Glossary of Terms
The air flow in axial fans is in the direction of the impeller axis of rotation and they are used where a high air flow is required without high pressure demands. Axial fans can be divided into equal pressure fans (the air only gains higher speed) and positive pressure fans (the static pressure behind the impeller is higher than in front of it). Equal pressure axial fans include classic domestic fans for bathrooms and toilets, as well as ceiling fans that ensure air movement in the room. The category of positive pressure axial fans includes industrial axial fans for wall mounting or duct axial fans for connection to circular ventilation ducts.
Overrun timers are electrical accessories for fans (most often small axial fans and small centrifugal fans). The timer allows the fan to continue running after it has been switched off using the wall switch. Most often, Overrun timers are adjustable (for example, 3 to 15 minutes), some have a fixed overrun time (for example, 8 or 15 minutes). This function is particularly suitable for ventilating rooms with high humidity, such as bathrooms or toilets.
EC energy-saving motors are brushless DC motors (or electronically commutated motors) for fans, which are controlled by external electronics - 0-10V potentiometers. EC modern energy-saving motors achieve relatively high air flow despite their small size. EC motors are characterized by low operating noise and smooth operation. Compared to AC motors, EC motors achieve up to 30% energy savings.
Noise / Acoustic pressure
The noise or acoustic pressure of fans depends on the diameter of the suction opening and its power. In ventilation technology, the rule is that the more powerful the fan, the greater the noise level. The overall noise level/acoustic pressure is influenced by many factors - the method of installation, the method of connection to the ventilation duct, the shape and material of the ventilation duct, and the noise caused by air flow. Guidelines for quiet solutions include fans with ball bearings, flexible connections for connection to the air duct, anti-vibration kits (silent blocks), and reputable fan manufacturers. Among the quietest fans on the market are Silent, Silent Design, and TD Silent circular duct fans.
A humidistat or humidity sensor is an electronic device that switches and regulates fans depending on the relative humidity in the room. The fan switches on or off according to the set percentage value of humidity. The humidity unit is given in %RH (relative humidity). The hygrostat/humidity sensor can be external or integrated directly into the fan (the most common are small axial fans with a humidistat or small centrifugal fans with a humidistat). Fans with humidity sensors are used in rooms where there is increased humidity and we want to prevent mold growth.
One of the most common problems in homes and family houses when it comes to ventilation is condensation in air ducts. Condensation in HVAC ducts can cause aesthetic and functional damage. Condensation in ducts usually occurs when the duct route passes through cold rooms in the building or outside. This phenomenon is associated with condensate leaking into the fan or building structures, which results in considerable economic losses when repairing the damage caused. The solution to steam condensation in ventilation ducts is to use thermally insulated flexible ducts (or circular ducts with rubber thermal insulation) and condensate drains.
IP rating
The IP rating indicates the resistance of electrical equipment to the ingress of foreign bodies and liquids, especially water. The IP code is expressed by two digits - the first digit indicates protection against dangerous contact and the ingress of foreign objects, the second digit indicates the degree of protection against water ingress.
Against the ingress of foreign objects
IP 0x - no protection
IP 1x - palm of the hand (>5×5 cm)
IP 2x - finger (>12.5×12.5 mm)
IP 3x - tool (>2.5 mm)
IP 4x - tool, wire (>1 mm)
IP 5x - any tool, partially dustproof
IP 6x - any tool, completely dustproof
Protection against water ingress
IP x0 - no protection
IP x1 - protected against dripping water 1+0.5 mm per minute
IP x2 - protected against dripping water 3+0.5 mm per minute
IP x3 - protected against water spray. Water sprays onto the device at an angle of 60° vertically, at a rate of 10 liters per minute
IP x4 - protected against splashing water. Same as IP x3, except that water is sprayed at all angles
IP x5 - protected against water jets. Water is directed at all angles with a 6.3 mm nozzle at a flow rate of 12.5 liters per minute at a pressure of 30 kN/m2 for at least 3 minutes from a distance of 3 meters.
IP x6 - protected against intense water jets, water is directed from a 12.5 mm nozzle at all angles at a flow rate of 100 liters per minute at a pressure of 100 kN/m2 for at least 3 minutes from a distance of 3 meters
IP x7 - protected against immersion in water for 30 minutes to a depth of 1 meter
IP x8 - protected against submersion in water, the device is capable of continuous submersion in water under conditions specified by the device manufacturer
IP x9 - protected against high-pressure hot water jets
Ball bearings are used to mount the fan motor in order to achieve the best transfer of rotational force between the motor and the fan impeller. Fans with ball bearings are characterized by long service life, higher air performance, and the possibility of installation in any position (on the ceiling or wall). Ball bearings allow the transmission of both axial and radial forces. The service life of ball bearings is significantly longer than that of sliding bearings.
