A fan coil unit (fan coil unit, or FCU) is a relatively simple device, consisting of a pipe or heat exchanger and a fan. It is part of the air conditioning systems in residential, commercial or industrial buildings.
Generally, fan coil units air-condition a room (or several) connected to a network of pipes that provide thermal energy (heat or cold), and have their own regulation system, generally an “all or nothing” thermostat. They can have different designs, including horizontal (ceiling mounting) and vertical (floor console mounting).
Due to their simplicity, they are cheaper to install than a ducted air conditioning system with an air handling unit (AHU). However, they regulate ambient humidity less well and can cause noise, since the fan is in the same air-conditioned room.
Design
A fan coil unit can have different shapes and types and can usually be installed exposed or hidden under the ceilings.
The ones seen can be the so-called console ones, resting on the floor, usually under the windows, or they can be hanging from the ceiling. All of them have a protective casing, which includes the air intake and delivery grilles.
The hidden ones are normally placed behind an accessible false ceiling. The intake and discharge grilles can be in the same appliance, or the intake (or discharge) can be carried through a short duct to separate the two functions, or it can be used for intake duct, as a plenum, the gap above the false ceiling.
Operation
The fundamental element is a heat exchange battery, which receives thermal energy (cold or heat) from a production center, through pipes. It also has a fan that moves ambient air through the batteries and control and regulation systems. In its case, it also has a casing to house all these systems inside.
Therefore, the battery receives hot or cold water produced in a thermal power plant and transfers the energy to the air and the fan propels it into the premises. Regulation normally consists of an internal thermostat, which takes the temperature of the room air at the return inlet, but a separate room thermostat can be installed. In certain buildings, regulation is done through an integrated control system, which moves the heat transfer inlet valve in the fan coil unit, following the indications of an ambient sensor, linked to the central control through a network.
Fan Coil (Units)
Introduction
A fan coil unit (fan coil unit, or FCU) is a relatively simple device, consisting of a pipe or heat exchanger and a fan. It is part of the air conditioning systems in residential, commercial or industrial buildings.
Generally, fan coil units air-condition a room (or several) connected to a network of pipes that provide thermal energy (heat or cold), and have their own regulation system, generally an “all or nothing” thermostat. They can have different designs, including horizontal (ceiling mounting) and vertical (floor console mounting).
Due to their simplicity, they are cheaper to install than a ducted air conditioning system with an air handling unit (AHU). However, they regulate ambient humidity less well and can cause noise, since the fan is in the same air-conditioned room.
Design
A fan coil unit can have different shapes and types and can usually be installed exposed or hidden under the ceilings.
The ones seen can be the so-called console ones, resting on the floor, usually under the windows, or they can be hanging from the ceiling. All of them have a protective casing, which includes the air intake and delivery grilles.
The hidden ones are normally placed behind an accessible false ceiling. The intake and discharge grilles can be in the same appliance, or the intake (or discharge) can be carried through a short duct to separate the two functions, or it can be used for intake duct, as a plenum, the gap above the false ceiling.
Operation
The fundamental element is a heat exchange battery, which receives thermal energy (cold or heat) from a production center, through pipes. It also has a fan that moves ambient air through the batteries and control and regulation systems. In its case, it also has a casing to house all these systems inside.
Therefore, the battery receives hot or cold water produced in a thermal power plant and transfers the energy to the air and the fan propels it into the premises. Regulation normally consists of an internal thermostat, which takes the temperature of the room air at the return inlet, but a separate room thermostat can be installed. In certain buildings, regulation is done through an integrated control system, which moves the heat transfer inlet valve in the fan coil unit, following the indications of an ambient sensor, linked to the central control through a network.
Hot or cold water circulates through the battery depending on the needs of the premises. There can be two exchangers, one for hot water and one for cold water. The control system is responsible for letting water pass through one or the other. The water, hot or cold, is prepared in a technical room, using a boiler "Boiler (heating)") or a water chiller plant, respectively.
The pipes that link the fan coil units with the generators in the technical room can be arranged in two ways: with two and with four pipes. In the first case they have a flow pipe and another return pipe and with this system only one service (heating or cooling) can be provided at a time to all the devices in the network. In the case of four pipes, one pair will be a round trip for heat and the other pair will be a round trip for cold; Often these four-pipe fan coil units have two batteries, one for each service, but it is not absolutely necessary, since the controls are perfectly capable of operating one service or another according to the needs of the premises. This type of four pipes is mainly used in buildings where there may be areas that require heating while others require cooling (due to causes such as different sunlight, occupancy, orientation, etc.).
The pipe network that feeds the devices can be made with direct return or inverted return, such as hot water heating networks.[1].
Depending on the temperatures of the cold water and the relative humidity of the air-conditioned spaces, condensation will occur in the coils and must be discharged into the drain. The condensate would be collected in a condensate tray included in the device, with an outlet to connect to the drain and, if there are several fan coil units, a drainage network must be installed. If necessary due to the arrangement of the appliances, the drainage could be done using a pump and, if it were done to the general drainage network, an odorless closing device (normally a siphon) would have to be used to prevent odors from the network from reaching the inhabited spaces.
