Skip to main content




Technical terms made easy

On these pages, you will find technical explanations and clarifications of technical terms.

2-point control (ON/OFF control)

Control algorithm, which e.g. switches off the output when the set temperature is exceeded and switches it back on when the temperature falls below it. The temperature in the room is always subject to certain fluctuations (control deviations). The fluctuations are due to the switch temperature difference of the controller and the characteristics of the room, such as heat-up speed, heat loss, etc.

3-point control

With a 3-point control, the controller can switch between operation modes heat, neutral zone and cool.


Electronically controllable valve for regulation, e.g. for the flow of hot water in heating systems. These can be divided into ON / OFF actuators and proportional actuators. Proportional valves are for connecting controllers with constant control performance.

Air conditioning, 2-pipe ventilator convector (fan coil)

2-pipe climate systems are fed with hot or cold water as needed through the same pipe system using two pipes (flow and return flow).

Air conditioning, 4-pipe ventilator convector (fan coil)

4-pipe climate systems are fed with hot or cold water as needed through hot or cold circulation (4 pipes).

Bimetallic strip

Thermobimetal is generally made from two approximately equally thick layers of metal or alloy that are firmly connected and have a different thermal expansion. This leads it to bend with temperature changes so that when it heats up, the side where the components with the lower thermal expansion are located, becomes concave. The heat is transmitted using the charge, radiation or convection to the surrounding area (indirect heating).

Changer (bimetallic)

This is a switch with an open contact and a closed contact. Function as described under open and closed contact.

Closer (bimetallic)

Closer (bimetallic): The control contact closes when the temperature increases and opens again when it decreases (for “cooling”).

Continuous management

The controller releases an analogue output signal. The value of the output signal changes constantly, i.e. not in stages, depending on the output signal.

Cooling ceiling

Ceiling cooling belongs to the group of surface heating systems. Cooling ceilings are frequently used in offices for passive cooling. There, cold water (max. of 16°C) flows through a pipe network and cools the air in the room. Low flow temperatures are not possible due to condensation.


Defrosting is what we call when the heat exchanger or cooling unit is de-iced or heated up, to maintain the efficient operation of the system. Intrinsic safety (JTU, JTL) intrinsic safety/cold protection: The devices are intrinsically safe, i.e. the loss of the sensor medium, for example from a sensor break, switches the burner off. As negative temperatures can have the same effect by reducing the volume of the sensor medium, the devices are set, using “cold screws” so that the burner does not switch off until it gets below -15°C. The burner can only be switch on again manually at temperatures higher than -5°C using the manual set button


A condenser or liquefier is a heat exchanger in a cooling unit, in which a vaporous medium is condensed by discharging heat. In the condenser, there is usually a further cooling of the cooling agent. The evaporator produces the reversed process, evaporating the liquid medium by heating it.

Heat pump

Heat pumps cool and heat rooms. Modern systems allow efficient heating and cooling as they allow a reversible process inversion.

Neutral zone

The control range in which neither heating nor cooling takes place is called the neutral zone.

Opener (bimetallic)

The control contact opens when the temperature increases and closes again when it decreases (for “heating”).

Proportional band (p band)

The proportional band is the range either side of the set value for which the controller releases a constant output signal. This means that the temperature of the room is kept constant within the proportional band (if the heating power is sufficient).

PWM (Pulse width modulation)

The procedure for producing quasi-continuous transmission behaviour in a controlled system. By varying the duty cycle at the entrance, the time constant of the transmission behaviour on its output produces a quasi-continuous signal process.

Range restriction (mechanical)

The “adjuster flags” (red and blue) for a mechanical min./max. temperature limit of the adjustment range are located beneath the adjuster knob. Therefore, any unwanted adjustment, e.g. in children’s rooms or public buildings, can be avoided.

Reversing valve

A reversing valve (4 directional control valve) enables a reverse cycle by turning the condenser (liquefier) into an evaporator and warming or defrosting the cooling unit.

Switching differential (hysterisis)

The difference between switching the heating or controller on and off.
a) There is a switch temperature difference for the controller – this is dependent on the construction of the device.
b) There is a switch temperature difference for the room – this is dependent on the performance of the entire control system, i.e. floor structure, effect of foreign heat sources, of the place where the controller has been mounted and of the controller itself. The stated switching difference always refers to the controller. It does not indicate the actual resulting switch temperature difference of the controlled system. This changes depends on the place of use and the conditions. The temperature in the room is always subject to fluctuations. The fluctuations are due to the switch temperature difference of the controller and the characteristics of the room, such as heat-up speed, heat loss, etc.

Split system / Multi-split system

Climate split systems consist of a minimum of two heat exchangers, with one being installed as an evaporator in the room to be cooled and the other as a condenser for the dissipation of heat. Most split systems enable a reverse operation, to heat the room when it is too cold. Multi-split systems consist of several evaporators, which are attached to one condenser (liquefier).

Temperature feedback (FB)

With an additionally installed heating resistor, the controller is quickly switched off in the heating process. This reduces a temperature overshoot in the room and there is a small switch differential.

Temperature reduction (TR)

TR is carried out using a resistor as in thermal feedback. This resistor is activated using a remote control or a clock. As a result, an approx. 4 K higher temperature than actually exists in the room is simulated to the bimetallic strip. Consequently, the temperature of the room can be lowered to a maximum of 16°C from 20°C for instance, by adjusting the controller. If the temperature lowers further, the heating switches back on and off again at > 16°C. The level of the setback temperature, which is to be implemented, is dependent on the insulation of the building and the time period for the setback period (one night, weekend, holiday)




If you have any questions about our products,

please contact an electrician, plumber or heating installer you know and trust, or drop us a note.

Close Menu