Mysa smart thermostat for electric baseboard / line-voltage heaters (V1, V2, Gen3): quick sheet

Covers: Mysa line-voltage thermostats for electric baseboard and in-wall heaters: V1 (MYSA-V1-1), V2 (BB.2.0.01.NA-US), Gen3 (BB.3.0.01.SV) and Mysa LITE. Separate Mysa models exist for in-floor heat and mini-splits (not covered).

Cross-checkedBrands: Mysa7 components

A Wi-Fi thermostat that switches 120 V or 240 V heater current directly. It is powered by its own neutral or L2 connection (no power stealing), so it needs 3-4 wires in the box, not the 2 wires of an old single-pole baseboard thermostat. Line voltage makes every service step a CAUTION job; local code may require a licensed electrician.

Safety first

LINE VOLTAGE (120/240 V): CAUTION. Turn off and verify the breaker before any work
On 240 V circuits the heater may still have one live leg when the thermostat is off
Local code may require a licensed electrician
Never connect to a 24 V system

How it works

Mysa connects to L1 (line), to L2 or neutral (power for the thermostat itself), and switches the load wire to the heater. It switches with a silent triac, so there is no relay click.

Internally it works as a single-pole switch. On a 240 V circuit one leg can still be live at the heater even when Mysa shows the heat off: always kill the breaker before touching the heater or thermostat wiring.

Setup is done in the Mysa app over Bluetooth LE and 2.4 GHz Wi-Fi. A green light at first power-up confirms supply; if it does not appear, the L1 supply connection is the first suspect.

V2 and Gen3 measure current and voltage for energy reports; the LITE drops energy monitoring and humidity sensing.

Components & tests

Unlock all 7 components, specs, service mode and teardown

Full library + AI assistant + the OnCall Tech app for iPhone & Android. $34.90, one time.

Get lifetime access

Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

Mysa thermostat for electric baseboard heaters: product and specs

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Ductless mini-split indoor head mounted high on a wall by NEOSiAM, Pexels License

Diagnostic guides for this appliance

Guide · Thermostat

Furnace / air handler 3 A low-voltage fuse keeps blowing (finding the 24 V short)

A blown 24 V fuse is a symptom of a short in the thermostat wire, outdoor unit wire or a load (contactor coil, damper, humidifier). Isolate circuits one at a time instead of replacing fuses.

8 steps ~60 minmoderate

Guide · Thermostat

Zoned system: one zone not heating or cooling (damper and zone panel checks)

If only one zone fails, the cause is almost always that zone's damper, actuator, thermostat or wiring, not the furnace or AC. Simulate a call at the panel and check whether the damper actually moves.

8 steps ~45 minmoderate

Guide · Thermostat

Field pattern: thermostat replaced, now nothing works or the wrong thing runs (fuse, system type, O/B)

Almost every post-install failure comes from one of four things: a 24 V short during install that blew the board fuse, a missing C wire, the wrong equipment type in the installer menu, or the O/B (reversing valve) setting reversed. The wrong turn is assuming the new thermostat is defective or that the furnace failed the same day; check the install before ordering anything.

7 steps ~40 mineasy

Other thermostats manuals

Manual · Thermostat

Google Nest Thermostat (2020, mirror face, no ring): quick sheet

Google Nest Thermostat launched October 2020 (model G4CVZ, sold as GA01334-US and color variants). Not the Nest Learning Thermostat (3rd/4th gen) or the Nest Thermostat E, which have their own sheets/notes.

9 components5 common failuresGoogle Nest

Manual · Thermostat

ecobee3 lite smart thermostat (EB-STATE3LT-02 and Pro EB-STATE3LTP-02): quick sheet

ecobee3 lite retail (EB-STATE3LT-02) and contractor/Pro version (EB-STATE3LTP-02). Now listed as discontinued by several distributors but very common in the field. ecobee Premium/Enhanced have their own sheet.

9 components5 common failuresecobee

Manual · Thermostat

Honeywell Home T5 / T5+ Smart Thermostat (RCHT8610WF, RCHT8612WF, RTH8800WF): quick sheet

Honeywell Home / Resideo T5 Smart Thermostat RCHT8610WF (no C-wire adapter in the box), T5+ RCHT8612WF (ships with the THP9045A C-wire adapter) and RTH8800WF retail variant. T6 Pro, T9 and T10 have their own sheets.

7 components5 common failuresHoneywell Home, Resideo