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Boiler Lockout Causes


Seeing you on this page, chances are, you just experienced a boiler lockout, and you are wondering what it means, what caused it, or even how to fix it. Well, the good news is you’ve come to the right place. In this guide, you are going to learn about boiler lockout and its various causes. We will also throw in a tip or two about fixing a boiler lockout.

What Is a Boiler Lockout?

A boiler lockout is a self-lock mechanism in most modern boilers which initiates a shut-down procedure when there is a serious fault within the boiler system. This safety feature prevents your boiler from operating when it has an issue that can escalate and cause an explosion, fire, or damage to boiler components.

How can I Identify a Boiler Lockout?

The most common sign of boiler lockout is the system grinding to a halt, meaning there will be no hot water or heating for your home.

If you have an older boiler model, it will let you know of a boiler lockout by flashing red or green lights. On the other hand, in the newer boiler models with a display panel, you’ll find it displaying a fault code that is often a string of letters and numbers.

How Do I Deal with A Boiler Lockout?

Finding your boiler flashing red and green lights or displaying fault codes or even both can send you into a panic. However, there is no need to worry as you can quickly solve this issue on your own. Some lockouts, however, may be due to some severe faults, and you may need to call a certified boiler tradesman to fix them.

That said, here is a summary of how to address a boiler lockout issue.

  1. Begin by checking your owner’s manual. In most cases, the boiler manual contains all possible boiler lockout codes. By checking the explanation for the fault code, you will determine the cause of the boiler lockout.
  2. Search the error code online. If the fault code is not listed on your owner’s manual or you’ve misplaced your copy, you can always search the fault code online. Alternatively, you can specifically head to the manufacturer’s website to get a list of all fault codes and their causes.
  3. Call the manufacturer’s customer support line. If you are still unable to understand the source of the fault code, or your boiler is an older version that doesn’t display fault codes, proceed to call the manufacture’s customer support. If they are familiar with the cause of the problem, they will tell you, and if not, they’ll recommend contacting a certified gas engineer.
  4. Fix the problem. After identifying the cause of the boiler problem, you can opt to reset. Alternatively, you can proceed to fix the underlying problem for a long-lasting solution.

What Are the Causes of Boiler Lockout?

  1. Ignition Failure

One of the leading causes of boiler lockout is ignition failure – that is, the boiler failing to fire up for central heating or hot water provision. Most boilers will shut down after three failed ignition attempts.

Some of the causes of ignition failure in a boiler include:

  • A faulty gas valve due to incorrect adjustment, blockages, seizure, or damaged wired connections. If the gas valve lets in too much gas, the PCB will deem it too dangerous and will lock out the boiler. On the other hand, if the valve is blocked, little gas will be passing, so the boiler locks out as this is a gas supply issue.
  • Blocked burner due to accumulation of soot. The good thing is, you can easily fix this problem by cleaning the carbon-build-up.
  • Gas supply issues such as low or high gas pressure. Just as with a faulty gas valve, gas supply issues will result in ignition failure, leading to a boiler lockout. Freezing of the gas meter regulator in cold weather will also result in failed ignition.
  • Faulty ignition lead and electrode marked by clicking/ticking noises when attempting to ignite
  • Debris is blocking the jet for the boiler pilot light. When even a speck of dirt clogs the jet, the pilot light on your boiler will go out, and the boiler won’t reignite. The good thing is that these jets are easy to replace. Alternatively, you can remove, clean, and reinstall them to fix the problem.
  1. Faulty Pump

When your boiler’s heating pump develops a fault, blows a seal, or seizes up, it may result in a boiler lockout.  To determine whether the lockout is due to a problem in the pump, use your hand to feel it. Under normal circumstances, it should not be scalding, and you should feel vibrations coming from it.

However, if the pump is faulty, it will be very hot since its internal parts may be jammed. You will also fail to register any vibrations in this case.

To fix a jammed pump, gently give it a gentle tap, and you’ll be good to go.

  1. Power Outage

No power supply to the boiler will automatically result in a boiler lockout. Recent power cuts, tripped electrics and blown fuses are mostly to blame for a boiler lockout due to power outage. In rare cases, this issue may be traced back to the PCB, and if this is the case, you should be worried.

  1. System Blockage

Boiler lockout due to a system blockage in most cases results from the accumulation of sludge in the boiler, pipework, or radiators. Freezing of the condensation pipe during winter and on cold mornings may also result in a boiler lockout.

To fix boiler lockout caused by a sludge blockage, we recommend hiring a certified and experienced boiler tradesman to flush the system.

  1. Low or High Water Pressure

Most boilers will initiate a boiler lockout when the water pressure is too high or too low.  Most boilers lock out when the pressure is below 0.6 bar and when it is above 3 bar. To avoid this from happening, ensure your boiler operates around the optimum pressure at all times.

To fix boiler lockout caused by low pressure, repressurise the boiler by adding water via the filling key or water-filling valves. On the other hand, if the lockout is due to high pressure, lower the boiler pressure by bleeding the radiator valves.

  1. Faulty Fan

Many people, when they hear the term boiler fan, automatically assume it cools down the boiler. Well, they couldn’t be more wrong. The fan in your boiler isn’t for cooling purposes. Instead, its primary function is to create a draught that pushes out harmful exhaust gases such as carbon monoxide from the boiler.

The harmful gases eliminated from the boiler are pushed into the flue, which carries it outside your home and releases it into the atmosphere.

If your fan is faulty or stopped working, the boiler’s printed circuit board (PCB) will not recognise it. Once the PCB determines that the fan isn’t operational, it will initiate boiler lockout as it would be dangerous to let the boiler continue running.

To know whether the boiler lockout results from a faulty boiler fan, try to ignite the boiler. If it doesn’t ignite and you can’t hear the boiler running, this is definitely the culprit.

Replacing a boiler fan is quite expensive, so if possible, try repairing it rather than replacing the whole unit.

  1. Heat Exchange Blockage

It is not uncommon for the heat exchanger in your boiler to be blocked by limescale buildup. Limescale buildup is often indicated by whistling or kittling sounds originating from your boiler. The presence of large amounts of limescale in your boiler will result in water temperatures rising too high, thus triggering a boiler lockout.

As the cost of repairing a damaged heat exchanger is relatively high, it might be more efficient to replace it entirely.

What Next?

After identifying the cause of the boiler lockout and fixing it, the next step is to reset the boiler and get it firing again.  If your boiler is a relatively modern one, check for a reset button on the display board. Press the reset button and hold it down for 5 to 10 seconds, and you’ll be good to go.

If you have an older version that doesn’t have a reset button, there is no need to worry. Just consult your owner’s manual for the correct procedure or search it online.

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