Humidifier
Pro Setup will show an Activate setting to specify whether heat needs to be activated for humidification
to turn on. Bypass humidifiers should use the Hum. + heat option while steam, independent, or on-
demand humidifiers should use the Hum. only option.
Dehum with A/C
Also known as AC integrated dehumidifiers, these systems require cooling to be activated to turn on
dehumidification.
Dehum Standalone
These dehumidifiers can be turned on independently and do not require heating or cooling to be active. Pro
Setup will show a “To dehum” option where you can choose whether the Star wire should be energized or not
to turn on dehumidification.
Multi-Speed Fans
The Nest Learning Thermostat is compatible with most multi-speed fans (up to 3 speeds) on systems that use
standard 24 volt wiring. It will control the fan differently depending on how many fan wires are connected.
If your customer has a multi-speed fan with a single wire, the system will control the fan speed, not the Nest
thermostat. This means they’ll be able to use the Nest Learning Thermostat to adjust the temperature and turn
the fan on or off , but they won’t be able to manually control the fan speed.
If there’ s more than one fan wire installed, the Nest Learning Thermostat will automatically set the fan speed
Your customer will also be able to select a speed in the Fan menu.
Not all multi-speed fan wires are compatible with Nest thermostats. Compatible wires will have labels similar
to the following:: G, G1, G2, G3,GL, GM, or GH
When using multiple fans speeds some HVAC functions will become unavailable. For example, since the Y2
connector is used for fan speed 2 a second stage of cooling cannot be configured. Stage 3 heat, emergency
heat and humidifier/dehumidifier will become unavailable when a third fan speed is used.
Variable speed fans, high voltage forced air systems with fans, and proprietary systems with fans are not
compatible with the Nest Thermostat.
Two Stage Heat Pumps
The Nest Thermostat will automatically recognize your customer’s
system as a two-stage heat pump if you’ve connected Y1, Y2, and O/B
wires. Nest Thermostat assumes the Y1 wire will be used to activate 1st
stage heating and cooling for your heat pump.
Use Pro Setup to configure the Y2 wire to be used for 2nd stage cooling
and heating, 2nd stage cooling only, or 2nd stage heating only as well as
specify the delivery mechanism (such as forced air or radiant).
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