Plain-language definitions of 164 terms: from basic concepts to the refrigeration cycle, refrigerants, and maintenance and tender terms.
A flow switch is a safety device that detects whether there is flow in the water circuit and prevents the chiller compressor from running when there is none. It is a critical protection against evaporator freezing.
Related service →An accumulator is a vessel fitted at the compressor suction that traps any liquid refrigerant coming from the evaporator so that only vapor enters the compressor. It prevents liquid slugging from damaging the compressor and is especially found in heat pumps.
Breakdown maintenance is an unplanned intervention to diagnose and repair a problem after equipment has failed. At facilities with a maintenance contract, breakdown calls are generally handled with priority and within defined timeframes.
Related service →A fault code is diagnostic information in which the air conditioner's control board shows a problem it has detected as a combination of letters and numbers on the remote, display or LED. Since the meaning of codes varies by brand and model, they should be interpreted together with the service documentation.
Related service →A positive cold room is generally a room between 0 °C and +8 °C used to store products such as fresh fruit and vegetables, dairy products and medicines; a negative cold room is generally a room where frozen products are stored at -18 °C and below. The type of product determines the required temperature and humidity range.
Related service →Subcooling is the difference showing how far the liquid line temperature at the condenser outlet is below the condensing temperature at that pressure. It indicates that enough liquid has formed in the condenser; values around 3-6 K are generally expected, and it is used to assess the refrigerant charge.
Related service →Nitrogen brazing is the practice of passing a low flow of nitrogen through copper pipes while they are brazed to prevent an oxide (scale) layer from forming on the inner surface. Otherwise, the oxide particles can clog filters, capillaries and EEVs.
Related service →A nitrogen pressure test is a leak test performed by charging dry nitrogen into a new or repaired refrigeration circuit and monitoring pressure drop over a set period. The test pressure is chosen according to the values given by the equipment manufacturer; it is done before vacuuming.
Related service →BACnet is a standard protocol developed for building automation and control networks that allows devices from different manufacturers to communicate in a common language. It has versions such as BACnet/IP and BACnet MS/TP.
Related service →Relative humidity is the amount of water vapor currently in the air expressed as a percentage of the maximum amount of vapor the air can hold at the same temperature. In comfort areas, a range of 40-60% is generally targeted.
A maintenance contract is a service agreement between a service company and a customer that defines the number of periodic maintenance visits, the equipment covered, response times, and spare parts and labor terms. It provides budget predictability and priority service.
Related service →A balancing valve is a valve, usually with a measuring point, that is adjusted so that the design flow passes through each branch or terminal unit in water circuits. In unbalanced systems, some fan coils receive too much water and others too little.
Related service →A pressure-independent control valve combines flow limiting, automatic balancing and control functions in a single body and maintains the set flow even when system pressure changes. It is increasingly used on fan coil and air handling unit coils.
Related service →A pressure-temperature chart is a reference table showing the saturation temperatures of a refrigerant at different pressures. From the measured pressure, evaporation and condensing temperatures are found and superheat and subcooling are calculated.
Coil chemical cleaning is the cleaning of dirt, grease and biological deposits on condenser and evaporator coils using suitable chemicals and pressurized water. It improves heat transfer, brings pressures back to normal and reduces energy consumption.
Related service →A BMS is an automation system in which a building's air conditioning, ventilation, lighting and other technical systems are monitored and controlled from a single center. Chillers, VRF systems and air handling units are generally connected to the BMS via protocols such as Modbus or BACnet.
Related service →BTU is a British unit of heat that expresses the amount of heat needed to raise the temperature of one pound of water by 1 °F. Air conditioner capacities are given in practice as BTU/h, the heat transferred per hour; 1 kW is approximately equal to 3,412 BTU/h.
Related service →BTU/h is a capacity unit showing the amount of heat an air conditioner removes from or delivers to a space in one hour. Values such as 9,000, 12,000, 18,000 and 24,000 BTU/h are the standard capacity classes for home and office air conditioners on the market.
Related service →The vapor compression refrigeration cycle is the basic refrigeration principle in which a refrigerant moves heat from a cold space to a warm one by going through the steps of compression, condensation, expansion and evaporation. Most HVAC equipment, from split air conditioners to chillers, works with this cycle.
A chiller is a central cooling unit that uses a refrigeration cycle to cool water or glycol-water and pumps it to fan coils, air handling units or process equipment. It is common in large buildings, hospitals and industrial facilities.