The power emitted by the fan coil units can be regulated by varying the fan speed. Some manufacturers achieve speed control by adjusting the taps of an AC transformer that supplies power to the fan motor. This would typically require an adjustment at the commissioning stage of the building construction process and is therefore set for life. Other manufacturers provide custom wound permanent split capacitor (PSC) motors with speed taps on the windings, set to the desired speed levels for the fan coil design. This can be done through a manual speed selector (stop-low-medium-high) that can be controlled by the user, or through automatic systems regulated by a room thermostat.
Speed control of the fan motors within a fan coil unit is effectively used to control the desired heating and cooling output of the unit. A simple speed selector switch (off/high/medium/low) is provided for the local room occupant to control the fan speed. Typically, this speed selector switch is built into the room thermostat and is manually adjusted or automatically controlled by the digital room thermostat. Building energy management systems can be used for automatic control of fan speed and temperature. Fan motors are usually shaded pole AC or permanent split capacitors. Among the most recent developments are electronically commutated brushless direct current designs. While these motors offer significant energy savings, the initial cost and return on investment must be carefully considered.
EC/DC motor powered fan coil units
These motors are sometimes called DC motors, sometimes EC motors, and sometimes EC/DC motors ("DC" means 'direct current' and 'EC' means 'electronically commutated').
Direct current motors allow the speed of the fans within a fan coil unit to be controlled by means of a 0-10 volt input "signal" to the motor (or motors); In this case, the transformers and speed switches associated with AC fan coil units are not required. Up to a signal voltage of 2.5 volts (which may vary depending on different fan/motor manufacturers), the fan will be in a stopped condition, but as the signal voltage increases, the fan will increase its speed without any problem until reaching its maximum speed at a signal voltage of 10 volts. Fan coils will generally operate between about 4 and 7.5 volts, because, below 4 volts, air volumes are ineffective, and, above 7.5 volts, the fan coil is likely to be too noisy for most commercial applications.
The 0-10 volt signal voltage can be set using a simple potentiometer or sent to the fan motors via the terminal controller on each of the fan coil units. The first is very simple and economical, but the second opens up the possibility of continuously modifying the fan speed depending on various external influences or conditions. These external influences or conditions could be “real-time” heating or cooling demand, occupancy levels, window switches, time clocks, or any number of other inputs to the unit itself, the building management system, or both.
The reason why, despite their apparent relative complexity, these direct current fan coil units are becoming more popular is because of their improved levels of energy efficiency compared to their AC motor-driven counterparts from just a few years ago. A direct switch from alternating current to direct current will reduce electrical consumption by 50%, and the application of demand- and occupancy-dependent fan speed control can take savings up to 80%. In areas of the world where there are legal energy efficiency requirements for fan coil units (such as in the UK), direct current fan coil units are quickly becoming the only option.
Spaces where it is used
The fan coil unit is an excellent solution for all-water air conditioning in large residential buildings and commercial premises. In these cases, the device is mounted on the false ceiling of the toilets or hallways (they usually require less headroom) and recirculates the air in the air-conditioned rooms, with the possibility of turning it off in unused rooms or areas at certain times, to save energy.
A variant of fan coil units, simplified to the maximum, called heater or aerotherm, is used as an economical installation in warehouses, hallways and even in large sports halls.
Facility
In high-rise residential construction, each fan coil generally requires a rectangular penetration into the concrete slab on which it sits. There are usually 2 or 4 ABS, steel or copper tubes running through the floor. The pipes are usually insulated with cooling insulation, such as flexible acrylonitrile butadiene/polyvinyl chloride (AB/PVC, Rubatex or Armaflex brands) foam in all pipes or at least in the cold lines.
Fan coil unit with outside air
This variant is mainly used in classrooms, hotels, apartments and tenement houses. The difference is that it is connected to the outside through a duct, so that it can introduce air for ventilation, which it conditions before blowing it into the room it serves. This solves one of the most important problems of many fan coil installations, ventilation.
The European market
The fan coil unit is composed of a quarter of 2-pipe units and three-quarters of 4-pipe units, and the best-selling products are “with casing” (35%), “without casing” (28%), “cassette” (18%) and “ducted” (16%).[2].
In 2010, the European market by country was divided as follows:
References
[1] ↑ Véase el manual de la ASHRAE «2008 Systems & Equipment», capítulo 12 (en inglés).
Hot or cold water circulates through the battery depending on the needs of the premises. There can be two exchangers, one for hot water and one for cold water. The control system is responsible for letting water pass through one or the other. The water, hot or cold, is prepared in a technical room, using a boiler "Boiler (heating)") or a water chiller plant, respectively.
The pipes that link the fan coil units with the generators in the technical room can be arranged in two ways: with two and with four pipes. In the first case they have a flow pipe and another return pipe and with this system only one service (heating or cooling) can be provided at a time to all the devices in the network. In the case of four pipes, one pair will be a round trip for heat and the other pair will be a round trip for cold; Often these four-pipe fan coil units have two batteries, one for each service, but it is not absolutely necessary, since the controls are perfectly capable of operating one service or another according to the needs of the premises. This type of four pipes is mainly used in buildings where there may be areas that require heating while others require cooling (due to causes such as different sunlight, occupancy, orientation, etc.).
