Technical terms
Switching difference (hysteresis):
The difference between the switching on and switching off of the heater or the controller. a) There is the switching temperature difference of the controller, which depends on the design of the device. b) There is the switching temperature difference of the room, which is dependent on the behaviour of the entire control path, i.e. on the floor design, the action of external heat sources, the installation location of the controller and the controller itself. The switching temperature difference always refers to the controller. It does not express the actual switching temperature difference of the control path. The latter changes according to the deployment location and conditions. Any indoor temperature is constantly subject to variations. This devia- tion results from the switching temperature difference of the controller and the properties of the room, such as heating speed, heat loss etc.
NO contact (bimetal):
NO contact (bimetal): The control contact closes with increasing temperature and opens at dropping temperature (for “cooling”).
Toggler (bimetal):
This is a toggler with an NC contact and an NO contact. It operates as described for NC and NC contacts.
Split unit / Multi-split unit:
Split AC units consist of at least two heat exchangers in which one is installed as a vaporiser in the rooms to be cooled and the other serves as a con- denser for heat dissipation. Most split units allow reverse operation for heating the rooms if this is required. Multi-split units consist of several vaporisers connected to a condenser (liquefier).
Valve actuator:
Electrical controllable valve for regulating, for example, the hot water flow in heating systems. A distinction is made here between ON / OFF valve actuators and proportional valve actuators. Proportional valves are designed for connecting controllers with a continuous control mode.
Continuous control:
The controller provides an analogue output signal. The value of the output signal changes continuously, i.e., without any steps or jumps, in response to the output signal.
Temperature reduction (TR):
The TR is also implemented via a resistor, as is the case with thermal recirculation. This resistor is activated manually or by a timer. As a result, the bimetal is made to feel a simulated temperature that is about 4 K higher than the actual temperature in the room. Consequently, in a room with a controller setting of, for example, 20 °C, the temperature in the room can drop to a value 4 K lower, to max. 16 °C. If the temperature drops further, the heating system switches on again, and at > 16 °C, it gets switched off. The magnitude of the temperature reduction to be actually achieved depends on the insulation of the building and the reduction period (one night, weekend, holiday).
Thermal recirculation (RF):
By means of an additional integrated heating resistor, the controller is made to switch off at the right time during the heating process. As a result, exceeding the desired room temperature is minimised, and there is a smaller switching difference.
Heat pump:
Rooms can be cooled or heated with heat pumps. Modern systems allow efficient heating and cooling operation since they allow reversible process reversing.
Reversing valve:
A reversing valve (4-way control valve) facilitates a reversing cycle by turning the condenser (liquefier) into an evaporator which causes the cooling unit to heat up or defrost.
Valve protection function
Valve and pump protection serves to prevent the valve seat and/ or pumps from corroding during long downtimes. It is recommended to activate valve protection for hot water heating systems. If valve and pump protection is activated, the valve or a heating pump is operated once on Mondays between 1100hrs and 1200hrs for 5 minutes. Valve and pump protection only becomes active if no heating has taken place within the last week. This avoids unnecessary additional heating at times of year when heating is in use and does not affect the control system.
Evaporator / Liquefier:
A liquefier or condenser is a heat exchanger in a cooling unit that liquefies a gaseous medium through the dissipation of heat. Usually, further cooling of the cooling agent takes place in the liquefier. According to the definition of terms in the European Standard EN 378 Part 1, the condenser in cooling units is called the liquefier in order to easily distinguish it from an electrical condenser. The vaporiser implements the opposite process, evaporating the liquid medium by heating it up.
Catalogue 2022 | Page 239
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