Related service →COP is a dimensionless efficiency value: the ratio of the thermal output of a heat pump or cooling unit to the electrical power it consumes. For example, a unit with a COP of 4 provides about 4 kW of heat from 1 kW of electricity; the value is generally used for heating mode.
Related service →A CRAC (computer room air conditioner) is a DX-based precision air conditioning unit with its own compressor and refrigerant circuit. Condenser heat is generally rejected to an outdoor air-cooled condenser or dry cooler.
Related service →A CRAH (computer room air handler) is a precision air conditioning unit with no compressor that cools air through a coil supplied with chilled water from a chiller. It is used with a central chilled water system in large data centers.
Related service →The dew point is the temperature at which water vapor in the air begins to condense when the air is cooled while its moisture content stays constant. Condensation forms on pipes and ducts whose surface temperature falls below the dew point, which is why insulation is needed.
A damper is a blade element, operated manually or by a motor, used in air ducts to adjust flow or shut it off completely. It is used in system balancing and zone control.
Related service →A DC inverter compressor is a compressor whose speed is continuously adjusted by a frequency converter so that its capacity can vary with demand. Because it keeps running at low speed instead of cycling on and off, it reduces temperature swings and improves seasonal efficiency.
Related service →A DDC (direct digital control) controller is a programmable automation controller that processes information from sensors in software and operates elements such as valves, dampers, fans and pumps. It is a core component in the automation of air handling units.
Related service →Defrost is the process of melting and clearing ice that builds up on the evaporator at set intervals. It can be done with electric heaters, hot gas or ambient air, and the duration and termination temperature are managed by the controller.
Related service →Commissioning is putting a newly installed HVAC system into operation for the first time in line with design values, through checks, adjustments and tests. For systems such as VRF and chillers it is generally carried out by authorized service providers and is important for starting the warranty.
Related service →A drain heater is a heating cable wrapped along the drain pipe in negative cold rooms to prevent defrost water from freezing in the pipe. If it fails, the drain line freezes and water can overflow into the room.
Related service →Drainage is the removal of condensate water formed in the indoor unit during dehumidification, through a sloped pipe or a drain pump. A clogged drain line is one of the most common causes of water dripping and ceiling damage.
Related service →A dry cooler is a heat exchanger unit that passes water or glycol-water through a closed-circuit coil and cools it with fans using air only, without evaporation. Because it uses no water, it is preferred in precision air conditioning, process cooling and free cooling applications.
Related service →Sensible heat is the component of heat that changes only the dry-bulb temperature of the air without changing its moisture content. Most of the heat gain from the sun, lighting and equipment is sensible heat.
An EC fan is a high-efficiency fan with an electronically commutated DC motor whose speed can be adjusted continuously. Compared with conventional AC motor fans, it provides significant energy savings, especially at partial load.
Related service →EER is the ratio of a cooling unit's cooling capacity under specified rated conditions to the electrical power it draws. Since it is expressed as W/W in Europe and as BTU/h per W in the US, the unit should be checked when comparing.
EKAP is the platform operated by the Public Procurement Authority on which public tender announcements, document downloads, bidding and results are handled electronically. Bidders must be registered in the system to take part in tenders.
Related service →Electric defrost is a defrost method in which ice is melted by heating elements placed in the evaporator coil. It is simple to implement and widely used in negative cold rooms.
Related service →An electronic expansion valve is an expansion device driven by a stepper motor that precisely adjusts refrigerant flow based on a signal from the control board. It adapts quickly to changing load in inverter air conditioners, VRF systems and chillers.
Related service →The suction line is the usually larger-diameter copper pipe that carries low-pressure refrigerant vapor from the evaporator to the compressor. It must be insulated to prevent condensation and efficiency loss.
Related service →The energy efficiency class is the classification shown on the energy label, in which air conditioners are rated with letters such as A+++ to D according to their seasonal efficiency values. A higher class means lower annual electricity consumption at the same capacity.
Related service →Evaporator icing is the freezing of moisture in the air on the surface of an evaporator running at low temperature, forming a layer of ice. Because ice reduces airflow and heat transfer, regular defrost is needed; excessive icing can point to a door left open, low refrigerant or a defrost fault.
Related service →An evaporator is the heat exchanger in which low-pressure refrigerant absorbs heat from the space or water and evaporates, producing the cooling. In a split air conditioner it is the coil in the indoor unit; in a chiller it is the heat exchanger that cools the water.
