Installation Manual

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.

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Dehum with A/C

Also known as AC integrated dehumidifiers, these systems require cooling to be activated to turn on

dehumidification.

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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.

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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.

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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.

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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.

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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

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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.

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Variable speed fans, high voltage forced air systems with fans, and proprietary systems with fans are not

compatible with the Nest Thermostat.

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Two Stage Heat Pumps

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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.

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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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