UNDERFLOOR HEATING SYSTEMS
Underfloor heating systems are modern, comfortable, and energy-efficient heating solutions in which heat energy is distributed homogeneously into the space from beneath the floor. While heat is emitted from specific points in traditional radiator systems, in underfloor heating systems the entire floor surface operates like a large low-temperature heating surface. In this way, a more balanced temperature distribution is achieved in the space, air movement is reduced, and user comfort is increased.
Underfloor heating systems are generally divided into two main groups:
Water-based underfloor heating systems
Electric underfloor heating systems
The operating principle, equipment used, energy source, application area, and operating costs of these two systems are different from each other. Water-based underfloor heating systems are generally preferred in large areas, residences, villas, hotels, hospitals, and commercial buildings, while electric underfloor heating systems are mostly used in bathrooms, kitchens, small-volume areas, renovation projects, and local heating applications.
WATER-BASED UNDERFLOOR HEATING SYSTEMS
Water-based underfloor heating systems are high-efficiency heating systems that operate by circulating hot water through pipes installed beneath the floor. The system is generally supplied by a condensing boiler, heat pump, solar-assisted system, or central heating source. Thanks to its low-temperature operation, its energy efficiency is quite high.
In water-based underfloor heating systems, the water temperature is generally selected between 35°C and 45°C. This value is quite low compared to radiator systems. While radiator systems may require 60°C-75°C hot water, low temperature is sufficient in underfloor heating. Therefore, it operates very compatibly with condensing boilers and heat pumps.
Basic heat load calculation: Q = U × A × ΔT
Here; Q = Heat loss or heating demand (W) U = Heat transfer coefficient (W/m²K) A = Area (m²) ΔT = Indoor and outdoor temperature difference (K)
For example, if the unit heating demand of a 40 m² space is 80 W/m²: Q = 40 × 80 = 3.200 W
In this case, approximately 3,2 kW heating capacity is required for the relevant space. Pipe spacing, water temperature, floor covering, screed thickness, and space heat loss should be determined according to this capacity.
WATER-BASED UNDERFLOOR HEATING PIPES
One of the most important components of water-based underfloor heating systems is the underfloor heating pipes. These pipes are generally selected from PEX-A, PEX-B, PE-RT, or oxygen-barrier multilayer pipes. The oxygen barrier prevents oxygen from entering the system water, reducing the risk of corrosion in the pump, manifold, boiler heat exchanger, and metal connection elements. Underfloor heating pipes must be resistant to high temperature, pressure, and mechanical stresses.
Pipe diameters are generally preferred as 16×2 mm, 17×2 mm, or 20×2 mm. Pipe installation spacings may be 10 cm, 15 cm, or 20 cm depending on the heat loss of the space. Pipe spacing is reduced along external wall edges and in areas with high heat loss. Circuit lengths should not be too long; otherwise, pressure loss increases and hydraulic balancing becomes difficult. In practice, it is recommended that a single circuit should not exceed 80-100 meters.
MANIFOLD GROUP
The manifold group is the main distribution equipment that enables hot water to be distributed to different underfloor heating circuits. Hot water coming from the boiler or heat pump is divided into rooms or zones through the manifold. The flow rate of each circuit can be adjusted separately. In this way, the system is hydraulically balanced and each space receives the amount of heat it requires.
Modern underfloor heating manifolds include flow meters, valves, air vents, drain valves, thermometers, and actuator connection points. Thanks to flow meters, the amount of water passing through each circuit can be monitored. According to signals from room thermostats, electrothermal actuators open and close the circuits. Thus, room-based temperature control is achieved. When selecting a manifold, the number of circuits, total flow rate, pressure loss, connection diameters, and control system should be taken into consideration.
THERMAL INSULATION BOARD
The thermal insulation board is an important application element used in underfloor heating systems to reduce heat losses that may occur downward. Thanks to EPS, XPS, or special studded underfloor heating boards placed under the pipes, heat energy is directed to the living area above instead of escaping to the lower floor or ground. This increases system efficiency and reduces fuel consumption.
The insulation thickness is determined according to the floor structure of the building, the temperature condition of the space below, and energy performance targets. Higher insulation thickness should be preferred for floors in contact with the ground or above unheated spaces. If thermal insulation is not sufficient, the system heats up more slowly, energy consumption increases, and the floor surface temperature may not reach the desired level. Therefore, in underfloor heating projects, insulation board selection is at least as important as pipe selection.
ROOM THERMOSTAT AND CONTROL SYSTEM
Room thermostats are automation components that control the room temperature in underfloor heating systems. Since the temperature demand of each room may be different, zone control provides a major advantage. The thermostat measures the room temperature and opens or closes the actuators on the manifold according to the specified set value. In this way, unnecessary energy consumption is prevented.
Smart thermostats can offer functions such as weekly programming, remote control, night mode, holiday mode, and energy monitoring. Especially in large residences, villas, and commercial buildings, room-based control significantly reduces operating costs. Since underfloor heating systems are slow-response systems, the control strategy must be established correctly. Stable and balanced operation should be preferred instead of sudden temperature changes.
CIRCULATION PUMP
The circulation pump is the equipment that enables hot water to circulate through the underfloor heating circuits. When selecting a pump, total flow rate, circuit pressure losses, manifold losses, pipe lengths, and mixing valve losses should be taken into consideration. An incorrectly selected pump may cause insufficient flow in the system, noise, uneven heating, or unnecessary electricity consumption.
The following formula can be used in total flow rate calculation: Qsu = P / (1,16 × ΔT)
Here; Qsu = Water flow rate (m³/h) P = Heating capacity (kW) ΔT = Supply-return water temperature difference (°C)
For example, if ΔT = 10°C is taken in a system with a capacity of 20 kW: Qsu = 20 / (1,16 × 10) = 1,72 m³/h
This value gives the approximate total water flow rate of the system. The pump should be selected to meet this flow rate and overcome the system pressure losses.
MIXING VALVE AND LOW TEMPERATURE CONTROL
Since underfloor heating systems operate at low temperature, a mixing valve must be used in some applications. Especially in systems where the boiler water temperature is high, the temperature of the water to be sent under the floor must be reduced. The mixing valve mixes the hot supply water with the return water, ensuring that water at a suitable temperature is sent to the underfloor heating circuits.
This equipment is important for controlling the floor surface temperature. Excessively high water temperature may cause uncomfortable surface temperature on the floor, deformation in parquet or wooden coverings, and energy loss. Therefore, water temperature control must be carried out correctly in underfloor heating systems. Especially in hybrid installations where a condensing boiler and radiator system are used together, the mixing valve is an important balancing element.
ELECTRIC UNDERFLOOR HEATING SYSTEMS
Electric underfloor heating systems are systems that operate with heating cables, heating mats, or carbon film elements installed beneath the floor. There is no hot water circulation in these systems. Electrical energy is converted directly into heat energy and transferred to the floor. They offer a fast and practical solution especially in small areas, bathrooms, kitchens, entrance halls, office sections, and renovation projects.