Related service →A fan coil is a terminal unit that passes chilled or hot water from a chiller or boiler through a coil and conditions the room air with the help of a fan. It comes in types such as wall, ceiling, cassette and concealed ceiling.
Related service →A filter drier is a desiccant filter fitted in the liquid line that traps moisture, acid and solid particles in the refrigerant. It is recommended to replace it every time the system is opened, especially after a compressor burnout.
Related service →The EN 779 filter classification is the former European standard that grouped air filters as coarse (G1-G4), medium (M5-M6) and fine (F7-F9). Although it has been replaced by ISO 16890, terms such as G4 pre-filter and F7 fine filter are still widely used in the market.
Related service →Free cooling is cooling with outdoor air or a dry cooler, without using the compressor or with a reduced compressor load, when the outdoor temperature is low enough. It provides significant energy savings in data centers that need cooling all year round.
Related service →F-gas is the short name for the regulatory area covering fluorinated greenhouse gases such as HFCs and the equipment that uses them. In Türkiye as well, under the regulation on fluorinated greenhouse gases, equipment above certain sizes is subject to obligations such as periodic leak checks, record keeping and certified personnel.
Related service →A gateway is an interface device that translates the native communication protocol of a VRF or air conditioning system into building automation protocols such as Modbus, BACnet or KNX. It allows systems of different brands to be brought together under a single BMS.
Related service →Refrigerant recovery is taking the refrigerant in a system into a recovery cylinder with a special device, without releasing it into the atmosphere, before repair or removal. Under F-gas regulations, releasing refrigerant into the atmosphere is prohibited.
Related service →Refrigerant charging is adding refrigerant of the type and amount specified by the manufacturer to a refrigeration system. The correct method is to charge the refrigerant by weighing it on a scale after the leak has been fixed and a vacuum has been pulled; a low charge does not occur without a leak.
Related service →An expansion tank is a pressurized vessel, usually with a diaphragm, that absorbs the volume change of water caused by temperature variation in closed water circuits and keeps system pressure within a set range. Its pre-charge pressure must be checked periodically.
Related service →A thermostatic expansion valve is a valve that senses superheat at the evaporator outlet, automatically adjusts the amount of liquid refrigerant going to the evaporator and reduces its pressure. It is widely used in cold rooms and commercial systems.
Related service →Latent heat is the component of heat associated with the condensation or evaporation of water vapor in the air without a change in temperature. People's perspiration and the moisture in fresh air create a latent heat load; the air conditioner's dehumidification function handles this load.
Glycol is an antifreeze mixed into water in a set proportion in chiller and heat pump water circuits to lower the freezing point. As the glycol ratio increases, freeze protection increases, but heat transfer decreases and pump energy rises; propylene glycol is generally preferred in food facilities.
Related service →The safety class is the classification that groups refrigerants by toxicity (A/B) and flammability (1, 2L, 2, 3). For example, R410A is class A1 (non-flammable), R32 is A2L (mildly flammable) and R290 is A3 (highly flammable).
GWP is the factor expressing the warming effect a gas creates in the atmosphere over a given period (usually 100 years) relative to the same mass of CO₂. The higher the value, the greater the climate impact if the gas leaks; it is the basic criterion of F-gas regulations.
A progress payment (hakediş) is the payment document and process in which the quantity and value of work a contractor has completed in a given period under the contract are documented and submitted to the contracting authority or client. In maintenance contracts it is generally issued monthly or periodically.
Related service →External static pressure is the available pressure that a ducted indoor unit, air handling unit or fan can provide to overcome the resistance of ducts, grilles and filters outside its own casing. If the duct design exceeds the ESP value, airflow drops.
Related service →Precision air conditioning is a type of air conditioner designed to control temperature and humidity within tight tolerances, all year round and without interruption, in spaces such as data centers, server and UPS rooms, and laboratories. It features a high sensible heat ratio, redundant operation and continuous monitoring.
Related service →Airflow rate is the volume of air carried by a fan, grille or duct per unit of time and is generally expressed in m³/h. Along with capacity, it is the most basic parameter in the design of air conditioning and ventilation systems.
Related service →Air changes per hour is the value showing how many times a space's volume of air is renewed in one hour. It is found by dividing hourly airflow by the room volume, and different targets are set depending on the type of space.
