Programmers and Timers: Scheduling Heating and Hot Water
The programmer sets when heating and hot water switch on and off through the day, working alongside the room thermostat and cylinder thermostat rather than instead of them.
The programmer sets when heating and hot water switch on and off through the day, working alongside the room thermostat and cylinder thermostat rather than instead of them. A confusing or failing programmer often gets blamed for faults that actually sit elsewhere in the controls chain.
What it does
It holds a schedule, usually with separate settings for heating and hot water, and sends demand signals at the programmed times regardless of what the thermostats are reading.
How it fails
The battery backup fails and it loses its clock and programme after a power cut, internal relays wear out, or the display simply dies.
Repair or replace
A programmer is generally replaced rather than repaired, since diagnosing internal faults isn't cost-effective against the price of a new unit.
Common programmer confusion worth clearing up
- Setting a time doesn't override the thermostat once temperature is reached
- A programmer set to 'on' all day still won't heat past the thermostat's target
- Losing the clock after a power cut but keeping the old schedule stored
- Separate hot water and heating schedules being mixed up
Who does the work
- Gas Safe registered engineers — registration 554328
- Worcester Bosch accredited installer
- John The Plumb Ltd, company registration 10026483
Sort out a confusing heating schedule
Tell us what the programmer is actually doing versus what you've set, and we'll work out whether it's the unit or how it's wired in.
Questions we get asked
Is programmer work Gas Safe-only?
No, this is electrical controls work rather than gas work.
Can I replace a programmer myself?
Many models are designed for straightforward replacement, though correctly wiring heating and hot water outputs is worth having checked if you're not confident.
Why does my heating come on outside the programmed times?
That usually points to a wiring or thermostat issue rather than the programmer itself, since a fault programmer typically stops working rather than runs early.