Electric underfloor heating systems are easier to install compared to water-based systems. They do not require a boiler, manifold, pump, or pipe installation. However, since the unit cost of electricity is high, using them as a continuous main heating system in large areas may not be economical. They are mostly preferred for comfort heating or regional heating purposes.
In electric systems, capacity calculation is generally made based on power per square meter: Ptoplam = A × Pm²
Here; Ptoplam = Total power demand (W) A = Area to be heated (m²) Pm² = Unit area power (W/m²)
For example, if 150 W/m² power is selected for an 8 m² bathroom: Ptoplam = 8 × 150 = 1.200 W
In this case, approximately 1,2 kW electrical power is required for the system.
ELECTRIC HEATING CABLES
Electric heating cables are the main heat generation elements of electric underfloor heating systems. These cables consist of special resistance wires and convert electrical energy into heat energy. The cables can be installed inside the screed, under ceramic tiles, or on special application boards. Cable spacing is determined according to the desired surface temperature and the target heating power per square meter.
In electric heating cables, power is generally expressed in W/m. Cable length and installation spacing must be calculated correctly. Incorrect cable spacing may cause local overheating on the floor or insufficient heating problems. Direct drilling, cutting, or heavy mechanical intervention must not be carried out over heating cables. Therefore, furniture layout, fixed cabinet areas, and sanitaryware positions should be taken into consideration before application.
HEATING MAT SYSTEMS
Heating mat systems are ready-to-install products in which electric heating cables are fixed onto a mesh at specific intervals. They offer practical installation especially under ceramic, granite, marble, or natural stone floor coverings. Mat systems are laid in rolls and significantly shorten the installation time.
These systems are generally used in bathrooms, kitchens, corridors, and small commercial areas. Thanks to their thin structure, they can be applied in renovation projects without significantly increasing the floor level. When selecting a heating mat, the area size, unit power value, floor covering type, and thermostat control type should be taken into consideration. Electric underfloor heating mats provide comfort temperature in a short time thanks to their fast response time. However, they must be used together with a thermostat with a floor sensor in order to keep energy consumption under control.
FLOOR SENSOR AND THERMOSTAT
In electric underfloor heating systems, the thermostat and floor sensor are critically important for safe and efficient operation. The thermostat switches the system on and off by measuring the room temperature or floor temperature. The floor sensor prevents the floor surface temperature from exceeding the specified limits. This is especially important for wood, laminate parquet, and sensitive floor coverings.
Thanks to programmable thermostats, the system can be operated only during the hours when it is needed. This reduces energy consumption. In bathrooms, programming can be arranged according to morning and evening usage hours. Since uncontrolled operation in electric systems may cause high electricity bills, thermostat selection is very important. Smart Wi-Fi thermostats provide remote control capability, increasing user comfort and energy management.
ELECTRIC UNDERFLOOR HEATING INSULATION BOARD
In electric underfloor heating systems, the insulation board prevents heat from escaping downward and ensures that it reaches the surface faster. Especially in applications on reinforced concrete floors or above unheated spaces, if an insulation board is not used, the system response time becomes longer and energy consumption increases.
Thin insulation boards provide a major advantage in renovation applications. These boards both reduce heat loss and create a smooth surface for under-ceramic applications. For an electric underfloor heating system to operate efficiently, suitable thermal insulation must be placed under the heating cable or mat. In this way, comfort temperature is achieved faster with lower electricity consumption.
ADVANTAGES OF UNDERFLOOR HEATING SYSTEMS
Underfloor heating systems provide high comfort thanks to homogeneous temperature distribution. Since heat is emitted from the floor, a warmer environment is created at foot level and a more balanced environment is created at head level. This temperature profile is considered ideal for the human body. Hot-cold zones and air currents seen in radiator systems are at a minimum level in underfloor heating.
Thanks to low-temperature operation, energy efficiency is high. Especially when water-based underfloor heating systems are used together with condensing boilers and heat pumps, operating costs are reduced. The absence of radiators on the walls provides architectural freedom. Since dust circulation is lower, it is advantageous for users with allergic sensitivity. It is frequently preferred in modern buildings due to its quiet operation, long service life, and low maintenance requirement.
APPLICATION AREAS OF UNDERFLOOR HEATING SYSTEMS
Underfloor heating systems are widely used in residences, villas, residential complexes, hotels, hospitals, schools, mosques, sports halls, shopping malls, offices, showrooms, and industrial facilities. While water-based underfloor heating systems offer a more economical solution in large areas and continuously used buildings, electric underfloor heating systems are preferred in small areas and local comfort heating.
Electric systems provide the advantage of rapid heating in bathrooms, kitchens, and ceramic-covered areas. Water-based underfloor heating systems are more commonly preferred in villas, luxury residences, and energy-efficient buildings. Since they operate compatibly with heat pumps, solar energy, and condensing boilers, they have an important place in sustainable building designs.
HEATING SYSTEMS WITH RADIATORS
Heating systems with radiators are one of the most common central heating systems based on the principle of transferring heat energy in buildings to radiators through hot water and then transferring it to the indoor environment. They have been used safely for many years in residences, villas, apartments, hotels, hospitals, schools, offices, and commercial buildings. The system operates on the basis of delivering hot water produced at the heat source to the radiators through the piping installation and distributing heat from the radiator surfaces to the space.
In radiator heating systems, heat transfer occurs through both radiation and natural convection. While the heat emitted from the radiator surface increases the room temperature, the heated air is distributed throughout the entire space through the air movement formed around the radiator. A properly designed radiator system provides high comfort, reliable operation, and long service life.
OPERATING PRINCIPLE OF HEATING SYSTEMS WITH RADIATORS
In radiator systems, hot water produced by a boiler, condensing boiler, central boiler room, or heat pump is sent to the radiators by means of a circulation pump. The hot water circulating inside the radiator transfers heat energy to the environment through metal surfaces.
The cooled water is sent back to the boiler through the return line and is reheated, creating a continuous cycle within the system. Thanks to this cycle, spaces are kept at the desired temperature. In system design, water temperatures, flow rates, pressure losses, and space heat losses are taken into consideration.
EQUIPMENT USED IN RADIATOR SYSTEMS
RADIATOR TYPES
Radiators are terminal heating elements that enable heat energy to be transferred to the environment through hot water. Today, radiators are produced in different types, including panel radiators, aluminum radiators, cast iron radiators, and towel radiators. When selecting a radiator, the heat loss of the space, operating temperatures, architectural structure, aesthetic expectations, and system type should be taken into consideration. A correctly selected radiator increases energy efficiency while also improving user comfort.