Related service →An air duct is a duct system made of galvanized sheet, aluminum or prefabricated panel that carries conditioned, fresh or exhaust air from the air handling unit or fan to the spaces. Sealing and insulation are important to prevent both energy loss and condensation.
Related service →An air-source heat pump is a type of heat pump that extracts heat from outdoor air and is relatively simple to install. Air-to-water models can supply underfloor heating, radiator and fan coil systems; their efficiency drops in very cold weather.
Related service →An air-cooled chiller is a type of chiller that rejects condenser heat directly to outdoor air by fans and is usually installed outdoors, such as on a roof or on the ground. Because it needs no cooling tower, installation and maintenance are simpler.
Related service →A flare connection is a solder-free pipe connection method in which the end of a copper pipe is flared into a cone with a special tool and tightened with a flare nut. It is used for the indoor-outdoor unit connections of split air conditioners; failure to apply the correct torque is one of the most common causes of leaks.
Related service →A HEPA filter is a high-efficiency air filter, classified under EN 1822 or ISO 29463, that traps very small particles with very high efficiency. The H13 and H14 classes are widely used in applications such as operating rooms, cleanrooms and laboratories.
Related service →A hermetic compressor is a compressor whose motor and compression mechanism are sealed in a single welded casing and cannot be opened in the field. In semi-hermetic compressors the casing is bolted, so overhauls and part replacement are possible.
Related service →An inverter is an electronic drive that continuously adjusts the speed of compressor, fan or pump motors by changing the frequency and voltage of the mains electricity. It allows capacity to match demand, lowers starting current and reduces energy consumption.
Related service →IPLV is a part-load efficiency indicator obtained by combining a chiller's efficiencies at 100%, 75%, 50% and 25% load points with standard weightings. Because chillers run at part load for most of the year, it is often more meaningful than full-load efficiency when selecting one.
Related service →Heat recovery VRF is a VRF system in which some indoor units can cool while others heat at the same time, and heat taken from one zone is transferred to another. It is generally a three-pipe or special distribution box design and is efficient in buildings with multiple facades.
Related service →A heat recovery unit is a device that transfers the heat of exhaust air leaving a building to the incoming fresh air, reducing energy loss from ventilation. An HRV transfers only sensible heat, while an ERV transfers moisture along with heat.
Related service →A heat pump is a device that runs the refrigeration cycle in reverse, transferring heat drawn from air, water or ground to the building or domestic hot water at a higher temperature. Because it can produce several times as much heat as the electricity it consumes, it is an efficient heating solution.
Related service →A heat load calculation is the engineering study that determines the required equipment capacity by calculating the heat gains and losses of a space from walls, glass, roof, people, lighting, equipment and fresh air. Choosing the right capacity is fundamental for comfort, energy consumption and equipment life.
Related service →ISO 16890 is the international standard that classifies general ventilation filters into the ISO ePM1, ePM2.5, ePM10 and ISO Coarse groups according to their capture efficiency at PM1, PM2.5 and PM10 particle sizes. For example, "ePM1 55%" means the filter captures at least 55% of particles of PM1 size.
Related service →OHS is the set of measures taken to protect workers against workplace accidents and occupational diseases. In HVAC service work, training and personal protective equipment are important because of risks involving working at height, electricity, pressure vessels and flammable refrigerants.
A jet fan is a type of fan that moves air toward exhaust points in enclosed car parks on the principle of thrusting it along, without ducts. It is designed both for daily CO removal and for smoke control in a fire.
Related service →A leak detector is an electronic device that senses refrigerant vapor so that the leak point can be found. It can be used together with methods such as foaming liquid, UV dye and nitrogen-hydrogen mix.
Related service →A public tender is the purchasing process in which public institutions open their purchases of goods, services and construction work to competition under the procedures defined in public procurement legislation. In HVAC, equipment purchases, installation and annual maintenance-repair services are frequently put out to tender.
Related service →A ducted air conditioner is an indoor unit type concealed in the false ceiling that distributes air to multiple points through ducts and grilles. It offers an aesthetic and quiet solution; external static pressure is important when selecting one.
Related service →A capillary tube is a copper tube with a very small inner diameter and a set length that acts as an expansion device by dropping pressure through friction. It is simple and inexpensive; it is used in small-capacity air conditioners and refrigerators, but cannot adjust to load.
