Intelligent Temperature Control for Hydronic Heating Systems

The LK SmartComfort is an electronic temperature-control system from LK Armatur, designed to regulate a mixing valve automatically in hydronic heating applications.

The system continuously monitors temperature conditions and adjusts the connected mixing valve to maintain the required supply temperature. Depending on the selected version, SmartComfort can operate as a constant-temperature controller, weather-compensated controller, indoor-temperature controller, or combined weather- and indoor-temperature controller. 

A key feature is its automatic selection of actuator direction, allowing the controller to adapt to the installation direction of the mixing valve. LED indicators show whether the controller is opening or closing the valve.

Key Features

• Automatic valve-direction selection
• Electronic mixing-valve temperature control
• Push-button adjustment
• LED status indication
• LED display for selected/current values
• Minimum and maximum supply-temperature limitation
• Compatible with new and existing mixing valves
• Mounting kits available for mixing valves from other manufacturers
• Power-outage memory
• Manual valve operation
• 24 VDC actuator supply
• CE type approval
• Optional room-temperature unit
• Optional wireless room-temperature unit
• Optional circulating-pump control

How LK SmartComfort Works

The basic control principle is:

Temperature Sensor → LK SmartComfort → Mixing Valve Actuator → Hydronic System

The controller receives temperature information from the connected sensors and determines how the mixing valve should be positioned.

For example:

Supply Temperature Too Low
→ Controller opens the mixing valve further
→ More hot water enters the circuit
→ Supply temperature increases

Supply Temperature Too High
→ Controller closes the mixing valve
→ Less hot water enters the circuit
→ Supply temperature decreases

This provides automatic temperature regulation without requiring continuous manual adjustment.

LK SmartComfort Product Versions

The SmartComfort family consists of several configurations designed for different temperature-control strategies.

LK 100 SmartComfort CT

The LK 100 SmartComfort CT is a constant-temperature controller.

It is designed to maintain a selected supply temperature in:

• Underfloor heating systems
• Return circuits to solid-fuel boilers
• Other hydronic systems requiring constant-temperature control

The adjustable flow/supply temperature range is:

5–99°C

The standard package includes:

• Temperature controller
• 24 VDC adapter
• Mounting kit for mixing valve
• Supply-temperature sensor with 1 m cable

LK 110 SmartComfort

The LK 110 SmartComfort is a weather-compensated temperature controller.

It measures:

• Supply temperature
• Outdoor temperature

The controller then adjusts the mixing valve according to the outdoor conditions and the programmed heating curve.

The objective is to provide the building with the required amount of heating according to actual outdoor conditions.

This type of control can help avoid supplying unnecessarily high water temperatures when outdoor conditions are mild.

LK 110 Components

The standard package includes:

• Temperature controller
• 24 VDC adapter
• Mixing-valve mounting kit
• Supply-temperature sensor
• Outdoor-temperature sensor
• 15 m outdoor-sensor cable
• Protective casing for outdoor sensor

LK 120 SmartComfort

The LK 120 SmartComfort is an indoor-temperature controller.

It measures:

• Supply temperature
• Indoor temperature

The controller regulates the mixing valve according to the actual indoor temperature and required heating level.

The LK 120 is supplied with a room-temperature unit that allows the user to set the desired indoor temperature.

Two room-unit configurations are available:

• SmartComfort RT – wired
• SmartComfort RTW – wireless receiver

LK 130 SmartComfort

The LK 130 SmartComfort combines:

• Supply-temperature measurement
• Outdoor-temperature measurement
• Indoor-temperature measurement

It is therefore a weather-compensated indoor temperature controller.

The controller uses these measurements to regulate the mixing valve according to both outdoor conditions and actual indoor temperature.

This provides a more comprehensive control strategy than the LK 110 or LK 120 alone.

Room Temperature Unit

The SmartComfort room-temperature unit is available in two versions:

SmartComfort RT

Wired room-temperature unit with a fixed cable.

SmartComfort RTW

Wireless room-temperature unit with a wireless receiver.

The room unit provides additional functions including:

• Indoor temperature adjustment
• Preset programs
• Timer functions
• Holiday settings
• Temperature setback
• Outdoor-temperature indication

Nine Preset Programs

The SmartComfort room-temperature unit includes nine preset programs designed to support energy-saving operation.

Users can also create customized programs.

This allows the heating system to automatically change the target temperature according to the operating schedule.

For example, a building can use different temperature settings during:

• Normal operating hours
• Nighttime
• Weekends
• Holidays

Booster Function

After a temperature setback, the SmartComfort room-temperature unit provides a booster function.

The controller temporarily increases the supply temperature to help the system reach the desired indoor temperature more quickly.

This can be useful after:

• Night setback
• Weekend setback
• Holiday mode

Automatic Airing Detection

The room-temperature unit can also recognize a sudden temperature change, such as when a window is opened for ventilation.

LK states that the system disregards this sudden temperature change for approximately 30 minutes.

This helps prevent the controller from unnecessarily increasing heating output because of a short-term temperature disturbance.

Pump Control – SmartComfort PC

The SmartComfort system can be combined with the optional SmartComfort PC pump-control module.

When there is no heating requirement, SmartComfort PC can stop the circulating pump.

To prevent the pump from becoming stuck after a long period of inactivity, the system exercises the pump every two days.

This provides two potential benefits:

• Reduced pump operating time
• Reduced risk of pump seizure after long periods of inactivity

Power Failure Protection

One useful feature of SmartComfort is its behavior during a power outage.

