How do I set my heating timer to come on?

Set the clock to the correct time, choose the on and off periods (tabs pushed in on a dial timer, or on and off times on a digital programmer), then put the selector switch to timed or auto. On and off on the selector override the timer completely.

Which way do the pins go on a heating timer?

On most dial timers, tabs pushed in towards the centre, or down, are the on periods, and tabs left out are off. Some models are the other way round, so check with a short test: set a tab on for the next 15 minutes and listen for the boiler.

Why is my heating timer an hour out?

Usually because the clocks have changed or the power has been off. Mechanical dial timers never adjust themselves, and many digital programmers do not either. Reset the clock and the programme will be right again.

What is a good heating timer setting for winter?

Two periods suit most households: on about 30 minutes before you get up until you leave, and on from late afternoon until shortly before bed. Let the room thermostat control the temperature within those times.

Does a combi boiler timer control the hot water?

No. A combi heats water only while a tap is running, so hot water is available whenever you need it. The timer only controls the heating, plus a preheat setting on some models.

My timer is on but the boiler will not fire. What is wrong?

Check the room thermostat is set above the current room temperature, the selector is on timed or on, the boiler has power and normal pressure, and there is no fault code showing. If all of that is fine, the fault is in the controls or the boiler and needs an engineer.

How to Set a Heating Timer, and the Hot Water With It

To set a heating timer, first set the clock to the correct time, then choose the times you want the heating on and off, then put the selector switch to timed (sometimes labelled auto) rather than on or off. On a round dial timer you set the clock by turning the dial clockwise until the current time lines up with the arrow, and you choose the on periods by pushing the small tabs or pins around the edge. On a digital programmer you press the clock or set button, adjust the time with the arrows, then step through each on and off period. If your programmer has two channels, the hot water has its own times and its own switch, and it needs setting separately from the heating. The clocks go back at the end of October, which is the moment most timers end up an hour out, so it is worth checking yours now as the heating season starts.

First, work out which kind of timer you have

Almost every heating control in a London home falls into one of three types, and the method is different for each. Look at the front of the unit, usually on the boiler itself, in the airing cupboard next to the hot water cylinder, or on a wall in the hall or kitchen.

A round mechanical dial with 24 hours printed around it and small tabs, pins or segments on the edge. Very common on combi boilers and older system boilers.
A digital programmer with a small screen and buttons marked something like set, day, time, program, advance or boost. Many have separate buttons or rows for heating and hot water.
A smart thermostat controlled from a phone app, with a small wall unit or a receiver near the boiler. These are set through the app, and the physical unit mainly shows the temperature.

How to set a mechanical dial timer

The dial rotates slowly through the day. The time it is set to is whatever number sits against the small arrow or pointer printed next to the dial.

Set the clock: turn the outer dial clockwise, never backwards, until the current time lines up with the arrow. Remember it is a 24 hour dial, so 7pm is 19.
Set the on periods: each tab or pin covers a short slot, usually 15 minutes. Push the tabs towards the centre (or down, depending on the model) for every slot you want the heating on. Tabs left out are off.
Check the pattern: a typical winter setting is two blocks, for example from half an hour before you get up until you leave, and from late afternoon until bedtime.
Set the selector switch to timed, auto or the clock symbol. On means the heating runs constantly, and off means it never comes on, whatever the tabs say.

A dial timer does not know about the clocks changing. Twice a year you have to turn the dial on by an hour, or back by 23 hours in autumn, since you should only ever turn it clockwise. After a power cut it also stops and restarts at the wrong time, so check it after any outage.

How to set a digital heating programmer

Button names vary by brand, so keep the instructions if you still have them, or search the model number printed on the front or under the flap. The sequence is almost always the same.

Set the day and time. Press set, clock or time, adjust with the plus and minus or arrow buttons, and confirm. Some programmers ask for the day of the week first.
Choose the programme type if asked. A 24 hour programme repeats the same times every day. A 5/2 programme lets weekdays and weekends differ. A 7 day programme lets every day differ.
Enter the on and off times. Most programmers give you two or three periods a day, shown as on 1, off 1, on 2, off 2. Step through each one and adjust.
Repeat for the hot water channel if there is one. It usually has its own button, marked with a tap or the letters HW, and its own set of times.
Return the programmer to its normal running mode, often auto or run, so it follows the times you have just entered.

