How Nest thermostats replace your programmer, thermostat, or frostat

The Google Nest thermostat saves energy like a programmer, keeps you comfortable like a thermostat, and protects your home like a frostat.

If you reside in the UK or Ireland, you probably control the heat in your home with some combination of programmer, thermostat and frostat. In general, the Nest thermostat replaces these systems, but it depends on what equipment you have.

  • Programmer: Saves energy by shutting the heat off for hours of the day you’ve scheduled. This is efficient but gives you no way to track or control how cold it gets in your home.
  • Thermostat: Allows you to see and change the temperature in your home by turning the heat on and off according to the room temperature.
  • Frostat; This boiler add-on turns up the heat automatically if there’s a chance your pipes will freeze in severe cold weather.

Programmer off-times save energy, but leave your home unprotected if it gets very cold. Instead, frostats are used to turn on the heat if your pipes are in danger of freezing. But you shouldn’t have to rely on two different devices to manage heat: one that puts your home at risk, one that saves it in an emergency. Your home should never be at risk in the first place.

How it works

Nest thermostats combine all these capabilities and improves on them. Everything is captured in one schedule, which automatically adapts to your life and can easily be adjusted in one place. After you install your Nest thermostat, you won’t use your programmer or frostat again.

After installation and setup, it will be time to teach your Nest thermostat your daily schedule. It’ll save the most when it learns good habits from you. You teach it by simply adjusting the temperature - down when you leave the house, up when you come home, down when you go to bed. Within days, the thermostat’s Auto-Schedule feature will learn what temperatures you like and when. Then it adds them to your schedule.

Learn about Auto-Schedule >

What to do with your programmer if your heating system isn't using it anymore

What happens to your programmer depends on which model of Nest thermostat you have.

How to tell which Nest thermostat you have >

  • Nest Thermostat E: If you’re installing your thermostat yourself, the app will help you to disconnect the programmer’s heating channel by setting it to Always On so the Nest thermostat can manage heat without interference.
    Note: Nest Thermostat E can’t control your domestic hot water schedule. So if you have a separate hot water tank, we recommend purchasing the 3rd gen Nest Learning Thermostat to take advantage of those options.
  • 3rd gen Nest Learning Thermostat: Your installer will simply disconnect and remove your programmer. Your programmer will also be disconnected if it controlled your domestic hot water since 3rd gen Nest Learning Thermostats can control hot water.
  • 2nd gen Nest Learning Thermostat: Your installer may disconnect your programmer entirely. But if it also controls domestic hot water they will disconnect the programmer’s heating channel by setting it to Always On so the Nest thermostat can manage heat without interference. In this case, your installer will put a sticker on your programmer to remind you not to adjust the heating channel.
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