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Opentherm boilers & controls - compatibility guide

18/04/2020

 

What is an Opentherm and why is it significant? Which products use Opentherm?

‘Opentherm’ is a common language developed by Honeywell that can be adopted by any boiler or heating control manufacturer so their products can work together. Baxi, Ideal, Viessmann, Ferroli and Main all manufacture combi boilers using the Opentherm technology. These boilers are compatible with many mainstream smart and standard heating controls, including Nest, Tado and Honeywell. We guide you on which products are Opentherm below and your alternatives if they are not.

Guide overview

Opentherm products.

If you are fitting an advanced control with your new combi boiler it must have one of the following features to comply with Boiler Plus: 1) weather compensation, 2) load compensation or 3) automation/optimisation features. ‘Compensation’ controls (1 & 2) must be compatible with your preferred boiler and currently only Opentherm products are compatible with each other.

Non-Opentherm options.

If your existing boiler, or preferred new boiler, is not Opentherm you have two options: 1) opt for the boiler manufacturer’s own advance heating control as it will definitely by compatible, for example a Worcester Combi with Worcester Easy smart control or 2) use any advanced control with 'optimisation' features as this uses AI to optimise any boiler.

Overview of Opentherm

Most new boilers are ‘modulating’, i.e. they can adjust the amount of gas they use between a set range of outputs, for example between 5kW and 18kW. This makes them very efficient as they can reduce their output during warmer periods.

Both weather and load compensation thermostats are designed to work with modulating boilers and control what kW output the boiler should be operating at. However the thermostat and boiler must speak the same ‘language’. In technical terms this is referred to its ‘communication protocol’.

Most manufacturers use a unique language for their own boilers and controls. This means that the number of compensation control brands that will work with a specific boiler is limited. A recent study from the BRE (Evidence Gathering – Compensation and TPI Heating Controls) reported that of 28 compensating heating controls reviewed, 74% used manufacturer specific communication protocols and only 26% used Opentherm.

Opentherm is available to for any boiler or heating control manufacturer to use and means that different brands are compatible with each other. We guide you on which brands use the Opentherm language below.

New Boiler Plus requirements

A new combi boiler must have an ‘advanced feature’ i.e. weather compensation, load compensation or automation & optimisation functions. The new regulations differ however for heat only and system boilers and existing installations, as follows:

New installations of a combi boiler:

require a programmable room thermostat with an ‘advanced’ energy saving feature, i.e weather compensation, load compensation or smart controls that combine automation and optimisation features. For compensation controls, they must speak the same language.

New installations of a heat only or system boiler:

require a programmable room thermostat or a thermostat with separate programmer. You can still opt to install an advanced control and we guide you compatibility below.

Existing boiler installations:

have no minimum requirement for heating controls. You can replace your room thermostat with another room thermostat and nothing more. Again you can opt for an advanced control or may wish to have the functionality of an internet control and we guide you suitable products below.

Opentherm boilers and boiler branded controls

Table 1 below shows which boilers are Opentherm compatible. It is great to see that Baxi, Main, Ferroli, Ideal and Viessmann have signed up to this technology. The controls listed are the manufacturer's own controls so they should work fine, however as a cautionary note not all boiler manufacturers have made their Opentherm boilers compatible with third party Opentherm controls.

Boiler Manufacturer Baxi Ferroli Ideal Main Viessmann
Models 600 Combi iBoiler Combi i29 Logic Combi + C24, C30, C35 Eco Compact Combi 25kW, 30kW Vitodens 100W WB1A, WB1B, WB1C, B1HA, B1KA
  400 Combi   Logic Combi C24, C30, C35    
  200 Combi   Vogue Combi C26, C32, C40    
  100 Combi        
Boiler branded Opentherm controls uSENSE   Touch Connect    
       
      Ideal 204789 Rf wireless programmable room thermostat    
         

 

Third party Opentherm controls

In theory, any of the third party controls below will operate any of the boilers listed in the above table, but this is not always the case in practice. Third party Opentherm controls are not always 100% compatible with Opentherm boilers. Our advice is to confirm with the boiler manufacturer that their boilers are 100% compatible with the third party control you wish to use. Out of seven third party controls, five are internet controls and two are standard programmable room thermostats. As they all carry load compensation controls (Opentherm) they are all compliant under Boiler Plus.

