NOTE: A new version of Thermostat Controller was introduced in platform 2.3.3, featuring a new "parent" Thermostat Controllers app used to create new Thermostat Controller instances and a new table-based interface for setup. Existing Thermostat Controller installations will continue to work. This document refers to the latest version.
In most circumstances, a properly located thermostat will work well to maintain comfortable temperatures. However, the performance of a heating and cooling system may suffer when the thermostat is not in the right location or there is significant heat gain or loss in parts of the your home. Some thermostats also lack an Auto mode, which may result in difficulties during conditions that require both heating and cooling. The Thermostat Controller app allows more control of your connected thermostat by creating a virtual thermostat device to manipulate the setpoints of the controlled thermostat, thus taking over most of its functionality and becoming the controller thermostat for establishing setpoints of your heating and cooling system.
NOTE: Do not confuse Thermostat Controller, which addresses the unique case mentioned above, with Thermostat Scheduler, which allows automating a thermostat setpoint based on time or mode.
Improperly located thermostats are an all too common issue, but the powerful features in Thermostat Controller can help keep the temperature in your living space even by averaging multiple temperature sensors, rather than just using the sensor built into the thermostat. Many motion sensors and some door/windows sensors include temperature readings. These can be combined with the sensor in the thermostat, providing the capability to offset a given sensor's readings, or place more or less weight toward the average from each sensor.
Hysteresis is the difference between the temperature at which a thermostat switches OFF, and the temperature at which it switches ON again. By careful adjustment of the hysteresis value, the efficiency of the heating and cooling system can be optimized, ensuring maximum comfort in the conditioned space. With a lower hysteresis value, the system will cycle more frequently and the temperature swings in your living space will be lower. A wider hysteresis will result in the heating and cooling system cycling less frequently, thus resulting in correspondingly larger temperature swings. For example, with a default hysteresis value of 1.0 ˚F, and a thermostat setting to 75 °F, cooling will be called for when the temperature exceeds the 75 °F plus half of the hysteresis, or 75.5 °F. Once cooling begins. The system will remain ON until the average temperature has been reduced to 75 °F minus half the hysteresis value, or 74.5 °F.
Once the Thermostat Controller app takes control of a thermostat, its heating and cooling operation becomes automatic and will be dependent on the established setting of the controller thermostat. A heating and cooling system will typically move at least 3 °F between on and off cycles. As an example, when the average temperature falls below the thermostat setting (less half the hysteresis), heating will be called for. Should the temperature rise above the heat setting (plus half the hysteresis), the system will return to idle. If the temperature continues to rise and reaches the cooling setpoint (plus half the hysteresis), cooling would be called for.
If Auto mode is not desired, and you only want the system to operate cooling or heating independently, simply adjust the setpoint for the unwanted mode well out of a meaningful range.
WARNING! The Thermostat Controller app takes over control and most safeguards of the existing thermostat. Be sure to set the minimum and maximum values so that if the hub were to fail, the actual thermostat will not end up in a run-away condition.
To add scheduling for the controller thermostat, it may be selected in the Thermostat Scheduler app.
WARNING! Do not use the Thermostat Scheduler app directly on an actual thermostat that is already under the control of the Thermostat Controller app.
The controller thermostat created by the Thermostat Controller app will inherit fan modes from the actual thermostat. Fan speed adjustments made to either the actual or virtual thermostats will mirror each other.
NOTE: Thermostat fan mode may also be set on the controller thermostat by the Thermostat Scheduler app, which would then set it on the actual thermostat that the Thermostat Controller app is manipulating.
From the sidebar of your hub, select Apps and press the Add Built-In App button.
Choose Thermostat Controller from the list of Hubitat Elevation Built-In Apps
Select Create New Thermostat Controller inside the Thermostat Controllers app.
Select the actual thermostat under Select Thermostats to Control. (Thermostat Controller will take over control of this device with the creation of a virtual controller thermostat device.)
Select the temperature sensors to use under Select Temperature Sensors. If multiple sensors are selected, a simple average will be used by default, but see below for weighing and other options.
If a temperature sensor's readings are out of balance with the other temperature sensors used or you prefer to weigh sensor values differently, it may be necessary to enter a Temperature Offset value, or adjust the Weighting to place more or less weight toward the average for each sensor. A Minimum Value or Maximum Value can also be entered for each sensor, which will use the specified minimum or maximum value instead of the actual sensor reading if the sensor ever reports a value below or above the specified value.
Look at the Controlled Thermostat table, which will display current readings and settings for the controlled (real) thermostat. To enable Thermostat Controller to take control of this thermostat, you must choose "Controlled" under the "Controlled" column. A value of Free is the default value and indicates that the Thermostat Controller app is not currently controlling the thermostat.
If you are using Auto mode, enter a Required setpoint Separation. This will prevent endless cycling between cooling and heating when their respective setpoints have been reached, but slightly exceeded.
From the Devices page, you can access the controller thermostat device to manually adjust settings, or control the device state with Rule Machine rules or other apps.
When the thermostat is controlled, you will generally want to use this controller thermostat device in apps or when manually making adjustments — remember, it takes control over the "real" thermostat, so any changes you make to the real thermostat directly may soon be overridden.
To stop Thermostat Controller from manipulating the actual thermostat, toggle the value in the Controlled column in the Controlled Thermostats table for the desired thermostat(s) to Free (as opposed to Controlled). Return the thermostat to Controlled if you want Thermostat Controller to again take over.