This article explains how Flair switches between heating and cooling when Mode is set to "Auto Heat/Cool" for systems with mini splits and integrated smart thermostats. For systems with non-integrated thermostats, Flair will examine the duct temperature to determine if the system is heating or cooling and operate Smart Vents accordingly.
Pro tip: the auto changeover differential is 3F. This is 2F above and below the set point, plus 1F hysteresis. These values can be adjusted by contacting Support.
In this section:
- Implicit Heat-To and Cool-To Set Points
- Accounting for Hysteresis
- Mode Switching
- Auto Heat/Cool Example
- What Values are Adjustable?
When you set Mode to "Auto Heat/Cool", Flair essentially creates a 3F range around the set point for switching modes. This is the number of degrees past the set point the home needs to get before switching from one mode to another.
So for example, let's say the home set point is 72F. Flair will not switch to heat mode until the home temperature drops below 69F, and it will not switch to cool mode until the home temperature rises above 75F. Read further to understand the details of operation.
Implicit Heat-To and Cool-To Set Points
First let's understand what Flair does when Mode is set to "Auto Heat/Cool". Flair will create two implicit set points: a heat-to set point and a cool-to set point. By default, these are 2F below and above the home set point (2F range).
So, for a home set point of 72F, the heat-to set point is 70F and the cool-to set point is 74F.
Accounting for Hysteresis
Next, let's understand how Flair uses these two set points. For systems with Smart Vents, Flair uses the default hysteresis value of 1F around the set points for operating Smart Vents.
While this hysteresis value is not used for mini split set point handling per se, it is used in the calculation for switching mini splits between heating and cooling as you'll see in the next section.
Finally, as the home temperature rises above or drops below the heat-to and cool-to set points - plus the hysteresis value - Flair will switch systems between heating and cooling depending on the current state.
For a system that's currently heating, when the room temperature goes 1F above the cool-to set point, Flair will switch to cooling. For a system that's currently cooling, when the room temperature drops 1F below the heat-to set point, Flair will switch to heating.
This example shows when switching occurs based on a 72F home set point:
Let's look at an example of how this all works.
Auto Heat/Cool Example
The graph below represents a home's temperature over two hours. It's Fall, so the temperatures are fluctuating a lot. The blue areas are when the AC is on and orange area is when the heat is on. The home begins cooling, switches to heating, and then switches back to cooling again. Let's see why.
The home set point is 72F, so the heat-to set point is 70F and the cool-to set point is 74F. The mode switching temperatures are 69F and 75F.
The timeline starts while the AC is running (blue). As the home temperature dips 1F below the heat-to set point, the heat comes on (orange). As the home temperature rises 1F above the cool-to set point, the AC comes on (blue).
We can see the home temperature beginning to drop again. As the timeline progresses, if it dips 1F below the heat-to set point, Flair will switch back to heating.
What Values are Adjustable?
These values are used for calculating modes switches:
- Heat Cool Mode Hysteresis: the 2F range around the home set point for creating the heat-to and cool-to set points
- Vent Hysteresis: the 1F range around a set point that determines when Smart Vents open/close and when mode switching occurs
These values are adjustable by contacting Support.