A cassette air conditioner is an indoor unit type mounted recessed in the suspended ceiling that usually blows air in four directions. It provides even air distribution in large spaces such as stores, offices and restaurants.
Related service →A site survey is the on-site inspection of the space, the existing installation, installation conditions and requirements before a quote is prepared. A proper survey allows equipment capacity and installation cost to be determined reliably.
Related service →The kilowatt is the SI unit of power, equal to 1,000 watts, used to express both cooling/heating capacity and electricity consumption. In technical catalogs, capacity is given in kW and consumption generally in kW or kWh.
Superheat is the difference between the suction line temperature at the evaporator outlet and the saturation (evaporation) temperature at that pressure. It shows whether the evaporator is being fed correctly; in TXV systems about 5-8 K is generally targeted, and a low value points to a risk of liquid flooding back.
Related service →An air handling unit is a modular central air treatment device that filters, cools, heats, humidifies or dehumidifies air and delivers it into the duct system with fans. Fresh air, mixing and heat recovery sections are selected as needed.
Related service →The compressor is the main component that draws in low-pressure refrigerant vapor, compresses it to high pressure and temperature, and drives flow in the cycle. It is called the "heart" of the refrigeration system and accounts for most of its energy consumption.
Related service →Compressor overhaul is dismantling semi-hermetic or open-type compressors and renewing worn parts such as bearings, valves, gaskets and windings, or replacing a faulty compressor entirely. System cleaning and an oil change should also be carried out with the overhaul.
Related service →Compressor oil is the special oil that lubricates the moving parts of the compressor and must be compatible with the refrigerant. POE or PVE is generally used in HFC systems and mineral oil in older R22 systems; oils must not be mixed.
Related service →Compressor burnout is the failure of the compressor motor windings due to overheating, loss of insulation or an electrical problem. Because acid and contamination can form in the system after a burnout, replacing only the compressor is not enough; cleaning, filter drier replacement and an acid test are required.
Related service →A condenser is the heat exchanger that liquefies the hot, high-pressure gas from the compressor by giving its heat to air or water. In split air conditioners it is located in the outdoor unit; fouling raises pressures and causes efficiency loss.
Related service →A manifold gauge set is service equipment with low- and high-pressure gauges, valves and hoses that connects to a refrigeration system for pressure measurement, vacuuming and refrigerant charging. Digital models can directly calculate saturation temperature, superheat and subcooling.
Related service →A megger is an instrument that applies a high DC test voltage to measure insulation resistance of compressor windings and cables at the megohm level, and is also the common name for this measurement. Low insulation resistance points to a risk of leakage current due to winding deterioration or moisture.
Related service →A grille is an air distribution element, with adjustable blades or a fixed grating, through which air is supplied from an air duct into a space or drawn out of it. Correct selection and placement prevent drafts and noise.
Related service →A central control panel is a control device that switches on and off, programs and monitors all indoor units in a VRF or multi air conditioning system from a single point. It can offer functions such as locking, time scheduling and energy reporting.
Related service →Modbus is an open communication protocol widely used for data exchange between devices, available in RTU (serial) and TCP/IP versions. It is often preferred for connecting chillers, precision air conditioners and energy analyzers to a BMS.
Related service →A monoblock refrigeration unit is a compact cooling unit in which the compressor, condenser, evaporator and control elements are combined in a single casing and mounted on the wall or ceiling of a cold room. It allows quick installation in small and medium-sized rooms.
Related service →A multi split air conditioner is a system in which several indoor units are connected to a single outdoor unit. In apartments and offices where outdoor unit space is limited, it allows several rooms to be conditioned with one outdoor unit.
Related service →Response time is the maximum time from receiving a fault report to the technical team reaching the site or starting a remote intervention. Shorter response times are defined for critical facilities such as data centers and hospitals.
Related service →An NTC sensor is a thermistor whose electrical resistance decreases as temperature rises, used by air conditioner boards to measure room, pipe and discharge line temperatures. A sensor whose resistance has drifted out of range can cause incorrect operation or a fault code.
Related service →ODP is the value of the damage a substance does to the ozone layer relative to R11. It is greater than zero for HCFCs such as R22 and zero for HFCs such as R32, R410A and R134a.
A clamp meter is an electrical measuring instrument that measures current by clamping around a cable with its jaws, without cutting the cable. It is used to compare the current drawn by compressor and fan motors with nameplate values.
