The thermostats regulate the operation of heating and cooling systems in such a way that the temperature is kept constant at the specified desired level. The evolution of technology has highlighted the usefulness of these devices, while at the same time introducing additional parameters that we should take into account before choosing the right one.

Compatibility with Heating/Cooling System

Each thermostat is designed to be connected to specific types of heating/cooling systems. Therefore, your future thermostat should state in its technical specifications that it is compatible with the system installed in your space (e.g. system with a burner, heat pump, convectors).

Tip: Note that there are thermostat models that can be connected and control the operation simultaneously in more than one heating/cooling systems.

Bimetallic or Electronic

Bimetallic

Bimetallic thermostats regulate temperature with the help of a bimetallic strip (two joined metals that behave differently when heated/cooled). More specifically, the heating system is activated/deactivated when the bimetallic strip bends due to a change in temperature from the desired level. However, in order for this temperature change to be perceived by the bimetallic strip (and consequently by the thermostat), it must be significant (approximately 3oC).

Electronic

Electronic thermostats use electronic sensors to monitor the room temperature and activate the heating/cooling system when the temperature changes by a small amount from the set desired level. It should be noted that in many electronic thermostat models it is possible to adjust their "sensitivity" to temperature changes. That is, you can define whether a change of 0.5oC will be perceived by the thermostat or not.

Due to their immediate response to temperature changes in the space, electronic devices are more efficient than metallic ones, as they maintain the temperature at the desired level for a longer period of time, avoiding large fluctuations, while achieving reduced system consumption.

PID or On/Off

On/Off

On/Off thermostats allow the operation of the heating/cooling system until they perceive that the space has reached the desired temperature. They then stop the operation of the system and restart it when they perceive a deviation from the desired temperature level. This specific operation has the disadvantage that the heating system can overheat/underheat depending on how quickly the thermostat detects these deviations.

PID (Proportional Integral Derivative)

PID thermostats are equipped with a microprocessor which:

• Compares the desired temperature with the current temperature at regular time intervals
• Records how quickly the deviation between the desired and current temperature changes
• Predicts future deviations

Based on the aforementioned analysis, the thermostat selects the operation of the heating system in such a way as to reach and maintain the desired temperature with the fewest possible adjustments.

Programming capability

Programmable

Programmable thermostats provide the ability to program the desired temperature for various time periods of the day and for different days. Therefore, with their help, you can set the temperature you want to have in the space at any time of the day, so that you do not have to constantly deal with turning the heating/cooling system on and off, as well as changing the temperature. Depending on the freedom provided by each thermostat in configuring the aforementioned schedule per day, you can distinguish them into the following categories:

5-2 Day Program

They support the existence of two different programs. This specific category of thermostats is aimed at people who have the same program throughout the weekdays, which varies on weekends but in a similar way.

7 Day Program

They have the ability to enter a different program for each day of the week. The newer models of this category support the function of copying the program from one day to another. This facilitates entry in case there is no differentiation of the program between the days.

5-1-1 Day Program

They support the existence of three different programs. This specific category of thermostats is aimed at people who have the same program throughout the weekdays but different programs on the two days of the weekend.

1 Week Program

They only support one program that is followed for all days of the week.

Tip: In addition to the aforementioned categorization, you should also be concerned about the number of periods per day for which you can set different temperatures. Usually, their number ranges from 2 to 4 (per day).

Tip: Programmable thermostats are equipped with a screen that digitally displays all relevant indicators.

Non-programmable

Non-programmable thermostats only provide temperature adjustment to a specific desired level, which remains unchanged until manually adjusted. Non-programmable thermostats are suitable for individuals who spend most of their day in the space. Non-programmable thermostats can be categorized as digital and mechanical.

Digital (non-programmable)

They are equipped with a display on which all relevant indications are shown digitally.

Analog

Temperature adjustment is done manually in a mechanical way. They are intended for people who are not familiar with the digital display of indications and prefer operation with the help of a rotary knob.

Additional Features

1. Program Suspension - If the programmable thermostat supports this functionality, you can bypass the recorded operating program permanently or for the duration you desire.
2. Keyboard Lock - If the thermostat supports keyboard locking, you can prevent intentional or accidental changes to the temperature setting and the recorded programs.
3. Automatic Switching Between Cooling/Heating Modes - This feature refers to the automatic switching that the thermostat can perform between cooling and heating modes when the room temperature exceeds a certain limit.
4. Backup Battery - If the thermostat is powered by the main power supply of the space, the presence of a backup battery helps maintain the recorded settings in case of a power outage.
5. Remote Control - There are thermostat models that allow remote control either using a suitable remote control (within the space where the thermostat is located) or using a mobile phone via the internet.
6. Humidity Measurement - There are thermostat models that, in addition to measuring temperature, also take into account the existing humidity in the space.