solutionssmart thermostat
Ideal Logic Boilers and Smart Thermostats: OpenTherm With Nest, Hive and tado
Yes, Ideal Logic boilers support OpenTherm. Ideal says its Logic boilers have OpenTherm wiring connections. Its current Logic Combi2 and Logic Max Combi2 spec sheets list OpenTherm controls as compatible. Here is what each maker documents. We also cover what a Nest Heat Link warning light means.
Sumcraft Editorial Team7 min read
Checked on 24 October 2026. Everything below comes from the makers' own documents and from named retailer listings. They are linked at the end. We have not installed these thermostats ourselves. Have a Gas Safe registered engineer make any connection inside the boiler.
The short answer
| Question | Answer | Source |
|---|---|---|
| Do Ideal Logic boilers support OpenTherm? | Yes. Ideal says "Ideal Logic boilers have OpenTherm wiring connections" | Ideal blog |
| Which current models? | The Logic Combi2 and Logic Max Combi2 (24, 30 and 35kW) spec sheets list "other OpenTherm controls" as compatible | Ideal spec sheets |
| What kind of connection is it? | "a standard 2-wire low voltage and polarity-free connection" | Ideal blog |
| Does Ideal make its own OpenTherm thermostat? | Yes. Halo Lite is a wired OpenTherm thermostat. Ideal says it is powered through the OpenTherm wiring, so it needs no batteries | Ideal Logic2 controls guide |
| Can I still use on/off control? | Yes. Ideal's older Logic Combi manual describes room thermostat terminals for switched controls | Ideal installation manual, 2014 |
What OpenTherm does on an Ideal boiler
Ideal says that with an OpenTherm thermostat "the central heating requirement is calculated, and the boiler will operate at the minimum rate at which this can be achieved". It adds that turning down as the room nears its set temperature limits overshoot. An on/off thermostat cannot do this. It fires the boiler at its set flow temperature until the room is warm, then switches it off.
Ideal also links OpenTherm control to Boiler Plus rules. It says an OpenTherm thermostat can provide "Enhanced Load Compensation for Boiler Plus compliance". Ideal does not publish a savings figure we can quote. Treat any percentage in adverts with care.
What each thermostat maker documents
| Thermostat | What the maker or retailer documents | Notes |
|---|---|---|
| Ideal Halo Lite | Wired OpenTherm thermostat, powered by the OpenTherm wiring | Ideal's own control, so no compatibility question |
| Ideal Halo Combi, RF and Wi-Fi | Ideal says the Halo range suits "any Logic2 or Vogue boiler range". The Halo Smart Interface fits in the boiler's front aperture | The aperture is the slot people on forums call the "aperture connector" |
| Google Nest Learning (3rd gen) with Heat Link | Google's spec page says Heat Link "works with OpenTherm (heating and hot water)". Google's wiring guide names the OpenTherm wires OT1 and OT2 | Heat Link gives the thermostat 12V DC power |
| Hive V4 OpenTherm | Screwfix lists the Hive V4 as "OpenTherm compatible", for combi boilers. Its receiver is mains-powered and wired to the boiler | A retailer guide says OpenTherm cannot run alongside Hive multizone or Hive radiator valves |
| tado X | tado says tado X is "compatible with most boilers and heat pumps (Relay or OpenTherm)". In its wireless starter kit, the Programmer X is the part that controls the boiler | tado does not name Ideal on these pages |
Ideal's own controls guide lists two older Ideal controls that are not compatible with Logic2 boilers. These are the PRT3 RF programmable thermostat (216131) and the mechanical timer (215390).
Nest Heat Link lights: what they actually mean
People often search for a "flashing orange" Heat Link. Google's lights guide does not describe an orange light on either Heat Link model. The closest colour it lists is yellow.
| Heat Link model | Light | What Google says |
|---|---|---|
| Heat Link E | No light | Usually means everything is working. If Heat Link has lost power, the light is also off and the app shows an error |
| Heat Link E | Blinking yellow | "Something needs your attention". Check the thermostat screen for an error code |
| Heat Link E | Pulsing blue | Connecting to the thermostat |
| Heat Link E | Pulsing green | Heating is on, controlled by the thermostat |
| Heat Link E | Solid green | Heating is on manually, from the Heat Link's button |
| Heat Link (3rd gen) | Steady green | Online, powered and working |
| Heat Link (3rd gen) | Steady yellow | The thermostat has disconnected and "can't control heating or hot water" |
Google says you can press the Heat Link's button to turn the heating on and off until the connection comes back. Some forum posts mention an H73 code on Nest with OpenTherm boilers. We could not find H73 in Google's published help codes. Note the full code and ask Google Nest support.
