This application note shows how to create a Z-Wave-based heating control system that will control the heating source based on time of day and the room's temperature. This is a common scenario in most Home Automation systems.
The aim of this project is to control a boiler or underfloor heating system:
- Turn On heating when the room's temperature is below the thermostat's setpoint
- Turn Off heating when the room's temperature is above the thermostat's setpoint
- The thermostat's setpoint is changed automatically for particular times of the day - morning, day, evening, & night
- Enable the thermostat to directly control the heating while using the Z-Wave controller as the scheduler
- Note - the setpoint is simply the temperature you set the thermostat to, for instance 21°C if you wish the room to be 21°C
For this project I used a Z-Wave home automation system comprising of:
The Secure Wall Thermostat and Secure Boiler Receiver were chosen as they are easy to install and work well as a directly 'associated' pair. Other thermostats or relays can be used as well. The VERA Lite controller is used for configuration and set-up, after which it is only used to changed the thermostat's setpoint temperature at predefined times of the day.
To configure the Secure Thermostat and Receiver in the Z-Wave system, follow the instructions in Application Note 20 - Adding and Configuring the Secure Thermostat and Receiver.
Time and Temperature Control
In a traditional heating system the heating is only active during predefined periods of the day, and the temperature is determined by the setpoint on the thermostat. Configuring the VERA controller in a similar manner is possible, but it requires LUA coding rather than creating simple scenes. Although the LUA coding is not complex for this type of situation, I preferred to use a number of scenes that control the heating by changing the thermostat's setpoint temperature at different times of the day. This also has the advantage that you can have the system automatically change your room's temperature during the day rather than simply having it On or Off.
The time and temperature scheme I chose for this project is shown in figure 1.
Figure 1 - Heating Schedules and setpoint temperatures
To enable VERA to control this we will create four schedule-based scenes:
- Morning - scheduled at 6.00am to change setpoint to 18°C
- Day - changes setpoint to 10°C at 8.30am
- Evening - setpoint changed to 20°C at 5.00pm
- Night - setpoint reduced to 3°C at 10.30pm
Create the Morning Scene
Scenes are created and edited in VERA's Automation Tab, to create the 'Morning' scene:
- Go to the Automation tab and click New Scene
- Give the new scene a name - for example 'Heating_Morning_18'
- Select the Setpoint temperature on the Secure Thermostat - this example uses 18°C
- Choose a Room from the drop-down list - I selected 'Demo'
Create the Morning Schedule
The 'Morning' scene will be controlled by a dedicated schedule that activates it at the correct time and day:
- Go to Schedules, click the blue Add Schedule button
- Give the new schedule a name - for example 'Heating Morning'
- Select 'Day of Week based' - this enables you to select the time and day(s) that this schedule will trigger the scene
- Select the day(s) you would like this schedule to be active - I choose 'Monday - Friday' Select'At a certain time of the day' and choose the time - this example uses 6.00am
- Click 'Done' to save this new schedule
- Click the green 'Confirm Changes' button to save the Scene
- Click the red 'Save' button to save changes to VERA
- When VERA has saved the scene, click the blue 'Continue' button on the 'Save Data' screen.
Create the Day, Evening and Night ScenesTo create the other scenes for Day, Evening and Night; follow the same process as for the Morning scene:
- Go to the Automation tab, click New Scene
- Name the Scene
- Set the thermostat's setpoint temperature
- Go to the 'Schedules' tab and create a new schedule and name it
- Configure the schedule for the correct time and days
- Make sure you click 'Confirm Changes' and 'Save'
We now have four scenes that will control the heating's temperature at various times during the day.