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Domestic hot water control

Some Google Nest thermostats can control hot water in addition to heating your home. Depending on your thermostat model, it may work with a simple On/Off hot water tank, an OpenTherm hot water tank or an OpenTherm combi boiler.

Before you start

Make sure that your Nest thermostat works with your domestic hot water system. Refer to the table below.

How to tell which Nest thermostat you have

 

Nest Thermostat E

3rd-gen Nest Learning Thermostat1

Separate hot water tank with On/Off control

-

check-mark image

OpenTherm2 combi boiler (hot water temperature)

check-mark image

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Proprietary systems

-

-

Electric hot water tanks

-

-

1 Only the models listed in the table above can control hot water. The 2nd-gen Nest Learning Thermostat doesn't control domestic hot water.

2 Check for the OpenTherm logo Opentherm logo on your boiler, or contact your system’s manufacturer and ask about your model. To save more energy, learn more about how the Nest thermostat works with OpenTherm.

Separate hot water tanks (On/Off or OpenTherm)

If your system has a separate On/Off or OpenTherm hot water tank, and your Nest thermostat is compatible (check the table above), then your thermostat can control when your system heats the water in your tank.

Tip: If you have a combi boiler, these features aren't available because hot water is produced on demand.

Set up a hot water schedule

By default, your Nest thermostat heats water from 6.00 a.m. to 8.00 a.m. (06:00–08:00) and from 4.00 p.m. to 10.00 p.m. (16:00–22:00).

You can always change your hot water schedule with the Nest app, just like you can change your heating schedule. You can set the time and duration for heating water, as well as set a different schedule for every day of the week.

With the Nest app

  1. Open the Nest app Nest app.
  2. Select Hot water Hot water icon (droplet)  and then Schedule Nest app schedule icon.
  3. Select a day that you’d like to edit. You can add a new scheduled heating time or select one that already exists and edit or delete it.

On your thermostat

  1. Press your thermostat's ring and select Settings Nest settings icon and then Hot water schedule.
  2. Choose to EnableDisable or Edit your domestic hot water schedule.
  3. To scroll through the days of the week, turn the thermostat ring. To add a new heating schedule, press the ring while an empty time is selected. To edit or delete it, press the ring when an existing schedule is selected.

Automatically stop heating water when nobody's home

Your thermostat can stop heating the water in your tank after it detects that your home has been empty for at least 48 hours. While your system is turned off, it shouldn't follow your hot water schedule until your system detects that someone has come home again.

With the Nest app

  1. Open the Nest app Nest app.
  2. Select Hot water Hot water icon (droplet) and then Settings Nest settings icon and then Home/Away Assist.
  3. To turn Home/Away Assist on or off, tap the slider.

On your thermostat

  1. Press your thermostat's ring and select Settings Nest settings icon and then Home/Away Assist and then Hot water.
  2. Choose Enable or Disable.

Note: If you have a 3rd-gen Nest Learning Thermostat and you have Bacteria Prevention turned on, your thermostat can still periodically heat the water in your tank.

How the Nest thermostat helps prevent Legionella bacteria

Get hot water on demand (Boost)

 If you need hot water for longer or at a different time than what’s scheduled, you can use Boost to heat the water for a specified duration. After that, your hot water tank goes back to its regular schedule.

With the Nest app

  1. Open  the Nest app Nest app .
  2. Select Hot water Hot water icon (droplet).
  3. Tap the large Boost button.
  4. Choose how long you want to boost hot water.

On your thermostat

  1. Press your thermostat's ring and select Hot water Hot water icon (droplet).
  2. To select how long you want to boost hot water, turn the ring, then press your thermostat ring to start.

Note: The menu should say 'Stop boost' if hot water is already being boosted.

Manually turn water heating on or off

If you’ll be away for an extended period, you can manually turn off the heating for your hot water tank. When you want to go back to your existing hot water schedule, you need to turn the heating back on again.

With the Nest app

  1. Open the Nest app Nest app.
  2. Select Hot water Hot water icon (droplet) and then Settings Nest settings icon.
  3. To switch your hot water on or off, tap the slider.

