Technical terms
Range limitation (mechanical):
Below the adjusting knob, there are “setting flags” (red / blue) for mechanically delimiting the min. / max. temperature range. In this manner, an undesired mis-setting of the setpoint can be prevented, for example, in children’s rooms or public buildings.
Bimetal:
Thermo-bimetal is generally constructed of layers of metal or alloys of more or less the same thickness, which are firmly joined to one another and have different coefficients of thermal elongation. As a result, they bend under temperature changes, so that upon heating, the side with the component that has a lower heat elongation becomes hollow. The heat is transferred by conduction, radiation or convection from the surroundings (indirect heating).
Defrosting:
Defrosting is the regular de-icing or heating up of the heat exchanger or cooling unit to maintain efficient operation of the system.
Intrinsic safety (JTU, JTL)
Intrinsic safety / protection against cold: The devices are intrinsically safe, i.e., upon loss of the sensor medium owing to sensor rupture, for example, the burner is switched off. Since minus temperatures generate the same effect through volume reduction of the sensor medium, the devices are adjusted by means of the “cold screw” such that they switch off the burner only at temperatures below –15 °C. They can only be switched on again manually at temperatures above approx. –5 °C by means of the manual reset button.
Air conditioner, 2-pipe fan convector (fan coil):
The 2-pipe air conditioners are supplied with heating or cooling water for heat exchange, depending on the requirement, through the same pipe system via 2 pipes (inflow and outflow).
Air conditioner, 4-pipe fan convector (fan coil):
The 4-pipe air conditioners are supplied with heating or cooling water for heat exchange, depending on the requirement, through a heating circuit and a cooling circuit (4 pipes).
Cooling ceiling:
The cooling ceiling belongs to the group of panel heaters. Cooling ceilings are used often in office spaces for passive cooling. In such systems, cold water (usually at 16 °C) flows through a network of pipes and cools the room air. Lower inflow temperatures are not possible because of condensation water formation.
Neutral zone:
The control range in which neither heating nor cooling takes place is called the neutral zone.
Break contact (bimetal):
The control contact opens with increasing temperature and closes at dropping temperature (for “heating”).
Proportional band (p-band):
The proportional band is the range around the target temperature within which the controller delivers a steady output signal. This means that the room temperature is kept more or less constant within the proportional band by the controller (if the heating capacity is sufficient).
2-point control (ON / OFF control):
Control algorithm which, for example, switches off the output when the set temperature is exceeded and switches it on again when the current tempera- ture falls short of the setpoint value. The temperature in the room is always subject to certain variations (control deviations). This deviation results from the switching temperature difference of the controller and the properties of the room, such as heating speed, heat loss etc.
3-point control:
In a 3-point control system, the controller can change between the operating modes heating, neutral zone and cooling.
PWM (pulse width modulation):
Process for generating a continuous-like transmission behaviour in a control path. By varying the power-on time at the input, owing to the time constant of the transmission path, a continuous-like (smooth) signal waveform is generated at its output.
Catalogue 2022 | Page 238
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