Sušičky vzduchu tlakový rosný bod +3 °C
What a +3 °C dew point means and why it matters
A pressure dew point of +3 °C is the value most often quoted for classic refrigeration (cooling) dryers for compressed air. It means that when moist compressed air is cooled to +3 °C, water vapour begins to condense into liquid water. Air with a +3 °C dew point therefore still contains a certain amount of moisture, but so little that under normal operating temperatures (usually above +5 °C) no condensate settles in the pipework. This dew point value matters because it represents the basic level of drying sufficient for many applications. +3 °C is a compromise between air quality and economy – the air is dry enough for indoor and mild outdoor environments, while avoiding the cost of deeper drying. Practically every ordinary compressor system in industry or a trade workshop uses a dryer reaching around +3 °C, because that covers most needs and prevents the usual condensate problems.
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Suitable applications and use in practice
A +3 °C dew point suits most standard compressed air applications in environments where frost is not a risk. Typically that includes air distribution in halls and workshops where temperatures stay above zero. In an engineering workshop or car repair shop where work is done at room temperature, for instance, +3 °C ensures that water does not condense in the pressure lines and then spurt from hoses and tools. For pneumatic tools and machines used inside buildings, air dried to +3 °C is sufficient – it protects pneumatic motors, valves and cylinders from corrosion and from gumming up with dirt carried in condensate. In paint shops and when spraying paint it is likewise standard to use air dried by a refrigeration dryer (dew point a few °C above zero), so that water does not build up in the air pipes or hoses and cause paint defects. Another typical use is PET bottle production and other plastic blow moulding – there, high-pressure compressors are used with an aftercooler and a dryer set to about +3 °C, which prevents droplets of water in the product. Essentially anywhere compressed air is consumed relatively soon after compression and in an environment above freezing, a +3 °C dew point suffices. This value also corresponds to class 4 to ISO 8573-1 for water vapour content, an acceptable minimum for many industrial devices. If the air were to be used outdoors in winter or in extremely sensitive technologies, +3 °C might not be enough – dryers with -25 °C, -40 °C and so on serve those purposes. For most ordinary operations, however, +3 °C is the optimal choice in terms of price/performance.
Which types of dryer reach a +3 °C dew point
A +3 °C dew point is the domain of refrigeration dryers for compressed air. A refrigeration (cooling) dryer works by cooling the air stream: a refrigeration circuit lowers the temperature of the incoming compressed air to roughly 0–3 °C, so that most of the moisture it contains precipitates as condensate. This is then drained from the system and the dry air (already reheated by a heat exchanger to about room temperature) continues into the distribution system with a pressure dew point of around +3 °C. Most industrial refrigeration dryers are designed to reach a +3 °C dew point at the rated air flow. Some smaller or simpler models (for trade workshops, say) may have a slightly higher outlet dew point, typically +5 °C – in practice that works similarly (see the dew point +5 °C category). Adsorption dryers can of course also deliver air with a +3 °C dew point (and much lower), but deploying them for such a „high“ dew point would not be efficient – they are intended for deeper drying and running them would be needlessly costly. In systems where an adsorption dryer is already installed (because part of the technology requires -40 °C, for example), its output can sometimes be controlled so that it supplies air of „only“ +3 °C quality to less demanding branches of the network. That, however, is a special case. Membrane dryers can theoretically also be set to an outlet around +3 °C, but they are usually used to reach lower dew points where a refrigeration dryer cannot be installed. In short, a refrigeration dryer is the standard solution for +3 °C – simple, reliable and economical for most flows. Refrigeration dryers from different makers differ in detail (some have automatic control of cooling capacity by load, others integrated filters), but the principle and the resulting +3 °C dew point remain the same.
Advantages and disadvantages of a +3 °C dew point
Advantages: The advantage of a +3 °C dew point is that it can be reached with simple, inexpensive technology. Refrigeration dryers have relatively low purchase costs and are undemanding to run – they consume only a certain amount of electricity to drive the refrigeration compressor and fan, but they do not consume compressed air from the circuit (unlike adsorption and membrane dryers, which release part of the air). +3 °C ensures that in the vast majority of indoor applications no condensate forms, so it is effective protection for pneumatic systems against water. At this level of drying a small relative humidity also remains in the air, which can be beneficial for some applications – lubricated pneumatic tools, for instance, may work better, because extremely dry air could dry out the seals. Air with a +3 °C dew point is still dry enough that water does not condense unintentionally in the pipework, provided the temperature does not fall below 0 °C. Another advantage is lower energy consumption compared with drying to lower dew points – a refrigeration dryer draws only the power needed to cool the air, which is generally far less than the energy needed to regenerate a desiccant down to -40 °C. +3 °C is therefore an energy-efficient choice for drying air in a warm environment. Refrigeration dryers are moreover simple to maintain – apart from occasionally cleaning the condensers and checking the condensate drain, they require no expensive media or frequent servicing.
Disadvantages: The drawback is the limitation of this technology – +3 °C is not sufficient if the air can come into contact with temperatures below +3 °C. Condensation would then occur. If you run a hose with air dried this way out into frost, for instance, the water in it will condense and may even freeze. For outdoor use in winter, or for storing air in a vessel in the cold, +3 °C is not enough and adsorption drying (a lower dew point) must be chosen. Another disadvantage is that even at +3 °C a certain water vapour content remains in the air. That does not bother mechanical equipment, but it can matter in chemical processes sensitive to moisture, or in powder coating, where drier air (-20 °C and drier) is sometimes recommended for the highest surface quality. In food production or pharmaceuticals, too, +3 °C can sometimes pose a risk of condensation in cooler places, so those fields tend to choose -40 °C for hygiene certainty. Refrigeration dryers additionally require an electricity supply and good ventilation – in places without power or with a high ambient temperature they can be problematic. In such situations a membrane dryer, which needs no electricity (but loses air), is sometimes used. In short, +3 °C is an excellent and sufficient solution in most cases, but bear in mind that it is not universal: in frost or with sensitive processes a lower dew point is necessary. For comparison, the dew point -25 °C and dew point -40 °C categories describe situations calling for more drying.
