Protherm Thermolink B, P, RC, LUX – differences and which one suits your boiler
Protherm Thermolink B, P, RC, LUX – differences and which one suits your boiler
If you own a Protherm gas boiler and are considering installing the original control unit, you have most likely come across the Thermolink series. This is a product family of room thermostats and controls that Protherm developed specifically for its own boilers – that is, for the Panther, Leopard, Tiger, Lynx and other series. At first glance it can be confusing that there are several variants: Thermolink B, Thermolink P, Thermolink RC and Thermolink LUX. Each of them is designed for a slightly different type of user, a different way of communicating with the boiler, and a different level of control comfort.
In this article, we will discuss each of these variants in detail – what they can and cannot do, which boilers they work with, and in which situations they are the right choice. If you want to understand the broader context of choosing a control unit – for example, the differences between a room thermostat and weather-compensated control – we also recommend reading our other article Room thermostat vs. weather-compensated control – which is better for your boiler. And if you are not sure what the term "eBus" actually means and why it matters, we explain it in the article What is the eBus and why does control-boiler compatibility matter.
What the Thermolinks have in common – the basis of the whole series
Before we get into the differences, it's useful to know what all the Thermolinks share. The entire series is based on one concept: they are original controls made specifically for Protherm boilers, approved by the manufacturer and supported under warranty service. This is not just a marketing claim – it has a practical impact.
When you connect a non-original control or a cheap thermostat from another manufacturer, the boiler usually only functions as an "on/off" device. The control either turns it on (when the room is cold) or turns it off (when the desired temperature is reached). The boiler behaves reactively – it simply fires up to maximum and then switches off. This is energy-inefficient and causes unnecessary wear on the appliance.
Original Thermolinks – and this applies to all variants – communicate with the boiler via the eBus bus. This is a two-wire digital line through which the thermostat sends the boiler precise requests (for example "heat the water to 52 °C"), and the boiler, in turn, informs the thermostat about its current status, error codes or storage tank temperature. The result? Smooth, gradual output modulation, lower gas consumption and a longer boiler lifespan.
Another common feature: all Thermolinks are wired controls. They have no WiFi or Bluetooth – this is not a disadvantage, rather a matter of simplicity and reliability without the need for a network or an app. If you're looking for a smart control with smartphone operation, you'll need to look at a different solution.
Thermolink B – the basic model for common households
Protherm Thermolink B is the entry-level model of the series. "B" probably refers to "Basic" – basic functions, simple operation, low price. Nevertheless, it's not just a cheap thermostat: even the Thermolink B communicates with the boiler via the eBus, which means output modulation and two-way communication.
Thermolink B offers:
- Setting the desired room temperature in the range of 5 – 30 °C (in 0.5 °C steps)
- Easy switching between modes: comfort, setback (ECO), summer (hot water only)
- Display of the current room temperature on the screen
- Frost protection – automatic activation when the temperature drops below the set value
- eBus communication with the boiler
What the Thermolink B does not have: a time program. This means you cannot set "on weekdays, heating from 6:00 to 8:00 and from 16:00 to 22:00". The thermostat simply holds the temperature you set manually, and you change the mode yourself as needed (switch to comfort in the morning, switch to setback in the evening). For families where someone is home most of the day and doesn't mind occasionally turning a knob, this is a sufficient solution. For working couples whose house is empty all day, it is inconvenient and less energy-efficient.
Who is Thermolink B suitable for? For households where someone is home most of the day, or where the requirements are simple and there's no interest in programming. It also works as a reliable replacement for an old faulty control, when the owner doesn't want to change habits and just needs the boiler connected to the thermostat via eBus (for example, after replacing the boiler with a new Panther Condens model).
Thermolink P – the programmable variant for working families
Thermolink P is essentially the same physical unit as Thermolink B, but with an added time program function. So "P" corresponds to "Programmable". This is in practice the most commonly used variant, since most households have at least a basic need to automatically change the temperature throughout the day.
Thermolink P adds:
- 7-day weekly program (each day individually)
- Up to 3 temperature levels per day: comfort, setback, setback2
- Adjustable switching times for each day of the week
- Display of the daily program and current status on the screen
In terms of eBus communication and basic functions, Thermolink P is identical to model B. Same display, same physical dimensions, same installation method. The difference is purely in the software – the program stored in the device's memory.