Third Party manufacturers that will work with all Opentherm boilers Drayton Nest Tado Honeywell Honeywell Honeywell Salus
 
Model Wiser (Kit 1, 2 and 3) Thermostat E Tado Smart thermostat (with extension kit) Lyric T6R and T6R-HW T4R, TRM Evohome RT520 + RT520 RF
Base unit/thermostat - suitable combi boilers £135.00 £199.00 £200.00 £242.00 £127.00 £249.99 £70.00
Additional costs for separate hot water control NA Included Included Included No included No
Combined costs for heating and hot water £149.99 Kit 2 - heating and hot water control £199.00 May require an extension kit - £89.99 £242.00 NA 249.99 NA
Warranty/guarantee 1 year 2 years 2 years 1 year 1 years 1 year 5 years
Heating controls Yes Yes Yes Yes Yes Yes Yes
Hot water time/boost Kit 2 model Yes Yes (possible extension kit) Yes No Yes No
Weather compensation, load compensation or smart automation and optimisation Load compensation and smart automation and optimisation Load compensation and smart automation and optimisation Load compensation w/Opentherm boilers and Smart automation and optimisation Weather and load compensation Load compensation and weather compensation (T4M) Load compensation Load compensation
Works with Smart TRVs Yes - Drayton Wiser Smart TRV Yes - Energenie Yes - Tado Smart TRVs No No Yes No
TPI software No Yes Yes 'Fuzzy logic' 'Fuzzy logic' Yes Yes
OpenTherm No Yes Yes Yes Yes Yes Yes
Boiler Plus compliant for combis? Yes Yes Yes Yes Yes Yes Yes
Boiler Plus compliant for heat only and system? Yes yes Yes Yes Yes Yes Yes
Heating zone capabilities 1 (Kit 2 gives 2 channels - 1 heating and 1 hot water) 3 zones with pipework adjustment or more with Energenie smart TRVs 1 heating zone 1 heating zone 1 heating zone Multiple with additional pipework or via Smart TRVs 1 heating zone
Geo location features Yes - via IFTTT Yes Yes Yes No Yes - via IFTTT No
compatible boiler types Combi, heat only and system Combi, heat only and system Combi, heat only and system Combi, heat only and system Combi, heat only and system Combi, heat only and system Combi, heat only and system

Alternatives to Opentherm

Remember that only combi boilers must be fitted with an advanced control under Boiler Plus, although that is not to say you cannot fit a advanced control on other boiler types or on older boilers. We guide you on options for non-combi boilers and older boilers below. For those having a new combi boiler fitted, your options fall into two categories:

1) Stick with the boiler manufacturer’s controls:

Six boiler manufacturers produce their own Boiler Plus complaint internet heating control that will work with some of their range of boilers. Table 3 shows advanced controls from size boiler manufacturers with compatible boiler models from their range.

2) Use controls with Automation and Optimisation features:

Unlike compensation controls that adjust the gas valve, optimisation controls build up patterns of use to operate the boiler most efficiently. These can work with all boilers to improve their efficiency. Table 4 below shows third party smart controls that offer optimisation features and these will be compatible with most boilers.

Boiler branded advanced controls + compatible boilers

Product Worcester EasyControl (replaces the Worcester Wave). Vaillant Vsmart Ideal Touch Baxi Usense Smart room thermostat Glow Worm MiGo Vitoconnect Typ OPT10 + Vitoconnect 200
 
Base unit/thermostat - suitable combi boilers £210.00 £160.00 £160.00 £160.00 £190.00 £343.00
Additional equipment/ costs for separate hot water control £132 integral gas valve Different vSMART controller NA NA £67 hot water control Included
Combined costs for heating and hot water £332.00 £225 for vSMART control with hot water function NA NA £257.00 £343.00
Warranty/guarantee 8-10 years when fitted with a new Worcester boiler 2 years 5-10 years when fitted with Ideal boiler (matches boiler warranty length) 3 years Upto 7 years when fitted with a new Glow Worm boiler 2 years
Heating controls Yes Yes Yes Yes Yes Yes
Hot water time/boost Yes Yes - with hot water control model No No Yes Yes
Compatible boiler ranges Combi Greenstar i range: Junior, Si, CDI compact and Cdi Classic. Systen Greenstar: 12i-24i, 27i-30i and Cdi Classic System All ecoTEC boilers Logic Combis, Vogue Combis, Logic Max Combi and Vogue Max Combi Baxi 600, 400, 200 and 100 (Duotec and Platinum require flue weather compensation in addition to uSense control) All Glow Worm boilers Vitodens 200-W B2HB and B2KB
Compatible boiler types Combi and system Combi, heat only and system Combi Combi Combi, heat only and system Combi and system boilers
Not compatible with: Heat only boilers ecoFIT range System and heat only boilers System and heat only boilers NA Heat only boilers
Weather compensation, load compensation or smart automation and optimisation Weather and load compensation Weather compensation and load compensation Load compensation and smart automation and optimisation Load compensation Weather compensation Weather compensation
Works with Smart TRVs Yes - Bosch Smart TRVs Yes - AmbiSENSE No No No No
TPI software No No No No No  
OpenTherm No No Yes Yes No No
Boiler Plus compliant for combis? Yes Yes Yes Yes when paired with a compatible boiler Yes Yes
Boiler Plus compliant for heat only and system? Yes Yes Yes Yes Yes Yes
Heating zone capabilities Yes with Bosch Smart TRVs 1 + plus hot water 1 heating zone 1 heating zone 2 + plus hot water 1 + hot water
Geo location features No No No Yes No No

