Heatmiser Slimline V4 Programmable Thermostat User Manual

The Heatmiser Slimline V4 is a programmable thermostat from the Heatmiser Slimline Series. It can work in two modes: Programmable Thermostat Mode for heating control and Time Clock Mode for timed output control.

The official manual covers installation, mode selection, clock setup, comfort levels, temperature control, temperature hold, holiday mode, frost protection, optional features, error codes, time clock operation, wiring diagrams, and Heatmiser support details.

What Is a Programmable Room Thermostat?

A programmable room thermostat combines two functions:

The manual explains that increasing the thermostat temperature does not make the room heat faster. Heating speed depends on the heating system design and size. For better energy use, the thermostat should be set to the lowest comfortable temperature and allowed to follow the schedule.

Key Features

The Heatmiser Slimline V4 includes:

• Programmable thermostat mode
• Time clock mode
• Flush-mounted design
• 35mm minimum back box requirement
• Air sensor, floor sensor, and combined sensor options
• 5/2 day, 7 day, and 24-hour programming
• Manual and programmable thermostat operation
• Four comfort levels: Wake, Leave, Return, Sleep
• Temperature hold
• Holiday mode
• Frost protection
• Keypad lock
• Output delay setting
• Switching differential setting
• Floor temperature limit
• Countdown mode in Time Clock Mode
• Boiler, volt-free, and spring return valve wiring options

Important Installation Notes

The Slimline V4 is designed to be flush mounted and requires a 35mm minimum depth back box.

Installation Do’s and Don’ts

The wiring diagrams state that this product must only be installed by a qualified electrician and must comply with local installation regulations.

Parts and Controls

The Slimline V4 has an LCD screen and six front buttons.

Main Controls

Product Specifications

How to Install the Heatmiser Slimline V4

Installation Steps

1. Separate the front from the back plate
   Place a small flat-head terminal driver into the slots on the bottom face of the thermostat and carefully separate the front half from the back plate.
2. Place the thermostat front safely aside
   Keep the front section protected while wiring and mounting.
3. Connect the wiring
   Terminate the thermostat according to the diagrams on pages 39–41 of the manual.
4. Secure the back plate
   Screw the thermostat back plate securely into the back box.
5. Clip the front back on
   Reattach the front half of the thermostat to the back plate.

Mode Select and Factory Reset

The Slimline V4 can operate in two modes.

Thermostat mode is the default setting.

How to Change Mode

Changing mode also performs a factory reset.

1. Hold the Power button to turn off the display.
2. Press and hold Power + Up together until the LCD powers up.
3. All icons will appear briefly.
4. Use Up/Down to select the desired mode.
5. Select 01 for Programmable Thermostat or 02 for Time Clock.
6. Press A to confirm.
7. Press the Power button to turn the display back on.

Mode 1: Thermostat Mode

Thermostat LCD Display

Setting the Clock in Programmable Mode

1. Turn the thermostat on.
2. Press the Clock key twice.
3. Use Up/Down to set the hour.
4. Press H to confirm.
5. Use Up/Down to set the minutes.
6. Press H to confirm.
7. Use Up/Down to set the day of the week.
8. Press A to save and return to the main display.

The manual notes that when Feature 11 is set to Manual Mode, the clock button does not respond.

Temperature Display and Sensor Options

The Slimline V4 can be set up to use:

• Air sensor
• Floor sensor
• Air and floor sensor together
• Remote air sensor
• Remote air and floor sensor together

The display shows either Room Temp or Floor Temp to show which sensor is being controlled. When both sensors are used, room temperature is shown by default. To view floor temperature, press and hold the A key until the floor temperature appears.

Comfort Levels and Programming

The Slimline V4 supports three programming modes:

Comfort Levels

The four comfort periods are:

• Wake
• Leave
• Return
• Sleep

How to Program Comfort Levels

1. Press the Clock key once.
2. Use Up/Down to enter the required Wake time.
3. Press H to confirm.
4. Use Up/Down to enter the Wake temperature.
5. Press H to confirm.
6. Repeat the steps for Leave, Return, and Sleep.
7. For unused periods, enter –.–.
8. Press A to confirm and return to the main display.

In 7-day mode, each day can be programmed independently. In 5/2 day mode, weekdays and weekends can have separate schedules.

Locking the Thermostat

The Slimline V4 includes a keypad lock.

Lock or Unlock the Thermostat

1. Press and hold A + Down together for 10 seconds.
2. The lock symbol appears when the keypad is locked.
3. Repeat the same step until the lock symbol disappears to unlock it.

Temperature Control

To adjust the set temperature:

1. Press Up or Down.
2. The display shows SET and the desired temperature.
3. Use Up/Down to change the set value.
4. Press A to confirm.

In programmable mode, this temperature override stays active only until the next programmed comfort level. In non-programmable mode, the thermostat maintains the selected temperature constantly.

Temperature Hold

Temperature Hold lets users override the program for a selected time and temperature.

Set Temperature Hold

1. Press H.
2. Use Up/Down to enter the required hold time.
3. Press H to confirm.
4. Use Up/Down to enter the hold temperature.
5. Press A to confirm.

