How to set a boiler timer: dial pins, digital programmers and the clocks-change fix

A boiler timer decides when your heating and hot water come on and go off. Most problems come from the timer's own clock being wrong, often after the clocks change or a power cut. Below, one example runs from heating that comes on an hour early to a flat that's warm exactly when it should be, with a drawing for every step.

Our example: Amira's heating comes on an hour early

Every step below follows one story, and each drawing shows that exact moment. The clocks went back on Sunday 25 October, and since then the combi boiler in Amira's kitchen cupboard has been heating the flat an hour before she gets up. The boiler has a round dial timer on the front. She wants heat from 7:00 to 8:00 in the morning and from 18:00 to 22:00 in the evening.

Part 1: Set a round dial timer

1. Find the timer and its parts.

   

   In our story: Amira opens the cupboard and looks at the round dial on the front of the boiler.

   A mechanical timer is a round dial with a 24-hour clock in the middle and pins or segments around the edge (Vaillant). A fixed arrow or marker shows the current time. Nearby is usually a small switch for the mode.

2. Turn the dial to the right time.

   

   In our story: It's 19:20. Amira's dial says 20:20, an hour out since the clocks went back. She turns it until 19:20 lines up with the arrow.

   Turn the dial until the current time points at the arrow (Vaillant). Use the 24-hour time: 7 in the evening is 19. Many dials only turn one way; if it resists, try the other way and don't force it.

3. Push in the segments for the morning.

   

   In our story: Amira wants the flat warm from 7:00, so she pushes in the segments from 6:30 to 8:00.

   Each segment is usually 15 minutes (Vaillant, Viessmann), so four segments make an hour. Push them in for the times you want heat (Vaillant). Start about 30 minutes before you need the warmth, so the radiators have time to heat up (Vaillant). Some models work the other way round, so check your manual if you're unsure.

4. Add the evening and leave the rest out.

   

   In our story: She pushes in 17:30 to 22:00 for the evening and checks that every other segment is out.

   Segments left out are times the heating stays off (Viessmann). The dial repeats the same pattern every day (Viessmann); for different times at weekends you need a digital programmer.

5. Switch to Timer mode.

   

   In our story: Amira slides the switch from On to the clock symbol, Timer.

   The boiler follows your times only in Timer mode (Vaillant). The other positions usually keep it on all the time or off all the time (Viessmann). Symbols differ between makers; look for a clock or the word Timer or Auto.

6. Check it the next morning.

   

   In our story: At 7:00 the next morning, the radiator in Amira's living room is already warm.

   If the heating still comes on at the wrong time, check the dial's time against your phone again. If a radiator stays cold at the top while the others are warm, it may need bleeding.

Part 2: Set a digital programmer

1. Check the clock, then set your on and off times.

   

   What if Amira had a digital programmer? She'd check the date and time on the screen first, then turn on the schedule and enter the same morning and evening times.

   Set the correct date and time first; some programmers do this automatically, but check (Vaillant). Then switch on scheduling and choose your on and off times (Vaillant). Buttons differ a lot between models, so follow your manual (Viessmann). Many digital programmers let you set different times for different days (Viessmann).

   • Auto or Twice: on and off at your set times each day (Viessmann).
   • All day or Once: from your first on time to your last off time (Viessmann).
   • 24hrs or On: on until you change it. Off: off until you change it (Viessmann).
   • +1hr or Boost: one extra hour of heat. Advance: jumps to the next on or off time (Viessmann).

Part 3: Germany: a night setback instead of off

1. Set a lower night temperature in the time programme.

   

   What if Amira lived in Germany? Her controller would lower the temperature at night instead of switching the heating off.

   Many German controllers have a time programme (Zeitprogramm) with a lower night temperature. The path is often Menü, Heizung, Heizkreis, Zeitprogramm, but it differs between controllers (Viessmann DE). Day temperature is usually around 20 °C; Viessmann suggests not going below 17 °C at night. It says a setback can help older homes that aren't insulated, but usually isn't worth it in new, well-insulated homes or with underfloor heating, which is slow to warm up again. Rooms kept too cold for long can get damp; see stopping condensation and mould.

Tips

• Check the timer every time the clocks change in March and October: mechanical timers often don't change by themselves (Vaillant, Viessmann).
• After a power cut, many boilers reset to midnight, so set the time again (Viessmann).
• Write your on and off times on a sticky note inside the cupboard door so anyone at home can check them.

If something goes wrong

Related: How to top up your boiler pressure · How to bleed a radiator · Stop condensation and mould in winter.