Related service →Periodic maintenance is planned maintenance work in which HVAC equipment is inspected and cleaned at set intervals with respect to filters, coils, drainage, electrical connections, pressure and current values. In commercial systems it is generally carried out at least once or twice a year, at seasonal changeovers.
Related service →A strainer is an element with a screen that traps solid particles in water circuits to protect pumps, valves and heat exchangers. The screen should be removed and cleaned during periodic maintenance.
Related service →A reciprocating compressor is the classic compressor type that compresses gas with a piston moving back and forth in a cylinder. It is still widely used in cold room and commercial refrigeration applications, especially in semi-hermetic models.
Related service →A plate heat exchanger is a compact heat exchanger in which two fluids exchange heat between thin metal plates without mixing. It is used for chiller evaporators, free cooling and circuit separation; it needs maintenance against scale and fouling.
Related service →A plenum is the volume where air is collected before being distributed at the outlet of a ducted air conditioner or fan, or where return air is collected, such as the ceiling void. It helps equalize pressure at grille connections.
Related service →A pressure switch is a safety or control switch that opens its contact and stops the compressor when system pressure exceeds a set lower or upper limit. The high-pressure switch protects against condenser problems, and the low-pressure switch protects against low refrigerant or blockage.
Related service →A primary-secondary circuit is a piping arrangement in which the production side (chiller or boiler) and the distribution side run on separate pumps and are hydraulically separated by a decoupler tank or common pipe. It lets the producer's constant flow and the distribution's variable flow be met together.
Related service →A psychrometric chart is an engineering tool that shows the properties of moist air, such as temperature, humidity, enthalpy and dew point, on a single graph. It is used in designing air handling unit processes (cooling, dehumidification, mixing, heating).
Related service →A radial (centrifugal) fan is a fan type that discharges air perpendicular to its axis and provides high pressure; an axial fan moves air along its axis and suits high-flow, low-pressure applications. Radial fans are generally used in air handling units, and axial fans in exhaust and condensers.
Related service →A rooftop unit is a packaged air conditioning unit that combines compressor, condenser, evaporator, fan and filter sections in a single casing and is usually installed on a roof. It is used with ducts in large single-volume spaces such as shopping malls, supermarkets, factories and sports halls.
Related service →A rotary compressor is a compact, quiet compressor type that compresses by an eccentric rotor turning inside a cylinder. It is generally used in wall-mounted split and small-capacity air conditioners.
Related service →R134a is a single-component HFC refrigerant used especially in screw and centrifugal chillers, automotive air conditioning and some commercial refrigeration equipment. It has relatively low operating pressures.
Related service →R22 is a refrigerant from the HCFC group that damages the ozone layer and has been phased out under the Montreal Protocol. It may still be found in old equipment; when servicing these systems, refrigerant supply and conversion options should be considered.
Related service →R290 is propane, a natural hydrocarbon, used as a refrigerant. Its GWP is very low, but because it is in the highly flammable (A3) class its charge amount is limited and service work requires special safety precautions.
Related service →R32 is a single-component HFC refrigerant widely used in new-generation split air conditioners to replace R410A. Its GWP is about one third that of R410A and it is in the mildly flammable (A2L) class.
Related service →R404A is an HFC blend with a very high GWP that was widely used for a long time in low- and medium-temperature commercial refrigeration and cold rooms. Because of F-gas regulations, it is being replaced by lower-GWP alternatives such as R448A and R449A.
Related service →R407C is a zeotropic HFC blend made of R32, R125 and R134a, developed to replace R22. Because of temperature glide, it must be charged into the system in the liquid phase.
Related service →R410A is an HFC refrigerant made of an approximately equal blend of R32 and R125; it does not harm the ozone layer but has a high GWP. It was the standard refrigerant of split and VRF systems for many years and is gradually being replaced by low-GWP refrigerants.
Related service →R744 is the name of carbon dioxide used as a refrigerant, and its GWP is 1. It requires very high operating pressures and a transcritical cycle; it is used in supermarket refrigeration and high-temperature heat pumps.
Related service →A centrifugal compressor is a dynamic compressor type in which an impeller rotating at high speed gives the gas kinetic energy and converts it to pressure. It is generally used in very large water-cooled chillers; oil-free versions with magnetic bearings are also available.
Related service →SCOP is the seasonal coefficient showing a heat pump's average heating efficiency over the heating season under varying outdoor temperatures and part loads. In Europe, separate values are given for different climate zones: average, warmer and colder.
