flow setting if you live on a large property with many radiators.

An engineer will also check to make sure the pump isn’t blocked.

The engineer will first bleed the pump with the bleed screw. A pump with an airlock can restrict its circulation.

While they are removing the boiler casing, they will take apart the pump and clean it. This debris is caused by heating sludge, which builds up in the heating system.

If the pump shaft and bearings are in good shape, they can be re-fitted to clear the L1 fault code from your Ideal boiler.

How can I stop this from happening again?

This debris has likely come from rust. That breaks off the inside of radiators, towel rails and copper pipe.

This is the quickest and most effective way to avoid it.

  • To get rid of central heating sludge, fill the system with a central heating inhibitor.
  • Add a limescale inhibitor to the heating system.
  • To catch any debris, install a magnetic boiler filter

What does the PCB have to do with L1 fault codes?

If the boiler engineer still can’t find why the Ideal boiler is showing L1, there’s a good chance it’s due to a faulty PCB or Printed Circuit Board.

Your boiler’s control panel is made up of the PCB. Your boiler will not work properly if it isn’t working correctly.

It needs to read the readings from a thermistor. It may also lock the boiler if it isn’t translating the readings correctly.

What can a boiler engineer do to check if PCB has a problem?

The first thing they can do is do a visual check or inspection. They’ll be looking for loose wiring and any possibilities of other faults, such as burnt-out connections. If they find any, these need to be fixed right away.

They will need to test the unit using a multimeter if nothing happens with a visual inspection. This will tell you if the PCB is defective.

You will need to replace the PCB in your boiler if it is defective. A new PCB will generally cost between £400 and £500, depending on which model boiler you have.

Do I need a new boiler?

If your boiler has started showing L fault codes or others like the Ideal F2 fault or F1 fault code then it may be time to consider how old it is.

Older boilers can start to cost money in terms of repairs and a higher gas and energy bill.

An Ideal fault code and other boiler issues could mean the start of more problems if it is over ten years old.

See the cost of a new boiler here to see if it is cheaper in the long run.

Speak to a qualified engineer when you get your annual service.

They may give you a better idea of your unit’s state.

If your error code is worse than L1, then why not get a quote online in under 20 seconds to see how much a new boiler costs?


How to prevent the Ideal L1 fault code from occurring, relating to limescale buildup or central heating pump problems?

To prevent the Ideal L1 fault code from recurring, especially due to limescale build up or central heating pump issues, certain measures can be taken. Firstly, consider using limescale removers or heating silencers produced by manufacturers like Fernox and Sentinel to break up limescale deposits in the central heating system.

Additionally, installing a magnetic boiler filter can help catch debris and prevent clogs in the system. Regular servicing, including bleeding the central heating pump to remove airlocks and cleaning the pump to clear debris caused by heating sludge, can also mitigate the risk of fault codes like L1.

Is there a way to see if my Ideal boiler’s PCB is faulty causing the L1 fault code, and what are the potential repair costs?

If you suspect that your Ideal boiler’s PCB is faulty and causing the L1 fault code, a qualified Gas Safe boiler engineer can perform several tests to determine the issue. A visual inspection will be conducted to check for loose wiring or burnt-out connections on the PCB.

If necessary, the engineer will use a multimeter to test the PCB’s functionality and work out if it needs replacement. The cost of repairing or replacing the PCB can vary depending on the model of the boiler but generally ranges between £400 to £500 for a new PCB.

Should I consider replacing my boiler if it displays fault codes like L1, F1, or F2 and it’s over ten years old?

If your boiler frequently displays fault codes like L1, F1, or F2, especially if it’s over ten years old, it might be worth considering replacing it with a newer model. Older boilers can become more prone to faults and may incur higher repair costs and energy bills. Upgrading to a newer boiler model can offer benefits such as improved energy efficiency, reliability, and potentially lower service costs in the long run.

However, the cost implications of upgrading to a new boiler will depend on factors such as the type and size of the boiler, installation fees, and any additional features or warranties included with the new model.

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