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Links – other dew points and dryers
For ordinary purposes +3 °C is generally the right choice. If you are dealing with air drying, though, it is worth knowing the other options: if you need even simpler drying and slightly moister air is acceptable, the dew point +5 °C variant is available. Conversely, for outdoor use in winter or special applications, consider dryers with a dew point of -25 °C or –40 °C. Our website carries the complete range of refrigeration dryers for +3 °C as well as information on other types. In the Types of air dryer section you can learn how the individual technologies work: from refrigeration through adsorption to membrane dryers. That lets you choose the optimal combination of dew point and dryer type for your needs and so ensure moisture is removed from the compressed air effectively.
All compressed air dryers and more information about air drying and the dew point are in this article from our advice centre: Measuring the dew point temperature and Why and how to dry air
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RDP condensation dryers; pressure dew point +3 °C
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Condensation dryers WDF; dew point +3°C with filters
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HDI air dryers; pressure dew point +4°C
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RDL condensing dryers; pressure dew point +5°C
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ADRY air dryers; smaller adsorption -40°C
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BDRY air dryers; large adsorption -40°C
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MADRY air dryers; membrane -40°C
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Activated carbon columns; activated carbon separation
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Product sorting
List of products
Condensation dryer for compressed air to +3°C dew point. Maximum inlet pressure is 14 bar with a flow rate of up to 35 m³/hr (583 l/min) and connection via external G3/4"...
The WDF-70 condensing air dryer provides efficient moisture removal from compressed air with a flow rate of 70 m³/h (1,166 l/min) and a pressure dew point of +3 °C. Thanks to...
The WDF-155 condensing air dryer effectively removes moisture from compressed air and achieves a pressure dew point of +3 °C. With a flow rate of 155 m³/h (2 583 l/min), it is...
The WDF-53 condensing air dryer efficiently removes moisture at a flow rate of 53 m³/h (883 l/min) and reaches a dew point of +3 °C. Integrated 1 µm and 0.01 µm filters ensure...
The WDF-100 condensing air dryer provides efficient compressed air drying with a flow rate of 100 m³/h (1 667 l/min) and a pressure dew point of +3 °C. Integrated filters of 1...
Refrigeration dryer for compressed air down to a dew point of +3°C. Maximum inlet pressure is 14 bar, with a flow rate of up to 20 m³/h (333 l/min) and connection via a G3/4"...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 235 m³/h (3,916 l/min) and connection via external thread G1...
Refrigeration dryer for compressed air down to a dew point of +3°C. Maximum inlet pressure is 14 bar, with a flow rate of up to 100 m³/h (1 666 l/min) and connection via a G1"...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 380 m³/h (6,333 l/min) and connection via external thread G1...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 180 m³/hour (3,000 l/min) and connection via external thread...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 72 m³/hr from the compressor at a 3°C dew point enables use in...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 1,500 m³/hour (25,000 l/min) and connection via external...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 260 m³/hr from the compressor at a 3°C dew point enables use in...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 75 m³/hr (1,250 l/min) and connection via external thread...
Condensation dryer for compressed air to +3°C dew point. Maximum inlet pressure is 14 bar with a flow rate of up to 144 m³/hour (2,333 l/min) and connection via external thread...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 25 m³/hr from the compressor at a 3°C dew point enables use in...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 1,150 m³/hour (19,166 l/min) and connection via external...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 1,300 m³/hour (21,666 l/min) and connection via external...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 1,900 m³/h (31,666 l/min) and connection via external thread...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 300 m³/hour (5,000 l/min) and connection via external thread...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 480 m³/hr (8,000 l/min) and connection via external thread G1...
Condensation dryer for compressed air to +3°C dew point. The maximum input pressure is 14 bar with a flow rate of up to 50 m³/h (833 l/min) and a G1" external thread connection....
Condensation dryer for compressed air to +3°C dew point. The maximum input pressure is 14 bar with a flow rate of up to 600 m³/h (10,000 l/min) and connection via external...
Condensation dryer for compressed air to +3°C dew point. Maximum input pressure is 14 bar with a flow rate of up to 750 m³/hour (12,500 l/min) and connection via external thread...
Refrigeration dryer for compressed air down to a dew point of +3°C. Maximum inlet pressure is 14 bar, with a flow rate of up to 950 m³/h (15 833 l/min) and connection via a G2"...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 108 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 12 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 1,300 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 144 m³/hr from the compressor at a 3°C dew point allows for use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 180 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 225 m³/hr from the compressor at a 3°C dew point allows use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 300 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 360 m³/hr from the compressor at a 3°C dew point allows use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 42 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 480 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 54 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 600 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 780 m³/hr from the compressor at a 3°C dew point enables use in...
The extremely quiet and dust-free operation of the compressed air condensation dryer up to a flow rate of 950 m³/hr from the compressor at a 3°C dew point enables use in...
The WDF-38 condensing (refrigeration) compressed air dryer with a capacity of 633 l/min up to 16 bar ensures reliable removal of moisture from compressed air up to a pressure...