Boiler messages to rule out first
A thermostat problem can be a boiler problem. Ideal's Logic Max Combi2 user guide (October 2022) uses text messages on the boiler screen. These are the ones it tells owners how to handle:
| Boiler message | What Ideal tells owners to do |
|---|---|
| Water Pressure | With the boiler off and the system cold, fill to 1.0 bar. Bleed the radiators. Refill to 1.0 bar and restart |
| Room Thermostat Fault | Check the room thermostat batteries |
| Ignition Lockout | Check other gas appliances work. Restart. Call your installer if it persists |
| Too Many Restarts | Turn the power off and on at the fused supply |
| Low Mains Voltage | Contact your electricity provider |
For anything else on the screen, Ideal says to contact an installer. Ideal's consumer helpline is 01482 498660.
What we could not confirm
One video in the search results says Ideal does not connect OpenTherm on its boilers by default. We could not confirm this in Ideal's documents. Ideal's 2014 Logic Combi manual does describe a pre-fitted link wire between the room thermostat terminals. Ideal says the link "creates a permanent call for heat and must be removed when adding a room thermostat/programmer". That link sits on the switched connection. It is not the OpenTherm connection.
Forum posters also disagree on whether connecting OpenTherm on a Logic means opening the boiler's sealed case. On a room-sealed boiler, the front panel can form part of the seal. Settle it the safe way and use a Gas Safe registered engineer.
Quick answers
- Do Ideal boilers support OpenTherm? Ideal says its Logic boilers have OpenTherm wiring connections. Its current Logic Combi2 and Logic Max Combi2 spec sheets list OpenTherm controls as compatible.
- Can I use a Nest thermostat with an Ideal Logic boiler? Google says the Heat Link works with OpenTherm. Ideal says its Logic boilers accept OpenTherm controls. Neither names the other, so ask both before you buy.
- Can I use Hive with an Ideal Logic boiler? Hive sells V4 OpenTherm models for combi boilers. If you want Hive radiator valves or multizone, a retailer guide says the receiver must run in relay mode instead.
- Does tado X work with Ideal? tado says tado X works with relay or OpenTherm boilers. It does not name Ideal on its product pages, so check with tado.
- Why won't my Nest thermostat connect to the Heat Link? Check the Heat Link's light first. Steady yellow on a 3rd gen Heat Link means the thermostat has disconnected. Blinking yellow on a Heat Link E means there is an error on the thermostat screen.
Before you buy: a four-point check
- Find your boiler model. It is on the data badge. Logic Combi2 and Logic Max Combi2 are the current combi ranges.
- Decide what else you want. Hive radiator valves and multizone can rule out OpenTherm on Hive. Check the thermostat maker's rules before you buy extras.
- Ask in writing. Send your boiler model to the thermostat maker. Ideal's technical helpline is 01482 498663. Keep the replies.
- Use a Gas Safe registered engineer. The connection is inside the boiler casing.
Sources, checked 24 October 2026:
- Ideal: the benefits of OpenTherm connectivity
- Ideal: Logic Max Combi2 spec sheet
- Ideal: Logic Combi2 spec sheet
- Ideal: Logic2 controls guide
- Ideal: Logic Max Combi2 user guide (October 2022)
- Ideal: Logic Combi 24, 30 and 35 installation manual (January 2014, hosted by InspectApedia)
- Google Nest Help: Heat Link lights and what they mean
- Google Nest Help: Nest Thermostat E Heat Link wiring
- Google Nest Help: manually control heating when Heat Link is disconnected
- Google Store: Nest Learning Thermostat (3rd gen) tech specs
- Screwfix: Hive V4 Wireless Heating OpenTherm Smart Thermostat
- Quality Heating: Hive V4 guide (retailer)
- tado shop: Smart Thermostat X (Wired)
- tado shop (UK): Wireless Smart Thermostat X starter kit
- DIYnot: installing an OpenTherm control on a Logic Max combi (November 2022)
- Smart thermostat
- Ideal
- OpenTherm
- Boilers
- Home heating