To program a current Honeywell Home T3 or T4 thermostat, press Menu, select the heating schedule, choose the day and period, then set its time and temperature with +/−. Save each value with the confirm button and return to the home screen when the week is complete.
Honeywell and Honeywell Home names appear on many different UK heating controls, so identify the model before pressing buttons. T3, T3R, T3M, T4, T4R and T4M use similar menus. Older CM, ST and Sundial controls, and connected T6 or evohome products, have different instructions. The model is usually printed on the front, under a flap or on an accessible label.
What the heating schedule means
A programmable thermostat gives each part of the day a target room temperature. When a period begins, the thermostat compares that target with the temperature it measures. It asks for heat only when the room is cooler, so the boiler will not necessarily run for the entire period.
Current T3 models normally offer up to four periods a day. T4 installation options allow four or six periods, although the homeowner menu only shows the number configured. The day’s periods must run in time order.
Before changing the programme
- Confirm the model: T3/T3R/T3M or T4/T4R/T4M.
- Check the day, date and clock.
- Photograph or write down the existing programme.
- Plan the times people wake, leave, return and sleep.
- Make changes only in the normal user menus, not the installer configuration.
The wireless R versions have a separate receiver connected to the boiler. The M versions can communicate through OpenTherm. These differences affect installation and fault diagnosis, but the ordinary schedule menu remains broadly similar.
How to program a Honeywell Home T3 or T3R
Resideo’s official T3 user guide gives the following sequence:
- Press MENU to open the main menu.
- Use + or − to select the schedule symbol, then press the centre confirm button.
- Use + or − to select the day you want to adjust and confirm.
- Select the period, such as P1, P2, P3 or P4, and confirm.
- Adjust the start time with + or − and confirm.
- Adjust the target temperature and confirm.
- Repeat for the remaining periods and days.
- Use the home or back control shown on the screen to save and return to normal operation.
Check Monday through Sunday even if several days should match. The official guide also provides a Copy function: select the source day, choose Copy, then choose the destination day. Open the copied day afterwards to confirm it is correct.
How to program a Honeywell Home T4 or T4R
The T4 menu adds an Edit step and can show four or six periods:
- Press the Menu button.
- Use + or − to find the heating schedule and confirm.
- Select EDIT and confirm.
- Choose the day or day group to change.
- Select the period you want to edit.
- Set its start time and confirm.
- Set the end time if the screen asks for it, then confirm.
- Set the target temperature and confirm.
- Repeat for all required periods and use Home to save and leave the menu.
A T4 may be configured as a one-day, 5+2-day or seven-day schedule and for four or six periods. Those options are normally set during installation. If the menu does not offer the pattern you expected, do not enter advanced settings casually; ask the installer or controls engineer to confirm the configuration.
Choosing times and temperatures
Use occupied times rather than copying a generic timetable. A typical plan has a comfortable morning target, a lower daytime target if the home is empty, another comfortable target in the evening and a lower overnight target.
Energy Saving Trust says the lowest comfortable room-thermostat setting is usually between 18°C and 21°C for most people. The right value depends on the property and occupants. Babies, older people and anyone with a health condition may need a warmer or more consistent room.
Do not compensate for slow warming by setting 28°C. A room thermostat does not make the boiler heat the room faster; it simply keeps requesting heat until the higher target is reached. Bring the period forward if the house consistently warms too late.
Automatic, manual, temporary and timed overrides
Automatic operation
Auto follows the programmed schedule. On the T3, changing the temperature in Auto creates a temporary override and the programme resumes at the next setpoint.
Manual operation
Manual holds one target continuously. If the schedule appears to be ignored, check that the thermostat has not been left in Manual.
Timed override
The T3 has a one-hour override control. The T4 can hold an adjusted target for a selected duration. These are useful for an unusual evening without rewriting future days.
Schedule off or standby
On supported models, schedule off runs the thermostat as a simple adjustable control. Standby stops normal heating while retaining low-temperature frost protection. Neither setting follows the weekly programme.