Real-world example: A customer who works from 7:00 to 15:30 sets the program so that the boiler wakes up at 5:30 to a temperature of 21 °C (so they can comfortably make breakfast), drops to 16 °C at 7:15 (setback during the day while at work), rises back to 21 °C at 15:00 (so the house is warm when they get home), and drops to 18 °C at 22:00 for the night. A Thermolink P set up this way can reduce gas consumption by 10–20% compared to keeping the thermostat at a comfortable temperature all day, even when the house is empty.
Who is Thermolink P suitable for? For the vast majority of ordinary households – working couples, families with a regular daily rhythm. It offers the best balance of functionality and price in the entire Thermolink family.
Thermolink RC – remote control for a two-zone or more complex system
Thermolink RC is a bit different case. "RC" refers to "Remote Control" or, in some sources, to "Room Controller" with extended functions. While Thermolink B and P are intended for direct control of the boiler from one location (typically a hallway or living room), Thermolink RC was designed primarily for systems where you want greater control over the boiler's settings – including domestic hot water temperature, weather-compensation curve settings, or other parameters.
Thermolink RC provides:
- Comprehensive access to boiler parameters – not just room temperature, but also DHW temperature, weather-compensation curves, heating priorities and other settings
- Display of more information from the boiler (primary circuit temperature, DHW heating status, error messages)
- Time program (similar to Thermolink P)
- Interface for service technicians – the ability to set boiler parameters without having to open the boiler cover and use the control panel directly on the appliance
In practice, Thermolink RC is interesting mainly for service companies and installers who want convenient access to boiler parameters, and for more advanced users who want to monitor the status of the entire system from one place. An ordinary household doesn't need Thermolink RC – the hot water temperature or weather-compensation setting is usually set by a service technician when commissioning the boiler and is not revisited for years afterward.
Note on availability: Thermolink RC is not always available in every distribution network. If a customer specifically requests it (for example, for a larger system with multiple circuits), it is advisable to check current availability with the distributor.
Thermolink LUX – comfort model with a larger display and weather compensation
Protherm Thermolink LUX is the premium variant of the series and clearly the most comprehensive. "LUX" really does correspond to a luxury design here – a larger backlit display, a clearer graphical interface, and, most importantly from a technical standpoint: integrated support for weather-compensated control.
Thermolink LUX includes:
- Large backlit LCD display with a graphical view of the weekly program
- 7-day weekly program with multiple temperature levels
- Input for an outdoor temperature sensor – this is a key difference compared to B and P
- Weather-compensated control – the boiler automatically adjusts the heating water temperature based on the outdoor temperature
- Domestic hot water (DHW) temperature control
- Summer and winter operating mode
- Display of boiler operating parameters
Weather-compensated control is the key advantage of Thermolink LUX. The principle is that the system monitors the outdoor temperature and proactively (not reactively) adjusts the water temperature in the heating circuit based on it. When it's –10 °C outside, the boiler heats the water to 70 °C; when it's +5 °C outside, 50 °C is enough. This leads to smoother operation, fewer on/off cycles and real gas savings. We discuss this topic in more detail in the article Room thermostat vs. weather-compensated control – which is better for your boiler.
For the weather compensation to work, you need to connect an outdoor temperature sensor to the Thermolink LUX. For Protherm boilers with an eBus bus, the suitable option is the Protherm outdoor temperature sensor (wired) for boilers with an eBus bus. Installation is not complicated – the sensor is mounted on the north-facing wall of the house (away from direct sunlight and rain), from where the cable is routed to the Thermolink. You can find more on this topic in the article Installation and setup of an outdoor temperature sensor for weather-compensated control.
Who is Thermolink LUX suitable for? For households in well-insulated houses with underfloor heating or a low-temperature radiator system, where weather compensation will bring the greatest benefit. Also for owners who value comfortable operation and a clear display. And for anyone who wants to get the most out of a modern Protherm condensing boiler – weather compensation is a prerequisite for the boiler to actually condense for most of its operation and achieve its declared energy classes.
Clear comparison of all four variants
To give you a clear picture, here's an overview of the key features side by side:
| Feature | Thermolink B | Thermolink P | Thermolink RC | Thermolink LUX |
|---|---|---|---|---|
| eBus communication | ✓ | ✓ | ✓ | ✓ |
| Time program | ✗ | ✓ | ✓ | ✓ |
| Weather-compensated control | ✗ | ✗ | ✗ | ✓ |
| Outdoor sensor input | ✗ | ✗ | ✗ | ✓ |
| Boiler parameter management | ✗ | ✗ | ✓ | partially |
| DHW control | indirectly | indirectly | ✓ | ✓ |
| Display | simple LCD | simple LCD | extended LCD | large backlit LCD |
| Suitable for | simple requirements | ordinary household | advanced user/service | comfort + weather compensation |
Compatibility with Protherm boilers – what you need to know before buying
Not every Thermolink works with every Protherm boiler. The key condition is the presence of an eBus interface on the boiler. Protherm boilers manufactured from 2005 onwards, i.e. the Panther, Leopard, Tiger (with eBus), Lynx series and other modern condensing boilers – all of these have an eBus and fully support communication with Thermolinks.
