Boiler lockouts: frequent causes and how to solve them

The boiler is an essential part of a heating system inside the home. In the winter period, doing without a boiler is almost impossible, but in general, it is important to have a fully functioning boiler whatever the season. It is the boiler that supplies radiators or obtains domestic hot water.

Domestic heating boilers differ according to the type of fuel used, such as LPG or methane gas, the combustion of which raises the temperature of the water or air that passes through the system, to feed it into all rooms and heat the house, or to provide domestic hot water.

In addition to the type of fuel used, boilers differ in another characteristic, the presence or absence of a condensing system. In practice, compared to conventional models, condensing boilers can recover part of the heat generated for combustion, optimising the performance of the boiler itself, making it more efficient.

Given the important role that a boiler plays in the home, it is very unpleasant when this appliance malfunctions. A common situation, for example, is a problem with the water heating system just when you are taking a shower or want to run a bath. Whatever the reason for the malfunction, it usually causes the boiler to go into lockout.

Understanding the reasons why the boiler is going into lockout allows us to solve the problem ourselves or, in more serious situations, to solve the boiler blockage by calling in a specialised technician.

Why a boiler goes into lockout

Before finding out how to solve our specific problem, it is important to clarify what is meant by the term “boiler lockout”. A boiler is said to go into lockout when something in the heating system prevents the device or the system connected to it from functioning properly. A boiler lockout, therefore, occurs for safety reasons. If there is a malfunction, the device stops working to prevent more serious problems from arising. Therefore, the boiler itself is seldom to blame for a boiler lockout; there are various external causes capable of triggering it.

The most frequent causes of a boiler lockout are:

• Limescale

• Interruption of the gas supply

• Damage to the electrical system, e.g. caused by a storm;

• High or low water pressure;

• Insufficient exhaust gas draught;

• Condensate in the flue.

Once you understand why your boiler has gone into lockout, you can either try to solve the problem yourself, if it is not serious and easy to solve, or you can contact a service engineer to will help you identify the cause of the boiler lockout with certainty and repair the damage.

How to solve a boiler lockout

After identifying the cause, all that remains is to find out how to solve the boiler lockout. We should first of all be able to define the severity of the problem: is it something we can do ourselves or do we need to call in a professional? To find out whether resolving the boiler lockout is within our grasp, let’s take a look at what should be done in the cases identified above:

• If we believe that the boiler lockout is caused by limescale, which tends to obstruct the natural passage of hot water causing a consequent reduction in flow, we can call in a specialist service engineer, who will proceed with cleaning the exchanger using an acidic fluid capable of dissolving the limescale without ruining the system. It is also possible to add a limescale filter (polyphosphate dosing unit) or a sludge filter to the boiler to reduce the problem.

• If the boiler lockout is caused by a lack of gas, the boiler cannot function because it cannot ignite the pilot flame necessary for its correct operation. This may occur in the event of a temporary interruption of service, for maintenance work by the operator, or, where your home uses a tank of LPG for heating and domestic hot water, you may simply run out of fuel and need to refuel. Another reason for a gas interruption could be a breakage or the obstruction of the valve supplying the boiler. In this case, you will have to contact a specialist service engineer, as a DIY intervention is not advisable.

• For example, if a fault were to occur in the house's electrical system, or, quite simply, the power were to fail temporarily, the boiler would be switched off, because without electricity it is not possible to ignite the spark that drives the boiler's pilot flame. In such cases, all you can do is either fix the fault or wait for the power to return.

• If the boiler has entered lockout due to pressure problems, you can intervene independently by checking the pressure gauge. The pressure should be at a level between a minimum of 1.2 bar and a maximum of 1.5 bar; try not to go lower or higher than these two levels. If the pressure should fall below 1.2 bar, the boiler will go into lockout, because it is not sufficient to guarantee its proper operation. To raise the pressure to the required level, the knob must be turned manually, always remembering not to exceed 2 bar. If, on the other hand, the pressure is too high, i.e. above 2 bar, you can simply vent a radiator or towel heater in the house, lowering it to below the maximum recommended level.

• An obstruction in the flue gas draught systems prevents this process, trapping the flue gases and sending the boiler into lockout. In these cases, you will have to call in a specialist service engineer to carry out a thorough cleaning.

   

• In condensing boilers, if the condensate drain pipe freezes and becomes blocked with ice, this causes the boiler to go into lockout. In the vast majority of cases, these problems occur where the condensate drainage pipe is located outside the building, and it is always best to seek professional help from a specialist service engineer to solve the problem.