What is a room thermostat?Room thermostat , we call the device used to regulate the temperature of a room.
The sense of room temperature is subjective and depends on various factors such as humidity, outside temperature and of course on the preferences of each person. Older people e.g. feel better at higher room temperatures, unlike younger people who may even feel discomfort at high room temperatures.
In any case, the fluctuation of the room temperature is annoying, since the human body perceives the temperature difference of 1οC as “heat / cold”
The mission of a good room thermostat is to manage the heating / cooling system of our room in such a way that the room temperature is maintained at constant levels, without annoying fluctuations.
Today, there are many models of thermostats on the market, with different purchase costs, different capabilities and most importantly, with different accuracy in setting the desired temperature.
Room thermostats are divided into categories1. Depending on the system they manage (heating, cooling system, heating and cooling system)
Based on this categorization, thermostats are divided into heating thermostats (suitable for heating only) and fan coils thermostats (suitable for cooling and heating). The second special category, includes room thermostats with the ability to control the fan of the fan coil and on the market today there are models with manual or automatic selection of the operating level of the fan.
2. Depending on how they work
– Simple room thermostats
The simplest form of thermostat is the bimetallic element thermostat:
This type of thermostat supports its operation at the beginning of the bimetallic element, and has an electrical contact as in the figure above, which is closed (current passes = operating command) when the bimetallic element is cold, while it opens (no current passes = the operation) when the bimetallic element is sufficiently heated by room temperature.
The thermostats of this type have a knob for adjusting the sensitivity of the bimetallic element. The user rotates the knob and adjusts the desired temperature. These simple thermostats are very cheap, but they lag behind in temperature measurement accuracy.
– Electronic room thermostats
The next category of thermostats are electronic thermostats, which measure the room temperature with an electric thermocouple and not with a bimetallic plate. These thermostats offer greater accuracy in measuring and regulating the temperature than ordinary ones.
We should not confuse the “electronic thermostat” with the existence or not of a digital screen. There are electronic thermostats that have a rotary knob on the outside and not a digital display.
PiD control room thermostats
Both simple and electronic room thermostats operate “on / off”, opening and closing their contact when the room temperature reaches the desired setting. This means that the on / off room thermostats ignore the actual temperature in the room and all they perceive is whether or not the room has a certain temperature (the one we set at the controller). In fact, they realize it, since the temperature has (or does not have) the specific value, that is, when it is late.
This digital (0 = no, 1 = yes) state, results in the room temperature not being constant and equal to the desired, but there is a variation, which depending on the quality of the conventional thermostat or inertia of the house, can become very annoying.
The phenomenon is especially noticeable in houses with poor insulation that cool quickly, in which especially in spring and autumn (when winter is not very heavy) we feel alternately warming and cooling.
In addition to being annoying, this phenomenon is also costly, because the extra energy consumed to raise the temperature beyond the desired limit, is wasted and not only does not please us, but instead bothers us.
PiD control thermostats, unlike conventional ones, not only know if the room has or does not have a specific temperature, but they know at all times not only what the room temperature is, but also how fast it goes up (or down), with As a result, PiD control thermostats can predict the time at which the temperature will reach the desired value in advance, and activate the heating (solenoid valve or burner) in advance, so that the room temperature is equal to the desired.
PiD control thermostats can and do achieve excellent comfort conditions since the temperature is stable, but also maximum economy, because the room does not heat up more than it should.
The installation of a PiD control thermostat in underfloor installations (where the inertia of the heating system is high) drastically improves the time lag of the temperature in relation to the value that we set in the thermostat.
3. Depending on the existence or not of a digital screen
There are two main types of thermostats here, those with a rotary control and those with a digital display. The presence of the digital display helps to indicate the current temperature and to precisely adjust the room temperature. Only electronic thermostats and PiD control thermostats can carry a digital display.
4. Depending on their supply
There are models of thermostats that operate on mains voltage (230V) and thermostats that operate on an additional battery. The second category of thermostats is preferable, because the operation of the thermostat and its programming are not affected by PPC interruptions, but attention must be paid to the type of battery so that it has a long life and is easy and economical to replace. We prefer thermostats that run on common AA or AAA batteries.
5. Depending on the additional functions
The room thermostats , depending on the model, can offer additional functions, such as:
– Additional command for hot water with separate button (for heating thermostats)
– Additional fan speed selection command (concerns fan coils thermostats)
– Automatic winter / summer switch (for cooling / heating thermostats)
– Possibility of remote control with switch or modem (to activate the installation remotely by phone)
Ability to display humidity
– Ability to lock setting width (so that a visitor can not change the setting beyond certain limits)
6. Depending on the possibility of scheduling
Thermostats that have a schedule can set different temperatures in the room, according to a schedule entered by the user.
With such a thermostat, it is possible to schedule the time in such a way that during the day we have a temperature e.g. 21οC and at night to have a temperature e.g. 18οC and the change of the desired temperature to be done in such a way that we do not have to remember to turn on or off the heating every day.
Scheduling offers a number of benefits, such as the ability to find our space in the morning when we wake up at the desired temperature.
More economical operation of the cooling heating system.
It is common for timed thermostats to offer up to 3 heating periods, so 6 day / night temperature variations per twenty-four hours. Thus, we can e.g. to set a timetable so that:
- from 7:00 to 8:00 in the morning to have a temperature in the room 21οC (1st heating period)
- from 8:00 to 12:00 to have a room temperature of 18οC
- from 12:00 to 14:00 to have a room temperature of 21οC (2nd heating period)
- from 14:00 to 17:00 to have a room temperature of 18οC
- from 17:00 to 22:00 to have a room temperature of 21οC (3rd heating period)
- from 22:00 until the next day in the morning to have at 18oC.
1. Thermostats with daily schedule, where we can enter the same schedule for all days of the week
2. Semi-weekly timers to which we can insert a different schedule for weekdays and weekends and
3. Weekly thermostats where we can enter a different schedule for each day of the week separately.