Older boilers (for example, the original Tiger without eBus support, some old Protherm Grizzly or Medveď models) may only have two-wire terminals for a standard thermostat (230 V or a potential-free contact). For these boilers, Thermolinks either don't work at all, or work only in a limited scheme (without digital communication). Always check your boiler's technical parameters before purchasing.
Practical tip: Look for the label "eBus" or "BUS" (sometimes also "EBU") on the boiler's terminal block. If you only see "RT" (room thermostat) terminals without eBus, you probably have an older model without digital control. In that case, consult a service technician or contact the distributor.
It's also interesting to compare this with Vaillant controls – since both manufacturers belong to the same parent group, some technical principles are similar. For example, the Vaillant VRT 50 is the equivalent of a simple programmable thermostat for Vaillant boilers (with an eBus), just as Thermolink P is for Protherm. You can find more about this comparison in the article How to choose the original control for a Protherm or Vaillant boiler.
Storage tank system and NTC sensor – when it needs to be added to the Thermolink
If you have a system with an external domestic hot water storage tank (boiler cylinder), it's important to have the correct temperature sensor in the tank. The boiler needs to know when the tank has reached a sufficient water temperature and when heating needs to be started. Protherm boilers combined with an external storage tank typically use an NTC temperature sensor – a small resistive temperature sensor with a value of 10 kΩ at 25 °C.
If this sensor is damaged or missing (for example, when installing a new storage tank), the boiler either cannot properly regulate the tank, or reports an error. In that case, replacement or addition is necessary – for example, the NTC sensor kit for storage tank 10 kΩ is a suitable original solution for most tanks compatible with Protherm and Vaillant systems. You can read more about this topic in the article NTC temperature sensor for storage tanks – what it is and when it needs to be replaced.
In a system with Thermolink LUX, where DHW temperature control is active, proper functioning of the storage tank sensor is an essential condition. Without a functional NTC sensor, tank heating control will be unreliable.
Installation and wiring – what to know before installation
All Thermolinks are mounted on a standard electrical box (or directly on the wall using the included holder). The physical dimensions are compact – typically around 88 × 88 mm on the front, with a depth of up to 30 mm. The location should be in the room where you spend the most time (living room), on an interior wall, at a height of about 1.5 m, away from heat sources (radiator, surfaces directly exposed to sunlight, television).
Electrical connection: Thermolinks are connected to the boiler's eBus using a two-wire cable (approx. 0.5–1.5 mm², cable length can be up to 50 m, polarity on the eBus usually doesn't matter). The thermostat receives power directly from the boiler via the eBus (DC 15–20 V), so no separate power supply is needed. This is another advantage of digital eBus control compared to older systems with 230 V thermostats.
Important notice: even though the installation is relatively simple, work on heating and gas appliances should always be performed by a qualified technician. Improper installation risks not only malfunction of the device, but also loss of the boiler's warranty. A regular electrician or a handy homeowner can usually manage pulling the cable and connecting it to the thermostat's terminal block, but the boiler parameter settings should always be verified by a service technician. You can find a detailed procedure in the article How to connect a Vaillant VRT 50 room thermostat to a gas boiler – although it's about Vaillant, the wiring principles are almost identical.
Typical real-world scenarios – which model we recommend for whom
Scenario 1: A family house from the 1990s, old boiler replaced with a new Protherm Panther Condens 25 KKV
The customer was used to an old thermostat (a simple bimetallic one) and had no interest in programming. We recommend Thermolink B – full eBus communication with the system, simple operation, no learning curve. The boiler will modulate its output, the customer simply sets the desired temperature, and that's it.
Scenario 2: A new apartment in a residential building, a working couple, Protherm Panther 12 KTO boiler
They leave at 7:30 in the morning and return at 17:30. They're home all day on weekends. That's why Thermolink P with a weekly program is suitable – setback during the day on workdays, comfort in the morning and evening, and comfort all day on weekends. Savings compared to a constant temperature can be 15–20% on gas costs.