The screen shows Hold For and counts down the remaining time. When the timer ends, the thermostat returns to the normal program.

Cancel Temperature Hold

Repeat the same steps and reduce the hold time to 00:00.

Holiday Mode

Holiday mode reduces the set temperature to the frost protection temperature while users are away.

How Holiday Mode Works

• The thermostat maintains the frost temperature during the holiday period.
• It returns to the programmed schedule when the holiday ends.
• The holiday period starts at 00:00 the next day.

Example: if a 2-day holiday is set on Friday, Saturday is counted as the first day, and the thermostat returns to the programmed schedule at 00:00 on Monday.

Set Holiday Mode

1. Press H three times until the suitcase icon appears.
2. Use Up/Down to enter the number of holiday days.
3. Press A to confirm.

To cancel Holiday Mode, repeat the steps and reduce the duration to 00 days.

Frost Protection

Pressing the Power button once places the thermostat into frost protection mode.

In Frost Protection Mode:

• The frost icon appears.
• Heating turns on only if the room temperature drops below the frost set temperature.
• The flame icon appears if heating activates.
• Pressing the Power button again cancels frost mode.

The frost temperature range is 7°C to 17°C, with 12°C as the factory default.

Heating On and Off

The heating is active when the flame icon appears. If the flame icon is absent, there is no heating demand, but the thermostat remains active.

Turn the Thermostat Off Completely

Press and hold the Power button.
The display and heating output turn off completely.

Turn It Back On

Press the Power button once.

Optional Thermostat Features

Adjusting Optional Features

1. Press and hold the Power button to turn the thermostat off.
2. Press and hold the Clock key until the optional feature screen appears.
3. Use the Clock key to move through features.
4. Use Up/Down to change the setting.
5. Press A to confirm.
6. Press the Power button once to turn the thermostat back on.

Re-Calibrating the Thermostat

1. Press and hold the Power button to turn the thermostat off.
2. Press and hold Power + Down together until the temperature appears.
3. Use Up/Down to set the new calibration temperature.
4. Press A to confirm.
5. Press Power once to turn the thermostat back on.

Error Codes

Mode 2: Time Clock Mode

Time Clock Overview

The Slimline V4 can also work as a time clock to control devices around the home, such as:

• Hot water
• Towel rails
• Lighting

The manual advises users to refer to the manufacturer’s instructions when wiring to these devices.

Time Clock LCD Display

Setting the Clock in Time Clock Mode

1. In Countdown Mode, press the Clock button once.
2. In 5/2, 7-day, or 24-hour mode, press the Clock button twice.
3. Use Up/Down to set the hour.
4. Press H to confirm.
5. Use Up/Down to set the minutes.
6. Press H to confirm.
7. Use Up/Down to set the day of the week.
8. Press A to confirm and return to the main display.

Locking the Time Clock

1. Press and hold A + Down together for 10 seconds.
2. The lock symbol appears.
3. Repeat the same step until the lock symbol disappears to unlock it.

Setting the Switching Times

1. Press the Clock button once.
2. Use Up/Down to select the Timer ON time for the Wake switching period.
3. Press H to confirm.
4. Use Up/Down to select the Timer OFF time.
5. Press H to confirm.
6. Repeat the steps for Leave, Return, and Sleep periods.
7. Set unused periods to –:–.
8. In 5/2 day mode, repeat the process for the weekend.
9. Press A to confirm and return to the main display.

Countdown Mode

Countdown Mode turns the output on for a selected duration.

Use Countdown Mode

1. Use Up/Down to set the countdown duration.
2. Press A to confirm.
3. Hold For appears and shows the remaining time.
4. The output remains active while Hold For is displayed.

To cancel countdown, reduce the time to 00:00.

Timer Override

The time clock can override its current timer status.

If the current status is Timer ON, pressing A switches it to Timer OFF. The timer status flashes to show that the programmed output has been overridden. The time clock returns to the program at the next scheduled switching time.

Holiday Mode in Time Clock

Holiday Mode keeps the time clock output OFF while the user is away.

Set Holiday Mode

1. Press H once until the suitcase appears.
2. Use Up/Down to enter the number of holiday days.
3. Press A to confirm.

Holiday mode starts at 00:00 the next day and returns to the normal schedule when the selected holiday period ends.

Optional Time Clock Features

Wiring Diagram

The manual includes wiring diagrams for multiple heating setups.

The diagrams include terminals such as RT2, RT1, -, A2, A1, N, and L. The manual also notes that the unit must be protected by a fuse or RCD in the volt-free and spring return valve diagrams.

Troubleshooting Guide

Heatmiser UK Ltd Support

Heatmiser provides technical support, PDFs, FAQs, videos, and product specifications through its official channels.

Phone: +44 (0)1254 669090
Website: www.heatmiser.com
Twitter/X: @heatmiseruk
Facebook: facebook.com/thermostatsAddress:
Heatmiser UK Ltd
Units 1–5 Hurstwood Court, Mercer Way
Shadsworth Business Park
Blackburn, Lancashire, BB1 2QU
United Kingdom

Official User Manual (PDF)