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HVAC (Heating, Ventilation and Air Conditioning) equipment needs a control system to regulate the operation of a heating and/or air conditioning system. [1] Usually a sensing device is used to compare the actual state (e.g. temperature) with a target state. Then the control system draws a conclusion what action has to be taken (e.g. start the ...
The thermostat controls the fan speed and/or the flow of water or refrigerant to the heat exchanger using a control valve. Due to their simplicity, flexibility, and easy maintenance, fan coil units can be more economical to install than ducted 100% fresh air systems (VAV) or central heating systems with air handling units or chilled beams .
Air handlers in Europe and Australia and New Zealand now commonly use backward curve fans without scroll or "plug fans". These are driven using high efficiency EC (electronically commutated) motors with built in speed control. The higher the RTU temperature, the slower the air will flow. And the lower the RTU temperature, the faster the air ...
A thermal expansion valve or thermostatic expansion valve (often abbreviated as TEV, TXV, or TX valve) is a component in vapor-compression refrigeration and air conditioning systems that controls the amount of refrigerant released into the evaporator and is intended to regulate the superheat of the refrigerant that flows out of the evaporator ...
The control circuit in a household HVAC installation. The wires connecting to the blue terminal block on the upper-right of the board lead to the thermostat. The fan enclosure is directly behind the board, and the filters can be seen at the top. The safety interlock switch is at the bottom left.
A thermostat exerts control by switching heating or cooling devices on or off, or by regulating the flow of a heat transfer fluid as needed, to maintain the correct temperature. A thermostat can often be the main control unit for a heating or cooling system, in applications ranging from ambient air control to automotive coolant control.
A fan clutch is a thermostatic engine cooling fan that can freewheel at low temperatures when cooling is not needed, allowing the engine to warm up faster, relieving unnecessary load on the engine. As temperatures increase, the clutch engages so that the fan is driven by engine power and moves air to cool the engine.
Diagramatic operation of a thermal wheel Ljungström Air Preheater by Swedish engineer Fredrik Ljungström (1875–1964). A thermal wheel, also known as a rotary heat exchanger, or rotary air-to-air enthalpy wheel, energy recovery wheel, or heat recovery wheel, is a type of energy recovery heat exchanger positioned within the supply and exhaust air streams of air-handling units or rooftop ...