The ecobee3 lite can support standard 24VAC controls:
Conventional HVAC Systems
- up to 2-stages of forced air heating (W1, W2) and up to 2-stages of forced air cooling (Y1, Y2)
Heat-Pump HVAC Systems
- up to 2-stages of heat pump (Y1, Y2) and up to 2-stages of auxiliary heat (W1, W2).
- O/B (Reversing valve change-over) is a configurable setting during the thermostat HVAC configuration.
Please note, the ecobee3 lite doesn't have the Accessory terminals to control a whole home humidifier, dehumidifier or ventilator.
- up to 2-stages of heating (W1, W2)
The ecobee3 lite can support both a heating boiler and forced air cooling on the same thermostat. This is a 2-transformer configuration.
- RH = 24VAC from heating transformer
- RC = 24VAC from cooling transformer
- C = Common of 24V transformer
- G = Fan control
- Y1 = 1st stage of compressor
- Y2 = 2nd stage of compressor
- W1(aux1) = 1st of heating(conventional systems) or 1st stage of auxiliary heat(heat-pump systems)
- W2(aux2) = 2nd of heating(conventional systems) or 2nd stage of auxiliary heat(heat-pump systems)
- O/B = Heat-pump reversing valve (RV) change-over. (O = engage RV on call for cooling / B = engage RV on call for heating)
Due to variations in other thermostat manufacturers, this is a guideline to determine if the existing thermostat terminal designations are compatible:
- V+/V- > not compatible
- VG+/VG- > not compatible
- B > can be referred to as 24V(Common). If the existing thermostat already has a C(Common) wire then B refers to RV change-over
- X > can be referred to as 24V(Common)....connect to C terminal
- X2 > commonly referred to as auxiliary/emergency heat. If you do not have W1/W2 then this wire would connect to W1 on the ecobee3
- E > commonly referred to as emergency heat. If you do not have W1/W2 then this wire would connect to W1 on the ecobee3. If you have W1/W2 then E wire is disconnected...it is not needed
- G2 > ecobee3 only supports one fan relay...not supported
- G3 > ecobee3 only support one fan relay...not supported
- S1/S2 > these are applicable with some heat-pumps and connect to an outdoor temperature sensor. This is not needed, the ecobee3 utilized internet weather to accomplish the same functions...disconnect
- L > heat-pump failure light. Not supported - the L wire does not need to be connected to an ecobee thermostat.
- HUM > humidifier control. Not compatible with the ecobee3 lite. Compatible with the ecobee3 or ecobee4 models.
- OAT > outdoor ambient temperature sensor...not supported
- SRTN > return air duct sensor...not supported