Opentherm boilers & controls - compatibility guide
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 (but we have to warn you that even Opentherm labelled products are not always compatible!). We guide you on which products are Opentherm below and your alternatives if they are not. Our advice is to check with the manufacturer first.
New Boiler Plus requirements
A new combi boiler must have an ‘advanced feature’ i.e. weather compensation, load compensation or automation & optimisation functions (or a flue gas recovery unit, but this is little used with limited efficiency benefits). 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 of which Opentherm is a common 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 100 |
| 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 | ESi | Drayton | Nest | Tado | Honeywell | Honeywell | Honeywell | Salus |
|---|---|---|---|---|---|---|---|---|
 |
 |
 |
 |
 |
 |
 |
 |
|
| Model | ESRTP6WHW | 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 | £140.00 | £135.00 | £199.00 | £200.00 | £242.00 | £127.00 | £249.99 | £70.00 |
| Additional costs for separate hot water control | Included | NA | Included | Included | Included | No | included | No |
| Combined costs for heating and hot water | £140.00 | £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 | 3 years | 1 year | 2 years | 2 years | 1 year | 1 years | 1 year | 5 years |
| Heating controls | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Hot water time/boost | Yes | Kit 2 model | Yes | Yes (possible extension kit) | Yes | No | Yes | No |
| Load Compensation and optimisation. Smart automation available as an optional upgrade | 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 | No | Yes - Drayton Wiser Smart TRV | Yes - Energenie | Yes - Tado Smart TRVs | No | No | Yes | No |
| TPI software | Yes | No | Yes | Yes | 'Fuzzy logic' | 'Fuzzy logic' | Yes | Yes |
| OpenTherm | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Boiler Plus compliant for combis? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Boiler Plus compliant for heat only and system? | Yes | Yes | yes | Yes | Yes | Yes | Yes | Yes |
| Heating zone capabilities | 1 heating zone and 1 hot water | 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 | No | 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 | 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 | ESRTP4 TOUCH | 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 | £90.00 | £199.00 | £242.00 | £200.00 | £132.00 | £135.00 | £180.00 |
| Additional equipment/ costs for separate hot water control | Included | Included | Included | Included | NA | NA | Included |
| Combined costs for heating and hot water | £90.00 | £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 | 3 years | 2 years | 1 year | 2 years | 2 years | 1 year | 1 year |
| Heating controls | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Hot water time/boost | Yes | Yes | Yes | Yes (possible extension kit) | Yes | Kit 2 model | Yes |
| Load Compensation and optimisation. Smart automation available as an optional upgrade | 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 | Yes | 'Fuzzy logic' | Yes | No | No | No |
| OpenTherm | Yes | 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 | Yes |
| Heating zone capabilities | 1 heating zone and 1 hot water | 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 | No | 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 | Combi, heat only and system |