Voltage [V]
The voltage of fans and their accessories provides information about the power supply used by the electrical equipment. The most common voltages in the range of fans and ventilation equipment are classic 12V (safe voltage, fans suitable for ZONE 1 in bathrooms), single-phase 230V, and three-phase 400V. Single-phase motors are controlled by voltage regulators (e.g., REB), while three-phase motors are controlled by frequency converters.
Motion sensor
A passive infrared sensor (PIR sensor) is an electromagnetic sensor that measures and responds to infrared radiation (IR) / movement emitted from objects in the sensor's field of view. The sensor is activated when the infrared signal (movement) is interrupted. Motion sensors can be external or built directly into fans (most often small axial fans and small centrifugal fans).
Explosive atmospheres
Explosive atmospheres can be classic spaces such as commercial and industrial buildings, underground garages, or warehouses. This category also includes buildings with a high risk of explosion, such as factories, refineries, gas stations, paint shops, or chemical industry facilities. The air in these areas may contain gases, vapors, or other flammable substances.
When selecting a suitable explosion-proof fan, it is necessary to know the zone for which the fan is being selected. Areas are differentiated according to what can cause an explosion and the extent to which an explosion can occur there.
Description of possible designs
For example:
II 2G Ex e II T3
Product group II
II – Equipment for potentially explosive atmospheres
Product category
2G – ZONE 1 with explosive atmosphere consisting of gases and vapours
3G – ZONE 2 with explosive atmosphere consisting of gases and vapours
Protection against ignition
c – safe construction
explosiveness subgroup – classification according to EN 60 079-14
IIB – subgroup IIB, fan with transmission
IIB+H2 – subgroup IIB, direct drive fan
Required temperature class
T3 – temperature class T3 (< 200 °C), motor in secured design
T4 – temperature class T4 (< 135 °C), motor with fixed closure
Areas with a risk of vapour and gas explosion (designation G)
- Zone 0 – this is an area where an explosive mixture is constantly present or occurs for long periods
- Zone 1 – in this area, an explosive mixture may occasionally occur during normal operation
- Zone 2 – this designation is used for areas where the occurrence of an explosive mixture is unlikely and, if it does occur, only for a short period of time
Areas with a dust explosion hazard (designation D)
Dust explosions are most common in agriculture or where starch, flour, sugar, cocoa, dyes, medicines are processed or where wood dust is generated. Practically any dust is involved, with the exception of inorganic substances and metal salts.
- Zone 20 – An explosive atmosphere is permanently, for long periods, or frequently present in the form of clouds of combustible dust.
- Zone 21 – An explosive atmosphere in the form of clouds of combustible dust may occasionally occur during normal operation.
- Zone 22 – this is an area in which an explosive atmosphere is not likely to occur. If it does occur, it is only for a short period of time.
Type of protection
There are many types of protection, which differ from each other in terms of atmospheres or zones, for example. For illustrative purposes, we list some types of protection:
- Ex IA – protection consists of spark safety and is used for type G (gas medium) and D (dust medium) atmospheres. It is used in ZONE 0, ZONE 1, ZONE 2, ZONE 20, ZONE 21, and ZONE 22.
- Ex IB - intrinsic safety, used in atmospheres of type G (gas medium) and D (dust medium) in ZONE 1, ZONE 2, ZONE 21, and ZONE 22
- Ex ec - design for atmosphere G (gas medium) for ZONE 2
- Ex nA - type n protection suitable for atmosphere G in ZONE 2
Centrifugal industrial fans are designed for longer ventilation ducts with high pressure loss. Centrifugal fans are designed for industrial or agricultural applications such as cooling machines or products, post-harvest lines, grain cleaners, grain silos, aeration needles, or pneumatic transport. Centrifugal fans have a higher number of blades and push air perpendicularly to the axis of rotation using centrifugal force. They have higher pressure and can transport air over longer distances.
Synthetic rubber is an insulating material for cooling, ventilation, air conditioning, solar technology distribution, heating, and is also widely used for insulating recreational vehicles. Rubber is a synthetic polymer material characterized by high elasticity, i.e., the ability to deform significantly under the effect of external forces and then return to its original shape; it is a so-called elastomer. Synthetic rubber is produced by polymerization. Rubber thermal insulation is supplied in strips for thermal insulation of ventilation and air conditioning systems.