Compatibility Guide — for Central HVACUpdated 7 days ago
Mysa for Central HVAC Compatibility and Configuration Overview
Mysa for Central HVAC is a 24-volt (low-voltage) smart thermostat designed for central heating and cooling systems. Because its features depend on your system’s wiring and voltage, it’s important to confirm compatibility before installation. This guide combines a clear compatibility overview with a detailed Configuration Code Matrix for both homeowners and installers.
For Installers: Mysa’s Installation Training materials include wiring diagrams, terminal layouts, and best practices referenced below. For homeowners, see the quick checklist at the bottom for easy pre-purchase checks.
Supported HVAC System Types
Below are the HVAC system types Mysa for Central HVAC supports, along with wiring notes and configuration recommendations.
| System Type | Supported | Heating / Cooling Type | Stages | Fan Control | Recommended Config Code(s) | C-Wire or CWA | Notes & Requirements |
|---|---|---|---|---|---|---|---|
| Forced-Air Furnace (Gas/Oil) | ✅ Yes | 1H / 1C | 1 – 2 | Single / Multi-speed | 11B, 61B | Required (CWA if missing) | Mysa manages fan logic and staging automatically. |
| Forced-Air Furnace (Electric) | ✅ Yes | 1H / 1C | 1 – 2 | Single / Multi-speed | 21B, 71B | Required (CWA if missing) | Uses faster cycle rates; staging controlled via app. |
| Heat Pump (with / without Aux Heat) | ✅ Yes | 1H / 1C + Aux | 1 – 2 + Aux | Auto / Multi-speed | 31P, 31L, 81P, 81L | Required (CWA if missing) | Use 31P for O-valve (energized for cooling), 31L for B-valve (energized for heating). |
| Boiler / Radiant (Hydronic) | ✅ Yes | 1H / 0C | 1 – 2 | — | 41B, 91B | Required (CWA if missing) | Ideal for radiant heat or fan-coil units with hydronic control. |
| Hybrid / Dual Systems (Boiler + Air Handler) | ⚠️ Partial | 1H / 1C (Dual Transformer) | 1 – 2 | Single | 41B + 11B | C on both transformers | May require isolation relay; professional install recommended. |
| Fan Coil / PTAC (24 V) | ⚠️ Partial | 1H / 1C or Fan only | 1 | G1 / G2 / G3 | 45B, 55B | Required | Verify manufacturer wiring; supports multi-speed mapping. |
| Line-Voltage Heaters (Baseboards / In-floor Electric) | ❌ No | — | — | — | — | — | Use Mysa for Baseboard; Central HVAC is for 24V systems only. |
| Millivolt Systems (Legacy Gas) | ❌ No | — | — | — | — | — | Not compatible with millivolt circuits. |
| Communicating / Proprietary Thermostats | ❌ No | — | — | — | — | — | Digital communicating protocols not supported. |
| Systems with Separate O & B Wires | ❌ No | — | — | — | — | — | May require professional rewiring or alternate control solution. |
Feature & Electrical Support Summary
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 (Coming soon.)
Voltage: 24 V AC only (low-voltage HVAC systems).
C-Wire: Required — use the Mysa C-Wire Adapter (CWA) if missing.
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 C-Wire Adapter (CWA).
Confirm your system type: forced-air, boiler/radiant, heat pump, or fan-coil/PTAC.
If unsure, share your wiring photo with Mysa Support.
Need help? Upload your wiring photo at help.getmysa.com or email [email protected] for a quick compatibility check.