Wiring Guide

This guide provides detailed wiring instructions for Mysa for Baseboards. Follow the diagram that matches your system voltage.

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.

How Mysa Switches Power (Single-Pole)

Mysa for Baseboards is a single-pole device — it switches power only between L1 and Load, like a standard single-pole thermostat. It breaks one leg of the circuit (L1 to Load) to turn the heater on and off. The second connection (L2/N) is not switched; it stays connected to keep Mysa powered.

Note for 240V systems — Because Mysa only breaks the L1 leg, the L2 leg remains energized to the heater even when the heater is off. This is normal for a single-pole device. Some regions or installations (for example, where the breaker panel is not in the same unit as the heater, such as certain multi-family buildings) require a double-pole thermostat that breaks both legs. Mysa for Baseboards does not break both legs. If local code requires a double-pole device, check with a licensed electrician.

Mysa Wire Leads

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. Connecting the heater return back to L1 instead of L2 will result in an H2 error.

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:

1. Strip about 1/2 inch of insulation from each wire if needed

2. Hold the Mysa wire and your house wire together

3. Twist the wire nut clockwise until tight

4. 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

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

1. Double-check all connections match the correct diagram

2. Ensure no bare wire is exposed outside the wire nuts

3. Carefully fold wires into the gang box

4. Attach the thermostat to the base plate

5. 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

• Mysa for Baseboards - V2 User Manual (PDF)

• Mysa LITE for Baseboards User Manual (PDF)

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