Setting the hot water times

If you have a hot water cylinder heated by the boiler, the programmer almost certainly has a separate hot water channel. The heating times decide when the radiators come on. The hot water times decide when the boiler heats the cylinder. A common setting is an hour or so before the morning rush and another before the evening, which gives the cylinder time to recover. Our guide on how long does hot water take to heat up explains how much time a typical cylinder needs.

Whether to run the hot water on constant rather than timed depends mainly on how well insulated the cylinder is, and our guide to constant hot water weighs up the cost. On some older gravity fed systems the hot water cannot be switched off while the heating is on, which is normal for that design rather than a programmer fault.

A combi boiler has no stored hot water, so its timer only controls the heating. Hot water comes on whenever a tap is opened, whatever the timer says. If your cylinder is heated by an electric immersion rather than the boiler, it has its own separate timer, and our immersion heater timer guide covers setting that one.

The timer and the thermostat do different jobs

A timer decides when the heating is allowed to run. The room thermostat decides how warm the house gets during those times. If the room is already warmer than the thermostat setting, the boiler will not fire even though the timer says on, which is often mistaken for a fault.

So set the timer for the hours you need warmth, and set the room thermostat to a comfortable temperature, then leave it. Turning the thermostat right up does not heat the house any faster. It only means the heating keeps running past the point you wanted. Radiator valves with numbered heads let you fine tune individual rooms on top of that.

Useful buttons: advance, boost and holiday

These save you reprogramming the timer for a one off change. If you find yourself pressing boost every day, the times themselves need changing.

Advance moves the programmer on to its next period early. Pressed during an off period, it turns the heating on until the next programmed off time.
Boost, or +1hr, runs the heating or hot water for a set time, usually an hour, without changing your programme.
Holiday or frost mode holds the heating off for a set number of days while keeping low temperature protection. Useful if you are away in winter and do not want pipes to freeze.

Timer set correctly but nothing happens

If the timer shows on, the selector is on timed, the thermostat is turned up above room temperature and still nothing happens, work through a few quick checks before calling anyone. Is there power to the boiler and the programmer? A blank screen often means a tripped fused spur or a flat battery in a wireless thermostat. Is the boiler pressure gauge in the normal range? Is the boiler showing a fault code?

If the heating comes on but the hot water does not, or the other way round, the programmer is usually fine and the fault is in a valve or thermostat further along. Our guide to no hot water but the heating works covers the usual causes, and no heating or hot water covers what to check when both have gone at once.

If you have checked the settings and it is still not working, call us on 020 4652 5111 or send an enquiry. We have 20 engineers across London and can diagnose the fault, whether it is the programmer, the wiring, a valve or the boiler itself. Our rate is on the pricing page and agreed before we attend.

Questions we get asked

How do I set my heating timer to come on?: Set the clock to the correct time, choose the on and off periods (tabs pushed in on a dial timer, or on and off times on a digital programmer), then put the selector switch to timed or auto. On and off on the selector override the timer completely.
Which way do the pins go on a heating timer?: On most dial timers, tabs pushed in towards the centre, or down, are the on periods, and tabs left out are off. Some models are the other way round, so check with a short test: set a tab on for the next 15 minutes and listen for the boiler.
Why is my heating timer an hour out?: Usually because the clocks have changed or the power has been off. Mechanical dial timers never adjust themselves, and many digital programmers do not either. Reset the clock and the programme will be right again.
What is a good heating timer setting for winter?: Two periods suit most households: on about 30 minutes before you get up until you leave, and on from late afternoon until shortly before bed. Let the room thermostat control the temperature within those times.
Does a combi boiler timer control the hot water?: No. A combi heats water only while a tap is running, so hot water is available whenever you need it. The timer only controls the heating, plus a preheat setting on some models.
My timer is on but the boiler will not fire. What is wrong?: Check the room thermostat is set above the current room temperature, the selector is on timed or on, the boiler has power and normal pressure, and there is no fault code showing. If all of that is fine, the fault is in the controls or the boiler and needs an engineer.