PANEL RADIATORS
Panel radiators are the most widely used radiator type today. These radiators, manufactured from DKP steel sheets, have a wide range of applications from residences to commercial buildings thanks to their high heat transfer capacity, economical cost, and long-lasting structure. Panel radiators are manufactured in accordance with the EN 442 standard and are offered to the market in different heights, lengths, and numbers of panels.
TYPE 10 PANEL RADIATOR
Type 10 panel radiators consist of a single panel and do not have convector fins. Thanks to their slim structure, they provide an advantage in narrow spaces. Their heat output is lower compared to other panel radiator types. They are generally preferred in spaces with low heating demand or in decorative applications. They are easy to clean and can be used in modern architectural projects due to their compact structure. TYPE 11 PANEL RADIATOR
Type 11 panel radiators consist of a single panel and a single row of convector fins. Thanks to the convector fins, they provide higher capacity compared to Type 10 radiators. They are one of the most commonly preferred radiator types in residential projects. Thanks to their low depth, they can be easily applied under windows and in narrow spaces. They have a wide range of use due to their economical price and sufficient capacity.
TYPE 21 PANEL RADIATOR
Type 21 panel radiators include two panels and a single row of convector fins. Thanks to this structure, higher heat output is achieved. They are especially preferred in medium-sized rooms and spaces with high heat loss. They provide efficient heat transfer by using convection and radiation effects together. It is a highly successful radiator type in terms of energy efficiency. TYPE 22 PANEL RADIATOR
Type 22 panel radiators consist of two panels and two rows of convector fins. They are considered the most widely used panel radiator type in Turkey. Thanks to their high capacity, they are preferred in both residential and commercial buildings. They operate compatibly with condensing combi boilers and central heating systems. Since they offer an optimum solution in terms of heat output, cost, and size, they are considered the standard radiator type in the HVAC sector.
TYPE 33 PANEL RADIATOR
Type 33 panel radiators consist of three panels and three rows of convector fins. They are among the models with the highest capacity among panel radiators. They are used in large-volume areas with high heat loss. They are especially preferred in large living rooms, commercial areas, and spaces with high ceilings. Although they provide high capacity, their application area is determined according to project requirements because they occupy more space.
ALUMINUM RADIATORS
Aluminum radiators stand out with their lightweight structure, high thermal conductivity coefficients, and modern designs. Thanks to the high thermal conductivity of aluminum, they heat up very quickly and respond rapidly. This feature contributes to energy savings. Due to their modular structure, section addition or removal operations can be carried out easily.
Aluminum radiators are especially preferred in modern residential projects, villas, and decorative applications. Their corrosion resistance is high, and they provide an architectural advantage thanks to their aesthetic appearance. Their operation with low water volume enables the system to respond faster. They can operate compatibly with heat pumps and low-temperature systems.
CAST IRON RADIATORS
Cast iron radiators are among the oldest and most durable examples of traditional radiator systems. Thanks to their high thermal mass, they heat up slowly but can remain hot for a long time. This feature reduces temperature fluctuations and provides stable comfort.
They are frequently preferred in historical buildings, restoration projects, and buildings with classical architecture. Due to their heavy structure, their installation is more difficult, but their service life is quite long. Today, cast iron radiators have become popular again with decorative designs.
TOWEL RADIATORS (TOWEL WARMERS)
Towel radiators are special radiator systems used especially in bathrooms and wet areas. They provide both space heating and drying of towels and bathrobes. Thanks to this dual-function structure, they are among the indispensable equipment of modern bathrooms.
Towel radiators, which can be manufactured from steel, stainless steel, and aluminum materials, have different size and capacity options. They can operate compatibly with central systems, combi boiler systems, and heat pump applications. Models with added electric resistance can be used independently throughout the year. Thanks to their aesthetic designs, high corrosion resistance, and functional usage features, they are widely preferred in residences, hotels, hospitals, and commercial buildings.
THERMOSTATIC RADIATOR VALVE
Thermostatic radiator valves are energy-saving components that automatically control the room temperature. When the ambient temperature rises, they reduce the amount of hot water entering the radiator and prevent unnecessary energy consumption.
These valves provide significant energy savings, especially in individual combi boiler systems and central systems. With the use of thermostatic valves, fuel consumption savings between 15% and 25% can be achieved.
CIRCULATION PUMP
The circulation pump is the equipment that enables the system water to circulate between radiators. When selecting a pump, total flow rate, system pressure losses, pipe lengths, and building height are taken into consideration.
New-generation pumps with variable speed control reduce energy consumption and enable the system to operate more efficiently. Incorrect pump selection may cause insufficient heating, noise, and high energy consumption.
EXPANSION TANK
The expansion tank is used to compensate for the volume increase caused by the expansion of system water due to temperature. Closed expansion tanks are the most commonly used type today.
If an expansion tank is not used, the system pressure may rise excessively, causing safety valves to open or damage to the installation. Therefore, every hot water installation must include an expansion tank with a suitable volume.
COMBI BOILERS AND CONDENSING BOILERS
Condensing combi boilers and condensing boilers are among the most important heat sources of radiator systems. These devices achieve high efficiency by recovering the latent heat in the flue gas generated as a result of natural gas combustion.
Modern condensing devices can provide efficiency above 90% and offer environmentally friendly operation with low emission values. Condensing efficiency is higher especially in low-temperature radiator systems.
RADIATOR CALCULATIONS
In radiator systems, the heat loss of the space is first calculated.
Basic heat loss formula:
Q=U\times A\times \Delta T
Here;
• Q = Heat loss (W) • U = Heat transfer coefficient (W/m²K) • A = Area (m²) • ΔT = Indoor and outdoor ambient temperature difference (K)
For example;
If the heating demand of a 30 m² living room is calculated as 100 W/m²:
Total Heating Demand = 30 × 100 = 3.000 W
In this case, the total radiator capacity must be at least 3 kW.
The following formula is used for system flow rate calculation:
Q_{su}=\frac{P}{1.16\times \Delta T}
Here;
• Qsu = Water flow rate (m³/h) • P = Heating capacity (kW) • ΔT = Supply-return temperature difference (°C)
These calculations are used in pump and pipe diameter selections.
ADVANTAGES OF HEATING SYSTEMS WITH RADIATORS
Radiator systems offer economical solutions in terms of investment cost. Their installation is easy, and maintenance operations are quite practical. In case of system failures, intervention is easy. In addition, they respond faster than underfloor heating systems and enable the space to heat up in a short time.
Radiator systems can operate compatibly with different heat sources. They can be integrated with condensing boilers, central systems, heat pumps, and hybrid energy systems. This flexibility allows the system to be applied in different building types.
Thanks to thermostatic valve and room thermostat applications, energy efficiency can be increased and fuel costs can be reduced. A properly designed radiator system can provide an economic service life of more than 25 years.
