A thermostatic radiator valve (TRV) is a self-regulating valve fitted to hot water heating system radiator, to control the temperature of a room by changing the flow of hot water to the radiator.
A thermostatic radiator valve (TRV) is a self-regulating valve fitted to hot water heating system radiator, to control the temperature of a room by changing the flow of hot water to the radiator.
The classic thermostatic radiator valve contains a plug, typically made of wax (forming a wax motor), which expands or contracts with the surrounding temperature. This plug is connected to a pin which in turn is connected to a valve. The valve gradually closes as the temperature of the surrounding area increases, limiting the amount of hot water entering the radiator. This allows a maximum temperature to be set for each room.
As the valve works by sensing the temperature of the air surrounding it, it is important to ensure that it is not covered by material (such as curtains). If the controller is removed from the valve, the valve turns on and the radiator will always be hot.
Thermostatic radiator valve should not be installed in the same room where the room (air temperature) thermostat is installed. This is because in the case that the TRV set temperature is below the room thermostat set temperature, the TRV would shut off the radiator before the latter temperature is reached. The central heating boiler would continue to run in an attempt to reach the room thermostat set temperature, potentially heating the rest of the house to uncomfortably high levels if TRVs are not installed on the radiators in every room. If both TRV and thermostat set temperatures were set equally, unpredictable behaviour may occur with both devices attempting to control the room temperature. Therefore, in case of installing a TRV and an air temperature based boiler thermostat in the same room, the TRV should be set to a higher temperature than the room thermostat.[ citation needed ]
The replacement of a manual heating control with a conventional wax motor TRV has been estimated to save at least 280 kilograms (620 lb) of CO2 per year (in 2011 for a British semi-detached house with 3 bedrooms and gas heating [1] ). They are also considerably cost-efficient, using heat only when needed, and can reduce heating bills by up to 17 percent a year. [2]
As of 2012, electronically controlled TRVs have become more common, and some of these are marketed as smart thermostats or even smart TRVs. They frequently use electronic temperature sensing, and can often be programmed or remote-controlled so that individual radiators in a house can be programmed for different temperatures at different times of the day, or automatically respond to occupancy and occupancy patterns. Such increased control allows more advanced controls, which can result in even better energy and CO2 savings. [3] Some other possibilities with such systems is that the temperature sensor can be placed away from the radiator in another place in the room, which may result in a more relevant temperature reading in the room which can be used to set the TRVs operating point. Some electronically controlled valves run on batteries which must be changed at regular intervals, while others can be connected to the power grid. Electronically controlled variants may also require additional setup, for example by connecting to a mobile phone application through a smart home hub using wireless protocols such as Zigbee or Z-Wave.
Instead of marking the adjustment knobs with temperature in the Celsius scale, many manufacturers use a simpler scale, often from 1-5. As each TRV has some variations in their production, as the room size is unknown, as the level of insulation is unknown, and the radiator water temperature is unknown, it is impossible to predict exactly what temperature each setting will result in, but broadly manufacturers tend to manufacture under a set of assumptions that means 3 results in a "comfortable temperature". The table below gives some examples of conversion from proprietary scales to the Celsius scale.
| Position of TRV head | Temperature | Recommended use [4] [5] | ||
|---|---|---|---|---|
| Danfoss [4] [6] | Caleffi [7] | (°C) | (°F) | |
| ❄ | ❄ | 7 | 44.6 | Frost protection |
| 1 | 12 | 53.6 | Cellar, stairs | |
| 1 | 13 | 55.4 | ||
| 14 | ||||
| 15 | 59 | Laundry room | ||
| 2 | 16 | 60.8 | Entrance hall | |
| 2 | • | 17 | 62.6 | |
| • | • | 18 | 64.4 | Bedroom |
| • | • | 19 | 66.2 | Kitchen |
| 3 | 3 | 20 | 68 | Living room |
| • | • | 21 | 69.8 | |
| • | • | 22 | 71.6 | Bathroom |
| 4 | • | 23 | 73.4 | |
| 4 | 24 | 75.2 | ||
| 25 | ||||
| 5 | 26 | 78.8 | ||
| 27 | ||||
| 5 | 28 | 82.4 | ||
There are several different standards for the screw connection between the TRVs adjustment wheel and the thermostat on the radiator. Some common examples are: [8]
A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
Water heating is a heat transfer process that uses an energy source to heat water above its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating. In industry, hot water and water heated to steam have many uses.
