How to use Nest Cool to Dry

Nest cool to dry is a feature on a Nest Learning or Nest E thermostat that helps with the dehumidification of your indoor environment. This feature is mainly useful for homeowners that live in regions with a climate of high humidity.

Nest Cool to Dry is an important feature on Nest Thermostats because it helps reduce moisture and eventually reduces the risk of mold growth in a home.

There are two things that you need to know about this feature:

  1. It only works with air conditioners and
  2. Heat pumps

Depending on the model of any of the above-mentioned systems, they must have a dehumidification mode too for cool to dry to work properly.

How To Tell If an AC or Heat Pump Is Compatible With Nest Cool To Dry

Now, not every air conditioner is compatible with Nest cool to dry. To find out whether or not your system is compatible, you’ll have to check the wiring of your thermostat.

Basically, check if the star terminal is connected. You don’t have to open your thermostat, you can check for all this from your app or from your thermostat’s display interface, and here is how to do it. 

How To Check If There Is A Wire In The Star Terminal

Option 1. On your Nest thermostat

  • Press your thermostat ring to access the quick menu
  • Navigate to settings—–> Equipment.——> wiring
  • Now, if there is no wire in the star terminal, it’s most likely that your air conditioner or Heat pump doesn’t have dehumidification mode.

Option 2. from your Nest App

On your Nest App home screen app select the thermostat you want to check wiring for.

  • Tap Settings
  • Navigate to settings—->equipment–wiring

In both options 1 and 2, there should be a wire in the star terminal. If not, your System won’t make the nest cool to dry.

What to do if there is a wire in the Star Terminal

If there is a wire in the star terminal, be careful to check for any label on it. If it is clearly labeled dehum then it is possible that your system has a dehumidification mode or has a stand-alone dehumidifier.

In case your system has dehumidification mode, you will typically see the ‘cool to dry option’ in the Nest thermostat sense menu. 

In case there is a stand-alone dehumidifier, you won’t see the ‘cool to dry’ option in the Nest sense menu. So, your Nest thermostat will use your dehumidifier instead of Cool to Dry to control the humidity in your home.

If you still cannot tell whether or not your system has dehumidification mode and can use cool to dry feature, check the model number of your system and look it up on the internet. If this is not an option we advise that you consult a local professional for guidance on this issue.

Can you still use Nest cool to dry on a system without dehumidification mode?

Yes, it’s still possible to utilize the Nest cool-to-dry feature even if your system doesn’t have dehumidification mode but at a cost.

Air conditioners work by turning hot humid air into dry cold air. So when the Nest thermostat senses high humidity levels, cool to dry will take advantage and starts cycling the air conditioner on and off.

This is appreciated by the fact that during the cooling process for any air conditioner, warmer air is passed over the evaporator coil and this warm air sheds off the heat just like what happens when air passes on a  glass of water containing cold water. This condensation removes humidity from the air before it is recirculated back into your home.

However, to effectively reduce humidity in your home, your air conditioner will need to run a little longer to cool a bit lower than your set eco temperature (about 3 degrees lower.)

 That is why for a system without dehumidification mode, it is only advisable to use the Nest to cool features only if the climate in your region is very avoid energy wastage.

Disadvantages of using Cool to Dry on a system without dehumidification mode

Since the AC needs to cool a little lower than eco temperature points, this means that ‘Nest to dry’ on an AC system without dehumidification can be expensive. 

On the other hand, Nest to cool on Dehumidification mode systems will help you save energy by cycling the system on and off when you are away and only turning it on when humidity levels rise.

How Cool to Dry helps bring down humidity levels in your home

When you are away and humidity levels rise, it can cause mold to grow in your home. Nest cool to dry works by turning on the air conditioner when humidity levels rise above 70 when you are away and when they rise above 65 when you are home. If the nest thermostat senses that the humidity level is not dropping, it will automatically shut off the ac to prevent energy wastage.

How Nest Cool to Dry works on systems with dehumidification mode

Air conditioners under normal working conditions humidify the indoor air. This is achieved when the air is passed over the evaporator coil. The Evaporator coils remove moisture from the air and condense it then drip it through the drain.

But this process can be ineffective and can be energy costly in the long run. For a Nest thermostat that is controlling an air conditioner with dehumidification mode, it will lower the humidity more efficiently.

Nest’s cool to dry feature will provide more dehumidification without overcooling your home. It does this by lowering the fan speeds.

How to turn on Nest Cool to Dry if it is Not Working Properly

There are a few things to note here. Firstly, if your system has no dehumidification mode then cool to dry will be off by default. Secondly, however,  if your ac system has dehumidification mode then cool to dry will be on by default. But if Cool to Dry is not working properly, check the below:

 On your Nest app:

  • Select your thermostat from the apps home screen
  • Navigate to settings and tap Nest sense—->cool to dry

On your thermostat

  • Press the ring to access the quick view menu
  • Navigate to settings and select nest sense—–>cool to dry


In a nutshell, Nest cool to dry is a great feature that will help with your indoor air humidification. However, not all thermostats support this feature. It is only supported by Nest Learning and Nest E.  And for a system to properly work with cool to dry, it must have a dehumidification mode.

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