APPLICATION AREAS OF HEATING SYSTEMS WITH RADIATORS
Radiator heating systems are widely used in residences, apartments, villas, offices, schools, hospitals, hotels, public buildings, factories, and commercial buildings. They are especially preferred in renovation projects in existing buildings due to ease of application.
In cold climate regions, they offer effective solutions thanks to their advantage of operating at high temperatures. In addition, when used together with condensing boiler systems, they create an energy-efficient and economical heating alternative. Today, they continue to be one of the most common systems in central heating and individual heating applications.
HEATING SYSTEMS WITH FAN COILS
Heating systems with fan coils are modern air conditioning systems that operate on the principle of passing hot water through a coil and transferring it to the room air with the help of a fan. Since fan coil units can provide both heating and cooling, they are widely used today in hotels, hospitals, residences, office buildings, shopping malls, and commercial buildings.
In traditional radiator systems, heat transfer occurs through natural convection, while in fan coil systems heat transfer takes place much faster because fan assistance is used. In this way, the room temperature can reach the desired level in a short time. In addition, independent control of each space increases user comfort and energy efficiency.
Fan coil systems are generally used together with central boiler systems, condensing boilers, chiller systems, and heat pumps. The ability to provide both cooling in summer and heating in winter through the same system is one of their important advantages.
OPERATING PRINCIPLE OF FAN COIL SYSTEMS
Fan coil units operate by circulating hot water or cold water through the coils inside the device. The fan inside the device draws in room air, passes it over the coil, and blows the conditioned air back into the space.
In winter, the space is heated by passing hot water through the coil, while in summer the space is cooled with cold water coming from the chiller or heat pump. Therefore, fan coil systems are among the air conditioning solutions that can be used in all four seasons.
Fan speed can be adjusted manually or automatically, and the room temperature can be controlled precisely with the help of room thermostats.
EQUIPMENT USED IN FANCOIL SYSTEMS
FANCOIL UNIT
The fancoil unit is the main equipment of fan-coil systems and is the terminal unit that provides heating and cooling of the space. The unit includes a fan group, coil (heat exchanger battery), air filter, drain pan, and control equipment. The room air drawn in by the fan is passed over the coil, conditioned, and supplied back to the space. Fancoil units can be produced as cassette type, duct type, wall type, and floor type. In capacity selection, the heating and cooling loads of the space, air flow rate, sound level, static pressure, and purpose of use are taken into consideration. A correctly selected fancoil unit provides high comfort, low energy consumption, and long service life.
COIL (BATTERY)
The coil is the most important component that performs heat transfer in the fan-coil unit. Coils, generally manufactured from copper tubes and aluminum fins, transfer the energy carried by hot or cold water to the air stream. In heating mode, while hot water passes through the coil, the room air is heated; in cooling mode, the air temperature is reduced with the help of cold water. Coil performance varies depending on tube diameter, tube row, fin density, air flow rate, and water temperature. High-efficiency coils increase system efficiency by providing higher capacity with lower energy consumption.
FAN MOTOR
The fan motor is the equipment that enables room air to pass over the coil. Fans used in fancoil systems are generally designed to operate at low sound levels and provide high efficiency. Today, in addition to fans with AC motors, energy-saving fans with EC motors are also widely used. Fan motors can be operated at different speed stages to provide capacity control according to the room temperature. Since fan performance directly affects the air flow rate and therefore the unit capacity, flow rate, static pressure, energy consumption, and acoustic performance criteria should be taken into consideration during the selection stage.
AIR FILTER
Air filters are one of the important components that protect the indoor air quality of fancoil units. Dust, pollen, fibers, and other particles in the room air are captured by the filter, thus preventing contamination of the coil surface. Clean coil surfaces provide higher heat transfer performance and also reduce energy consumption. In fancoil units, washable filters of G2, G3, or G4 class are generally used. Regular cleaning or replacement of filters is of great importance for maintaining unit capacity. Unmaintained filters can reduce air flow rate and negatively affect both comfort and energy efficiency.
ROOM THERMOSTAT
The room thermostat is automation equipment that controls the room temperature in fan-coil systems. It manages the operation of the unit according to the temperature value set by the user. Modern thermostats can automatically adjust fan speeds, control motorized valves, and optimize energy consumption. Programmable models allow daily and weekly operating scenarios to be created. Thermostats that can operate integrated with smart building automation systems provide remote access and energy management capability. A correctly used room thermostat significantly increases user comfort while reducing energy consumption.
MOTORIZED VALVE
Motorized valves are equipment that control the amount of hot or cold water entering the coil. They open and close according to signals from the room thermostat, enabling the unit capacity to be adjusted automatically. Motorized valves, which can be produced in two-way and three-way types, are of great importance in terms of energy efficiency. They prevent unnecessary water circulation, reduce pump loads, and increase system efficiency. Especially in large projects, they provide central control capability by operating integrated with building automation systems. They are considered one of the most important control elements that provide energy savings in modern HVAC systems.
CASSETTE TYPE FANCOIL
Cassette type fancoils are units mounted inside the suspended ceiling and capable of distributing air in four directions. They are widely used in offices, hotels, meeting rooms, and commercial buildings because they provide homogeneous air distribution. Since the visible part consists only of the decorative front panel, they provide an aesthetically pleasing architectural appearance. Thanks to their wide air discharge area, they minimize temperature differences. Cassette type units are produced in different capacity options and are preferred in projects requiring high comfort.
DUCT TYPE FANCOIL
Duct type fancoils are concealed-mounted units that can supply one or more spaces through air ducts. Since they are located inside the suspended ceiling, they do not affect the architectural appearance. They are especially preferred in luxury residences, hotels, offices, and prestigious projects. Thanks to duct connections, air distribution can be carried out in a more controlled manner, and different spaces can be supplied from the same unit. They are considered the most preferred fancoil type in projects with high aesthetic expectations.
WALL TYPE FANCOIL
Wall type fancoils are preferred in small and medium-scale applications thanks to their compact structure and easy installation features. These wall-mounted units can provide heating and cooling quickly. Especially in renovation projects, their ability to be applied without requiring ductwork provides an important advantage. Thanks to their modern designs, they offer an aesthetic appearance in living spaces and also stand out with their energy-efficient operation features.
FLOOR TYPE FANCOIL
Floor type fancoils have a radiator-like appearance and are generally used in front of windows or along wall bases. Their heating performance is quite high and their installation is easy. They are especially preferred to reduce the cold air effect that may occur in spaces with large glass surfaces. Floor type units can be easily applied in both new projects and existing buildings. Thanks to their low sound level and high capacity features, they increase user comfort.
2-PIPE FANCOIL SYSTEMS
In 2-pipe systems, hot or cold water is circulated through the same piping installation depending on the season. In winter, the entire system operates in heating mode, while in summer the entire system operates in cooling mode.