 

Third party controls with optimisation features

Product Nest thermostat E Honeywell Lyric T6R - HW wireless smart programmable thermostat Tado smart thermostat Starter Kit V3+ Netatmo - Smart Thermostat Drayton Wiser thermostat Kit 1 Hive - Active Heating
 
Base unit/thermostat - suitable combi boilers £199.00 £242.00 £200.00 £132.00 £135.00 £180.00
Additional equipment/ costs for separate hot water control Included Included Included NA NA Included
Combined costs for heating and hot water £199.00 £242.00 May require an extension kit - £89.99 NA £149.99 Kit 2 - heating and hot water control £180.00
Warranty/guarantee 2 years 1 year 2 years 2 years 1 year 1 year
Heating controls Yes Yes Yes Yes Yes Yes
Hot water time/boost Yes Yes Yes (possible extension kit) Yes Kit 2 model Yes
Weather compensation, load compensation or smart automation and optimisation Load compensation and smart automation and optimisation Weather and load compensation Smart automation and optimisation Weather compensation and smart automation and optimisation Load compensation and smart automation and optimisation Smart automation and optimisation
Works with Smart TRVs Yes - Energenie No Yes - Tado Smart TRVs Yes Netamo NAV-UK Yes - Drayton Wiser Smart TRV No
TPI software Yes 'Fuzzy logic' Yes No No No
OpenTherm Yes Yes Yes No No No
Boiler Plus compliant for combis? Yes Yes Yes Yes Yes Yes
Boiler Plus compliant for heat only and system? yes Yes Yes Yes Yes Yes
Heating zone capabilities 2 zones with pipework adjustment or more with Energenie smart TRVs 1 or 2 heating zones 1 heating zone with Netamo Smart TRVs 1 (Kit 2 gives 2 channels - 1 heating and 1 hot water) 3 zones with pipework adjustment
Geo location features Yes Yes Yes Yes - via IFTTT Yes - via IFTTT Yes
Compatible boiler types Combi, heat only and system Combi, heat only and system Combi, heat only and system Combi, heat only and system Combi, heat only and system Combi, heat only and system
Compatible boiler ranges All (check manufacturer's website for small number of exceptions) All (check manufacturer's website for small number of exceptions) All (check manufacturer's website for small number of exceptions) All (check manufacturer's website for small number of exceptions) All (check manufacturer's website for small number of exceptions) All (check manufacturer's website for small number of exceptions)
Not compatible with: NA NA NA on/off boilers on/off boilers on/off boilers

 

Quick guide to finding a compatible advanced control

Use our quick guide below to find a compatible advance control according to boiler type and whether it is new or existing.

Options for new combi boilers

  • Pick a boiler and control that both use Opentherm protocol – see Tables 1 and 2
  • Pick the boiler manufacturer’s smart control and compatible boiler – see Table 3
  • Pick a smart control with optimisation features such – see Table 4

Options for new heat only or system boilers

  • Pick a boiler and control that both use Opentherm protocol – look for thermostats with hot water controls in Table 2.
  • Pick the boiler manufacturer’s smart control and compatible boiler – Worcester, Vaillant and Glow Worm manufacturer smart controls that include hot water controls – Table 3
  • Pick a smart control with optimisation features and hot water controls – Table 4.

Options for existing modulating combi boilers under 20 years old

  • Check to see if your old boiler uses the Opentherm protocol – if yes use Table 2.
  • Check to see if the manufacturer’s smart control is compatible with your old boiler – if yes use Table 3.
  • If all else fails, pick a smart control with optimisation features – Table 4.

Options for older on/off boilers

  • 1) Pick a smart control with optimisation features – Table 4
  • 2) Pick a control with TPI features – see Table 4 and find TPI controls listed or use our Guide to Advanced Heating Controls.
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