What does optimisation do?
Some T3 and T4 systems have optimisation enabled by the installer. Optimum Start learns how long the home takes to warm and can request heat before the scheduled time so the target is reached by that time. Delayed Start can postpone heating when the room is already close to target, while Optimum Stop may stop slightly early.
This can make a correct thermostat appear early or late if you expect every period to behave as a simple switch. Look for the optimisation symbol and ask the installer what has been enabled before changing advanced settings.
Why is my Honeywell thermostat not following the schedule?
Work through these checks:
- confirm the thermostat is in Auto and the schedule-on icon is visible;
- check the day, time and each period;
- look for a temporary, timed, Away or Manual hold;
- check whether optimisation explains an early or delayed start;
- make sure the target is above the current room temperature when heat is expected;
- on T3R or T4R, check the wireless signal and receiver power; and
- check the boiler display, pressure and power.
A heat-demand symbol means the thermostat is asking the system for heat; it does not prove the burner is running at that exact second. Resideo notes that boilers can cycle while controlling temperature. If there is no response after a reasonable period, the receiver, wiring, boiler or heating system may need attention.
Deleting or reducing unwanted periods
On the T3, the official guide allows a selected period to be disabled by holding the indicated button for three seconds and confirming; repeat to enable it again. Follow the screen and the exact user guide because button icons are easier to recognise there than in text.
On a T4, edit the existing periods rather than assuming the same shortcut. If six periods feel unnecessarily complicated, ask the installer whether four-period operation is appropriate. Do not alter unrelated installer values.
Clock changes and daylight saving time
An incorrect clock shifts every heating period. The T3 date-and-time settings are under Menu and SET. The T4 has Clock and Date items in its user menu and can be configured for automatic daylight-saving adjustment.
After a power interruption or battery change, check the displayed time and day before rewriting the schedule. If every event is consistently one hour wrong, correct the clock or daylight-saving setting rather than moving every period.
T3R and T4R wireless checks
The R models communicate with a receiver box wired to the heating system. The thermostat’s wireless icon and receiver light help distinguish a schedule issue from lost communication. Move a portable thermostat away from large metal objects and obvious interference if the official guide advises it.
Do not press a recessed reset button or start binding experiments without the model instructions. The T3 guide warns that its receiver pinhole can clear binding data. Do not open the receiver or alter mains wiring.
When the boiler may be at fault
Set a target above the actual room temperature and look for heat demand. If the symbol appears but the boiler remains cold, record the receiver light, boiler display, pressure and any fault code. Do not remove the boiler casing or attempt internal gas work.
Incredaboil’s fixed-price boiler repair service applies to eligible Baxi, Worcester Bosch and Ideal boilers. Tell the engineer the Honeywell Home model and whether the thermostat and receiver indicate demand so the symptom is clear.
Frequently asked questions
Are Honeywell and Honeywell Home the same for these controls?
Honeywell Home is the consumer heating-controls brand used under licence by Resideo. The exact model number, not just the name on the front, determines the instructions.
Can I use T3 instructions for an older CM707?
No. Older CM-series controls have different buttons and programming sequences. Find the exact model manual.
Why does the boiler turn off before the period ends?
The thermostat stops requesting heat once the room reaches the target and requests it again as the temperature falls. That is normal temperature control.
Why did my temperature change reset?
In Auto, a temporary override ends at the next programmed setpoint. Edit the schedule if the change should repeat every week.
Can I change from four to six periods?
T4 supports four or six periods when configured, while T3 is commonly a four-period control. Period-count changes belong in model-specific setup and may be best handled by the installer.
Related boiler-help guides
- Boiler not responding to the thermostat
- What temperature should my house be?
- Why does my boiler keep turning on and off?
- Boiler not firing up
Honeywell calling for heat but the boiler will not respond?
Book a fixed-price Incredaboil repair for an eligible Baxi, Worcester Bosch or Ideal boiler and have the heating fault checked.