Scenario 3: A passive family house with underfloor heating, Protherm Panther Condens 35 KKV condensing boiler
Here, Thermolink LUX is the clear choice. Underfloor heating operates with low water temperatures (35–45 °C), and weather-compensated control will ensure that the boiler operates in condensing mode for practically the entire season. Combined with an outdoor sensor, the system will proactively respond to weather changes. The customer will also appreciate the larger, clearer display.
Scenario 4: A service company, installation on a larger building with multiple circuits
Thermolink RC is suitable as a service interface – the technician can set boiler parameters directly from the thermostat, without having to open the boiler cover at every visit. It also displays detailed operating data, which makes diagnostics easier.
Frequently asked questions (FAQ)
Can I use Thermolink B or P instead of the originally supplied RC that has stopped working?
Yes, in terms of basic boiler control this is possible – all Thermolinks are mutually compatible in terms of the eBus protocol. However, you will lose the extra features that the RC has (for example, boiler parameter management or detailed system status display). If you only use the RC as a regular thermostat and don't use its extended functions, replacing it with B or P is fine. However, if a service technician set boiler parameters via the RC, it would be advisable to verify these settings after replacement.
Does Thermolink LUX work without an outdoor sensor?
Yes, it does. If you don't connect an outdoor sensor to it, the LUX works as a standard programmable thermostat with eBus communication – similar to Thermolink P, but with a more convenient display. The weather-compensation function is automatically deactivated when the sensor is not connected. You can add the outdoor sensor at any later time, for example when you decide to switch to full weather-compensated control.
Can I connect two Thermolinks to one boiler – one for each floor?
No, the standard eBus configuration only allows one main thermostat on the bus. If you want two-zone control (for example, the ground floor and upper floor separately), it's solvable, but it requires a different system architecture – for example, zone valves, a zone control unit, or a boiler with a separate output for a second circuit. This goes beyond the scope of the Thermolinks themselves. Consult a service technician.
Is Thermolink compatible with boilers from other manufacturers – for example Vaillant?
Technically, no. Although Protherm and Vaillant boilers come from the same group and the eBus is the same physical protocol, the software communication layers are tailored to a specific product family. Thermolink is designed for Protherm boilers, and Vaillant controls (such as the VRT 50) are designed for Vaillant boilers. In practice, we have encountered cases where an incorrectly matched control "somehow worked" but didn't function properly – for example, ignoring error codes or incorrectly controlling modulation. We do not recommend mixing brands.
What is the lifespan of Thermolinks and what should I do if they stop working?
Thermolinks are electronic devices designed for a typical lifespan of 10–15 years under normal use. The most common causes of failure are: damage to the eBus cable, power surges, moisture (incorrect placement in a bathroom or near a window), or simply electronics failure. In case of a fault, replacing the entire thermostat is usually easier than repairing it. You can find more about common faults and their diagnosis in the article Common faults of Protherm and Vaillant controls and thermostats – causes and solutions.
Is there a wireless version of the Thermolink?
Currently, there is no wireless version of the Thermolink in Protherm's portfolio as a direct replacement. Protherm and Vaillant offer smart controls with WiFi (such as the senso system or from other partners), but these are a different product category with a different price and feature set. For households that strictly want a wireless solution, it's worth looking at these smart systems – but be careful, their compatibility with a specific boiler model must be verified. More on this topic in the article Wired vs. wireless outdoor temperature sensor – which one to choose.
Conclusion – which Thermolink is the right one for you?
Choosing between Thermolink B, P, RC and LUX is not complicated once you know what you expect from the control. If you need simple, reliable control without a time program, the Thermolink B is sufficient. For most ordinary households with a regular daily rhythm, we recommend the Thermolink P – the best ratio of price and functionality. Thermolink RC is a specialized tool primarily for service companies and advanced users. And the Thermolink LUX is the right choice wherever you want full weather-compensated control with comfortable operation – that is, in modern, well-insulated houses, with underfloor heating, or wherever you want to truly make the most of your condensing boiler's potential.
In any case, the rule holds: an original control from the boiler manufacturer is an investment that pays off. The right control will extend the boiler's lifespan, reduce gas consumption and increase heating comfort. If you're not sure which control is compatible with your specific boiler model, check out the entire category of original boiler controls or read the general overview in the article How to choose the original control for a Protherm or Vaillant boiler.
Do you have a question about this topic?
Can't decide, or dealing with a specific situation in your household? Write to us - we'll be happy to help.