On your thermostat

  1. Press your thermostat's ring and select Settings Nest settings icon and then Hot water schedule.
  2. To turn your schedule on or off, choose Enable or Disable.

Note: If you have a 3rd-gen Nest Learning Thermostat and you have Bacteria Prevention turned on, your thermostat can still periodically heat the water in your tank.

How the Nest thermostat helps prevent Legionella bacteria

Set hot temperature (OpenTherm only)

If you have an OpenTherm hot water tank, you can control the temperature of the water.

Note: In many cases, your Nest thermostat should be able to control water temperature with OpenTherm boilers. However, because OpenTherm standards can vary, your boiler might not be able to do this.

With the Nest app

  1. Open the Nest app Nest app.
  2. Select Hot water Hot water icon (droplet) and then Settings Nest settings icon and then Set temperature.
  3. To set the water temperature, tap and drag the slider.

On your thermostat

  1. Press your thermostat's ring and select Settings Nest settings icon and then Hot water schedule and then Equipment.
  2. Continue to the next screen and choose Hot water temp.
  3. Select your desired water temperature.

Important: The minimum 55ºC (131ºF) temperature setting for hot water tanks is to help reduce the chance of Legionella bacteria contamination.

OpenTherm combi boilers

If you have a system that uses an OpenTherm combi boiler and your Nest thermostat is compatible (check the table above), then your thermostat may be able to control hot water temperature.

Tip: You don’t need to create a schedule or control when hot water turns on because combi boilers produce hot water on demand.

Set hot water temperature

In many cases, your Nest thermostat should be able to control water temperature with a combi boiler that’s OpenTherm compliant. So, you can turn up the water temperature in the winter for a warmer bath or shower, and turn it down in the summer to feel more comfortable in hot weather or to help save energy.

However, because OpenTherm standards can vary, your boiler might not be able to do this. If this is the case, you should be able to set the water temperature manually on your combi boiler.

To find instructions for setting hot water temperature, select your thermostat below.

Nest Thermostat E

Use your thermostat to set the hot water temperature.

  1. Press your thermostat's ring and select Settings Nest settings icon and then Equipment.
  2. Your current equipment and settings should appear. Select Continue.
  3. Select Hot water temp and then adjust the hot water temperature to your preference.

3rd-gen Nest Learning Thermostat

With the Nest app

  1. Open the Nest app Nest app.
  2. Select Hot water Hot water icon (droplet) and then Settings Nest settings icon and then Set temperature.
  3. To set the domestic hot water temperature, tap and drag the slider.

On your thermostat

  1. Press your thermostat's ring and select Settings Nest settings icon and then Hot water schedule and then Equipment.
  2. Continue to the next screen and choose Hot water temp.
  3. Select your desired domestic hot water temperature.

Tip: The minimum temperature setting for combi boilers with OpenTherm control (40ºC) (104ºF) is lower than hot water tanks (55ºC) (131ºF). Combi boilers do not store hot water in a tank and the risk of the formation of Legionella bacteria is very low.

Troubleshoot hot water control

If there aren’t any options

Check your thermostat model

Domestic hot water control is not available for the 2nd-gen Nest Learning Thermostat. In addition, not all Nest thermostats support all types of hot water systems. Check the table at the top of this article. If you’re not sure which thermostat you have, learn how to check which Nest thermostat you have.

Check the installation

If your thermostat is compatible with your hot water system but there are no hot water controls in the app or on the thermostat, you or your installer may have set up your thermostat to control heating only. If that’s the case, then hot water is controlled by your system programmer rather than your thermostat.

Contact a Pro installer

You can always contact a professional in your area to help you configure your thermostat to correctly control your domestic hot water.

If there are some options for hot water

Some of the options listed above don’t appear for certain types of hot water systems.

Simple hot water tank with On/Off controls

There's no option to control water temperature. That’s because this type of system doesn't support water temperature control through the Nest thermostat.

Combi boiler

Your combi boiler produces hot water on demand. So, there are no options to create a schedule, automatically switch temperature or boost your hot water.

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