The pipe network that feeds the devices can be made with direct return or inverted return, such as hot water heating networks.[1].
Depending on the temperatures of the cold water and the relative humidity of the air-conditioned spaces, condensation will occur in the coils and must be discharged into the drain. The condensate would be collected in a condensate tray included in the device, with an outlet to connect to the drain and, if there are several fan coil units, a drainage network must be installed. If necessary due to the arrangement of the appliances, the drainage could be done using a pump and, if it were done to the general drainage network, an odorless closing device (normally a siphon) would have to be used to prevent odors from the network from reaching the inhabited spaces.
The power emitted by the fan coil units can be regulated by varying the fan speed. Some manufacturers achieve speed control by adjusting the taps of an AC transformer that supplies power to the fan motor. This would typically require an adjustment at the commissioning stage of the building construction process and is therefore set for life. Other manufacturers provide custom wound permanent split capacitor (PSC) motors with speed taps on the windings, set to the desired speed levels for the fan coil design. This can be done through a manual speed selector (stop-low-medium-high) that can be controlled by the user, or through automatic systems regulated by a room thermostat.
Speed control of the fan motors within a fan coil unit is effectively used to control the desired heating and cooling output of the unit. A simple speed selector switch (off/high/medium/low) is provided for the local room occupant to control the fan speed. Typically, this speed selector switch is built into the room thermostat and is manually adjusted or automatically controlled by the digital room thermostat. Building energy management systems can be used for automatic control of fan speed and temperature. Fan motors are usually shaded pole AC or permanent split capacitors. Among the most recent developments are electronically commutated brushless direct current designs. While these motors offer significant energy savings, the initial cost and return on investment must be carefully considered.
EC/DC motor powered fan coil units
These motors are sometimes called DC motors, sometimes EC motors, and sometimes EC/DC motors ("DC" means 'direct current' and 'EC' means 'electronically commutated').
Direct current motors allow the speed of the fans within a fan coil unit to be controlled by means of a 0-10 volt input "signal" to the motor (or motors); In this case, the transformers and speed switches associated with AC fan coil units are not required. Up to a signal voltage of 2.5 volts (which may vary depending on different fan/motor manufacturers), the fan will be in a stopped condition, but as the signal voltage increases, the fan will increase its speed without any problem until reaching its maximum speed at a signal voltage of 10 volts. Fan coils will generally operate between about 4 and 7.5 volts, because, below 4 volts, air volumes are ineffective, and, above 7.5 volts, the fan coil is likely to be too noisy for most commercial applications.
The 0-10 volt signal voltage can be set using a simple potentiometer or sent to the fan motors via the terminal controller on each of the fan coil units. The first is very simple and economical, but the second opens up the possibility of continuously modifying the fan speed depending on various external influences or conditions. These external influences or conditions could be “real-time” heating or cooling demand, occupancy levels, window switches, time clocks, or any number of other inputs to the unit itself, the building management system, or both.
The reason why, despite their apparent relative complexity, these direct current fan coil units are becoming more popular is because of their improved levels of energy efficiency compared to their AC motor-driven counterparts from just a few years ago. A direct switch from alternating current to direct current will reduce electrical consumption by 50%, and the application of demand- and occupancy-dependent fan speed control can take savings up to 80%. In areas of the world where there are legal energy efficiency requirements for fan coil units (such as in the UK), direct current fan coil units are quickly becoming the only option.
Spaces where it is used
The fan coil unit is an excellent solution for all-water air conditioning in large residential buildings and commercial premises. In these cases, the device is mounted on the false ceiling of the toilets or hallways (they usually require less headroom) and recirculates the air in the air-conditioned rooms, with the possibility of turning it off in unused rooms or areas at certain times, to save energy.
A variant of fan coil units, simplified to the maximum, called heater or aerotherm, is used as an economical installation in warehouses, hallways and even in large sports halls.
Facility
In high-rise residential construction, each fan coil generally requires a rectangular penetration into the concrete slab on which it sits. There are usually 2 or 4 ABS, steel or copper tubes running through the floor. The pipes are usually insulated with cooling insulation, such as flexible acrylonitrile butadiene/polyvinyl chloride (AB/PVC, Rubatex or Armaflex brands) foam in all pipes or at least in the cold lines.
Fan coil unit with outside air
This variant is mainly used in classrooms, hotels, apartments and tenement houses. The difference is that it is connected to the outside through a duct, so that it can introduce air for ventilation, which it conditions before blowing it into the room it serves. This solves one of the most important problems of many fan coil installations, ventilation.
The European market
The fan coil unit is composed of a quarter of 2-pipe units and three-quarters of 4-pipe units, and the best-selling products are “with casing” (35%), “without casing” (28%), “cassette” (18%) and “ducted” (16%).[2].
In 2010, the European market by country was divided as follows:
References
[1] ↑ Véase el manual de la ASHRAE «2008 Systems & Equipment», capítulo 12 (en inglés).