Why You Should Switch Your Heating On Before It Gets Cold

Pick a cool evening in the next few weeks, turn the thermostat up and let the heating run. It sounds too simple to be worth a whole article, but this one habit catches more winter breakdowns early than anything else a householder can do. Here is why it works and exactly what to look out for.

Why should you test your heating before winter?

Because a heating system that has been idle for months is most likely to fail on the day you first need it. In summer a combi boiler only fires for hot water, so the heating side, the pump's full workload, the radiator valves and the room thermostat can go untouched from April to October. Testing early moves any fault to a month when engineers are easy to book.

If the heating fails on the first cold night, you are waiting alongside everyone else whose system did the same. If it fails on a mild afternoon in late summer, the only inconvenience is booking a repair at a time that suits you.

What can go wrong with a boiler over the summer?

Mostly things that stick, settle or drift while nothing is moving. Heating water sits still, so any sludge in the system settles in low points. Moving parts that normally work every day in winter get a long rest, and some do not like it. The most common summer casualties are:

• The circulating pump. It can stick after a long idle spell, especially on older systems with sludge. Many modern boilers exercise the pump briefly each day, but not all, and not every system benefits equally.
• The diverter valve. On a combi, this switches between hot water and heating. If it sticks on the hot water side, you get hot taps but cold radiators.
• Radiator valve pins. Thermostatic radiator valves left turned down all summer can stick closed, leaving one radiator cold while the rest warm up.
• Controls. Wireless thermostats run out of battery, timers lose their settings after power cuts, and smart controls lose connection.
• System pressure. A very slow leak may have lowered the pressure over several months without you noticing.

How do I test my central heating properly?

Set the programmer to heating on, turn the room thermostat well above the current room temperature and open every radiator valve fully. Let it run for 30 to 60 minutes. That is long enough for the whole system to warm through and for most faults to show themselves.

1. Note the pressure on the gauge before you start, with the system cold.
2. Turn the heating on and turn the thermostat up.
3. After ten minutes, check the flow pipe under the boiler is getting warm and the radiators nearest the boiler are heating.
4. After 30 minutes, walk round every room and feel the top and bottom of each radiator.
5. Check the pressure again. A small rise when hot is normal.
6. Run a hot tap while the heating is on to make sure a combi switches to hot water and back.
7. Turn the thermostat back down and check the boiler stops firing for heating.

What should I look and listen for?

Look for radiators that stay cold or heat unevenly, pressure that falls during the test, and water around the boiler or valves. Listen for new sounds: banging, gurgling, loud humming from the pump or a kettle-like rumble. Anything that was not there last winter is worth writing down.

For more on specific symptoms, see our guides to radiators that are cold at the bottom and how to bleed a radiator.

What can I safely fix myself?

You can bleed radiators, top up the pressure through the filling loop following the manufacturer's manual, change thermostat batteries, reset the timer and reset the boiler once using the reset procedure in the manual. That covers a surprising number of test-run problems.

Anything beyond that, including a pump that hums but does not turn, a stuck diverter valve, water leaking from inside the boiler or a lockout that returns after a reset, needs an engineer listed on the Gas Safe Register. Never remove the boiler casing to have a look, even if the fault seems obvious. If you smell gas at any point, turn off the supply at the meter and call 0800 111 999.

How often should I run the heating before winter?

Once is useful, but a short run every few weeks through late summer and early autumn is better. It keeps the pump and valves moving and means you notice any change quickly. Many households do this naturally from September onwards, but a deliberate test in August gives you the most breathing room.

The test run fits neatly alongside the rest of our winter boiler checklist, which also covers the condensate pipe, carbon monoxide alarm and stopcock.

Booking a check if your test run finds a problem

If your test run throws up something you cannot sort, it is far better to hear about it now than in December. A boiler service in Stoke-on-Trent is £90, and the engineer can look at anything you noticed during the test while they are there.

We also cover boiler service in Endon, boiler service in Alsager and the surrounding villages. Call 07896 677083 and tell us what you saw and heard during the test.