Since their initial investment costs are lower, they are frequently preferred in residential projects and small commercial buildings.
4-PIPE FANCOIL SYSTEMS
In 4-pipe systems, hot water and cold water lines are separate from each other. In this way, both heating and cooling can be provided at the same time in different spaces.
They are preferred in hotels, hospitals, and large office projects because they provide high comfort. Although the initial investment cost is higher, their operating flexibility is quite high.
FANCOIL CALCULATIONS
In fancoil selection, the heating and cooling loads of the space are calculated first.
Basic heat load calculation:
Q=U\times A\times \Delta T
Here;
• Q = Heat load (W) • U = Heat transfer coefficient (W/m²K) • A = Area (m²) • ΔT = Temperature difference (K)
For water flow rate calculation:
Q_{su}=\frac{P}{1.16\times\Delta T}
Here;
• Qsu = Water flow rate (m³/h) • P = Capacity (kW) • ΔT = Water temperature difference (°C)
These calculations are used in unit selection, pump selection, and pipe diameter determination.
ADVANTAGES OF HEATING SYSTEMS WITH FANCOILS
Fancoil systems provide fast heating and cooling capacity. The ability to control temperature on a room basis increases energy efficiency. The ability to provide both heating and cooling through the same system optimizes investment costs.
Since they can operate with low-temperature water, they provide high efficiency with heat pumps and condensing boilers. They also offer architectural flexibility and can be applied to all types of projects thanks to different capacity options.
APPLICATION AREAS OF HEATING SYSTEMS WITH FANCOILS
Fan-coil systems are widely used in hotels, hospitals, residences, office buildings, shopping malls, educational buildings, public buildings, and commercial facilities. They are one of the most commonly used terminal units, especially in projects where central air conditioning systems are preferred.
Thanks to their high comfort level, independent room control, low energy consumption, and ability to provide both heating and cooling, they are among the indispensable equipment of modern HVAC systems.
HEATING SYSTEMS WITH AIR HANDLING UNITS
Heating systems with air handling units are systems in which air handling units, located within central ventilation and air conditioning systems, provide heating by producing hot air or distributing conditioned air into the space. In these systems, heat energy is transferred directly through air. They are widely used especially in shopping malls, hospitals, hotels, airports, factories, business centers, educational buildings, and large commercial facilities.
Air handling units are not used only for heating purposes; they can also perform many processes such as ventilation, filtration, humidification, dehumidification, cooling, and heat recovery within the same casing. For this reason, they are considered one of the most important pieces of equipment in modern HVAC systems. Their ability to provide central control, ensure high air quality, and create homogeneous temperature distribution in large volumes is among their most important advantages.
OPERATING PRINCIPLE OF HEATING SYSTEMS WITH AIR HANDLING UNITS
In air handling unit systems, fresh air taken from the outdoor environment and return air are mixed at certain ratios and taken into the unit. The air first passes through filters, then passes over the heating coil and reaches the desired temperature. The heated air is sent to the air ducts by fans and distributed into the space through grilles and diffusers.
The heating process can be performed using a hot water coil, steam coil, electric heating coil, or natural gas air heaters. In modern systems, hot water coils and heat pump-supported solutions are widely preferred. In this way, both energy efficiency is achieved and indoor comfort is increased.
EQUIPMENT USED IN AIR HANDLING UNITS
AIR HANDLING UNIT CASING
The air handling unit casing is the main structure that contains all the equipment of the unit. It is generally manufactured from aluminum profiles and double-skin sandwich panels. Rock wool or polyurethane insulation is used between the panels to reduce heat and sound losses. Mechanical strength, air tightness, and hygiene criteria are of great importance in casing design. In Eurovent-certified air handling units, high leakage classes and low thermal bridge values are targeted.
HEATING COIL
The heating coil is the equipment that provides heating of the air in the air handling unit. It is generally manufactured from copper tubes and aluminum fins. The air temperature is increased by means of hot water or steam passing through it. When determining coil capacity, air flow rate, inlet-outlet temperatures, water temperatures, and total heat load are taken into consideration. High-efficiency coils reduce energy consumption while increasing system performance.
CENTRIFUGAL OR PLUG FANS
Fans used in air handling units ensure that conditioned air is transported into the building through air ducts. Today, high-efficiency plug fans with EC motors are widely used. These fans provide low energy consumption, low sound level, and precise flow control. When selecting a fan, air flow rate, total static pressure, duct resistances, and filter losses are taken into consideration.
AIR FILTERS
Air filters capture dust, pollen, particles, and other pollutants in the air entering the air handling unit. The filtration system directly affects indoor air quality. In air handling units, G4, M5, M6, F7, F8, and HEPA filter classes are generally used. High-efficiency filter systems are especially preferred in hospitals, clean rooms, and pharmaceutical production facilities.
HEAT RECOVERY SYSTEMS
Heat recovery systems provide energy savings by recovering the energy in the exhausted air. Plate heat exchangers, rotary heat exchangers, and run-around coil systems are the most commonly used solutions. Thanks to heat recovery units, fresh air taken from the outdoor environment is preconditioned and operating costs are significantly reduced.
HUMIDIFICATION SYSTEMS
Humidification systems are used to prevent low relative humidity, especially during winter months. Steam humidifiers, ultrasonic humidifiers, and high-pressure humidification systems are widely used in air handling units. Humidity control is of great importance especially in hospitals, laboratories, data centers, and production facilities.
TYPES OF AIR HANDLING UNITS
HYGIENIC AIR HANDLING UNITS
Hygienic air handling units are specially designed for hospitals, operating rooms, pharmaceutical production facilities, and clean rooms. In these units, high air tightness, antibacterial surfaces, stainless steel equipment, and high-efficiency filter systems are used. Special designs that prevent dirt accumulation on internal surfaces are preferred.
COMFORT TYPE AIR HANDLING UNITS
Comfort type air handling units are used in shopping malls, offices, hotels, and commercial buildings. The purpose is to keep indoor temperature, humidity level, and air quality at the optimum level. Energy efficiency and user comfort are the primary priorities.
INDUSTRIAL AIR HANDLING UNITS
Industrial air handling units are designed for production facilities, factories, and process areas. These units stand out with their high air flow rates, high filtration capacity, and structures suitable for heavy operating conditions.
AIR HANDLING UNIT HEATING CALCULATIONS
When determining air handling unit capacity, the total heat load of the space is calculated.
Basic heat load calculation:
Q=U\times A\times \Delta T
Here;
• Q = Heat load (W) • U = Heat transfer coefficient (W/m²K) • A = Area (m²) • ΔT = Temperature difference (K)
For air flow rate calculation:
Q=1.2\times L\times \Delta T
Here;
• Q = Heating capacity (W) • L = Air flow rate (m³/s) • ΔT = Air temperature difference (°C)
These calculations are used in the selection of the air handling unit, fan, coil, and air duct.
