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Frequently Asked Questions
Simply they have a different meaning that describes multiple systems of heating. First, AHU stands for air handling unit and usually connected to a central HVAC system. Second, FCU stands for fan coil unit and can function or be installed itself.
FCU (fan coil unit) device is consisted of heating and/or cooling heat exchange or coil and fan. Fan coil unit can be used in residential, commercial, and industrial buildings which is part of HVAC system. It has different types, like horizontal (ceiling mounted) or vertical (floor mounted).
The 4 pipe system consists of two separate cooling and heating water coils. Each coil has its own dedicated set of pipes (supply and return) and valve. You should note that for 2 pipe fan coil unit a changeover sensor is must determine the system mode (cooling or heating).
Fan coil units are divided into two types: 2 pipe fan coil units or 4 pipe fan coil units. 2 pipe fan coil units have one supply and one return pipe. You should notice that supply pipe supplies different temperature of water depending on the time of year.
It is used to re-condition and circulates air as part of a heating, ventilating and air-conditioning system. Actually, AHU is take in re-condition it and supply it as fresh air to a building.
VRF stands for variable refrigerant flow also known as variable refrigerant volume (VRV) Which is part of HVAC system invented by Daikin Industries Ltd. in 1982. This refrigerant is conditioned by a single outdoor condensing unit and is circulated within the building to multiple indoor units.
An HVAC (heating, ventilating, and air conditioning) cooling tower is used to dispose of (“reject”) unwanted heat from a chiller. Water cooled chillers are more energy efficient than air-cooled chillers because of heat rejection to tower water at or near wet-bulb temperatures.
It is a machine which removes heat from a liquid by a vapor compression or absorption refrigeration cycle. This liquid can be circulated through a heat exchanger to cool equipment, or another process stream (such as air or process water).
There are basically 5 types of air conditioner compressor which are used in the HVAC industry. Reciprocating. Scroll. Screw.Rotary and Centrifugal .
Hydronic air handlers (hydronic fan coils or hot/chilled water fan coils) are devices which take the heat from hot water and transfer it to a forced air duct. Forced air cooling can be accomplished from chilled water in the same manner.
Water is a better heat transfer medium than air, so hydronic heating is a more energy efficient heating system than a forced air system. Also, the age of the boiler/furnace is crucial. Note that newer heating appliances are much more energy efficient than older models.