Mysa Smart Thermostat Compatibility Guide
Last updated: June 11, 2026
Mysa Smart Thermostat Compatibility Guide
Mysa Smart Thermostat (formerly Mysa for Central HVAC) is a 3H/2C thermostat that controls standard 24-volt HVAC systems. This guide covers supported system types, configuration codes, and how to confirm your system is compatible before installation.
Supported HVAC Systems
System Type | Supported | Stages | Config Codes | Notes |
|---|---|---|---|---|
Forced-Air Furnace (Gas/Oil) | ✅ Yes | 1-2H / 1-2C | 11B, 61B | Mysa manages fan logic and staging automatically |
Forced-Air Furnace (Electric) | ✅ Yes | 1-2H / 1-2C | 21B, 71B | Uses faster cycle rates; staging controlled via app |
Heat Pump (with/without Aux) | ✅ Yes | 1-2H / 1-2C + Aux | 31P, 31L, 81P, 81L | Use 31P for O-valve, 31L for B-valve |
Boiler / Radiant (Hydronic) | ✅ Yes | 1-2H | 41B, 91B | Ideal for radiant heat or fan-coil units |
Fan Coil / PTAC (24V) | ⚠ Partial | 1H / 1C | 45B, 55B | Verify manufacturer wiring; supports multi-speed fan |
Millivolt Systems (Fireplaces) | ✅ Yes | 1H | — | Requires Mysa Power C-Wire Adapter |
Hybrid / Dual Systems | ⚠ Partial | 1-2H / 1-2C | 41B + 11B | May require isolation relay; professional install recommended |
Not Compatible
System Type | Why |
|---|---|
Line-Voltage Heaters (120/240V) | Use Mysa for Baseboard or Mysa for In-Floor instead |
Ductless / Mini-Split Heat Pumps | Controlled via proprietary thermostats or IR remotes — use Mysa for Mini-Splits instead |
Proprietary Communicating Thermostats | Digital communicating protocols not supported |
Systems with Separate O & B Wires | May require professional rewiring |
Note Nearly 50% of homes using the Mysa Compatibility Checker require the Mysa Power C-Wire Adapter — especially two-wire heat-only boilers, but it applies to any HVAC system missing a C wire.
Features & Electrical Support
Multi-stage Heat/Cool: W1/W2 and Y1/Y2 supported; staging adjustable in the Mysa app
Multi-speed Fan: G1–G3 supported on compatible fan-coil or PTAC systems
Aux / Emergency Heat: Automatically detected for heat pump systems
Sensor Terminals (S1/S2): Reserved for future hardwired sensor support
Voltage: 24V AC only (low-voltage HVAC systems)
C Wire: Required — use the Mysa Power C-Wire Adapter if missing
Note This is a five-relay thermostat and does not support controlling accessories like humidifiers, dehumidifiers, or ventilators. A future Mysa product is planned for accessory support.
Quick Compatibility Checklist
Take a photo of your existing thermostat wiring and your HVAC control board
Count and label wires (R, C, W/W2, Y/Y2, G, O/B)
Check for a C wire — if missing, plan to use the Mysa Power C-Wire Adapter
Confirm your system type: forced-air, boiler/radiant, heat pump, or fan-coil/PTAC
If unsure, share your wiring photo with Mysa Support
Troubleshooting: HVAC Not Working After Installation?
If your thermostat is on but your HVAC system isn't heating or cooling as expected, the most likely cause is an incorrect or missing configuration code.
First option: Use the Mysa app to set your thermostat's configuration code.
If you can't connect to Wi-Fi: You can get the configuration code from mysacodefinder.com and enter it manually via device settings. This is ideal for installers or situations where Wi-Fi setup isn't possible.
Get Support
Email: install@getmysa.com
Include your wiring photo for a quick compatibility check.