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Testing with Multimeter
Spark Electrodes
Fan Replacement

Most boiler breakdowns can be addressed within 1 to 2 sessions. However, it may not always be possible to find and rectify every fault in these number of visits, and here’s why:

At London Heating Expert, we believe that every boiler deserves a second chance. If boilers are serviced and repaired in time they could last for many working years.


Unlike many heating engineers, offering you a boiler replacement will not be our first option. We’d like to repair your boiler if we can. That’s why we give the choice to you. You can spend as much or as little as you like on your boiler repair, before you decide it’s time to have it replaced. In other words, we won’t give up on your boiler until you do.


Our boiler repair pricing is simple. You'll need to book an initial boiler diagnostic session to determine the fault(s) on your boiler. Once our engineer has evaluated the problem, a repair and estimated cost will be suggested to you. This is based on the estimated time required for the fix. If you agree, you will need to pay for the parts to proceed. The total will be determined by the actual amount of time taken for the fix, charged at £80 per hour, plus the cost of the parts. Most repairs last no more than 2-3 hours, but if they do we'll cap the labour charge to 3 hours.


If you decide that the repair is going to be too costly or not economical in the long run, we can allocate the cost of your diagnostic session (or up to £200 of any repair) as credit towards the replacement of your boiler, instead.

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Boilers have what’s known as an “ignition sequence”. That means they have to complete a number of steps to ignite and burn the gas. If there is a fault at one stage, the ignition sequence is interrupted and the boiler locks out until that fault is resolved and the boiler is able to move on to the next stage in the sequence.


The sequence of operation for most boilers is to run the pump, then the fan and then to open the gas valve and ignite. Each stage incorporates a checking mechanism, which is usually some type of sensor. If the pump runs successfully, a hydraulic pressure sensor picks up a pressure difference and understands that the water in the central heating circuit is circulating. The sensor sends a signal to the electronic circuit board verifying that the pump is running. If either the pump or the sensor fails, the ignition sequence will be interrupted at this stage and the boiler won’t move on to the next stage. Likewise, in the second stage after the fan starts, an air pressure sensor will sense the flow of air and the boiler is allowed to move on to the next stage.

When the pump and the fan have started and their operation is confirmed by the sensors, the circuit board will command the gas valve to open and the spark electrodes to attempt ignition. If the gas is lit, a flame should be detected by a flame sensor after which the ignition sequence will be complete.

In some cases, the electronic circuit board itself may be faulty and either not receiving the signals from the sensors, not interpreting them correctly, or not able to successfully send commands to other components. It may be hard to ascertain of a board failure and your engineer must have a good knowledge of electronic operations to perform the correct diagnosis.

If you have a pump or hydraulic pressure sensor failure, the ignition sequence won’t get passed the initial stage. That’s why it may not be possible to find faults with the fan and/or gas valve operations on the first visit or before some repairs.


By learning about the ignition sequence you can appreciate that it may not always be possible to diagnose and fix the problem in one go, and that there will be an element of uncertainty behind some repairs.


After a repair attempt, if the boiler doesn't become fully operational again, you must make a decision. You either commit to another repair session, or decide that spending more money on the boiler will be a false economy. The price of parts may also guide you in making this decision, as spare parts of some boiler manufacturers are more expensive or hard to find.


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We may also advise you to get a power flush done or have a magnetic filter installed on your system, if we find the system water quality to be affecting the breakdown.


In such cases, we may not be able to give you any warranty for the repair, unless the boiler is protected either by power flushing or adding a filter to the system.

We understand that cash at hand may be limited if you’re forced to take the straining financial decision to replace your boiler. For such occasions, London Heating Expert also gives you the option to pay for your parts and services using a credit card payment. We can also offer you Financing Options to replace your boiler.

If you need any further help or have any questions,  please feel free to contact us.


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To further protect you from pouring your money down the drain, we’re also giving you up to £200 of repair costs as credit towards replacing your boiler with us.


This would mean that, before replacing your boiler, you could essentially try a repair on it. If the repair fails and you decide to replace the boiler after the first attempt, you won’t have been set back hugely by the repair charges.

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To claim this special offer, simply book our boiler repair service online today! 

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