Common Boiler and Heating Problems and How to Avoid Them

FreeHeating Blog - 5th June 2020

Every year, around 20% of boilers in the UK develop a fault. Some problems can be easily rectified but most of them will require the attention of a fully qualified Gas Safe or Oftec registered engineer. Having your boiler serviced once a year and making sure your heating system is well maintained will avoid many of the potential issues you could face.

Losing pressure
The most common reason for a boiler losing pressure is a water leak inside the boiler itself or elsewhere in the system. Leaks should be traced and repaired as quickly as possible because if left unattended, they can cause further damage. For example, water leaking onto the main circuit board (PCB) could end up costing hundreds of pounds to rectify. Falling boiler pressure can also be caused by a faulty pressure relief valve, air vent, pressure vessel or the pressure gauge itself. Air in the radiators or other parts of the system can also be to blame.

Making noises
Gas boilers can make a loud bang when they first start up. If the boiler doesn’t light straight away, excess gas builds up and then ignites in one loud explosion. This is normally down to a fault with the ignition system and most boilers will lock out after three failed attempts to prevent further damage. Boilers can also make a variety of other noises such as tapping, vibrating and humming. Some noises are down to mechanical problems such as faulty ignition components or the pump. However, non-mechanical issues such as a build up of sludge or limescale, issues with water flow or pressure and air in the system can all be responsible.

Pilot light going out
This can potentially be a very dangerous situation, especially where gas is concerned and you should call out a qualified engineer as soon as possible. There may be a problem with the fuel supply, a blockage of carbon in the pilot itself, draughts in the flue or other mechanical causes.

Locking out or switching itself off
A boiler lockout is typically indicated by a red or orange warning light on the front panel. Modern boilers will also display a fault code that enables an engineer to quickly determine the root of the problem. Boilers can lock out if the pressure becomes too low or goes too high. They should run at around 1.2 bar but can lock out if they go below 0.5 bar or above 3 bar. Other possible reasons for a boiler locking out include problems with the fuel supply, blockages or freezing of the condensate system, ignition faults, electrical problems such as a failed PCB, blockages from sludge or limescale and mechanical problems with components such as the fan or pump.

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Radiators don’t heat up properly
One of the most common reasons for radiators not heating up correctly is the system being out of balance. Radiators are connected in a circuit with one pipe taking hot water to all the radiators and another pipe bringing cooler water back to the boiler. If some radiators aren’t heating up properly, they may not have enough water flowing through them. The flow around the system is adjusted by engineer’s valves at one end of each radiator. Another cause of radiators generally not being warm enough is faulty thermostats, either on the radiator itself or a main controller in the room. The thermostat thinks that the radiator or room is warmer than it actually is and stops allowing hot water into the radiator.

Radiators cold at the top
The most likely cause is radiators having air inside them. They need to be bled by opening a small valve at the top until water starts to appear. Bleeding radiators is best carried out when the heating is turned on and is one of the few tasks that can be attempted by a non-professional.

Radiators cold at the bottom or in the middle
This is a sign that there may be sludge in the system obstructing the flow of water. Minor sludging can be cleared by adding a cleaning agent to the system then draining and re-filling it after a few days. Badly affected systems will need to be drained and powerflushed. Once the system has been cleaned, it is a good idea to add an inhibitor to prevent sludge from building up in the future. A filter such as Magnaclean can also be installed.

No hot water or no heating
If the central heating works but the hot water is running cold or lukewarm, this normally indicates a problem with the diverter valve. It should prioritise hot water over heating so when you turn the hot taps on, water stops flowing to the heating system and diverts to the hot water side. A faulty or sticking diverter valve could therefore stop some or all of the hot water being sent to the taps. It can also fail the other way around where you may have hot water but the central heating isn’t working. If just the shower runs cold or lukewarm, this is most likely to be a problem with the shower itself unless it runs from the taps. Cartridge type showers are prone to failure which is normally rectified by inserting a replacement cartridge.

Water runs too hot
If the water is running too hot from the taps, this would generally point to a failed thermostat in a combi boiler or the cylinder thermostat in a conventional system. If the water is too hot at just the shower, again that would indicate a problem with the shower itself.

The best way to make sure you don’t experience any problems with your boiler is to have it serviced once a year. If your boiler is out of warranty, you can also take out a service plan that pays for the service itself and also covers you in the event of any faults or breakdowns. Many boiler manufacturers such as Worcester Bosch and Baxi offer service plans but you can also purchase them through other companies such as British Gas or Homeserve.

If you have any of the above problems with your boiler then you would be best advised to call a qualified professional. If you are repeatedly having your boiler repaired or it has been condemned or deemed beyond economic repair, then your only option may be to have it replaced with a new boiler. If you receive benefits or tax credits, then you could be entitled to a grant to help with the cost. To find out more, click here to fill in our short form and see if you qualify.

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