Which part of the system has stopped working?

Before changing settings, try a hot tap and check whether the radiators are cold when heating should be on. Also note whether the boiler has a display, shows a fault code or appears to start when either service is requested.

• Both heating and hot water are off: start with power, controls, pressure and any boiler fault message. The cause may still be elsewhere in the system.
• Hot water works, but radiators stay cold: check the thermostat, timer and accessible radiator valves. A circulation or heating-control fault may need investigation.
• Radiators heat up, but taps run cold: check more than one hot outlet. If every hot tap is affected, a boiler or hot-water-system fault is more likely than a problem at a single tap.
• Only one room is cold: the issue may be confined to a radiator or its valve rather than the entire system. See why a radiator may not be heating up for that narrower problem.

The observations help an engineer, but they are not a diagnosis. A combination boiler and a system with a separate hot-water cylinder can fail in different ways.

Safe checks before you call an engineer

Power and display

Look at the boiler display without opening its casing. If it is blank, check the accessible power switch and whether other equipment in the home has power. A tripped circuit can explain a shutdown; if it trips again when the boiler operates, leave it off and arrange an electrical or appliance check.

Thermostat, timer and programmer

Check that heating is scheduled to run and that the room thermostat is asking for heat. Review any holiday mode or manual override. If a wireless control uses replaceable batteries, check them. A connection problem with a smart control has its own checks in our smart thermostat connection guide.

Pressure and fault code

Read the pressure gauge and compare it with your boiler's user instructions; the expected reading depends on the appliance and whether it is operating. Write down any error code exactly as shown. If the manual permits a reset, follow its instructions once. Repeated pressure loss or a fault that returns after resetting requires investigation. Do not keep topping up or resetting the boiler to mask a recurring problem.

What else can cause a loss of heating or hot water?

A frozen condensate pipe

In freezing weather, an external condensate pipe may ice up and interrupt the boiler. Look for a relevant fault indication and check the boiler manual. Do not use a naked flame, climb to reach inaccessible pipework or attempt work inside the boiler. If the fault recurs, an engineer can assess the pipework.

Circulation or radiator problems

If the boiler is running but the radiators remain cold, an open valve or control setting is worth checking. Uneven warmth across several radiators may point towards trapped air or circulation issues. A pump, motorised valve or other system component can also be involved. A whole-system heating fault belongs with central heating repairs; a single radiator needs a narrower assessment.

Ignition, boiler controls or internal parts

A boiler may display a lockout or stop firing when it cannot operate normally. Ignition components, sensors, valves, pumps and electronic controls are possible causes, but a symptom or fault code alone cannot establish which part needs repair. If a boiler-specific problem has been identified, see help with emergency boiler repairs. A general loss of service with an unknown cause is better assessed through our emergency heating engineers service.

One service works but the other does not

On some combi boilers, a diverter-valve or control fault may affect heating and hot water differently. In a property with a cylinder, the cause could lie in the hot-water controls or another part of that system. Do not order a part based on the symptom alone; the layout and operation need checking first.

When should you arrange a professional check?

Book an inspection if the boiler repeatedly locks out, shows a recurring code, leaks, loses pressure again after topping up, makes an unusual noise or has power but will not provide the service requested. Tell the engineer which service has stopped, whether the problem is constant or intermittent, and what you saw on the display.

If the loss of heating or hot water is urgent, contact VR Central Heat with those details so the right type of visit can be arranged. Routine boiler servicing and maintenance has a different purpose from diagnosing an active breakdown.

If you suspect a gas or carbon monoxide problem

Do not remove the boiler casing or attempt gas repairs. Anyone employed to work on domestic gas appliances must be Gas Safe registered and competent for the relevant work, as HSE explains.