What is a room thermostat and why to use it?

What and how much will we gain using room thermocontollers (thermostats)? Different types of thermocontrollers. Where is the optimum installation position for maximum effectiveness?

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What is a room thermostat (thermocontroller or thermoregulator)?

The thermostat is a device that automatically responds to changes in ambient temperature by switching on or switching off a heating or cooling system to maintain the constant desired set temperature in a closed space (room).

The thermocontroller (thermostat) is only one part of a larger system for controlling the temperature in a particular room. For example, in a house, the panel, the stove, the radiator, the air conditioner, and so on are a part of the larger system that regulates and maintains the desired set temperature.

 

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What will we gain by using a thermostat?

We will use less energy – the greatest benefit of the use of thermocontrollers is the ability to set different temperatures for maintenance during the day, night and in times when we are not in the room. When optimizing the performance of the heating or cooling system or appliances in the long-term, it uses significantly less energy which in turn leads to a decrease in electricity bills by up to 30%.

Temperature control – it is possible to set a lower temperature (for heating) during the time of the day when we are not at home (work, school, appointments)and at the same time to program reaching and maintaining a comfortable temperature (with digital thermostats)when we go home. This leads to energy savings during the time we are not at home but at the same time when we get back home is waiting for us cozy and warm atmosphere.

Money – every 1⁰ С lower set temperature leads to 10% lower energy consumption and up to 10% lower bill = real money. The ability to set lower temperatures when we are not home at night or if the room is rarely used results in significant savings of energy and money.

Increased comfort – programmable thermocontrollers allow increased comfort during all winter mornings. Setting lower temperatures at night leads to significant savings, and there is nothing better than a warm and cozy room when we get out of bed every morning. The temperature and time of reaching and maintaining it are programmed in the thermostat and it complies with the program.

 

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What is the optimum installation position of a thermostat?

Thermocontroller has to be installed on an inside wall to avoid the possibility of direct sunlight. It has to be installed between 1.30 – 1.60 meters distance off the floor. The distance from doors and windows has to be at least 1.50 m. It should be a relatively long distance, at least 1m, from the heating or cooling appliances or orifices in the room. If the thermostat is too close to the controlled (heating or cooling) device, then it will work on “short cycles” and the repeated switching on and switching off can reduce the life of the system.

If every room is maintained at different temperatures in different time zones, it is optimal to have a thermostat in every room. If the home is heated by a single zone system, then is recommended the thermostat to be installed in the hallway and all doors of other rooms (bedrooms, living rooms, kitchens) to be left open. Heating or cooling with a multizone system registers significant energy savings by adjusting the operation of all devices in different rooms. Such systems allow the switching off of all appliances for heating and cooling in rooms that are not currently in use, for large periods of time, or if the rooms are rarely used.

 

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Now with a thermostat you can combine heating and cooling

Depending on what device it will control, the thermostat may be in heating or cooling mode or both. When the thermostat is in  “cooling” mode, it will turn on when the temperature of the surrounding air is higher than the set one. Conversely, if it is in “heating” mode, it will turn on when the ambient temperature is lower than the preset degrees of comfort.

If the average (normal) temperature of the controlled room is higher than the desired comfort temperature, it is recommended the thermostat to be only in cooling mode irrespective of the temperature outside. Conversely, when the normal temperature in the regulated room is lower than the desired one, it is recommended the thermostat to be constantly in heating mode.

 

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Different types of thermocontollers:

Two main types:

• digital
• bimetallic (analog)

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Digital electronic thermostats

A big part of digital thermocontrollers are programmable and their use leads to 30 percent energy savings for heating and cooling. The new digital thermostats have no moving parts for measuring the temperature and use semiconductor devices such as resistance thermometers.

Every digital thermostat has a screen (display), which displays the current and the set room temperature and the current program. Also, most digital thermocontrollers show the hour and the day of the week, the program mode, and so on. Some modern thermostats have a touch screen and the ability to work with private and building automation.

Some of the more expensive models have a built-in PID controller, ie the thermostat “knows” how the system will react to heating or cooling for a future period. Or more precisely, the thermostat controls the device for heating or cooling in a way that at a set temperature of 21 ⁰ С at 8:00 a.m., it will be exactly 21 ⁰ С at the preset time (8 a.m). An ordinary thermostat type can’t do that. It just will switch on the controlled device at 8:00 am.

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Bimetallic thermocontrollers

Central heating systems based on water and steam are usually accompanied by bimetallic thermostat control which is installed on a wall. By the differential expansion of the two metals, these kinds of thermostats react to changes in temperature and activate the switch on / off of the designated system.

The heating system will be turned on when the temperature drops lower than the set temperature point of the thermostat. The thermocontroller will turn off when the room temperature rises above a designated point within a range of a few degrees of hysteresis to avoid excessive switching.

Bimetal sensors are increasingly being replaced by electronic ones. Nowadays the main use of bimetallic thermostats is with individual electric heaters. The control is performed by turning on / off the device depending on the air temperature in the room and the desired set degrees. Analog thermocontrollers are used in conjunction with air conditioning systems for local control.

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History

Possibly the earliest recorded examples of thermostat control were built by the Dutch innovator Cornelis Drebbel around 1620 in England. He invented a mercury thermostat to regulate the temperature of a chicken incubator.

Modern thermostat control was developed in the 1830s by Andrew Ure, a Scottish chemist, who invented the bi-metallic thermostat. The textile mills of the time needed a constant and steady temperature to operate optimally, so to achieve this, Ure designed the bimetallic thermostat, which would bend as one of the metals expanded in response to the increased temperature and cut off the energy supply.

The first electric room thermostat was invented in 1883 by Warren S. Johnson of Wisconsin.

Albert Butz invented the electric thermostat and patented it in 1886.

One of the first industrial uses of the thermostat was in the regulation of the temperature in poultry incubators. The incubators incorporated an accurate thermostat to regulate the temperature so as to precisely simulate the experience of an egg being hatched naturally.