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Boilers - Frequently Asked Questions

The boiler might have locked out due to no gas or low pressure but most now will give a fault code to tell you about the cause of the lockout. Leaking, low pressure, no heating or hot water, boiler not responding to the thermostat, frozen pipes.

The first thing to check when boiler troubleshooting is to check the thermostat setting. Then check the fuse box or circuit panel for a blown fuse or tripped breaker.

If the boiler uses a standing pilot light, check to make sure it’s on. If using an RF thermostat to change the batteries, several makes of programmable thermostats only show a battery symbol when the batteries need changing and this is confused as a sign that the batteries are good. If you do change the batteries make sure that the replacements are put back the correct way round. Make sure the boiler is turned on and the dial that tells it how much heat to produce is not turned down or the boiler is on summer mode. Make sure that the gas has not been accidentally turned off at the ECV or if it’s a pre-paid meter that the credit has not run out.

There can be a whole range of reasons why a boiler stops working – please see common problems of boilers answers and look at our troubleshooting checks video on our homepage.

If your boiler seems to be functioning but the radiators are cold, then the likely cause could be a faulty boiler pump or your central heating controls. Make sure you check that the thermostat or timer is working correctly. Depending on the type of boiler this could be due to an issue with the pump or the zone or mid position valve if a conventional system or it could be that the flow temperature has been turned down on the boiler or summer mode selected if it’s a combi. Sometimes with combi’s, if hot water pre-heat has been selected but the boiler is in summer mode it appears that the boiler is firing but this is due to pre-heat and not the heating.

More often than not a lack of hot water is a thermostat issue, but it could also be a problem with your water or power supply, boiler settings, timer, or an issue with boiler pressure, a potential airlock, or frozen pipes. Depending on the type of boiler. If a conventional system with a hot water cylinder, it could be that the programmer is not calling for the cylinder to be heated, or it could be an issue with the zone valves or cylinder thermostat, or programmer. If it’s a pressurised system it could be a pressure issue, but most boilers will display a fault code or at least flashlights at you. If it’s a combi it could be that there is a fault with the boiler. People need to check all taps before thinking there is a problem with the boiler. It is quite common for people to say “ my shower is going hot and cold or the temperature won’t adjust” but their taps are all working so it’s a problem with the shower, not the boiler. Also, the combi boiler will stop producing hot water at low flow rates, normally about 0.5 ltrs per minute, below that the boiler sees the flow as a dripping tap

There are three main types of boiler combi, heat-only, and system. Heat only boiler can work with unvented and a system boiler can work with the vented cylinder. The difference is that a system boiler has the pump built into the boiler and a heat-only or regular boiler doesn’t, Combi boilers do indeed produce the hot water as well.

A broken internal component, such as a pressure sensor known as an F75 fault. valve. Loss of pressure, thermostat issues, and leaks are also the main causes of problems as well as flow sensors – if this fails the boiler stops producing hot water. System debris that has blocked the heat exchangers or caused component failure can also be the issue.
  • Get your boiler serviced every single year and make sure it’s covered with a care plan.
  • Switch your boiler back on a few times over the summer to run the heating for a short time to prevent parts from seizing up.
  • Prevent frozen pipes in winter by insulating your pipes and setting your thermostat so that your heating stays on low whilst you are out, or so that it switches on occasionally can help.
  • Bleed your radiators to release pressure.
  • Arrange a power flush to clean the system through a certified heating engineer.
  • Installation of a primary filter if one is not fitted.

Boiler pressure should generally be between 1 and 1.5 bars when central heating is turned off. The needle of the pressure gauge should always remain above the lower limit set by your boiler manufacturer. It is important that if the pressure is topped up that the filling loop is fully closed, leaving the filling loop open can cause damage to the boiler.

Many heating engineers are competent to wire the boiler back into the existing fused switched spur and to wire in the controls to the boiler, only if changes to the electrical circuit are needed would an electrician be needed.) Although a gas boiler is an electrical device, it is not normally referred to as an Electric boiler mainly because there are boilers that are only electric and have no gas. Therefore, boilers that use gas are referred to as gas boilers
No. Whilst you can do some of the donkeys work yourself such as installing the water pipes and radiators for a heating system, working on the gas boiler itself, and the final connection of the water pipework to the boiler must be done by a Gas Safe registered engineer. If you refer to all pipework associated with wet central heating systems as heating pipework it distinguishes between the pipework for the heating system and the potable water piping.

With a qualified heating engineer sourced, they can have your old boiler out and a new one installed and operational in less than a day.

The main difference between a plumber and a heating engineer is that a plumber does not carry any gas safe qualifications. Gas qualifications to work on a boiler normally referred to as ACS must be in place and the company registered with Gas safe. The gas qualifications alone do not allow someone to legally work on gas or gas appliances, must be done by a gas-safe registered engineer.