ADVANTAGES OF HEATING SYSTEMS WITH AIR HANDLING UNITS
Heating systems with air handling units provide homogeneous temperature distribution in large volumes. Their ability to perform ventilation, filtration, humidity control, and heating at the same time provides an important advantage. Thanks to heat recovery systems, energy consumption is reduced and operating costs are lowered.
Thanks to central control capability, the entire building can be managed from a single point, and indoor air quality can be kept under continuous control. Especially in buildings with high human density, healthy and comfortable indoor conditions can be created.
APPLICATION AREAS OF HEATING SYSTEMS WITH AIR HANDLING UNITS
Heating systems with air handling units are widely used in shopping malls, hospitals, hotels, office buildings, airports, factories, production facilities, educational buildings, conference halls, and public buildings. They are among the indispensable solutions especially in projects with high fresh air demand.
Air handling units, one of the basic pieces of equipment of modern HVAC systems, are considered advanced central air conditioning systems that can provide energy efficiency, indoor air quality, and user comfort at the same time.
RADIANT HEATING SYSTEMS
Radiant heating systems are high-efficiency heating systems that operate on the principle of transferring heat energy directly to the environment through radiation. In traditional heating systems, air is heated first, while in radiant systems, people, machines, equipment, and surfaces are heated directly. In this way, energy losses are reduced and more comfortable heating is provided.
Radiant heating systems are widely used especially in high-ceiling spaces, factories, warehouses, sports halls, aircraft hangars, logistics centers, mosques, and large commercial buildings. In large-volume buildings, they provide significant energy savings because they heat the occupied areas directly instead of heating all the air.
Modern radiant heating systems can operate with natural gas, LPG, electricity, or hot water. Radiant systems, produced in different types according to the purpose of use, are considered among the most efficient heating solutions in industrial and commercial buildings today.
OPERATING PRINCIPLE OF RADIANT HEATING SYSTEMS
In radiant heating systems, heat energy is emitted in the form of electromagnetic radiation. The generated infrared energy reaches people, the floor, walls, machines, and other surfaces directly and performs heat transfer.
In these systems, objects and surfaces are heated first, not the air. The heated surfaces then transfer heat to the surrounding air. Thus, the accumulation of hot air at the ceiling is reduced and energy efficiency is increased. Especially in buildings with a ceiling height of 5 meters and above, radiant systems provide much more economical results compared to conventional hot air systems.
EQUIPMENT USED IN RADIANT HEATING SYSTEMS
RADIANT TUBE HEATERS
Radiant tube heaters are one of the most common radiant systems operating with natural gas or LPG. The flame generated by the burner inside the system heats special steel tubes. Thanks to the reflectors on the heated tubes, infrared energy is directed downward.
These systems are widely used in factories, warehouses, and sports halls because they provide high efficiency, low operating costs, and effective heating of large areas. Tube diameter, length, burner capacity, and reflector design directly affect system performance.
CERAMIC PLATE RADIANT HEATERS
Ceramic plate radiant heaters are high-temperature radiant devices used in gas-fired systems. The energy generated by the burner is transferred to special ceramic surfaces, and intense infrared radiation is obtained from these surfaces.
These systems are especially preferred in open areas, semi-open areas, restaurants, cafés, terraces, and applications requiring local heating. Thanks to their fast response time, they provide comfortable temperature in a short time. Due to their high radiation intensity, they provide highly successful results in heating specific areas.
ELECTRIC RADIANT HEATERS
Electric radiant heaters are systems that convert electrical energy directly into infrared energy. They operate using resistance elements or carbon technology. They are especially preferred in buildings where gas installation is not available.
Electric radiant systems offer advantages such as no maintenance requirement, silent operation, and easy installation. They are widely used in cafés, restaurants, balconies, showrooms, places of worship, and commercial areas. The ability to provide precise temperature control is one of their important advantages.
REFLECTORS
Reflectors are equipment that direct the energy generated in radiant systems to the desired area. They are manufactured from aluminum or stainless steel materials. The purpose of reflectors is to reduce energy losses and ensure that radiation reaches the usage area directly.
Reflector design significantly affects system efficiency. Thanks to high-quality reflectors, the energy utilization rate is increased and operating costs are reduced. In industrial applications, reflectors with a high reflection coefficient are preferred.
BURNER SYSTEMS
Burners used in gas-fired radiant systems are the main equipment that performs the combustion process. These systems operating with natural gas or LPG have high combustion efficiency. When selecting a burner, capacity, combustion efficiency, emission values, and safety criteria are taken into consideration.
Modern burners increase energy efficiency thanks to electronic ignition, flame control, and modulation features. Thanks to combustion control systems, fuel consumption is optimized and emission values are reduced.
TYPES OF RADIANT HEATING SYSTEMS
GAS-FIRED RADIANT HEATING SYSTEMS
Gas-fired radiant systems operate using natural gas or LPG. Due to their low operating costs, they are the most widely used radiant systems in industrial facilities. They provide high efficiency in large-volume areas and reduce energy costs.
ELECTRIC RADIANT HEATING SYSTEMS
Electric radiant systems are especially preferred in local heating applications. Easy installation, silent operation, and low maintenance requirements are among their important advantages. They offer effective solutions in small and medium-sized areas.
HOT WATER RADIANT PANEL SYSTEMS
In these systems, hot water is passed through a panel or pipe to provide heating by radiation. They are especially used in offices, sports halls, educational buildings, and commercial buildings. They can provide high efficiency with heat pumps and condensing boilers.
RADIANT HEATING CALCULATIONS
In radiant systems, the total heat loss of the space is determined when calculating capacity.
Basic heat load calculation:
Q=U\times A\times \Delta T
Here;
• Q = Heat loss (W) • U = Heat transfer coefficient (W/m²K) • A = Area (m²) • ΔT = Indoor and outdoor temperature difference (K)
Area-based quick calculation method:
Q=A\times q
Here;
• Q = Total capacity (W) • A = Area to be heated (m²) • q = Unit area heat demand (W/m²)
For example;
If the heating demand of a 1000 m² factory is 120 W/m²:
Q = 1000 × 120
Q = 120.000 W
Q = 120 kW
In this case, approximately 120 kW total radiant capacity is required.
ADVANTAGES OF RADIANT HEATING SYSTEMS
Radiant heating systems provide significant energy savings in buildings with high ceilings. Since they heat people and surfaces directly instead of heating the air, heat losses are reduced and comfort is achieved in a shorter time. Their performance is especially high in industrial facilities where doors are frequently opened and closed.
In these systems, energy loss is reduced because hot air does not accumulate at the ceiling. Low maintenance costs, fast heating times, and zone-based control options reduce operating costs. In addition, since they do not create air movement, they minimize dust circulation.
