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Is My Smart Thermostat Compatible With My Boiler – What Is OpenTherm?

With rising energy bills, you may be considering investing in one of the many smart thermostats available with the hopes of bringing down your monthly energy consumption.

With the introduction of smart assistants, it has become much easier to manage everyday tasks without giving them much thought. Companies like Google Nest Thermostat, Hive and Tado all offer compelling products with promises of reducing energy consumption.

The issue is figuring out if your boiler actually supports a smart thermostat. If you have a new boiler, it is likely it will have OpenTherm technology. This guide will help you identify which smart thermostat if any will work with your boiler heating system.

First, we need to dig into the smart thermostats to see which is right for your home. Here are some of the more popular brands and how they match up with other smart devices you may have in your home.

If you have checked the smart thermostats website for compatibility and you cannot find yours listed, do not lose hope! Skip ahead to read about OpenTherm technology as it may still be compatible.

Which Smart Thermostat Should I Buy?

Smart Thermostat Voice Assistant Compatibility Energy Saving Claims Price Check Compatibility
Google Nest Learning Thermostat (Gen 3) Google Assistant, Amazon Alexa, Siri/ Apple Homekit Reduces energy bills by 8.4% and 16.5% annually £180-£219 Click to check compatibility
Tado Smart Thermostat (subscription required) Google Assistant, Amazon Alexa, Siri/Apple Homekit Save up to 30% on annual energy bills £129.99-£199.99 Click to check compatibility
Hive Google Assistant, Amazon Alexa, Siri/ Apple Homekit Save up to £110 annually on your energy bills £119-£179 (mini and main model available) Compatible with most gas and LPG boilers

If you cannot find your boiler on the compatibility tools, smart thermostats may work using a system called OpenTherm.

What Is OpenTherm?

OpenTherm is a piece of communication language developed by a company called Honeywell. It was created to allow boilers to communicate with heating controls – this has opened boilers up to a new wave of both standard and smart heating controls.

Many boiler manufacturers such as Baxi, Ideal Boilers, Viessmann and others use OpenTherm technology to be compatible with heating controls from Nest, Tado and others. Whilst the confirmation of OpenTherm on your boiler heating system is good news, compatibility is not always guaranteed. For complete peace of mind before purchasing a new smart thermostat, you should confirm with the boiler manufacturer.

Some boiler cover policies do cover smart thermostats. However, it is worth asking the question to confirm with your chosen provider.

How Do I Manually Check If My Boiler Is Compatible With Smart Thermostats?

If you’re still unsure about the compatibility of your heating system, figuring it means rolling your sleeves up.

Most modern boilers are compatible but a recurring theme for smart thermostats is the need for something called a c-wire (common wire). This is an ongoing power supply for a smart thermostat of run constantly. This is obviously required for any learning thermostat to automatically make adjustments to your home temperature.

Here’s how to check, and these instructions will come with most smart thermostats out of the box. So installation is relatively easy, even if DIY seems a little daunting.

  1. Turn your boiler off – better to be safe than sorry.
  2. You will need to remove your thermostat’s face plate (if you do not have a thermostat, you will need to have a Gas Safe engineer advise you).
  3. Carefully look to see if there’s a cable attached to the thermostats ‘c’ terminal.
  4. If you can’t see the cable, carefully pull the thermostat away from the wall. Do not force this.
  5. You can now check to see if there’s an unused c-cable tucked away.
  6. This c-cable will need to be attached to your smart thermostat – along with matching the other cables accordingly.
  7. If you cannot locate a c-cable you may need to purchase one along with your smart thermostat.
  8. Before removing any wiring, take a picture of the cable set-up to avoid confusion.

If at any point you become unsure, many of the smart thermostat companies have optional installation ranging anywhere from £60 – £200. More detailed instructions specific to your smart thermostat will come with your device.

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