Compatibility

This chapter introduces the device compatibility and describes the steps to check the compatible systems.

Compatible HVAC Systems

The thermostat is compatible with below systems:
  • Conventional HVAC System (Furnace/Boiler + Air Conditioner, up to 2-cool/2-heat)
  • Heat Pump System (Up to 2-cool/4-heat, or 2-cool/3-heat + 1-AUX heat)
  • PTAC

How to Check HVAC System Compatibility

  1. Power off the HVAC system by using the master switch or circuit breaker.
  2. To confirm power is off, adjust the temperature on the current thermostat and wait for a few minutes. If the system does not respond accordingly, the power is shut off successfully.
    Warning: Failure to follow these steps may result in personal injury and/or death from electric shock.
  3. Remove the current thermostat cover from the wall.

  4. If you see the system is labeled with wires L1 and L2, or any high-voltage indicators like 110V, 120V, or 240V, it means the thermostat is not compatible with this system. Otherwise, continue to the next step.
  5. Recognize the used wires by the old thermostat wire labels or wire terminals.
  6. Use Compatibility Checker to determine the system compatibility. Check whether all used wires are listed in the following table:
    Wire Label Description
    C Common wire of 24 VAC power. If no C wire,
    1. Check if this wire is labelled as other names (like B).
    2. It may need a C-wire Power Extender Kit. Please contact Milesight for the details.
    R Heating and cooling system power wire. If there is only one R wire, connect this wire to either RC or RH of the WT thermostat.
    RH If there are RC and RH wires, RH works as heating power wire for dual-transformer systems. If there is only one RH wire, RH works as both the heating and cooling power wire.
    RC If there are RC and RH wires, RC works as cooling power wire for dual-transformer systems. If there is only one RC wire, RC works as both the heating and cooling power wire.
    Y/Y1 & Y2 In conventional systems, Y/Y1 controls the 1-stage cooling and Y2 controls the 2-stage cooling. In heat-pump systems, Y/Y1 controls the 1-stage compressor for cooling/heating and Y2 controls the 2-stage compressor for cooling/heating.
    W or W1 In conventional systems, W/W1 controls the 1-stage heating. In heat-pump systems with auxiliary heat, W/W1 controls the 1-stage auxiliary heat.
    W2 or AUX In conventional systems, W2 controls the 2-stage heating. In heat-pump systems with auxiliary heat, W2/AUX controls the 2-stage auxiliary heat.
    G or G1 G controls the fan.
    GH & GL In 2-speed fan system, GL controls low speed and GH controls high speed.
    O/B In heat pumps, O/B controls the reversing valve to switch between heating and cooling. If there is only one O wire or B wire, connect this wire to O/B of the WT thermostat.
    E Some heat pumps have an E terminal for emergency heat on/off. Emergency heat is only used on very cold days when the heat pump is unable to maintain the temperature.
    AUX In heat-pump systems with auxiliary heat source, AUX controls the auxiliary heat for cold days to rise the temperature quickly.
  7. If there is any wire label not present in the above list or it is hard to determine the compatibility, take a photo of the wires connected to the terminals of the old thermostat and send it to a local professional installer or Milesight.
  8. Check if the relay current match the below conditions:
    Model Max. Current/Per Channel Max. Current/Total
    WT201 1A 1A
    WT211 3A 5A

Key Card Switch Compatibility

The thermostat is equipped with a dry contact input for connection to a key card switch. By default, two connected contacts=insert card, two disconnected contacts=remove card.