APPLICATION AREAS OF RADIANT HEATING SYSTEMS
Radiant heating systems are widely used in factories, production facilities, logistics centers, warehouses, sports halls, hangars, aircraft maintenance facilities, mosques, exhibition halls, shopping malls, restaurants, cafés, and outdoor applications.
Especially in high-ceiling volumes, they provide much more economical results compared to conventional hot air systems. Today, they have an important place among energy-efficient, low-operating-cost, and comfortable heating solutions.
NATURAL GAS-FIRED FAN HEATING SYSTEMS
Natural gas-fired fan heating systems are high-efficiency central or local heating systems that heat air using natural gas energy and distribute conditioned hot air into the space with the help of a fan. These systems are widely used in industrial facilities, factories, warehouses, sports halls, hangars, mosques, showrooms, and commercial buildings, especially because they provide rapid heating in large-volume areas.
In traditional radiator systems, first water, then radiator surfaces, and finally air are heated, while in natural gas-fired fan systems, air is heated directly. In this way, the ambient temperature rises in a much shorter time and user comfort is provided quickly. They offer important advantages especially in buildings with high air change rates, facilities with frequently opened and closed doors, and large-volume spaces.
Natural gas-fired fan heating systems are among the most preferred industrial heating systems today thanks to their low initial investment costs, fast installation features, and high capacity options.
OPERATING PRINCIPLE OF NATURAL GAS-FIRED FAN HEATING SYSTEMS
In natural gas-fired fan heating systems, heat energy is produced by burning natural gas with the help of the burner inside the unit. The energy generated as a result of combustion is passed over heat exchanger surfaces, and the air drawn by the fan is heated by means of these heat exchangers.
The heated air is sent directly to the space or to usage areas through air ducts by high-flow fans. The ambient temperature is continuously controlled with the help of thermostats and automation systems, and the unit capacity is automatically adjusted when needed.
In modern systems, fuel consumption is optimized, energy efficiency is increased, and operating costs are reduced by using modulating burners.
EQUIPMENT USED IN NATURAL GAS-FIRED FAN HEATING SYSTEMS
NATURAL GAS AIR HEATER UNIT
The natural gas air heater unit is the main equipment of the system. The unit includes a burner, heat exchanger, fan group, control panel, and safety equipment. The energy generated as a result of natural gas combustion is transferred to the heat exchanger surfaces, and the air is heated with the help of the fan and sent to the space.
These units can generally be manufactured from 20 kW up to capacities of hundreds of kW. When selecting capacity, building volume, heat loss, purpose of use, and air change rates are taken into consideration. Modern units provide high heating performance with low fuel consumption thanks to high-efficiency combustion technologies.
BURNER SYSTEM
The burner is the equipment that ensures controlled combustion of natural gas. The burner includes a gas valve, ignition electrode, flame control system, and combustion control elements. Modern burner systems have modulating operation capability and can automatically adjust the flame length according to the required capacity.
Thanks to this technology, unnecessary fuel consumption is prevented, unit efficiency is increased, and emission values are reduced. When selecting a burner, capacity, combustion efficiency, emission class, and safety criteria should be taken into consideration.
HEAT EXCHANGER
The heat exchanger is one of the most important components that transfers the energy generated as a result of combustion to the air. It is generally manufactured from high-temperature-resistant steel or stainless steel materials. While combustion gases circulate inside the heat exchanger, the air passed by the fan absorbs heat from these surfaces.
Heat exchanger efficiency directly affects the overall efficiency of the unit. High-quality heat exchangers provide greater heat transfer, reducing fuel consumption and increasing system performance.
FAN MOTOR
The fan motor is the equipment that enables the heated air to be transported to the space. Centrifugal or axial type fans can be used. When selecting a fan, air flow rate, static pressure, sound level, and energy consumption are taken into consideration.
High-efficiency fans with EC motors are widely preferred today. These motors provide low energy consumption and increase user comfort thanks to precise speed control.
AUTOMATION AND THERMOSTAT SYSTEMS
The automation system ensures that the unit operates safely and efficiently. The ambient temperature is continuously monitored by means of room thermostats, temperature sensors, and control panels. When the set temperature value is reached, the unit capacity is reduced or the system is stopped.
Modern automation systems can operate integrated with Building Management Systems (BMS) and provide remote monitoring capability. This feature facilitates energy management and reduces operating costs.
TYPES OF NATURAL GAS-FIRED FAN HEATING SYSTEMS
DIRECT-FIRED AIR HEATERS
In direct-fired systems, the hot air generated as a result of combustion is supplied directly to the space. These systems provide high efficiency, but they can only be used in areas where suitable ventilation conditions are available. They are especially preferred in industrial facilities and large-volume buildings.
INDIRECT-FIRED AIR HEATERS
In indirect-fired systems, combustion gases and room air do not mix with each other. Heat transfer is carried out through a heat exchanger. This is the most commonly used system type in spaces occupied by people. It provides safe use in hospitals, offices, sports halls, and commercial buildings.
DUCTED AIR HEATING SYSTEMS
In ducted systems, heated air is distributed to different spaces through air ducts. They are used as a central heating solution in large buildings. Ventilation and filtration processes can also be performed through the same system.
UNIT AIR HEATERS
Unit air heaters are compact units mounted directly inside the space. They are especially used in factories, warehouses, service areas, and logistics centers. They are widely preferred due to their ease of installation and low investment costs.
NATURAL GAS-FIRED FAN HEATING CALCULATIONS
In natural gas-fired fan heating systems, the total heat loss of the building or space is calculated first.
Basic heat load calculation:
Q=U\times A\times \Delta T
Here;
• Q = Heat loss (W) • U = Heat transfer coefficient (W/m²K) • A = Area (m²) • ΔT = Indoor and outdoor ambient temperature difference (K)
Air flow rate calculation:
L=\frac{Q}{1.2\times\Delta T}
Here;
• L = Air flow rate (m³/s) • Q = Heating capacity (W) • ΔT = Supply air temperature difference (°C)
Fuel consumption calculation:
V=\frac{Q}{\eta\times H_u}
Here;
• V = Natural gas consumption (m³/h) • Q = Heating capacity (kW) • η = System efficiency • Hu = Lower heating value of natural gas (kWh/m³)
These calculations are used to determine unit capacity, air flow rate, duct dimensions, and operating costs.
ADVANTAGES OF NATURAL GAS-FIRED FAN HEATING SYSTEMS
Natural gas-fired fan heating systems can heat the space very quickly and provide effective solutions in large-volume buildings. Since they do not require a water installation, initial investment costs are reduced and installation times are shortened. In addition, fuel consumption is optimized thanks to high-efficiency burner technologies.
These systems provide homogeneous temperature distribution in large areas, maintenance operations can be carried out easily, and capacity can be increased when required. They offer energy-efficient and economical solutions, especially in industrial buildings.
