Controls
The Basics.
Controls come in various forms. In this section, we focus on the controls used in homes to manage heating systems. Modern controls have evolved beyond simple on/off switches, incorporating smart features and connectivity for greater efficiency and convenience. Gas boilers have to be installed to a standard called boiler plus, which sets out certain regulations to improve efficiency. Boiler plus document here
Part L states Each room will be fitted with a thermostat controller, this means adding TRVs to every radiator. Except those in whichever room houses the central thermostat.
Every heating system requires a way to monitor the ambient temperature, this is done using room thermostats.
While the thermostat doesn’t directly control the radiators, it signals the boiler when the desired temperature has been reached, prompting it to turn off or reduce output. When the temperature drops below the set limit, the boiler switches back on to maintain the desired warmth. This cycle continues automatically.
In addition to the room thermostat, thermostatic radiator valves (TRVs) are installed on radiators to regulate their individual temperatures. Once a radiator reaches its set level (typically between 1 and 5), the TRV closes to prevent overheating. Different rooms can have different TRV settings based on personal preference and heating needs.
A heating system controlled by a room thermostat should have at least one radiator without a TRV—this is known as the control radiator. It helps regulate the room’s temperature without shutting off automatically like other radiators. Typically, the control radiator is placed in a hallway, where air changes frequently due to doors opening and closing. It should also be located in a room without additional heat sources, such as a fireplace or ovens etc.
Many modern room thermostats now include programmable heating schedules, allowing them to act as the primary control interface for the heating source, whether it’s a boiler, heat pump, or another system.
Heating systems housed in unheated spaces (garages etc) will usually have auxiliary thermostats to protect the system from freezing (frost stat). This is basically just a room thermostat set at a low setting within that space or connected to the pipework.
Thermostatic radiator valves (TRV’s).
A TRV, or thermostatic radiator valve, is a device that controls the temperature of a radiator by adjusting the flow of hot water. These can be standard or smart. Only one side of a radiator has a TRV, and the other has a restrictor valve called a lock shield, which can be used for system balancing and shutting off.
A smart thermostatic radiator valve (TRV) is a radiator valve that can be controlled remotely using a smartphone, tablet, or RF remote. The head of the TRV is what controls the temperature by forcing a pin to close the valve.
Most TRV heads can be interchanged, but the mechanical pin needs to be in good condition to continue working effectively.
Types of TRV’s.
- Wax capsule. Uses a wax plug to regulate the flow of hot water into a radiator.
- Liquid. Uses a liquid capsule which is more responsive to regulate the flow of hot water into a radiator.
- Smart. They can be controlled remotely to zone off parts of the property. Some can be used via smartphone apps
How It Works:
- The thermostat continuously measures the radiator’s temperature.
- If the radiator temperature reaches the desired set point, it restricts the flow of water.
- If the radiator temperature falls below the desired set point, it allows the flow of water.
Room thermostats.
A room thermostat is a device used to regulate the temperature in a room by controlling the heating system. It measures the air temperature and switches the heating on or off to maintain the desired temperature set by the user.
Types of Room Thermostats.
- Mechanical (Analogue). Thermostats. Usually just on and off via moveable dials.
- Digital Thermostats. Typically just on and off with visual readings.
- Programmable Thermostats. Allow users to set temperature schedules for different times of the day.
- Smart Thermostats. They can be controlled remotely via smartphone apps and often use AI to optimize heating/cooling.
How It Works:
- The thermostat continuously measures the room temperature.
- If the temperature falls below the set point, it turns the heating system on.
- If the temperature rises above the set point, it turns the heating system off.
How to Choose the Right Room Thermostat.
When selecting a room thermostat, consider the following factors:
Type of Thermostat
- Mechanical (Analogue) Thermostats – Basic, affordable, but less precise. Best for simple heating systems and good choice for visually impaired or elderly users. (usually hardwired)
- Digital Thermostats – More accurate and easier to read than mechanical ones. (usually battery operated and can be wireless RF)
- Programmable Thermostats – Ideal if you have a fixed daily routine and want to automate temperature settings. (usually battery operated and can be wireless RF)
- Smart Thermostats – Best for energy efficiency, remote control, and learning-based automation. (usually battery operated and can be wireless RF and Wi-Fi)
Compatibility with Your Heating System.
Ensure the thermostat is compatible with your heating system. Your installer should give you choices and confirm compatibility.
Features to Look For.
- Temperature accuracy – Look for one with high precision to avoid frequent temperature fluctuations.
- Wi-Fi or smart control – Allows remote control via apps (useful if you often travel).
- Zoning capability – If you want to control different rooms separately.
- Learning technology – Some smart thermostats learn your habits and adjust accordingly.
- Energy saving features – Helps reduce energy consumption and lower bills. (optimisation, load compensations)
Ease of Installation.
- Wired thermostats – Require professional installation, but are more reliable.
- Wireless (RF) thermostats – Easier to install and offer flexibility in placement.
Cost.
- Basic thermostats – £20-£50
- Programmable thermostats – £50–£150
- Smart thermostats – £150–£300+
Top Brands to Consider.
- Nest (Google) – Smart learning features.
- Salus – Smart learning features.
- Honeywell Home – Basic and smart options.
- Tado – Energy efficiency and zoning.
- Drayton Wiser – Ideal for UK homes with zonal heating.
- Hive (British Gas) – Smart learning features (may require subscription)
The technology.
Weather compensation.
Weather compensation is a heating system control that adjusts the flow temperature of the heating medium to match the outside temperature. An outdoor temperature sensor monitors the outside temperature and sends a signal to an internal electronic controller. The controller adjusts the flow temperature of the heating medium to maintain a comfortable indoor temperature. Operating at a lower temperature makes the boiler more efficient.
Optimisation.
Heating optimisation is a feature designed to enhance comfort and energy efficiency. By activating the boiler before the scheduled heating time, it ensures that the desired room temperature is reached precisely at the programmed time, rather than after a delay. The boiler automatically adjusts to use only the minimum energy needed to reach and maintain the target temperature, promoting economical operation.
Load compensation.
A load compensator is a device that measures the gap between the internal temperature of the home and what the user wants it to be. It then modulates the temperature of the boiler output so that it is just hot enough to provide the extra heat needed. This allows the boiler to operate in condensing mode for more of the time, thus saving more fuel than just standard time and temperature control.
Switches and stats & sensors.
Switches are on all heating systems and are not just on and off but can be used for safe isolation across the system. Stats and sensors can be throughout the system to monitor and shut down if problems arise like overheating or electrical failure.
Open therm. OpenTherm is a type of communication system that allows your gas boiler and room thermostat to interact with each other more effectively. Not all boilers incorporate OpenTherm technology. If you require this on your system is compatible, then ask your installer to confirm it is wired up correctly.
Balancing.
With our controls in place and the system commissioned, a good heating engineer will always balance the system. This is to make sure the water within our system flows to the furthest part of the system and allows all the radiators to be heat up how they should. It can be quite an art form, and the heat geek site has a good guide.