Understanding Configuration Codes

Configuration codes tell Mysa for Central HVAC how to behave with your system.
Each code represents a unique combination of system type, stages, and control logic.

You’ll choose or confirm this code during setup in the Mysa app or enter it manually on the thermostat.

How Codes Work

The Configuration Code is a 3-digit alpha-numeric code. Each digit has a distinct function:

• First character determines the Heating type

• Second character determines the Cooling type (also Fan Coil Modes)

• Third character determines the heat pump, fan, and emergency heat options

Why Configuration Matters

A correct configuration ensures:

• Your system heats and cools when it should

• The fan operates in the right modes

• Heat pump valves switch correctly

• Multi-stage or auxiliary heat functions as designed

If Mysa for Central HVAC is set to the wrong configuration, you may notice the fan running unexpectedly, heating during cooling, or other reversed behaviors. Don’t worry — this can be corrected easily within the app.

Common Configuration Codes for Mysa for Central HVAC

Conventional systems

Heat pump systems

FCU & PTAC systems (Multi-Speed Fan)

Two Ways to Enter Your Configuration Code

Option 1: Automatic Setup in the Mysa App

Pair your thermostat in the Mysa app:

• From the main menu click Add Mysa

• Answer No to "Is your thermostat installed and powered on" - this will bring you into the configuration flow

• Follow prompts to select connected wires and system type.

• The app auto-maps your system and summarizes the correct configuration code. Review for accuracy.

• At the end of the pairing flow, the configuration code that was determined will be automatically sent to your Mysa.

Option 2: Manual Entry on the Thermostat (No App Required)

• Power up your Mysa for Central HVAC after wiring.

• Hold the left-and-right arrows to enter the Preferences Menu (PREF will be displayed on the screen)

• Scroll right until CONF appears on the screen. This is the Configuration Menu.

• Use the up-and-down arrows to enter the code you determined from the above tables of common codes or from your printed install guide.

• Center tap to confirm your selection and apply the code. Mysa will function immediately with the selected logic.

Viewing Your Configuration Later

At any time:

• Open the Mysa app

• Select your Mysa for Central HVAC

• Tap Device Settings → Thermostat Configuration

Your current configuration code will appear here, along with the option to change your code if it's determined an incorrect code was applied.

How Mysa for Central HVAC Works With Your System Type

Supported system types include:

• Forced Air (Conventional Furnace/AC)

• Boiler or Radiant Heat

• Dual Systems (Boiler + Central AC)

• Heat Pumps (with or without auxiliary heat)

• Fan Coil / PTAC units

Each system type uses a specific combination of control signals. Let’s look at each.

System Types Explained

1. Forced Air Systems

Common in: Gas or electric furnaces with central AC
Typical wires: R, C, W, Y, G
Function: W activates heating; Y activates cooling; G controls the fan.

Example:
When the room drops below the setpoint, Mysa energizes W for heat. When cooling is needed, Y is activated and the blower (G) runs simultaneously.

2. Boiler or Radiant Systems

Common in: Hydronic (water-based) heating
Typical wires: R, C, W
Function: W closes a relay to open a zone valve or start the boiler.

Example:
Mysa acts as a simple on/off switch for heat, no fan control required.

3. Dual Systems (Boiler + Central AC)

Common in: Homes with a boiler for heat and separate AC system
Typical wires: RH, RC, C, W, Y, G
Function: Separate transformers for heating (RH) and cooling (RC).

4. Heat Pump Systems (with or without Auxiliary Heat)

Common in: Air-source heat pumps
Typical wires: R, C, Y, O/B, G, W/AUX

Function:

• Y: Compressor (both heating and cooling)

• O/B: Reversing valve

• W/AUX: Auxiliary or emergency heat

Example:
When in “heat” mode, Mysa energizes the compressor (Y). The O/B valve determines whether the refrigerant flow provides heating or cooling. AUX heat (W2) is used for backup heating in cold weather.

5. Fan Coil / PTAC Units

Common in: Apartments, condos, hotels
Typical wires: R, C, Y, W, G1/G2/G3 (multi-speed fans)
Function: Controls heating/cooling valves and fan speeds via relays.

Example:
Additional fan speed control for all fan modes.

When to Skip or Call a Pro

You can usually configure your system in the app yourself.
However, call a professional or Mysa Support if:

• Your system has two transformers (heating and cooling)

• You see unlabeled or non-standard terminals

• You have a zoned system with multiple thermostats and shared transformers

• You’re connecting to boilers with dry contacts (T/T)

• The system behaves unpredictably even after trying alternate config codes

Pro Tip: Taking a photo of your control board before setup can help our team confirm wiring remotely - simply email [email protected]