APPLICATION AREAS OF NATURAL GAS-FIRED FAN HEATING SYSTEMS
Natural gas-fired fan heating systems are widely used in factories, production facilities, warehouses, logistics centers, hangars, sports halls, mosques, service stations, showrooms, commercial buildings, and large-volume industrial areas.
They are among the most efficient solutions especially in buildings with high ceilings, structures with intense air circulation, and facilities requiring rapid heating. Thanks to their low investment costs and high performance, they are considered an indispensable part of industrial heating systems today.
HEATING SYSTEMS WITH UNIT HEATERS
Heating systems with unit heaters are high-efficiency industrial heating systems that operate on the principle of circulating hot water, high-temperature water, or steam energy through a coil and transferring it to the room air with the help of a fan. Unit heaters are widely used especially in high-ceiling spaces, large enclosed areas, and buildings requiring rapid heating.
These systems are preferred in factories, production facilities, warehouses, logistics centers, hangars, sports halls, workshops, service areas, mosques, and industrial facilities. Unit heaters continuously circulate the room air, providing homogeneous temperature distribution in a short time and allowing large volumes to be heated economically.
Today, thanks to high energy-efficiency EC motor fans, advanced automation systems, and high-performance coil technologies, unit heaters have become an important part of modern HVAC systems.
OPERATING PRINCIPLE OF UNIT HEATERS
In unit heaters, hot water, high-temperature water, or steam is sent into the coil. The room air drawn by the fan is heated by passing over the coil surfaces and is blown back into the space.
Thanks to this method, the ambient temperature rises in a short time and effective air circulation is provided in large areas. Especially in large-volume buildings, proper air direction and fan selection are of great importance in order to reduce the accumulation of hot air at the ceiling.
In modern systems, the room temperature is kept under continuous control by using room thermostats and automation equipment, and energy consumption is optimized.
EQUIPMENT USED IN UNIT HEATERS
UNIT HEATER CASING
The unit heater casing forms the main load-bearing structure of the device. It is generally manufactured from electrostatically painted galvanized steel sheets or stainless steel materials. The casing structure protects the fan, coil, and other equipment while also ensuring that the air flow is directed properly.
In unit heaters used in industrial environments, high mechanical strength, corrosion resistance, and long service life come to the forefront. The aerodynamic design of the casing increases the efficiency of the unit and reduces air flow losses.
HEATING COIL
The heating coil is the most important equipment that performs heat transfer in the unit. Coils are generally manufactured from copper tubes and aluminum fins. The energy of hot water, high-temperature water, or steam passing through the coil is transferred to the air passing through it by the fan.
Coil performance varies depending on tube diameter, tube row, fin density, air flow rate, and fluid temperature. High-efficiency coils provide higher capacity with lower energy consumption, reducing operating costs.
FAN MOTOR
The fan motor is the equipment that enables room air to pass over the coil. Axial fans are generally used in unit heaters. Fans blow air at high flow rates and provide homogeneous temperature distribution in large areas.
Thanks to modern EC motor technologies, energy consumption is reduced and fan speed control can be performed. In fan selection, air flow rate, sound level, throw distance, and energy consumption should be taken into consideration.
AIR DIRECTION BLADES
Air direction blades ensure that the hot air leaving the unit is directed to the desired areas. Thanks to their adjustable structure, the air flow can be directed at different angles.
This equipment is of great importance especially in high-ceiling buildings in terms of delivering hot air to the occupied area. Correct air direction increases energy efficiency and improves temperature distribution.
ROOM THERMOSTAT
Room thermostats continuously measure the room temperature and control the operation of the unit. When the set temperature value is reached, the unit is stopped or its capacity is reduced.
Thanks to programmable thermostats, energy savings are achieved and user comfort is increased. In large facilities, they can operate integrated with central building automation systems.
MOTORIZED VALVE
Motorized valves control the amount of hot water entering the coil. They open and close according to signals from the thermostat and automatically adjust the unit capacity.
In this way, unnecessary energy consumption is prevented and the system operates more economically. They provide significant advantages in terms of energy management, especially in facilities with a large number of unit heaters.
TYPES OF UNIT HEATERS
HOT WATER UNIT HEATERS
Hot water unit heaters are units that operate with hot water produced by central boiler systems or heat pumps. They are the most widely used unit heater type today. They have high energy efficiency and low operating costs.
They are widely used especially in factories, warehouses, and commercial buildings. When used together with heat pumps, they can provide high energy savings.
HIGH-TEMPERATURE WATER UNIT HEATERS
High-temperature water unit heaters are systems that operate with high-temperature water. They are preferred in large industrial facilities and areas with high heating demand.
They offer effective solutions in applications requiring high capacity. Pressure resistance and safety criteria are of great importance in system design.
STEAM UNIT HEATERS
Steam unit heaters are high-capacity heating systems that operate using steam energy. They are used in industrial facilities, production processes, and large-volume buildings.
Thanks to the high energy density of steam, high capacity can be achieved in a short time. They offer economical solutions especially in facilities where process steam is available.
UNIT HEATER CALCULATIONS
When selecting a unit heater, the total heat loss of the space is calculated first.
Basic heat loss calculation:
Q=U\times A\times \Delta T
Here;
• Q = Heat loss (W) • U = Heat transfer coefficient (W/m²K) • A = Area (m²) • ΔT = Indoor and outdoor temperature difference (K)
Air flow rate calculation:
L=\frac{Q}{1.2\times\Delta T}
Here;
• L = Air flow rate (m³/s) • Q = Heating capacity (W) • ΔT = Supply air temperature difference (°C)
Hot water flow rate calculation:
Q_{su}=\frac{P}{1.16\times\Delta T}
Here;
• Qsu = Water flow rate (m³/h) • P = Heating capacity (kW) • ΔT = Supply-return temperature difference (°C)
These calculations are used to determine unit heater capacity, coil selection, pump selection, and pipe diameters.
ADVANTAGES OF HEATING SYSTEMS WITH UNIT HEATERS
Unit heaters provide fast and effective heating in large-volume areas. Low investment costs, easy installation features, and high capacity options are among their important advantages. They can create homogeneous temperature distribution in large areas and provide comfort conditions in a short time.
Thanks to their compatibility with central boiler systems, condensing boilers, and heat pumps, their energy efficiency is high. In addition, easy maintenance operations and long service life reduce operating costs.
APPLICATION AREAS OF HEATING SYSTEMS WITH UNIT HEATERS
Heating systems with unit heaters are widely used in factories, production facilities, warehouses, logistics centers, sports halls, hangars, service stations, workshops, mosques, greenhouses, and large commercial buildings.
Especially in high-ceiling spaces and buildings requiring rapid heating, they offer more economical solutions compared to radiator and underfloor heating systems. Today, they are considered one of the most common and reliable applications of industrial heating systems.