A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning systems, which can both cool and warm interior spaces.
A storage heater or heat bank (Australia) is an electrical heater which stores thermal energy during the evening, or at night when electricity is available at lower cost, and releases the heat during the day as required. Alternatively, solar storage heaters are designed to store solar energy as heat, to be released during the night or other periods where it is required, often making it more cost effective than selling surplus electricity to the grid and buying it back at night.
A wax motor is a linear actuator device that converts thermal energy into mechanical energy by exploiting the phase-change behaviour of waxes. During melting, wax typically expands in volume by 5–20%.
Hydronics is the use of liquid water or gaseous water (steam) or a water solution as a heat-transfer medium in heating and cooling systems. The name differentiates such systems from oil and refrigerant systems.
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Electric heating is a process in which electrical energy is converted directly to heat energy. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical device that converts an electric current into heat. The heating element inside every electric heater is an electrical resistor, and works on the principle of Joule heating: an electric current passing through a resistor will convert that electrical energy into heat energy. Most modern electric heating devices use nichrome wire as the active element; the heating element, depicted on the right, uses nichrome wire supported by ceramic insulators.
A circulator pump or circulating pump is a specific type of pump used to circulate gases, liquids, or slurries in a closed circuit. They are commonly found circulating water in a hydronic heating or cooling system. Because they only circulate liquid within a closed circuit, they only need to overcome the friction of a piping system.
A programmable thermostat is a thermostat which is designed to adjust the temperature according to a series of programmed settings that take effect at different times of the day. Programmable thermostats are also known as setback thermostats or clock thermostats.
A heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air. Fins attached to the core tubes serve to increase surface area for heat transfer to air that is forced past them by a fan, thereby heating the passenger compartment.
The wax thermostatic element was invented in 1934 by Sergius Vernet (1899–1968). Its principal application is in automotive thermostats used in the engine cooling system. The first applications in the plumbing and heating industries were in Sweden (1970) and in Switzerland (1971).
A thermostatic mixing valve (TMV) is a valve that blends hot water with cold water to ensure constant, safe shower and bath outlet temperatures to prevent scalding.
A fan coil unit (FCU), also known as a Vertical Fan Coil Unit (VFC), is a device consisting of a heat exchanger (coil) and a fan. FCUs are commonly used in HVAC systems of residential, commercial, and industrial buildings that use ducted split air conditioning or central plant cooling. FCUs are typically connected to ductwork and a thermostat to regulate the temperature of one or more spaces and to assist the main air handling unit for each space if used with chillers. The thermostat controls the fan speed and/or the flow of water or refrigerant to the heat exchanger using a control valve.
Radiators and convectors are heat exchangers designed to transfer thermal energy from one medium to another for the purpose of space heating.
Automatic balancing valves are utilised in central heating and cooling systems that rely on flow of water through the system. They use the latest flow technology to ensure that the design flow rate is achieved at all times irrespective of any pressure changes within the system.
Smart thermostats are Wi-Fi thermostats that can be used with home automation and are responsible for controlling a home's heating, ventilation, and air conditioning. They perform similar functions as a Programmable thermostat as they allow the user to control the temperature of their home throughout the day using a schedule, but also contain additional features, such as sensors and Wi-Fi connectivity, that improve upon the issues with programming.
A hot water storage tank is a water tank used for storing hot water for space heating or domestic use.
Tankless water heaters — also called instantaneous, continuous flow, inline, flash, on-demand, or instant-on water heaters — are water heaters that instantly heat water as it flows through the device, and do not retain any water internally except for what is in the heat exchanger coil unless the unit is equipped with an internal buffer tank. Copper heat exchangers are preferred in these units because of their high thermal conductivity and ease of fabrication. However, copper heat exchangers are more susceptible to scale buildup than stainless steel heat exchangers.
The Nest Thermostat is a smart thermostat developed by Google Nest and designed by Tony Fadell, Ben Filson, and Fred Bould. It is an electronic, programmable, and self-learning Wi-Fi-enabled thermostat that optimizes heating and cooling of homes and businesses to conserve energy.