Related service →A scroll compressor is a compressor type that compresses gas between two spiral elements, one fixed and one moving in an orbit. With few moving parts, it is efficient and quiet; it is common in VRF, rooftop units and small to medium-capacity chillers.
Related service →SEER is the seasonal ratio showing an air conditioner's average efficiency across different outdoor temperatures and part-load conditions over the whole cooling season, rather than at a single test point. It reflects the real-world efficiency of inverter units better than EER and appears on the energy label.
Related service →A service report is a document in which the values measured during maintenance or repair, the parts replaced, findings and recommendations are recorded and signed by the customer. It is the basic record for tracking maintenance history and documenting progress payments.
Related service →A service valve is a valve on the outdoor unit or condensing unit that lets the system be opened and closed for installation, vacuuming, refrigerant charging and measurement. A manifold gauge set is connected to the service port on it.
Related service →ΔT is the difference between supply and return water temperatures in a water circuit. In chilled water systems a 5 K difference, such as 7/12 °C, is generally used as the basis; a ΔT below the design value can indicate that pumps are circulating more water than needed.
Related service →Temperature glide is the change of temperature over a range, rather than staying constant, as zeotropic blends evaporate or condense at constant pressure. Refrigerants with significant glide, such as R407C, are charged in the liquid phase so that the blend ratio is not disturbed.
Hot gas defrost is a defrost method in which hot gas leaving the compressor is routed to the evaporator through a valve arrangement, melting the ice from the inside. It can be faster and more energy-efficient than electric defrost, but the piping is more complex.
Related service →A circulation pump is a pump that circulates water between chillers, boilers, fan coils and air handling unit coils. Pumps with variable frequency drives provide significant energy savings in variable-flow systems.
Related service →A liquid receiver is a pressure vessel that collects the liquid refrigerant condensed at the condenser outlet and balances load variations in the system. In cold room and commercial refrigeration systems, it also holds the refrigerant during pump-down.
Related service →An SLA is an agreement that defines the service measures a service company commits to, such as response time, resolution time, working hours and reporting. It is generally included as an appendix or clause of the maintenance contract.
Related service →A cold room is a storage space built from insulated panels and cooled by a refrigeration unit, for storing food, medicines and similar products at set temperature and humidity conditions. It is designed as positive (storage) or negative (frozen product) temperature.
Related service →A cold room controller is a digital control device that manages room temperature, defrost timing, fan delays and alarms. Models with logging and remote monitoring make food safety tracking easier.
Related service →A cold room panel is a sandwich panel with both faces clad in painted sheet metal and a core filled with polyurethane or a similar insulation material. Panel thickness is chosen according to room temperature; thicker panels are generally used in negative rooms.
Related service →Cooling capacity is the total amount of heat a unit can remove from a space per unit of time under specified test conditions. It covers the sum of sensible and latent heat and is expressed in kW or BTU/h.
A cooling tower is equipment that cools condenser water toward the outdoor wet-bulb temperature through evaporation of part of the water. It needs water treatment, regular cleaning and maintenance against the risk of Legionella.
Related service →A refrigerant is the special chemical substance that carries heat in the refrigeration cycle by evaporating at low pressure and condensing at high pressure. It is commonly called "air conditioner gas"; each unit must be run only with the refrigerant stated on its label.
Related service →A split air conditioner is an air conditioner type in which the indoor unit and outdoor unit are separate and connected to each other with copper pipes and cables. It is the most widely used HVAC solution in homes and small offices.
Related service →A split refrigeration unit is a cold room cooling system in which the condensing unit is outside and the evaporator is inside the room, connected by refrigerant pipes. It lets heat be rejected away from the room surroundings and offers a wider capacity range.
Related service →Static pressure is the pressure that air inside a duct exerts on the duct walls in all directions, and the pressure a fan must produce to overcome resistance to flow. It is measured in pascals (Pa); as the filter gets dirty, system resistance and the required pressure increase.
Related service →A water-cooled chiller is a chiller type that transfers condenser heat to a water circuit, which is usually cooled in a cooling tower. It offers higher efficiency than an air-cooled one of the same capacity and is generally installed in a plant room.
Related service →Water treatment is processing the water of the installation and cooling tower by chemical or physical methods against scale, corrosion and biological fouling. It maintains heat exchanger efficiency and extends equipment life.