The controller retains its settings, while the actuator stops in its current position.

This means that the programmed settings do not need to be re-entered after a temporary power interruption.

The controller can also be disengaged so that the connected mixing valve can be operated manually.

Easy Installation

LK SmartComfort is designed to be installed on both:

• New mixing valves
• Existing mixing valves

LK Armatur also provides mounting kits for installation on mixing valves from other manufacturers.

The plug-in power adapter is designed to simplify installation.

This can be useful when upgrading an existing hydronic heating system without replacing the complete mixing-valve assembly.

Automatic Valve Direction

A particularly useful feature is the controller’s automatic orientation selection.

The SmartComfort controller automatically determines the direction required for the connected mixing valve.

This allows the same controller/actuator concept to accommodate different right- or left-hand installation arrangements.

LED indicators show whether the controller is:

• Opening the valve
• Closing the valve

This makes commissioning and troubleshooting easier.

Supply Temperature Limitation

For LK 110, LK 120 and LK 130, the controller allows the supply temperature to be limited by:

• Minimum temperature
• Maximum temperature

The technical data specifies:

Minimum supply temperature: 5–40°C

Maximum supply temperature: 20–99°C.

This provides an additional control layer to prevent the supply temperature from moving outside the desired operating range.

Heating Curve

The weather-compensated versions LK 110 and LK 130 use a heating-curve approach.

The specified curve slope range is:

1.0–9.9

The parallel displacement range is:

±10°C

This allows the relationship between outdoor temperature and required supply temperature to be adjusted according to the characteristics of the heating system.

Technical Specifications

Available Models and Article Numbers

LK Armatur currently lists the following SmartComfort configurations:

LK 100 SmartComfort CT

• 181242 – EU
• 181248 – UK

LK 110 SmartComfort

• 181243 – EU
• 181250 – UK

LK 120 SmartComfort

• 181244 – EU, wired RT
• 181245 – EU, wireless RTW
• 181252 – UK, wired RT
• 181254 – UK, wireless RTW

LK 130 SmartComfort

• 181246 – EU, wired RT
• 181256 – UK, wired RT
• 181247 – EU, wireless RTW
• 181258 – UK, wireless RTW

Accessories

The SmartComfort ecosystem includes several accessories and spare parts:

• 187099 – Temperature controller SmartComfort
• 187098 – Temperature controller SmartComfort CT
• 025010 – 24 VDC EU adapter
• 025011 – 24 VDC UK adapter
• 025012 – 24 VDC US adapter
• 181260 – LK mounting kit
• 025013 – Supply-temperature sensor, 1 m cable
• 025014 – Outdoor-temperature sensor, 15 m cable
• 025020 – Protective casing for outdoor sensor
• 187096 – SmartComfort RT room-temperature unit
• 187113 – SmartComfort RTW wireless room-temperature unit
• 187095 – SmartComfort PC pump control

Application in Hydronic Heating Systems

A typical SmartComfort installation can be represented as:

                 Outdoor Sensor
                       │
                       ▼
                  ┌───────────┐
                  │    LK     │
                  │SmartComfort│
                  └─────┬─────┘
                        │
                        ▼
                 Electric Actuator
                        │
                        ▼
                  Mixing Valve
                   ▲       │
                   │       ▼
             Return Water  Supply Water
                             │
                             ▼
                     Heating System

For LK 120 and LK 130, the room-temperature unit adds indoor temperature information to the control loop.

LK SmartComfort for Modern HVAC Systems

Although LK SmartComfort is primarily designed for hydronic heating systems, the control concept illustrates an important principle used throughout modern HVAC systems:

Sensor → Controller → Actuator → Control Valve

This same control architecture is widely used for:

• Heating systems
• Cooling systems
• Chilled-water systems
• Air-handling units
• Hydronic terminal units
• Heat-exchanger systems

However, LK’s published application for SmartComfort is specifically hydronic radiator and underfloor heating systems, with LK 100 CT additionally intended for constant-temperature control in underfloor heating and solid-fuel boiler return applications.

Therefore, it should not be described as a general-purpose data-center or chilled-water controller without confirming suitability for the specific application.

Advantages of LK SmartComfort

Automatic Temperature Regulation

The controller automatically adjusts the mixing valve according to measured temperature conditions.

Flexible Control Strategies

Four versions cover constant-temperature, weather-compensated and indoor-temperature control.

Easy Valve Installation

Automatic direction selection simplifies actuator installation.

Easy Upgrade

The same actuator is used for LK SmartComfort 110, 120 and 130, allowing an LK 110 system to be upgraded to LK 130 by adding the indoor controller. LK confirms this upgrade path in its current FAQ.

Energy-Saving Functions

Scheduled programs, holiday settings, temperature setbacks and optional pump control can reduce unnecessary heating operation.

Power-Outage Memory

The controller retains its settings during a power outage.

Manual Operation

The actuator can be disengaged to allow manual operation of the mixing valve.

Conclusion

LK SmartComfort is an electronic temperature-control platform designed to automate the operation of mixing valves in hydronic heating systems.

Its different versions allow the system to control temperature based on:

Constant Temperature → Outdoor Temperature → Indoor Temperature → Outdoor + Indoor Temperature

The combination of electronic control, automatic valve-direction selection, temperature sensors, room-temperature units, programmable schedules and optional pump control provides a flexible solution for modern hydronic heating systems.

For projects where an existing manual mixing valve needs to be upgraded to automatic temperature control, LK SmartComfort can also be installed on existing mixing valves, with mounting kits available for valves from other manufacturers.