Wiring Guide
Wiring Guide
This guide provides detailed wiring instructions for Mysa for Baseboards. Follow the diagram that matches your system voltage.
Warning Mysa for Baseboards connects to high-voltage (120/240V) wiring. Always turn off power at the breaker and verify with a voltage tester before touching any wires.
Before You Start
- Turn off power at the circuit breaker
- Use a voltage tester to confirm power is off
- Take a photo of your existing thermostat wiring
- Identify your system voltage (120V or 240V)
- Verify you have 4+ wires in the gang box
Wiring Requirements
Mysa for Baseboards requires 4 or more wires in your thermostat gang box — typically two bundles connected by wire nuts. One bundle brings power in from your breaker (line), and the other sends power out to your heater (load). This allows Mysa to power itself while controlling your heater.
Only see 2 wires? This is extremely rare. Check inside the gang box — extra capped wires are often tucked inside. Most setups have 4–6 wires total.
If you truly only have 2 wires, the thermostat location only breaks the circuit and cannot power a smart thermostat. Contact install@getmysa.com to discuss options.
See 24V / Low-Voltage Wiring?
If you see thin wires (often labeled R, C, W, Y, G, or O/B) behind your thermostat, you have a low-voltage (24V) system — not high-voltage baseboard wiring. This sometimes happens in homes where multiple baseboard heaters are connected to a relay that steps down to 24V for central thermostat control.
In this case, Mysa for Baseboards won't work. You need the Mysa Smart Thermostat (Model ST-V1-0) instead, which is designed for 24V systems.
Mysa Wire Leads
The base plate has three color-coded wire leads:
| Wire Lead | Purpose |
|---|---|
| L1 | Line voltage in (from breaker) |
| L2/N | Second line (240V) or neutral (120V) |
| Load | Power out to heater |
Use the wire nuts included with Mysa to connect these leads to your wiring — do not reuse existing wire nuts from your old thermostat.
For 240V
Most baseboard heaters in North America use 240V. You'll typically see two hot wires of the same color (both black, or black and red).
Connections:
- L1 ← Line (L1) from breaker
- L2/N ← Second line (L2) from breaker, joined with L2 going to heater
- Load ← Load wire going to heater
Note On a 240V circuit, both L1 and L2 carry voltage. There is no neutral wire.
For 120V
Some smaller heaters use 120V. You'll typically see a black (hot) wire and a white (neutral) wire.
Connections:
- L1 ← Line (L) from breaker, joined with line going to heater
- L2/N ← Neutral (N) from breaker, joined with neutral going to heater
- Load ← Load wire going to heater
Identifying Line vs Load
If your wires aren't labeled:
- Line wires bring power from the breaker to the thermostat
- Load wires carry power from the thermostat to the heater
Tip If you're unsure which is line and which is load, a licensed electrician can identify them quickly using a multimeter.
Wire Connections
Use the included wire nuts to connect wires:
- Strip about 1/2 inch of insulation from each wire if needed
- Hold the Mysa wire and your house wire together
- Twist the wire nut clockwise until tight
- Give a gentle tug to confirm the connection is secure
Warning Loose connections can cause overheating. Make sure all wire nuts are tight and wires don't pull free.
Multiple Heaters on One Circuit
You can control multiple heaters with one Mysa if they're on the same circuit and the total load is within limits:
| Voltage | Maximum Wattage | Maximum Amperage |
|---|---|---|
| 240V | 3800W | 16A |
| 120V | 1900W | 16A |
Add up the wattage of all heaters on the circuit. If the total exceeds these limits, you'll need separate thermostats on separate circuits.
Minimum Load (V2 Only)
Mysa for Baseboards - V2 requires a minimum 0.3A load for its power monitoring feature. Most heaters exceed this, but very small heaters may not.
Mysa LITE for Baseboards has no minimum load requirement.
After Wiring
- Double-check all connections match the correct diagram
- Ensure no bare wire is exposed outside the wire nuts
- Carefully fold wires into the gang box
- Attach the thermostat to the base plate
- Restore power at the breaker
The thermostat display should light up. If it doesn't, turn off power and recheck your connections.
Installation Video
Watch the installation video — filmed with V2, but the steps are the same for Lite.
User Manuals
Get Support
If your wiring doesn't match these diagrams, or you're unsure about any connection, contact our team with a photo of your wiring.
Email: install@getmysa.com