Related service →A blast freezer is a refrigeration room or cabinet in which products are frozen in a short time with very low air temperature and high air velocity. Rapid freezing forms small ice crystals and preserves the texture and quality of the product.
Related service →Fresh air is air taken from outdoors and supplied to a space to maintain indoor air quality. The required amount is determined by the number of occupants, the use of the space and the relevant standards.
Related service →A technical specification is the document that describes in detail the technical characteristics of the equipment, materials, services and work methods required in a tender or purchase. Bidders must document that the product and service they offer comply with the specification.
Related service →A thermostat is a control device that senses room temperature and switches an air conditioner, fan coil or heating unit on and off to maintain the set temperature. Programmable and remotely accessible models make energy management easier.
Related service →The ton of refrigeration is a unit of cooling capacity based on the heat needed to melt one ton of ice in 24 hours, equal to 12,000 BTU/h or about 3.517 kW. It is frequently used for chillers and large commercial systems.
Related service →A ground-source heat pump is a heat pump type that uses the ground temperature, which is relatively constant all year, through horizontal or vertical collectors placed in the ground. The initial investment is high, but its seasonal efficiency is generally higher than air-source systems.
Related service →TSE HYB is the Service Qualification Certificate issued by the Turkish Standards Institution to certify that after-sales services are provided in accordance with the relevant standards. It is granted following an audit of service infrastructure, personnel qualification and equipment, and is frequently required in public tenders.
Related service →Remote monitoring is continuous tracking of HVAC equipment operating data and alarms over the internet or a local network. It enables early response to faults, especially in precision air conditioning and cold rooms.
Related service →A three-way valve is a control valve that adjusts the amount of water going to a coil by mixing or diverting flow and routes the remaining water to a bypass line. It is used in constant-flow systems; two-way valves suit variable-flow systems.
Related service →Product load is the amount of heat that must be removed to bring the product entering a cold room down to the desired temperature. Daily product intake, entry temperature and product type are decisive in determining refrigeration unit capacity.
Related service →A vacuum pump is service equipment used to evacuate air and moisture from the refrigeration circuit after installation or repair. Insufficient vacuum can cause acid formation, icing and compressor failures in the system.
Related service →Vacuum is the process of removing air and moisture by lowering the pressure in the refrigeration circuit below atmospheric pressure. The level is measured with a micron gauge; the aim is generally to reach 500 microns or below and hold the vacuum for a period.
Related service →A screw compressor is a compressor type that compresses continuously with intermeshing helical rotors and is used at medium to large capacities. It is common in air- and water-cooled chillers and large industrial refrigeration systems.
Related service →A VRF (variable refrigerant flow) system is a central air conditioning system in which many indoor units are connected to one or several outdoor units and the amount of refrigerant going to each indoor unit is electronically regulated. VRV is one manufacturer's trade name for this technology; it is common in hotels, offices and hospitals.
Related service →The estimated cost is the amount the contracting authority calculates before a tender as the expected price of the work, based on market research and unit prices. It is used as a reference in bid evaluation and in inquiries into abnormally low bids.
Related service →A fire damper is a safety element placed in ducts passing through fire compartment walls or floors that closes in a fire to prevent flames and hot gases from spreading through the duct. Its operation must be tested periodically.
Related service →Wet-bulb temperature is the temperature shown by a thermometer whose bulb is wrapped in a wet wick under airflow, which is lower than the dry-bulb temperature because of evaporation. It is a basic input in cooling tower selection and psychrometric calculations.
Related service →An annual maintenance contract is a type of contract in which planned maintenance and fault response for HVAC systems are undertaken for a year on a fixed or unit-price basis. The scope generally includes maintenance intervals, reporting, and parts included/excluded terms.
Related service →A 2-pipe fan coil is a fan coil system connected to a single water circuit that receives either chilled or hot water through the same pipes depending on the season. The initial investment is low, but cooling and heating cannot be provided in different zones at the same time.
Related service →A 4-pipe fan coil is a fan coil system with separate supply and return lines for chilled and hot water, in which each unit can cool or heat independently. It is preferred in buildings where comfort is critical, such as hotels and hospitals.
Related service →A 4-way valve is a solenoid-operated valve in heat pump air conditioners that reverses the direction of refrigerant flow, swapping the roles of the indoor and outdoor units and enabling the switch between cooling and heating. It also changes position during defrost; if it fails, the unit may be stuck in one mode.
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