Electric Underfloor Heating Thermostat - Heatmiser Slimline-e v3

Heatmiser Slimline-E Programmable Thermostat V3 – Intelligent Control for Electric Underfloor Heating

The Heatmiser Slimline-E V3 is a smart, easy-to-use programmable thermostat designed to give you accurate control over electric underfloor heating systems. With a robust 16A switching capacity, flexible programming options and floor sensor control, it is a strong choice for bathrooms, kitchens, conservatories, living areas and other spaces where reliable temperature management matters.

If you are comparing controls, you can also read our Underfloor Heating Thermostats Guide for help choosing the right thermostat for your project. For wider planning, our Underfloor Heating Installation Guide and system selection guide can also help.

Why choose the Heatmiser Slimline-E V3?

This thermostat is built for homeowners and installers who want dependable, programmable control without needing app connectivity. It is ideal where you want straightforward operation, dependable floor temperature sensing and a clean, modern wall-mounted design.

16A switching relay suitable for electric underfloor heating loads up to 3,680W

Flexible programming modes including 5/2 day, 7 day and 24-hour options

Self-learning Optimum Start to help the room reach temperature when you need it

Multiple sensing modes including floor sensor only, air plus floor, and remote air plus floor

Holiday Mode and frost protection for improved energy management

Large white backlit display with auto-dim function for simple everyday use

Keylock and temporary hold for added practicality in busy homes

Flexible programming to match your routine

The Slimline-E V3 offers three programming modes, helping you tailor your heating schedule to how you actually use the room:

5/2 day programming for weekday and weekend schedules

7 day programming for different settings each day

24-hour programming for a simple repeated daily routine

This flexibility makes it easier to reduce unnecessary heating time while still keeping floors warm when you need them most.

Optimum Start for smarter comfort

The built-in Optimum Start function learns how quickly your room heats up and calculates when to switch the system on. Instead of heating for a fixed, wasteful period, it aims to reach your chosen temperature at the right time. That means better comfort, less guesswork and potentially lower running costs.

If you are also planning system size and efficiency, our Underfloor Heating Calculator can help you plan your project more accurately.

Floor sensor control for better protection

A 3-metre NTC 10K floor sensor is included in the box. This allows accurate floor temperature monitoring and helps protect sensitive floor finishes from overheating where required. Depending on your setup, the thermostat can be configured in different ways:

• Floor Sensor Only

• Air and Floor Combination

• Remote Air and Floor

This makes the Slimline-E V3 suitable for a wide range of heating mats, loose wire systems and other electric floor heating installations.

Simple design, practical features

The Slimline-E V3 is designed to be easy to live with day to day. The slim profile looks neat on the wall, while the large backlit display keeps settings clear and easy to read. Helpful built-in functions include:

Holiday Mode for reduced heating while you are away

Adjustable frost protection during colder periods

Temporary temperature hold for quick comfort changes

Keylock facility to prevent accidental adjustments or tampering

Technical specifications

Switch rating: 16 Amp / 3,680 Watts

Dimensions: 98mm (H) x 85mm (W) x 13mm (D after installation)

Mounting: Flush-mounted in a standard 35mm deep back box

Temperature range: Adjustable from 5°C to 35°C, with up to 45°C selectable

Sensor supplied: 3-metre NTC 10K floor sensor included

Best for

This thermostat is a strong option for customers who want:

• Reliable programmable control for electric underfloor heating

• A non-Wi-Fi thermostat with simple day-to-day use

• Floor temperature sensing for better comfort and floor protection

• A direct replacement for older Heatmiser Slimline-E models

Helpful related guides

• Underfloor Heating Thermostats Guide

• Electric Underfloor Heating Installation Guide UK

• Choose the Right Electric Underfloor Heating System

• Best Electric Underfloor Heating Systems UK – Buyer Guide

• Underfloor Heating Calculator UK

FAQ's

Is the Heatmiser Slimline-E V3 suitable for electric underfloor heating?

Yes. It is specifically designed for electric underfloor heating systems and is a strong option where accurate floor temperature control and programmable comfort are important.

Does the Slimline-E V3 need WiFi?

No. This is a programmable thermostat with local control, so it does not rely on WiFi, an app or cloud-based setup.

What is the maximum heating load it can control?

The thermostat has a 16A switching capacity, which makes it suitable for loads up to 3,680W.

Does it include a floor sensor?

Yes. A 3-metre NTC 10K floor sensor is included in the box for floor temperature monitoring and protection.

What is Optimum Start?

Optimum Start is a self-learning feature that works out how quickly the room heats up and switches the system on at the right time to reach the target temperature more efficiently.

Can it help reduce running costs?

It can help improve efficiency by using better scheduling, floor sensing and smarter start times, reducing unnecessary heating compared with less controlled systems.

Is this a good replacement for an older Heatmiser Slimline-E thermostat?

Yes. It is a sensible option for replacing older Slimline-E models where you want similar straightforward control with updated features.

Need help choosing the right thermostat for your underfloor heating project?

Start with our Underfloor Heating Thermostats Guide, check likely sizing with the Underfloor Heating Calculator, or read the Installation Guide for wider project planning.